ecri inspection and preventive maintenance procedures

Inspection and Preventive MaintenanceProceduresProcedure No. Procedure No.Anesthesia Unit Vaporizers . . . . . . . 436-0595Anesthesia Unit Ventilators . . . . . . . 461-0595Anesthesia Units . . . . . . . . . . . . . 400-0595Apnea Monitors . . . . . . . . . . . . . . 420-0595Argon Surgical Lasers . . . . . . . . . . 462-0595Aspirators . . . . . . . . . . . . . . . . . 433-0595Autotransfusion Units . . . . . . . . . . 449-0595Beds, Electric . . . . . . . . . . . . . . . 402-0595Blood Pressure Monitors, Electronic

Indirect . . . . . . . . . . . . . . . . . 454-0595Blood Pressure Monitors, Invasive . . . 434-0595Blood/Solution Warmers . . . . . . . . . 445-0595Capnometers and Multiple Medical

Gas Monitors . . . . . . . . . . . . . . 450-0595Carbon Dioxide Surgical Lasers . . . . . 446-0595Cardiac Resuscitators . . . . . . . . . . 421-0595Centrifuges . . . . . . . . . . . . . . . . 456-0595Circulating-Fluid Pumps . . . . . . . . . 412-0595Conductive Furniture and Floors . . . . 441-0595Critical Care Ventilators . . . . . . . . . 458-0595Cryosurgical Units . . . . . . . . . . . . 457-0595Defibrillator/Monitors . . . . . . . . . . 408-0595Defibrillators . . . . . . . . . . . . . . . 407-0595ECG Monitors . . . . . . . . . . . . . . . 409-0595Electrical Receptacles . . . . . . . . . . 437-0595Electrocardiographs . . . . . . . . . . . 410-0595Electrosurgical Units . . . . . . . . . . . 411-0595Frequency-Doubled Nd:YAG

Surgical Lasers . . . . . . . . . . . . 464-0595General Devices . . . . . . . . . . . . . . 438-0595Heart-Lung Bypass Units . . . . . . . . 430-0595Heated Humidifiers . . . . . . . . . . . . 431-0595Hemodialysis Units . . . . . . . . . . . . 413-0595Ho:YAG Surgical Lasers . . . . . . . . . 465-0595Hypo/Hyperthermia Units . . . . . . . . 414-0595

Infant Incubators . . . . . . . . . . . . . 415-0595Infusion Devices . . . . . . . . . . . . . 416-0595Intra-Aortic Balloon Pumps . . . . . . . 432-0595Isolated Power Systems . . . . . . . . . 439-0595Laparoscopic Insufflators . . . . . . . . . 466-0595Mammography Units . . . . . . . . . . . 467-0595Medical Gas/Vacuum Systems . . . . . . 440-0595Mobile C-arms . . . . . . . . . . . . . . 463-0595Mobile X-ray Units . . . . . . . . . . . . 468-0595Nd:YAG Surgical Lasers . . . . . . . . . 447-0595Oxygen-Air Proportioners . . . . . . . . 444-0595Oxygen Analyzers . . . . . . . . . . . . . 417-0595Pacemakers, External Invasive . . . . . 418-0595Pacemakers, External Noninvasive . . . 460-0595Peritoneal Dialysis Units . . . . . . . . . 455-0595Phototherapy Units . . . . . . . . . . . . 469-0595Physical Therapy Ultrasound Units . . . 470-0595Pneumatic Tourniquets . . . . . . . . . . 443-0595Portable Ventilators . . . . . . . . . . . 471-0595Pressure Transducers . . . . . . . . . . 435-0595Pulmonary Resuscitators,

Gas-Powered . . . . . . . . . . . . . . 448-0595Pulmonary Resuscitators, Manual . . . . 422-0595Pulse Oximeters . . . . . . . . . . . . . 451-0595Radiant Warmers . . . . . . . . . . . . . 419-0595Radiographic Units, General-Purpose . . 472-0595Radiographic/Fluoroscopic Units,

General-Purpose . . . . . . . . . . . . 473-0595Smoke Evacuators . . . . . . . . . . . . 452-0595Sphygmomanometers . . . . . . . . . . . 424-0595Suction Regulators . . . . . . . . . . . . 459-0595Temperature Monitors . . . . . . . . . . 425-0595Traction Units . . . . . . . . . . . . . . . 427-0595Transcutaneous O2/CO2 Monitors . . . . 453-0595Ultrasound Scanners . . . . . . . . . . . 474-0595

257941456-0595

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5200 Butler Pike, Plymouth Meeting, PA 19462-1298, USATelephone +1 (610) 825-6000 Fax +1 (610) 834-1275 E-mail [email protected]

IPM Procedures

009006436-0595

A NONPROFIT AGENCY


Anesthesia Unit VaporizersUsed For:Anesthesia Unit Vaporizers [10-144]

Also Called: By trade names (e.g., Fluotec 5, Vapor 19.1, Tec 6), which are registered trademarks and shouldbe used only when referring to the specific devices

Commonly Used In: Operating rooms, emergency rooms, delivery rooms, trauma rooms, and any areasrequiring the administration of an inhalation agent (with anesthesia units)

Scope: Applies to the various anesthesia vaporizers used to deliver a known concentration of vaporized liquidanesthetic

Risk Level: ECRI Recommended, High; Hospital Assessment,

ECRI-Recommended Interval UsedType Interval* By Hospital Time Required

Major 6 months months . hours

Minor NA months . hours

* Additional periodic calibration and preventive maintenance is normally required annually or biannually (seemanufacturers recommendation). Only qualified personnel trained and experienced in this function shouldperform this additional servicing.

OverviewAn anesthesia unit vaporizer is used to vaporize aliquid anesthetic agent and deliver a controlledamount to the patient.

According to the American Society for Testing andMaterials (ASTM)standard ASTM F1161-88, anestheticagent vaporizers are required to be concentration cali-brated (i.e., a calibrated knob controls the output con-centration). Older vaporizers, such as the CopperKettle and the Vernitrol, do not have a single controlfor selecting the concentration of anesthetic vapor.Where possible, these units should be removed fromservice. Contemporary concentration-calibrated va-porizers are of two types: variable bypass and heatedblender.

Conventional (variable-bypass) vaporizers. In avariable-bypass vaporizer, the total background gasflow that enters the unit is split into two streams. The

smaller stream, which acts as the carrier gas, passesthrough the vaporizing chamber containing the anes-thetic agent and becomes saturated with agent vapor;the remainder of the gas bypasses this chamber. Awick may be used in the vaporizing chamber to provideincreased surface area for efficient evaporation of thedrug and saturation of the carrier gas. The saturatedcarrier gas leaves the chamber and mixes with thebypass gas. One adjustment is made to set the desiredconcentration. This adjustment simultaneously bal-ances the carrier and bypass flows to produce the blendrequired for the set concentration. The mixture exitsthe vaporizer and is delivered from the anesthesiamachine as the fresh gas to be inspired by the patient.

Evaporation of the liquid agent contained in thechamber is driven by heat absorbed from the walls ofthe vaporizer; consequently, when evaporation is oc-curring, the vaporizer and its contents cool. Becausethe equilibrium vapor pressure of an agent changes

Procedure/Checklist 436-0595

with temperature, a temperature-sensitive mecha-nism is used to automatically adjust the carrier andbypass flows to compensate for temperature changes.Figure 1 presents a schematic of a variable-bypassvaporizer.

Desflurane (heated-blender) vaporizers. Desflu-rane, a volatile inhalation anesthetic marketed byOhmeda Pharmaceutical Products Division under thetrade name Suprane, has characteristics that differmarkedly from those currently in use enflurane, ha-lothane, and isoflurane; for example, its low solubilityallows rapid induction of and emergence from anesthe-sia. Thus, by increasing the speed of recovery, desfluranehas the potential to shorten hospital stays (although thishas not yet been consistently demonstrated).

The boiling point of desflurane 22.9C at 760 mmHg is just above room temperature; therefore, smallincreases in ambient temperature or decreases in atmos-pheric pressure can cause it to boil. Also, because ofdesfluranes high minimum alveolar concentration, orMAC (i.e., its low potency), evaporation of sufficientagent to achieve a given anesthetic effect would requiremuch more heat absorption from the vaporizer thanoccurs with other agents. Furthermore, the change invapor pressure of desflurane per change in temperatureis as much as three times that for the other volatileagents at sea-level atmospheric pressure. These pro-found effects of temperature and ambient pressure onthe vapor pressure of desflurane make stabilizing thedelivered concentration at a set point extremely difficultin a passive mechanical system, such as a variable-by-

pass vaporizer. As a result, the variable-bypass designwas abandoned for desflurane, and Ohmeda developeda new vaporizer, the Tec 6, based on a heated-blenderdesign. Figure 2 shows a schematic of this vaporizer.

A version of the Tec 6 (also manufactured by Oh-meda) has been adapted for Drager machines and iscompatible with the Drager triple-exclusion interlocksystem. As of this writing, neither Drager nor Sie-mens has developed its own desflurane vaporizer.

A desflurane vaporizer requires electrical power toheat the agent to a thermostatically controlled 39C,producing a stable, saturated vapor pressure of1,500 mm Hg. No wick is used, and no carrier gasenters the sump chamber. Instead, a stream of vaporunder pressure flows out of the sump; this streamblends with the background gas stream, which origi-nates from the anesthesia machines flowmeters, toachieve the desired concentration.

