Noninvasive Blood Pressure Measurement at BWH

James H Philip ME(E), MD, C.C.E.

© Copyright 2009, James H Philip, all rights reserved

Noninvasive Blood Pressure Measurement at BWH

James H Philip ME(E), MD, C.C.E.Anesthesiologist, Brigham and Women’s Hospital

Director of Bioengineering, Department fo Anesthesiology, Perioperative and Pain Medicine

Medical Liaison, Partners Department of Biomedical Engineering

© Copyright 2009, James H Philip, all rights reserved

Noninvasive Blood Pressure problems at BWH in 2008

July 2008 we had NIBP Measurement problemsAll those are solvedThey were:Cuff leaks Hose leaksNo reading and cuff stopped cyclingTemperature changed with ESU interference

Noninvasive Blood Pressure problems at BWH in 2008

CUFF LEAKSBWH had old cuffs

GE replaced all cuffs freeBWH agreed to replace cuffs according to AAMI StandardsAAMI Standard = 10,000 cycles

Cuff Life could be 3 months for AnesthesiaCuffs are being retired at least that fastManufacture date is printed on each cuff

Cuff Life could be several years for non-Anesthesia

Noninvasive Blood Pressure problems at BWH in 2008

HOSE LEAKSBWH had old hoses - up to 8 years oldNew GE PDMs (