The background gas stream passes through a fixed-flow resistor, producing a back pressure upstream ofthis resistor that is proportional to the background gasflow. The desired desflurane concentration is set on thedial of the adjustable metering valve in the vaporstream; this setting produces a predetermined aper-ture. The pressure in the vapor upstream of the aper-ture and the back pressure in the background gasstream are continually sensed by a differential pres-sure transducer. The transducer controls a pressure-regulating valve in the vapor stream between the sump

Figure 2. Schematic illustrating the basic elements of theOhmeda Tec 6 vaporizer

Figure 1. Schematic illustrating the basic elements of avaiable-bypass vaporizer

Inspection and Preventive Maintenance System

Inspection and Preventive Maintenance System2 1995 ECRI. All Rights Reserved.

and the adjustable metering valve. The pressure-regu-lating valve permits only that flow from the sumpnecessary to cause the pressure upstream of the ad-justable metering valve to equal the back pressure inthe background gas stream. In this way, the ratio ofthe adjustable metering valves resistance to the resis-tance of the fixed-flow resistor determines the ratio ofthe flows in each stream, and therefore, the concentra-tion of vapor in the blended output. If the flow from theanesthesia machines flowmeters through the vapor-izer is altered, the flow of vapor from the sump isautomatically adjusted so that the pressures at the twomonitored points remain equal, the flow ratio does notchange, and the output concentration continues tomatch its setting.

The control circuits and heating elements in thevaporizer are turned on by the act of connecting thevaporizer to electrical power. The unit then heats toand remains at operating temperature as long as itreceives power, whether it is delivering agent or is inthe standby mode. Consequently, it is warm to thetouch while plugged into a live socket.

Citations from Health DevicesAvoiding anesthesia mishaps through pre-use checks,

1982 May; 11:210-3.

Water in halothane vaporizers [Hazard], 1985 Aug;14:326.

Anesthesia units with a flowmeter-controlled vapor-izer [Hazard], 1986 Dec; 15:336.

Vaporizer leak with Mapleson breathing circuits [Haz-ard], 1986 Dec; 15:344-5.

Concentration calibrated vaporizers [Hazard], 1987Mar-Apr; 16:112-3.

Pre-use anesthesia check fails to find faults [Hazard],1988 Sep; 17:274-6.

Desflurane (Suprane): Considerations for introduc-ing the new inhalation anesthetic agent into clinicalpractice [Guidance article], 1994 Apr; 23:131-42.

Test apparatus and suppliesHalogenated anesthetics analyzer

Hoses and adapters

Special precautionsAs a general precaution, a vaporizer containing an

anesthetic agent should not be tipped. If such tippingoccurs, notify the user and follow the manufacturersrecommended procedures for airing or drying the unit.

Do not fill a vaporizer with an inhalation agentunless you are qualified to do so. Always use a scav-enging system or appropriate ventilation when in-specting vaporizers. For personal safety, wheninspecting vaporizers alone, notify other personnel ofyour location. Be sure that filler ports are tightlycapped before passing gas through the vaporizer.

ProcedureBefore beginning an inspection, carefully read this

procedure and the manufacturers instruction and serv-ice manuals; be sure that you understand how to oper-ate the equipment and the significance of each controland indicator. Also determine whether any special in-spection or preventive maintenance procedures or fre-quencies are recommended by the manufacturer.

Note: This procedure should be done simultaneouslywith Anesthesia Units Procedure/Checklist 400,where leak testing of the vaporizer has been includedwith the anesthesia unit.

Each vaporizer should have a separate controlnumber. Inspection documentation for up to threevaporizers (on one anesthesia unit) can be included onone inspection form (record each control number), butsome hospitals may prefer to use a separate form foreach vaporizer.

Be sure that the anesthesia system is level andsecure. Check that all hoses and fittings are tight.

1. Qualitative tests

1.1 Chassis/Housing. Examine the exterior of theunit for cleanliness and general physical condi-tion. Be sure that housings are intact, that allassembly hardware is present and tight, andthat there are no signs of spilled liquids or otherserious abuse.

1.2 Mount/Fasteners. Check security of mounts orsupport mechanisms. Verify that the vaporizeris firmly mounted on the anesthesia unit.

1.4 AC Plug. If the unit is so equipped, examine theAC power plug for damage. Attempt to wigglethe blades to determine that they are secure.Shake the plug and listen for rattles that couldindicate loose screws. If any damage is sus-pected, open the plug and inspect it.

1.5 Line Cord. Inspect the cord, if so equipped, forsigns of damage. If damaged, replace the entirecord, or if the damage is near one end, cut out thedefective portion. Be sure to wire a new power cordor plug with the same polarity as the old one.

Anesthesia Unit Vaporizers

Inspection and Preventive Maintenance System1995 ECRI. All Rights Reserved. 3

1.6 Strain Reliefs. Examine the strain reliefs atboth ends of the line cord, if so equipped. Be surethat they hold the cord securely.

1.7 Circuit Breaker/Fuse. If the device has aswitch-type circuit breaker, check that it movesfreely. If the device is protected by an externalfuse, check its value and type against thatmarked on the chassis, and ensure that a sparefuse is provided.

1.8 Tubes/Hoses. Check the condition of all tubingand hoses. Be sure that they are not cracked,kinked, or dirty.

1.10 Fittings/Connectors. Examine all gas and liq-uid fittings and connectors for general condition.Be sure all fittings are tight.

1.13 Controls. Before moving any controls, checktheir positions. If any of them appear inordinateor are left in the on position, consider the possi-bility of inappropriate clinical use or of incipientdevice failure.

Examine all controls for physical condition,secure mounting, and correct motion. Where acontrol should operate against fixed-limit stops,check for proper alignment, as well as positivestopping. During the course of the inspection, besure to check that each control performs itsproper function. Return all controls to the offposition following the test.

1.16 Fluid Levels. Check all fluid levels. If the fluidlevel is zero, we recommend that you have aqualified user fill the sump with anestheticagent to continue the inspection.

1.17 Battery. Inspect the physical condition of thebattery and battery connectors, if so equippedand readily accessible. Operate the battery-pow-ered functions of the unit for several minutes tocheck that the battery has an adequate charge.Check remaining battery capacity by activatingthe battery test function or measuring the out-put voltage. If it is necessary to replace a battery,label it with the date.

1.18 Indicators/Displays. During the course of theinspection, confirm the operation of all indica-tors and visual displays on the unit, if soequipped.

1.20 Alarms/Interlocks. Operate the device in sucha way as to activate each audible and visualalarm, if so equipped. If the device has an alarm-silence feature, check the method of reset (i.e.,

manual or automatic) against the manufac-turers specifications. Check that the vaporizerinterlock allows activation of only one vaporizerat a time.

1.21 Audible Signals. Operate the device in such away as to activate any audible signals. Confirmappropriate volume, as well as the operation ofa volume control, if so equipped.

1.22 Labeling. Check that all necessary placards, la-bels, conversion charts, and instruction cardsare present and legible.

1.24 Site Glass, O-Rings, Keyed Filler Mechanism. Ex-amine the physical condition of the site glass,O-rings, and keyed filler mechanism, if soequipped.

2. Quantitative tests2.1 Grounding Resistance. If the unit is electrically

powered, use an ohmmeter, electrical safety ana-lyzer, or multimeter with good resolution of frac-tional ohms to measure and record theresistance between the grounding pin of thepower cord and exposed (unpainted and not ano-dized) metal of the chassis. We recommend amaximum of 0.5

2.2 Leakage Current. For electrically poweredunits, measure chassis leakage current to thechassis of the device with the grounding conduc-tor of plug-connected equipment temporarilyopened. Operate the device in all normal modes,including On, Standby, and Off, and record themaximum leakage current. Leakage currentshould not exceed 300 A.

2.10 Concentration Check. Data for up to three va-porizers can be recorded as Items 2.10, 2.11, and2.12. Record the type and control number of thevaporizer being tested under each item.

2.11 See Item 2.10

2.12 See Item 2.10

Because there are various types of halogen-ated anesthetic analyzers, follow the manufac-turers procedure for setup and use of theanalyzer.

Vaporizers should usually be tested with anoxygen flow of 4 to 5 L/min (nitrous oxide mayaffect the readings of some vapor analyzers).Test the vaporizers at low, medium, and highconcentration settings in the normal clinical userange (e.g., 0.5%, 1.0%, and 3.0% for halothane).



At one concentration setting (e.g., 1.0% for ha-lothane, 10% for desflurane), test the vaporizerat another flow (e.g., 1 L/min). We recommendthat the concentration be 0.3% vapor or 10%of the measured value, whichever is greater. Iferrors in concentration are observed, allow thevaporizer to operate for a minute or two andrecheck the unit. Some units may require ashort stabilization period.

3. Preventive maintenance3.1 Clean the exterior.

3.2 Replace the battery, if so equipped (batteryshould be replaced at least once annually).

4. Acceptance tests

Conduct major inspection tests for incoming vapor-izers and, if a vaporizer is position sensitive, any timeit is demounted from an anesthesia unit.

Before returning to use

Return all controls to the off position, level andsecure the unit, and tighten all fittings and tubing.

Anesthesia Unit Vaporizers


238369461-0595

A NONPROFIT AGENCY


Anesthesia Unit VentilatorsUsed For:Anesthesia Unit Ventilators [10-145]

Commonly Used In: Delivery rooms and operating rooms

Scope: Applies to ventilators used to deliver inhalation anesthetic agents during surgical procedures thatrequire general anesthesia


ECRI-Recommended Interval UsedType Interval By Hospital Time Required

Major 6 months* months . hours


* Inspection and preventive maintenance intervals should be scheduled according to the manufacturersrecommendations. However, units should have a major inspection at least every six months. Pre-use checksshould be performed before each case by the anesthetist who will be operating the equipment.

OverviewPatients undergoing surgery under general anesthesiaare routinely paralyzed with muscle relaxants to sta-bilize the surgical field. Consequently, they are unableto breathe on their own and must be mechanicallyventilated either manually by the anesthetist, whosqueezes a reservoir bag in the breathing circuit, orautomatically by an anesthesia ventilator. A switchvalve allows the choice of the method by which venti-lation is to be supported. The anesthesia ventilator istypically turned on and off independently of the switch-ing between manual and automatic ventilation.

Anesthesia ventilators use positive pressure to in-flate a patients lungs and deliver a prescribed mixtureof gases and vapors to them. This mixture is producedby the anesthesia machine. The ventilator can be builtinto the anesthesia machine or can be a stand-aloneunit connected to the machine by gas tubing and,perhaps, sensor cables. Some anesthesia ventilatorshave built-in displays and alarms; others rely on thesensors, displays, and alarms of the anesthesia ma-chine to monitor their performance.

In general, an anesthesia ventilator is less sophisti-cated than a critical care ventilator, having only acontrol mode of operation, with time cycling. (However,there is at least one ICU-type ventilator that can beused to administer inhalation anesthetics.) A pressurelimit prevents exposure of the lungs to excessive pres-sure. Several other breathing waveshape parameters(e.g., inspiratory:expiratory [I:E] ratio, tidal volume,minute volume, flow) are settable by the operator andcontrolled by the ventilator. Ventilators designedsolely for anesthetic administration typically do nothave compressors.

During extended procedures and procedures involv-ing open breathing circuit configurations, a humidifiermay be included in the breathing circuit. Otherwise, acircle system with an absorber, along with one-wayinspiratory and expiratory valves, is used, typicallywithout a humidifier. The ventilators pressure-reliefand limit valve(s) should be connected to a waste gasscavenging system.

Citations from Health DevicesAnesthesia systems [Evaluation], 1988 Jan; 17:3.

Procedure Checklist 461-0595

Who should service anesthesia equipment [User Expe-rience NetworkTM], 1988 Feb; 17:70.

Barotrauma from anesthesia ventilators [Hazard],1988 Nov; 17:354.

Damage to elastic components from Loctite [Hazard],1989 Jul-Aug; 18:288.

Risk of barotrauma and/or lack of ventilation withventilatorless anesthesia machines [Hazard], 1994Jan-Feb; 23:54.

Test apparatus and suppliesLung simulator with adjustable compliance or ven-tilator tester

Pressure gauge or meter with 2 cm H2O resolutionfrom -20 to +120 cm H2O

Various breathing circuit adapters

Leakage current meter or electrical safety analyzer

Ground resistance ohmmeter

Additional items as required for specific manufac-turers procedures


procedure and the manufacturers instruction andservice manuals; be sure that you understand how tooperate the equipment, the significance of each controland indicator, and the alarm capabilities. Also deter-mine whether any special inspection or preventivemaintenance procedures or frequencies are recom-mended by the manufacturer.

Manufacturers recommended procedures for in-spection and preventive maintenance of mechanicalanesthesia ventilators vary in both methods and re-quired accuracy. In addition, ventilator controls canvary greatly among manufacturers and models. Thisprocedure provides the basic framework for completeventilator inspection and preventive maintenance.Manufacturers recommended procedures should beadded where appropriate. References to specific pagesof the manufacturers manual should be added to thechecklist. (The checklist includes blank spaces for theinsertion of these reference numbers.)

IPM Task ManagerTM, the software component of theInspection and Preventive Maintenance System, en-ables easy production of customized procedures andchecklists for specific ventilator models and clinicalneeds. Items performed by outside vendors can beexcluded from the checklist; a separate checklist for

use by outside vendors can be produced to ensure thatthose items agreed upon are performed by the vendor.

The following framework should be supplementedby the manufacturers recommended preventive main-tenance procedures for mechanical ventilators.


1.1 Chassis/Housing. Examine the exterior of theunit for cleanliness and general physical condition.Be sure that plastic housings are intact, that allhardware is present and tight, and that there areno signs of spilled liquids or other serious abuse.

1.2 Mount/Fasteners. Check that ventilatorsmounted in anesthesia machines are properlyinstalled. If the device is mounted on a stand orcart, examine the condition of the mount. If it isattached to a wall or rests on a shelf, check thesecurity of this attachment. Check the mountingsecurity of all components.

1.3 Casters/Brakes. If the device moves on casters,check their condition. Verify that they turn andswivel, as appropriate, and look for accumula-tions of lint and thread around the casters.Check the operation of brakes and swivel locks,if the unit is so equipped.

1.4 AC Plug. Examine the AC power plug for dam-age, if so equipped. Attempt to wiggle the bladesto check that they are secure. Shake the plug andlisten for rattles that could indicate loose screws.If any damage is suspected, open the plug andinspect it.

1.5 Line Cord. Inspect the cord for signs of damage,if so equipped. If damaged, replace the entirecord or, if the damage is near one end, cut out thedefective portion. Be sure to wire a new powercord or plug with the correct polarity. Also checkline cords of battery chargers.

1.6 Strain Reliefs. Examine the strain reliefs atboth ends of the line cord, if so equipped. Be surethat they hold the cord securely.

1.7 Circuit Breaker/Fuse. If the device has a switch-type circuit breaker, check that it moves freely. Ifthe device is protected by an external fuse, checkits value and type against that marked on thechassis, and ensure that a spare is provided.

1.8 Tubes/Hoses. Check the condition of all tubingand hoses. Be sure that they are not cracked,kinked, or dirty. Check that they are connectedto the correct locations.



1.9 Cables. Inspect any cables (e.g., for sensors) andtheir strain reliefs for general condition. Care-fully examine cables to detect breaks in the in-sulation and to ensure that they are securelygripped in the connectors at each end, which willprevent rotation or other strain. Where appro-priate, verify that there are no intermittentfaults by flexing cables near each end and look-ing for erratic operation or by using an ohmme-ter.

1.10 Fittings/Connectors. Examine all gas fittingsand connectors for general condition. Gas fit-tings should be tight and should not leak. Verifythat keyed connectors (e.g., pin-indexed gas con-nectors) are used where appropriate, that allpins are in place and secure, and that keying iscorrect. Connectors to hospital central pipedmedical gas systems should have the appropri-ate DISS or quick-connect fitting to eliminate theneed for adapters.

1.12 Filters. Check the condition of gas filters, if in-cluded in the unit. Check for corrosion residueindicative of liquid, gaseous, or solid particlecontaminants in the gas supply; if found, notifyappropriate personnel. Clean or replace if appro-priate, and indicate this on Lines 3.1 and 3.4 ofthe inspection form.

1.13 Controls/Switches. Before changing any con-trols or alarm limits, check their positions. If anysettings appear inordinate (e.g., alarm limits atthe ends of their range), consider the possibilityof inappropriate clinical use or of incipient devicefailure. Record the settings of those controls thatshould be returned to their original positionsfollowing the inspection.

Examine all controls and switches for physicalcondition, secure mounting, and correct motion.Check that control knobs have not slipped ontheir shafts. Where a control should operateagainst fixed-limit stops, check for proper align-ment, as well as positive stopping. Check mem-brane switches for damage (e.g., fromfingernails, pens). During the inspection, be sureto check that each control and switch performsits proper function.

1.15 Fan. Check physical condition and proper op-eration, if so equipped. Clean and lubricate ifrequired, according to the manufacturers in-structions, and note this on Lines 3.1 and 3.2 ofthe form.

1.17 Battery/Charger. Inspect the physical conditionof batteries and battery connectors, if so equippedand if readily accessible. Check operation ofbattery-operated power-loss alarms, if soequipped. Operate the unit on battery power forseveral minutes to check that the battery ischarged and can hold a charge. (The inspectioncan be carried out on battery power to helpconfirm adequate battery capacity.) Check bat-tery condition by activating the battery test func-tion or measuring the output voltage; forlead-acid batteries, measure the specific gravityand check the fluid level. Check the condition ofthe battery charger and, to the extent possible,confirm that it does, in fact, charge the battery.Be sure that the battery is recharged or chargingwhen the inspection is complete. When it is nec-essary to replace a battery, label it with the date.

1.18 Indicators/Displays. During the course of theinspection, confirm the operation of all lights,indicators, meters, gauges, and visual displayson the unit and charger (if so equipped). Be surethat all segments of a digital display function.Record the reading of an hour meter, if present.

1.20 Alarms/Interlocks. Inducealarm conditionstoac-tivate audible and visual alarms. Check that anyassociated interlocks function. If the unit has analarm-silence feature, check the method of reset(i.e., manual, automatic) against the manufac-turers specifications. It may not be possible tocheck out all alarms at this time since some mayrequire special conditions that must be establishedaccording to the manufacturers recommenda-tions; include these in Item 2.4. Verify that anyremote alarm indicator (e.g., within the main-frame anesthesia unit) functions properly.

1.22 Labeling. Check that all necessary placards, la-bels, and instruction cards are present and legible.

1.23 Accessories. Confirm the presence and conditionof accessories. Check the condition of reusableBain circuit and adapters, if available.

1.24 Bellows. Check the physical condition andproper operation of the bellows.

2. Quantitative tests

2.1 Grounding Resistance. Using an ohmmeter, elec-trical safety analyzer, or multimeter with goodresolution of fractional ohms, measure and recordthe resistance between the grounding pin of thepower cord and exposed (unpainted and not ano-dized) metal on the chassis of the ventilator or of

Anesthesia Unit Ventilators


the system in which the ventilator is mounted.We recommend a maximum of 0.5 . If theventilator is a component within an anesthesiaunit, grounding and leakage current measure-ments can be referenced to that unit.

2.2 Leakage Current. Measure chassis leakage cur-rent to ground with the grounding conductor ofplug-connected equipment temporarily opened.Operate the device in all normal modes, includ-ing on, standby, and off, and record the maxi-mum leakage current.

Measure chassis leakage current with all ac-cessories normally powered from the same linecord connected and turned on and off. This in-cludes other equipment that is plugged into theprimary devices accessory receptacles, as well asequipment plugged into a multiple-outlet strip(Waber strip) so that all are grounded througha single line or extension cord.

Chassis leakage current to ground should notexceed 300 A.

2.3 Modes and Settings. Anesthesia ventilators areusually equipped only with a control mode. How-ever, specialized units may have additionalmodes such as assist/control and pressure sup-port. Adjustable positive end-expiratory pres-sure (PEEP) may also be available. The functionof these modes should be inspected and verifiedfor proper operation. Check the operation andaccuracy of ventilation controls, which may in-clude tidal volume, breath rate, inspiratory time,expiratory time, I:E ratio, pressure limit, or flow.Typically, these tests are performed by attachingthe ventilator to a lung simulator or ventilatortester and comparing measured values to set-tings on the ventilator. The manufacturer shouldrecommend the appropriate ventilator settings(e.g., tidal volume, rate, inspiratory time) to ver-ify proper operation and accuracy (generallywithin 10%).

2.4 Monitors and Alarms. The following breathingcircuit parameters may be monitored by the ven-tilator or by the system in which the ventilatoris mounted. They should be inspected for accu-racy (generally within 10%) according to themanufacturers specifications:

Breathing rate

Inspiratory time

Airway pressure (e.g., PIP, PEEP, MAP, ap-nea)

Volume (e.g., tidal volume, minute volume,apnea)

Fraction of inspired oxygen (FIO2; see OxygenAnalyzers Procedure/Checklist 417)

Alarm settings (e.g., high PIP, low MAP, lowpressure, low FIO2) should be inspected forproper and accurate activation.

2.5 Gas Supply.

Pneumatic lines (including air filters). Verifythat appropriate gas-specific connectors areused. Check gas filters, if so equipped andaccessible.

Gas cylinders (and gauges and regulators, if soequipped). Verify that these are present, se-curely mounted, and in good condition andthat there is an adequate gas supply. Verifythat one and only one washer is used to sealthe tank to its yoke. Verify that all index pinsare present and protruding to the properlength to engage the hole in the tank valvestem and in the correct positions for the gas tobe supplied through the yoke.

2.6 Patient Circuit.

Breathing circuit (including filters). Verify thatthese components are compatible with the ven-tilator according to the manufacturers recom-mendations (see Health Devices 1988 Apr;17:109). Check for leaks, the absence of obstruc-tions, and proper flow direction in the breathingcircuit, ensuring the proper assembly and func-tion of fittings, adapters, the CO2 absorber, in-spiratory and expiratory valves and PEEPvalves, the APL valve, the scavenger, and othercomponents. With the ventilator connected tothe anesthesia system, check for leaks in theentire system, including the breathing circuit.This does not have to be duplicated if done aspart of the Anesthesia Units procedure (seeProcedure/Checklist 400).

Humidifiers. See Heated Humidifiers Proce-dure/Checklist 431.

Pressure-Relief Mechanism. Check the properoperation of the pressure-relief mechanism byoccluding the breathing circuit and measuringthe resulting peak pressure on the pressuregauge. Verify that pressure is vented in thebreathing circuit.

Absorber. See Anesthesia Units Proce-dure/Checklist 400.



3. Preventive maintenance3.1 Clean the exterior and interior, if needed.

3.3 Calibrate according to manufacturers instructions.

3.4 Replace components according to the manufac-turers instructions.

4. Acceptance testsConduct major inspection tests for this procedure

and the appropriate tests in the General Devices Pro-cedure/Checklist 438.

Before returning to useEnsure that all controls are set properly. Set alarms

loud enough to alert personnel in the area in which thedevice will be used. Other controls should be in theirnormal pre-use positions.

Attach a Caution tag in a prominent position so thatthe user will be aware that control settings may havebeen changed.

Recharge battery-powered devices, or equip themwith fresh batteries, if needed.

Anesthesia Unit Ventilators


009005400-0595

A NONPROFIT AGENCY


Anesthesia UnitsUsed For:Anesthesia Units [10-134]

Also Called: Anesthesia machines, anesthesia workstations

Commonly Used In: Operating rooms, emergency departments, trauma rooms, delivery rooms, any areaswhere anesthetic agents are used

Scope: Applies to anesthesia units; includes leak testing of vaporizers and should be used in conjunction withAnesthesia Unit Vaporizers Procedure/Checklist 436 (in the very rare case where an anesthesia unit may stilluse flammable anesthetic agents, refer to Conductive Furniture and Floors Procedure/Form 441); does notapply to oxygen monitors with an alarm, spirometers, other monitors, or ventilators that might be part of thebreathing system (see Anesthesia Unit Ventilators Procedure/Checklist 461)





Overview

Most surgical procedures are performed while the pa-tient is under general anesthesia. Usually, the patientis anesthetized by a narcotic or barbiturate injectionfollowed by administration of an inspired gas mixtureof oxygen, nitrous oxide, and the vapor of a volatileliquid anesthetic, typically a halogenated hydrocar-bon. The anesthesia unit administers this mixture ofanesthetic gases and life-sustaining oxygen, varyingthe proportions to control the patients level of con-sciousness. If respiratory assist is necessary (e.g., incases of muscular blockade), a ventilator may be con-nected to the patient breathing system to force the gasmixture into the patients lungs.

Improperly modified or inadequately maintainedanesthesia units have injured and killed patientsand hospital personnel. Gas leaks can adverselyaffect the accuracy of gas delivery to the patient, aswell as add anesthetic agents to the OR atmosphere.Trace levels of anesthetics have been implicated as

a health hazard to chronically exposed OR personneland unborn children. Inadvertent switching of gassupplies, failure of an alarm to respond to an exces-sively low oxygen pressure, and misconnected or im-properly calibrated flowmeters have also causedanesthesia-related accidents.

Because mishandling and mistakes can have severeconsequences, life-support devices such as anesthesiaunits should be operated and inspected only by quali-fied personnel who have a thorough knowledge of theunits and their functions. If you are unsure of anyaspect of the procedure, consult the manufacturer be-fore inspecting an anesthesia unit.

The anesthesia unit consists of four systems: the gassupply system, the gas control system, the vaporizers,and the breathing system.

Gas supply. This system delivers a variety of gasesto the patient. Cylinders containing oxygen and othergases at high pressure (see Table 1) are connected tothe high-pressure system of the anesthesia unit by


yoke fittings that comply with the Compressed GasAssociation (CGA) pin-index safety system (see Figure1). Unique placements of pins and mating holes on thepin-index fittings prevent connection of a gas cylinderto the wrong inlet. Inside the unit, each high-pressuregas flows through a filter, a check valve (for one-wayflow), and a regulator that reduces the pressure toapproximately 45 psi.

Because oxygen and nitrous oxide are used in rela-tively large quantities, they are usually drawn fromthe hospitals central gas supplies, which are moreconvenient and economical than compressed-gas cyl-inders. However, cylinders of these gases are also

normally attached to the anesthesia unit as a reservesource if the central supply fails or if central supplyoutlets are not available.

Centrally supplied gases are delivered directly to theintermediate-pressure gas control system at approxi-mately 50 psi through low-pressure hoses and connec-tors. These connectors may not comply with a universalstandard safety system, but each is designed to preventmismating the gas supply and the machine inlet.

Some units may provide an oxygen power outlet todrive auxiliary devices (e.g., a ventilator).

Gas control. This system regulates gas flow rates sothat the gases can be mixed and delivered under accu-rate, constantly metered control. The operator mustbe able to adjust the ratios or make rapid gross changesin flow rates without inducing system interactions thatcause temporary delivery of undesirable mixtures.

The flow of each gas is controlled by a valve andindicated by a glass-tube flowmeter. After gases passthe control valve and enter the low-pressure system,they can be administered to the patient.

A fail-safe provision in many anesthesia units pro-tects the patient against a fall in pressure of life-sus-taining oxygen. If the oxygen pressure drops belowabout 25 to 30 psi, some units shut off the flow of allother gases, while others reduce all gas flow rates inproportion to the drop in oxygen pressure. Neweranesthesia machines have additional safety systemsthat provide a minimum percent of oxygen (around25%) and/or deliver a minimum flow of oxygen (usually150 to 250 mL/min) (see Item 2.11).

Vaporizers. These devices add the vapor of a volatileliquid anesthetic (e.g., halothane, isoflurane, enflurane,sevoflurane, desflurane) to the gas mixture, when de-sired, and aid in controlling the vapor concentration.

According to the American Society for Testing andMaterials (ASTM) standard ASTM F1161-88, anes-thetic agent vaporizers are required to be concentra-tion calibrated (i.e., a calibrated knob controls the

TABLE 1. Gases Used in Anesthesia Machines

Gas ChemicalFormula

Color Code:U.S.

Color Code:International

Service Pressure,psi 21C, Full Cylinder

Oxygen O2 Green White 1,800-2,400*Carbon Dioxide CO2 Gray Gray 838Nitrous Oxide N2O Blue Blue 745Helium He Brown Brown 1,600-2,000*Air Yellow White and Black 1,800

* Depends on cylinder size.

Figure 1. Pin-index safety system

Gas Index PinsCGA ConnectorNumber

Oxygen 2-5 870Nitrous Oxide 3-5 910O2 - CO2 (CO27%) 1-6 940O2 - HE (He > 80%) 4-6 930O2 - HE (He < 80%) 2-4 890Air 1-5 950



output concentration). Older vaporizers, such as theCopper Kettle and the Vernitrol, do not have a singlecontrol for selecting the concentration of anestheticvapor. Where possible, these units should be removedfrom service. Contemporary concentration-calibratedvaporizers are of two types: variable bypass and heatedblender.

The variable-bypass (conventional) vaporizer isused for most volatile agents (e.g., halothane, isoflu-rane, enflurane, sevoflurane). The total backgroundgas flow that enters the unit is split into two streams.The smaller stream, which acts as the carrier gas,passes through the vaporizing chamber containing theanesthetic agent and becomes saturated with agentvapor; the remainder of the gas bypasses this chamber.A wick may be used in the vaporizing chamber toprovide increased surface area for efficient evapora-tion of the drug and saturation of the carrier gas. Thesaturated carrier gas leaves the chamber and mixeswith the bypass gas. One adjustment is made to set thedesired concentration. This adjustment simultane-ously balances the carrier and bypass flows to producethe blend required for the set concentration. The mix-ture exits the vaporizer and is delivered from theanesthesia machine as the fresh gas to be inspired bythe patient.

A heated-blender vaporizer is used only for desflu-rane. It requires electrical power to heat the agentto a thermostatically controlled 39C, producing astable, saturated vapor pressure of 1,500 mm Hg. Nowick is used, and no carrier gas enters the sumpchamber. Instead, a stream of vapor under pressureflows out of the sump; this stream blends with thebackground gas stream, which originates from theanesthesia machines flowmeters, to achieve the de-sired concentration.

(Desflurane, a volatile inhalation anesthetic mar-keted by Ohmeda Pharmaceutical Products Divisionunder the trade name Suprane, and sevoflurane,marketed by Abbott under the trade name Ultane,have characteristics that differ markedly from thosecurrently in use enflurane, halothane, and isoflu-rane. For example, their low solubilities allow rapidinduction of and emergence from anesthesia. Thus,by increasing the speed of recovery, desflurane andsevoflurane have the potential to shorten hospitalstays, although this has not yet been consistentlydemonstrated.)

Breathing system. Although it is designed primar-ily for sustained, efficient gas delivery to the patient,the breathing system may also remove carbon dioxideand provide mechanical or manual ventilation of a

patient who cannot breathe spontaneously, as well aspositive end-expiratory pressure (PEEP), if required.The breathing system typically includes a scavengingsystem to remove waste gases.

Two types of breathing systems are used to deliverthe anesthetic mixture from the unit to the patient,although they may assume a variety of configurations.

The T-piece or open system may be a nonrebreath-ing system consisting of a reservoir bag and a gas-de-livery hose connected through a nonrebreathing(one-way) valve to the face mask or endotracheal tube.The patient breathes the anesthetic mixture directlyfrom the machine, and exhaled gas is vented out of thesystem. T-piece systems that do not include the nonre-breathing valve may allow partial rebreathing, de-pending on the inflow of fresh gas.

The circle or closed system is a continuous loop inwhich check valves allow gas to flow in only one direc-tion. The patient inhales from and exhales into thesystem. Fresh gases from the anesthesia machineenter at one point, mix with previously exhaled gases,and pass to the patient, who inhales the mixture.Newly exhaled gases are channeled to a carbon dioxideabsorber, which removes almost all the carbon dioxideproduced by body metabolism and routes the scrubbedgases back toward the patient. En route, the scrubbedgases become mixed with fresh machine gases.

A scavenging system should be included to removewaste gas from the vent port of a T-piece breathingsystem or from the adjustable pressure-limiting (APL)valve and relief valve of a ventilator of a circle systemto reduce the quantity of gas that escapes into theoperating room. Such a scavenging system is neces-sary because trace levels of anesthetics are believed tocause an increased incidence of spontaneous abortion,congenital anomalies in offspring, and neoplastic dis-ease and may affect the mental and physical abilitiesof exposed personnel. The breathing system should bechecked before each use for leaking gases. It is alsorecommended that the concentration of waste anes-thetic gas in the operating room be surveyed quarterly.The scavenging system must include pressure-reliefmechanisms so that abnormal pressures cannot de-velop in the scavenging system and interfere withoperation of the breathing system.

Anesthesia units either come with physiologicalmonitors integrated into the unit or provide shelvingto support such monitors. Most also provide mountingfor a suction regulator and canister and other accesso-ries, along with storage for drugs, supplies, and relatedparaphernalia.

Anesthesia Units


Citations from Health DevicesAnesthesia units with a flowmeter-controlled vapor-

izer [Hazard], 1986 Dec; 15:336-7.

Vaporizer leak with Mapleson breathing systems[Hazard], 1986 Dec; 15:344-5.

Concentration calibrated vaporizers [Hazard], 1987Mar-Apr; 16:112-3.

Pre-use testing prevents helpful reconstruction ofanesthesia components [Hazard], 1987 May;16:178-9.

Anesthesia systems [Evaluation], 1988 Jan; 17:3-34.

Who should service anesthesia equipment [User Expe-rience NetworkTM], 1988 Feb; 17:70-1.

Pre-use anesthesia check fails to find faults [Hazard],1988 Sep; 17:274-6. (Contains pre-use checklist foranesthesia units.)

Anesthesia systems [Evaluation Update], 1988 Dec;17:366-7.

Anesthesia units and breathing systems [Standard],1989 Oct; 18:363.

Monitoring and anesthesia systems: integration and anew option, 1991 Mar-Apr; 20:131-2.

Use of inadequate (old) anesthesia scavenger inter-faces [Hazard], 1993 Dec; 22:592.

Anesthesia systems [Evaluation]. To be published in1996.

Test apparatus and suppliesPressure gauge or meter, -10 to +80 cm H2O (accu-racy 5 cm H2O at 30 cm H2O)

Flowmeters with ranges of approximately 0.1 to 1.0L/min and 1 to 10 L/min, 2% accuracy, calibratedseparately for each of the gases used with the anes-thesia machine, and one flowmeter for 10 to 100L/min (10% of reading)

Stopwatch or watch with a second hand

Hoses and adapters for connecting pressure gaugesor meters and flowmeters to equipment being in-spected

Cylinder of each type of gas used with the unitbeing inspected; each cylinder on a unit that isready for use should be more than half full if thegas is normally stored in gaseous form (e.g., oxy-gen) and should contain some liquid if the gas isnormally liquefied for storage; cylinders should

have a minimum pressure of 745 psi for nitrousoxide and 1,000 psi for oxygen

Nondisposable corrugated breathing hose (dispos-able tubing may not provide reliable connections)

Test lung (reservoir bag with 3 or 5 L capacity)

Sphygmomanometer bulb with tubing and adapter

Leak-detecting solution

Conductive lubricant for conductive casters (e.g.,Dow No. 41, graphited oil)

Trichloroethylene cleaning solvent or solvent rec-ommended by the manufacturer (be sure to reviewthe manufacturers Material Safety Data Sheet andsee the special precautions below)

Lubricant as specified by manufacturer

Special precautionsECRI is aware of a number of incidents in which

improperly serviced ventilation or anesthesia equip-ment was implicated in patient injury or death. Do notperform any procedures, adjustments, repairs, ormodifications unless you thoroughly understand thedevice and have verified the appropriateness of theintended actions. Resolve any questions or uncertain-ties with the manufacturer, the anesthetist, or ECRIbefore placing a unit into use.

To avoid the adverse effects of exposure to anes-thetic gases, all testing should be done with an operat-ing scavenging system in place or an alternative meansto vent excess gases from the vicinity of inspectingpersonnel. If a flammable anesthetic is used, be sureall traces of the gas are cleared away before performingany electrical tests. Check that all valves, includingthe gas cylinder stem valves, are turned off at thebeginning of the inspection. Turn all valves off againwhen the inspection is complete.

When testing cyclopropane flowmeters, observenoted procedures to avoid a buildup of explosive levelsof cyclopropane.

Trichloroethylene is a common solvent particularlyrecommended for cleaning oxygen fittings because itdoes not leave a residue that is flammable in high-con-centration oxygen. However, this solvent reacts withthe soda lime used in carbon dioxide absorbers to formseveral poisonous gases, including phosgene. Al-though concentrations may not be lethal, the presenceof these gases to any degree is highly undesirable.

To prevent the generation of these gases, make surethat equipment recently cleaned with trichlo-roethylene is completely dry before using. When clean-



ing parts of the anesthesia unit with this solvent, firstdisconnect the line to the carbon dioxide absorber.After cleaning, allow time for the solvent to evaporate.When the parts appear dry, take the added precautionof briefly flushing them with a high oxygen flow rate.


procedure and the manufacturers instruction andservice manuals; be sure that you understand how tooperate the equipment, the significance of each controland indicator, and the alarm capabilities. Also deter-mine whether any special inspection or preventivemaintenance procedures or frequencies are recom-mended by the manufacturer.


1.1 Chassis/Housing. Examine the exterior of theunit for cleanliness and general physical condi-tion. Be sure that plastic housings are intact,that all assembly hardware is present and tight,and that there are no signs of spilled liquids orother serious abuse.

1.2 Mount. Check any shelves, brackets, or sup-porting structures. Check the security of theattachments.

1.3 Casters/Brakes. If the device moves on casters,check their condition. Look for accumulations oflint and thread around the casters, and be surethat they turn and swivel as appropriate. Checkthe operation of brakes and swivel locks, if theunit is so equipped. Check that gas hoses do notlie on the floor or loop near the casters.

1.4 AC Plug/Receptacles. Examine the AC powerplug for damage. Attempt to wiggle the bladesto determine that they are secure. Shake theplug and listen for rattles that could indicateloose screws. If any damage is suspected, openthe plug and inspect it.

If the device has electrical receptacles for ac-cessories, insert an AC plug into each and checkthat it is held firmly. If accessories are pluggedand unplugged often, consider a full inspectionof the receptacle.

1.5 Line Cord. Inspect the cord for signs of damage.If damaged, replace the entire cord or, if thedamage is near one end, cut out the defectiveportion. Be sure to wire a new power cord or plugwith the correct polarity. Also check line cords ofbattery chargers.

1.6 Strain Reliefs. Examine the strain reliefs atboth ends of the line cord. Be sure that they holdthe cord securely.

1.7 Circuit Breaker/Fuse. If the device has aswitch-type circuit breaker, check that it movesfreely. If the device is protected by an externalfuse, check its value and type against thatmarked on the chassis, and ensure that a spareis provided.

1.8 Tubes/Hoses. Check the condition of all tubingand hoses. Be sure that they are not cracked,kinked, or dirty.

1.9 Cables. Inspect the cables (e.g., sensor, elec-trode) and their strain reliefs for general condi-tion. Examine cables carefully to detect breaksin the insulation and to ensure that they aregripped securely in the connectors of each end toprevent rotation or other strain.

1.10 Fittings/Connectors. Examine all gas and liq-uid fittings and connectors, as well as all electri-cal cable connectors and sockets, for generalcondition. Electrical contact pins or surfacesshould be straight, clean, and bright. Check thatpins used with the pin-index safety system com-ply (location and length of protrusion) and areintact. Check the yoke clamping screw andmake sure empty yokes have plugs. Check thatappropriate keyed or indexed fittings are beingused with corresponding gases.

1.12 Filters. Check the condition of all compressed-gas filters. Clean or replace as needed, and indi-cate this on Line 3.1 or 3.4 of the inspection form.

1.13 Controls/Switches. Before moving any controlsand alarm limits, check their positions. If any ofthem appear inordinate (e.g., a pressure alarmcontrol at maximum, alarm limits at the ends oftheir range), consider the possibility of inappro-priate clinical use or of incipient device failure.Record the settings of those controls that shouldbe returned to their original positions followingthe inspection.

Examine all controls and switches for physicalcondition, secure mounting, and correct motion.Where a control should operate against fixed-limit stops, check for proper alignment, as wellas positive stopping. During the course of theinspection, be sure to check that each control andswitch performs its proper function.

Anesthesia Units


Check that the concentration dial on eachvaporizer moves freely and that only one vapor-izer can be on at a time. Observe the float motionas its flow control valve is turned on. The valveshould turn smoothly with only slight drag.Each valve should have a definite shutoff posi-tion at which the float should be motionless atits zero level. Check for free play in the controlvalve by pushing, pulling, and gently rocking thestem from side to side without rotation. The stemshould feel firm, and the flowmeter float shouldnot move. The control valve knob should requireturning through at least 90 to change the flowrate from 10% to 100% of full scale. (Note: Allrecent anesthesia units should now have differ-ent sized and shaped knobs for oxygen and ni-trous oxide to aid in differentiating between thetwo controls.)

1.17 Battery/Charger. Inspect the physical condi-tion of batteries and battery connectors, if read-ily accessible. Check the battery-operatedpower-loss alarms on AC and pneumatic devices,if so equipped. Operate the unit on battery powerfor several minutes to check that the battery hasan adequate charge. Check remaining batterycapacity by activating battery test function ormeasuring the output voltage. If appropriate,check the condition of the battery charger and,to the extent possible, confirm that it does, infact, charge the battery. When it is necessary toreplace a battery, label it with the date.

1.18 Indicators/Displays. During the course of theinspection, confirm the operation of all lights,indicators, meters, gauges, and visual displayson the unit and charger, if so equipped. Be surethat all segments of a digital display function.

1.19 Directional Valves. Check that directionalvalves are free from cracks and chips and fitsmoothly against the valve seats. Check for freemovement by shaking or lightly squeezing thehose connecting the two valves. The valvesshould flutter up and down and should not stickto their seats.

Check for the possibility of reverse flowthrough directional valves by removing thebreathing hoses from the absorber and attach-ing a thin disposable reservoir bag to the exha-lation port. Attach a piece of hose to the bagmount, set the control for manual mode, closethe APL valve, and occlude the inspiratory portwith the palm of your hand. Then, connect a testlung to the hose and generate about 5 cm H2O

of pressure on the pressure gauge. Watch for anyinflation of the flattened bag as a sign of expira-tory valve leakage.

Reconnect the bag to the bag mount and thehose to the inhalation port. With your hand oc-cluding the expiratory port, use a test lung toagain generate about 5 cm H2O of pressure andcheck for inspiratory valve leakage by watchingfor any inflation of the bag.

1.20 Alarms/Interlocks. Operate the device in such away as to activate each audible and visual alarm.Check that any associated interlocks function(particularly the vaporizer interlocks, whichshould allow activation of only one vaporizer at atime). If the device has an alarm-silence feature,check the method of reset (i.e., manual or auto-matic) against the manufacturers specifications.

1.21 Audible Signals. Operate the device in such away as to activate all audible signals. Confirmappropriate volume, as well as the operation ofa volume control, if so equipped. Check that theaudible signals are appropriate for the test con-ditions used.

1.22 Labeling. Check that all necessary placards, la-bels, conversion charts, and instruction cardsare present and legible. Check for proper colorcoding for corresponding parts (e.g., green foroxygen, blue for nitrous oxide).

1.23 Accessories. Verify accuracy and function of anyaccessories (e.g., spirometer, sphygmomanome-ter gauge). (Inspect ventilators, vaporizers, andoxygen monitors separately using the appropri-ate procedures, and record on separate forms.)

1.24 Fail-Safe Oxygen Valves and Alarms. Close allcontrol valves. Open all cylinder stem valvesand external gas source valves. Connect gasscavenging or other evacuation system to com-mon gas outlet. Turn on the main gas control,and open the flow control valves until the flow-meter for each gas reads midscale. Then discon-nect or turn off all oxygen sources. The flow ofother gases should fall or stop as the oxygen flowdecreases to half its previous level. All gas flowshould cease when the oxygen flow reaches zero.(Cyclopropane flow rate normally falls moreslowly than the others.)

In addition to the automatic shutoff or reduc-tion of gas flow, audible or visual alarms signify-ing low oxygen pressure should have beenactivated, if the unit is so equipped. Silence the



alarm by raising the oxygen pressure above thepreset alarm limit. If the unit has an alarm thatdoes not respond, check for exhausted batteriesor other source of the malfunction.

1.25 Common Outlet Back-Pressure Check Valve.Most anesthesia units manufactured after 1968with mounted bubble-through vaporizers have acheck valve in the gas delivery system to preventpressures at the outlet (e.g., produced by a ven-tilator) from being transmitted to other parts ofthe unit where they could affect the accuracy ofgas delivery and the concentration of anestheticgases.

To test this check valve, attach the -10 to +80cm H2O pressure gauge or meter to the commongas outlet. Turn off all vaporizers, either filledor empty. Adjust the oxygen flow control valve tomaintain an outlet pressure of 30 cm H2O. Turnon the vaporizer flow, and readjust, if necessary,to maintain 30 cm H2O. Carefully open thevaporizer filler cap (to prevent a sudden flow ofoxygen into the vaporizer) and observe the outletgauge pressure. A sudden pressure drop sug-gests a leaky check valve. If the check valve ismissing or defective, replace it or alert appropri-ate personnel to replace the valve to avoid apossible hazardous buildup of vapor. Note: Thistest may not be possible on newer machines thatalways maintain a minimum flow of oxygen. Onsuch devices, follow the manufacturers instruc-tions for testing the common outlet back-pres-sure check valve.

2. Quantitative tests

2.1 Grounding Resistance. Use an ohmmeter, elec-trical safety analyzer, or multimeter with goodresolution of fractional ohms to measure andrecord the resistance between the grounding pinof the power cord and exposed (unpainted andnot anodized) metal on the chassis. We recom-mend a maximum of 0.5 .

If the device has an accessory outlet, check itsgrounding to the main power cord.

2.2 Leakage Current. Measure chassis and patientlead leakage current to the chassis of the devicewith the grounding conductor of plug-connectedequipment temporarily opened. Operate the de-vice in all normal modes, including on, standby,and off, with all monitors and accessories con-nected to the units accessory power receptacle(s),and record the maximum leakage current.

Measure chassis leakage current with all ac-cessories normally powered from the same linecord connected and turned on and off. This in-cludes other equipment that is plugged into theprimary devices accessory receptacles, as well asequipment plugged into a multiple-outlet strip(Waber strip) so that all are grounded througha single line or extension cord.

Leakage current should not exceed 300 A.

2.3 Oxygen Flush Valve. Attach the 100 L/min flow-meter to the common outlet. Set the oxygen flowrate to a 2 L/min indication on the machinesoxygen flowmeter and actuate the oxygen flushcontrol. The rate should rise to between 35 and75 L/min. The machine flowmeter indicationshould remain near 2 L/min unless the manufac-turers specification shows otherwise. If it fallsmore than 1 L/min, check for an inadequateoxygen supply, a partially occluded oxygen linein the machine, or a dirty oxygen inlet filter.

Cycle the flush control slowly several times; itshould move smoothly and not have a tendencyto stick. Check that the oxygen flow returns to2 L/min within 2 sec each time the flush valve isclosed.

2.4 High-Pressure Leaks. Close all flow controlvalves on the machine. Open all cylinder stemvalves one full turn, noting any motion of theflowmeter floats. Float movement indicates aleaky flowmeter valve. Record pressure gauge ormeter readings, verifying that they are close tothe service pressure values listed in Table 1.Close the cylinder stem valves. The pressuredrop over 30 sec should be negligible. Excesspressure drop indicates an unacceptable leakthat should be located and repaired.

2.5 Intermediate Pressure System. Close all flowcontrol valves on the anesthesia unit. Connectthe hoses to the external pipeline gas source andtest the supply line hoses with leak-detectingsolution. Note the pressure on the pipeline/cen-tral gas supply pressure gauge. (Most machinesshould have such a gauge. If not, contact themanufacturer for instructions for testing the in-termediate pressure system.) Disconnect the gassupply line hose from the machine, and checkthat the pressure drop in 30 sec is negligible.Excessive pressure drop indicates an unaccept-able leak that should be located and repaired.

2.6 Low-Pressure Leaks. Attach the -10 to +80 cmH2O pressure gauge or meter to the units common

Anesthesia Units


gas outlet and pressurize the outlet section, in-cluding vaporizers, to approximately 30 cm H2Oby opening the oxygen flow control valve slightly(this is about three times the average workingpressure). Now reduce the flow rate to 30mL/min. (Connect a flowmeter to the commongas outlet if necessary.) If the gauge or meterpressure continues to rise, the leak rate is lessthan 30 mL/min at 30 cm H2O (10 mL/min at 10cm H2O), which is acceptable. If the pressurefalls, the leakage rate is excessive. Locate theleak by shutting off all vaporizers and repeatingthe test with each vaporizer added in turn.

For anesthesia units for which low flow ratescannot be generated (units that deliver mini-mum flows of oxygen), the low-pressure systemcan be tested in combination with the breathingsystem. Connect the -10 to +80 cm H2O pressuregauge or meter to a piece of breathing systemtubing that is connected to the inspiratory andexpiratory valve outlets. Occlude the outlet tothe manual reservoir bag and close the APLvalve. Turn on the minimum flow of oxygen.The pressure gauge or meter should read at least30 cm H2O. A reading of less than 30 indicatesan unacceptable leak that should be corrected.Proceed to Item 2.7 to identify whether thebreathing system is the major source of the leak.Alternatively, follow the manufacturers recom-mendations for testing for low-pressure leaks.

2.7 Breathing System. Check the carbon dioxide ab-sorber housing for cracks or broken edges in theglass or plastic canister and in the check valvedomes.

Remove the canister from its holder, withoutinverting it, and inspect the gaskets for anyabsorbent dust and wear. Remove any dust fromthe bottom of the absorber. If the amount of dustseems excessive or if the canister appears seri-ously pitted, check for dust in the inspiratoryvalve and piping, and report the condition todepartment personnel.

Check the absorber-elevating mechanism andclamps for proper operation.

For anesthesia systems without minimumoxygen flows, connect a breathing hose from thepatient inspiration valve to the patient expirationvalve of the absorber. Close the pressure-limit-ing valve. Remove the reservoir bag, and replaceit with a -10 to +80 cm H2O pressure gauge ormeter. Pressurize the system with oxygen to a

steady 30 cm H2O, indicated on both the testgauge or meter and the pressure gauge in thebreathing system, and verify that both gaugeshave the same readings. The oxygen flow rateshould be less than 150 mL/min above the leakmeasured in Item 2.6.

For anesthesia systems with minimum oxy-gen flow, turn the anesthesia machine off andconnect the -10 to +80 cm H2O pressure gauge ormeter to a piece of breathing system tubing thatis connected to the inspiratory and expiratoryvalve outlets. Close the APL valve. Remove themanual reservoir bag. In its place, connect astopper with a fitting for a sphygmomanometersqueeze bulb. Use the bulb to pressurize thebreathing system to 50 cm H2O. It should takeat least 30 sec for the pressure to drop from 50to 30 cm H2O. Less time indicates a leak in thebreathing system that should be corrected.

Open the moisture-relief valve. (Note: Due todust and moisture, some of these valves on olderunits will not turn and might break when forceis applied.) The pressure should drop immedi-ately. If the pressure does not drop, clean thevalve of dried soda lime, repeat the pressuriza-tion, and open the relief valve again.

2.8 APL Valve. Leave the setup as in Item 2.7 butremove the pressure gauge or meter, replacing itwith the breathing bag, and restore the normalpressure-limiting valve setting.

If the APL valve is not the bleeding type,squeeze the bag and verify that the valve holdspressure until a specific level is exceeded, andthat it then opens. Check that the opening pres-sure is adjustable from approximately 1 to atleast 30 cm H2O. Other valves, such as theGeorgia and Drager valves, may operate in acompletely different manner and at a higherpressure and should be tested according to themanufacturers specified procedure.

2.9 Scavenging System. Insert the pressure gauge ormeter between the APL valve or exhaust port andthe scavenging system intake. Leave the setup asin Item 2.8, with the APL valve closed or in itsminimum-flow condition. With the scavengingsystem operating at maximum suction, the pres-sure gauge or meter reading should be between-0.5 and 0 cm H2O. Partially open the APL valve,and set a 10 L/min oxygen flow rate. With thescavenging system at the minimum vacuum, thegauge reading should be near ambient.



Repeat the last measurement with the APLvalve fully open while occluding the vacuum hoseand activating the flush valve for 5 sec. Thepressure should remain at less than 10 cm H2O.

2.10 Flowmeters. The following procedure applies toeach flowmeter on the anesthesia unit. Recordthe data on Line 2.10 (i.e., oxygen, nitrous oxide,and air). If other flowmeters are provided (e.g.,helium, carbon dioxide), make similar checksand enter data on the back of the form.

Examine flowmeters for signs of damage orabuse (e.g., internal nicks, scratches, cracks,condensation, debris).

For each flowmeter, observe the float motionas the associated valve is turned. The floatshould rise and fall freely as the flow is raised orlowered. At maximum flow, the float should stillbe visible at the top of the flow tube.

Connect one of the calibrated flowmeters tothe common gas outlet with its discharge di-rected into the scavenging or other gas evacu-ation system. Level the flowmeter. For each gasin turn, set the flow rates at a high and lowsetting for each flowmeter that lies within therange of the calibrated flowmeter. Record thereadings of both the machine and the calibratedflowmeters. Repeat the tests with the secondcalibrated flowmeter and the second group offlow rates.

The readings on the units flowmeters shouldagree with those on the calibrated flowmeters towithin 10% of set values or the manufacturersspecifications. If the error is excessive, check fordamaged, inverted, or interchanged flowmetertubes, condensation, or damaged floats.

2.11 Minimum Oxygen Flow and Percent. The follow-ing procedure applies to those systems that pro-vide a minimum flow of oxygen or a minimumpercent of oxygen.

Close the valve to the anesthesia units oxy-gen flowmeter. Connect the 0.1 to 1.0 L/minoxygen flowmeter to the common gas outlet.The flowmeter should read the minimum flow

stipulated by the manufacturer (usually 100 to250mL/min).

Set the flow of oxygen to around 200 mL/min.Turn off the flow of nitrous oxide. Using anoxygen monitor, verify that at least the mini-mum percent of oxygen (stipulated by the manu-facturer) is delivered as the flow of nitrous oxideis increased.

2.12 PEEP Valve. Set up the breathing system witha test lung. Use the -10 to +80 cm H2O pressuregauge or meter to measure the airway pressureat the test lung. Manually ventilate the test lungwith the PEEP valve set to deliver 0 cm H2Owater pressure. The end-exhalation pressure inthe breathing system should be less than 1 cmH2O, although this depends on the fresh gas flowand APL valve setting.

If the PEEP valve is calibrated, set it to deliver5 and 10 cm H2O water pressure. The pressurein the breathing system at the end of exhalationshould be within 1.5 cm H2O of the set value.

3. Preventive maintenance

3.1 Clean any excess leak-detection solution fromthe exterior and interior of the unit; clean allcompressed-gas filters, if needed.

3.2 Lubricate per the manufacturers specifications.

3.4 Replace compressed-gas filters and alarm bat-teries, if needed.

4. Acceptance tests

Conduct major inspection tests for this procedureand the appropriate tests in the General Devices Pro-cedure/Checklist 438.

Before returning to useDepressurize external gas supply; return all flow-

meters to zero position; turn all vaporizers to off posi-tion; and reconnect all tubing (e.g., main common gasoutlet tubing). Return all controls to pre-use settings.Attach a Caution tag in a prominent position so theuser is aware that control settings may have beenchanged.

Anesthesia Units


Apnea MonitorsUsed For:Apnea Monitors [12-575]Apnea Monitors, Recording [17-885]Impedance Pneumograph Monitors [12-621]Respiration Monitors [12-662]

Also Called: Cardiorespiratory monitors, apnea alarms and respiration monitors, ventilatory effort monitors,apnea detectors

Commonly Used In: Pediatric departments, homes, critical care units, nurseries, delivery rooms, ambulances

Scope: Applies to apnea monitors, which alarm if a patient stops breathing, and respiration rate monitors,which display the patients breathing rate and alarm when previously selected high or low limits are exceeded;applies to adult and infant monitoring units or modules, as well as impedance-, motion-, thermistor-, andairway-pressure-type monitors; does not apply to other types of monitors with respiration monitoring functions(e.g., capnometers, pulse oximeters); some apnea monitors also include other monitoring capabilities (e.g.,ECG and blood pressure), which should be checked using the appropriate procedure/checklist unless thefunction is very limited (e.g., heart rate alarm without other ECG features)




Minor 3 months * months . hours

* Minor interval applies only to units used for home care.

009007420-0595

A NONPROFIT AGENCY



OverviewOur evaluations of infant apnea monitors havestressed that apnea monitoring is still an imperfectscience. An ECRI poster (Poster HD 602-980) warnedof the susceptibility of these monitors to artifact andprovided succinct reminders and hints for clinical per-sonnel. An additional poster (Poster HD 625-290) andwarning notice (Health Devices 1990 Apr; 19:142-5)provide guidance for apnea monitors used in the home.

When inspecting these monitors, in addition tomaking a qualitative and quantitative inspection ofthe monitor itself, be alert to indications of incorrectequipment usage and misapplication. Confirm thatusers are aware of proper monitoring techniques andthe monitors limitations. See the devices operating

manual and the Health Devices evaluations cited belowfor specific information.

Some apnea monitors have documentation capabili-ties that typically can record two or more channels ofpatient event data ranging from several hours to sev-eral months, depending on the amount and format ofdata and the parameters stored. Recorded data areavailable in two categories: patient (respiratory rate,heart rate) and equipment (power on/off, low battery).Patient data can be recorded and printed as eithertabular data or waveforms. These data can be used toensure that the monitor is being used properly, todistinguish true from false alarms, and to troubleshootequipment problems.

Activation of memory waveform recording can beautomatic or continuous. Automatic activation is trig-gered when an event occurs that exceeds preset moni-tor limits. In the continuous mode, all data from theselected channels are recorded for a specific duration.The data stored in the memory can be managed one ofthree ways. Some units overwrite the old data withmore recent events; others keep the data that satisfyspecific criteria based on the duration of the events;and some documentation monitors stop storing datawhen the memory is filled.

Citations from Health DevicesInfant apnea monitors [Evaluation], 1980 Aug-Sep;

9:247-83.

Connection of electrode lead wires to line power [Haz-ard], 1987 Feb; 16:44-6.

Infant apnea monitors [Evaluation], 1987 Mar-Apr;16:79-88.

Infant home apnea monitors [Evaluation update],1987 Dec; 16:385-7.

Infant home apnea monitors: Essential safety fea-tures and practices, 1990 Apr; 19:142-5.

Infant home apnea documentation monitors [Evalu-ation], 1992 Oct; 21(10):342-79.

Air-Shields System V Model HRRM71-2 heart rate andrespiration monitor [User Experience NetworkTM],1992 Oct; 21(10):383.

Risk of electric shock from patient monitoring cablesand electrode lead wires [Hazard], 1993 May-Jun;22(5-6):301-3.

Infant home apnea documentation monitors [Evalu-ation update], 1993 Dec; 22(12):564-5.

Infant home apnea monitors: Essential safety featuresand practices [Hazard update], 1993 Dec;22(12):598-601.

Loose-lead alarms resulting from dried-out disposableelectrodes [User Experience NetworkTM], 1994 Jul;23(7):309-10.

Test apparatus and suppliesLeakage current meter or electrical safety analyzer

Ground resistance ohmmeter

Stopwatch or watch with a second hand

Respiration simulator (needed for impedance-typemonitors only) that includes controls to vary therespiration rate, variable base impedance from 100

to 5,000 , variable respiration resistance changeamplitude from 0.1 to 1 , and an apnea function;simulators with fewer capabilities may be used forinspection, but additional equipment may be requiredto supplement missing functions

ECG simulator with variable rate may be required(may be part of the respiration simulator or may bea separate unit)

Memory interface and documentation hardwareand software (where applicable)


procedure and the manufacturers instruction andservice manuals; be sure that you understand how tooperate the equipment, the significance of each controland indicator, and the alarm capabilities. If the monitorhas memory and documentation capabilities, make surethe memory contents have been successfully downloadedand documented. Also, determine whether any specialinspection or preventive maintenance procedures orfrequencies are recommended by the manufacturer.

Do not test the monitor while it is in use. If asubstitute monitor is not available, ask the nursingstaff whether the patient can be temporarily removedfrom the unit. It may be necessary for someone towatch the patient in the interim. Alternatively, ar-range to be notified when the monitor is available.


When performing IPM on apnea monitors with mem-ory and documentation capabilities, a log identifying theorder, type, and duration of patient and equipmentalarms and events should be recorded (e.g., using theIPM checklist). At the end of the procedure, the memorycontents should be compared to the log contents.

1.1 Chassis/Housing. Examine the exterior of theunit for cleanliness and general physical condi-tion. Be sure that plastic housings are intact,that necessary assembly hardware is presentand tight, and that there are no signs of spilledliquids or other serious abuse. If there are signsof fluid spills, inspect the interior of the monitorfor intrusion of fluids into electronic circuitry.The monitor top should not be used as a storagearea for other material (e.g., formula).

1.2 Mount. If the unit is mounted on a stand or cart,check the mounts condition. Be sure that allfasteners are tight and that the mount is sturdy.Apnea monitors should not be placed on top ofincubators where they can be easily dislodged



or obscure the view of an infant. A wall-sup-ported shelf or bracket dedicated to the monitoris recommended.

1.4 AC Plug/Receptacles. Examine the AC powerplug for damage. Attempt to wiggle the bladesto determine that they are secure. Shake theplug and listen for rattles that could indicateloose screws. If any damage is suspected, openthe plug and inspect it. If the device has electri-cal receptacles for accessories, insert an AC pluginto each and check that it is held firmly. Ifaccessories are plugged and unplugged often,consider a full inspection of the receptacle.

1.5 Line Cord. Inspect the cord for signs of damage.If damaged, either replace the entire cord or, ifthe damage is near one end, cut out the defectiveportion. Be sure to wire the new power cord orplug with the same polarity as the old one. Also,check battery charger line cords.

1.6 Strain Reliefs. Examine the strain reliefs at bothends of the line cord. Be sure that they hold thecord securely. If the line cord is detachable (bythe user), affix the cord to the unit so that itcannot be removed by the operator. (See HealthDevices 1993 May-Jun; 22[5-6]:301-3.)

1.7 Circuit Breaker/Fuse. If the device has aswitch-type circuit breaker, check that it movesfreely. If the device is protected by an externalfuse, check its value and type against thatmarked on the chassis, and ensure that a sparefuse is provided.

1.9 Cables. Inspect the cables (e.g., patient sensor,remote alarm) and their strain reliefs for generalcondition. Examine cables carefully to detectbreaks in the insulation and to ensure that theyare gripped securely in the connectors of eachend to prevent rotation or other strain. Elec-trode leads and cables are often fragile and maylack adequate strain relief; intermittent contactcan provide false indications.

The lead-electrode connector should be of thetype that cannot be inadvertently plugged into a115 VAC outlet or power cord. Attach a pair ofelectrodes to the patient cable and hold the RA andLA electrodes face to face. Connect the patientcable to the monitor, turn the unit on at maximumsensitivity, and jiggle the leads. If either breathsor lead faults are indicated, suspect damaged ca-bles or weak contact with the electrodes.

For monitors using belts, bands, a thermistor,a mattress pad, or other sensor, connect thesensor to the monitor, turn on the monitor, andjiggle the sensor cable, being careful not to dis-turb the sensor in such a way as to simulate abreath. Observe the monitor for artifacts thatwould indicate a defective cable or connector.

1.10 Fittings/Connectors. Examine all fittings andconnectors, including electrical cable connectors,for general condition. Electrical contact pins orsurfaces should be straight, clean, and bright.

1.11 Electrodes/Transducers. Confirm that any nec-essary electrodes and/or transducers are on handand check their physical condition. If disposableelectrodes are used, be sure an adequate supplyis on hand.

Verify that the insulation on thermistor sen-sors is intact. Check that air mattresses are freeof leaks and that the tubing that connects thesegments of the mattress to the manifold fitswell, without the use of tape. Keep spare tubingon hand to make necessary repairs. Carefullyexamine sensor belts, bands, or pads (magnetic,capacitive, or pressure transducer) for intact in-sulation. If there are cracks or defects in theinsulation, remove the sensor from service.

1.13 Controls/Switches. Before moving any controlsand alarm limits, check their positions. If anyappear inordinate (e.g., a gain control at maxi-mum, alarm limits at the ends of their range),consider the possibility of inappropriate clinicaluse or of incipient device failure. Investigatequestionable control settings on a home caremonitor. Consult with the patients physician todetermine correct settings. The parents shouldreceive additional training if required. Recordthe settings of those controls that should bereturned to their original positions following theinspection. Examine all controls and switchesfor physical condition, secure mounting, and cor-rect motion. Where a control should operateagainst fixed-limit stops, check for proper align-ment, as well as positive stopping. Check mem-brane switches for membrane damage (e.g., fromfingernails, pens). During the course of the in-spection, be sure to check that each control andswitch performs its proper function.

1.17 Battery/Charger. Inspect the physical condi-tion of batteries and battery connectors, if read-ily accessible. Check operation ofbattery-operated power-loss alarms, if so

Apnea Monitors


equipped. Operate the unit on battery power forseveral minutes to check that the battery ischarged and can hold a charge. Check the condi-tion of the battery charger and, to the extent pos-sible, confirm that it does, in fact, charge thebattery. When it is necessary to replace a battery,label it with the date.

1.18 Indicators/Displays. During the course of theinspection, confirm the operation of all lights,indicators, and visual displays on the unit andcharger, if so equipped. Be sure that all seg-ments of a digital display function.

1.19 User Calibration. Confirm that the calibrationor test function operates.

1.20 Alarms/Interlocks. Operate the device in sucha way as to activate each audible and visualalarm. Check that any associated interlocksfunction. If the device has an alarm-silence fea-ture, check the method of reset (i.e., manual orautomatic) against the manufacturers specifica-tions. Some apnea alarms that reset automat-ically when breathing resumes have a separateindication that an apneic episode has occurred;this reminds clinical personnel that the patientneeds closer attention. To verify that this indica-tor functions properly, halt simulated respira-tion until the apnea alarm sounds, then resumethe simulated respiration. Check that the resetcontrol functions. If the unit is used with aremote a

ecri inspection and preventive maintenance procedures

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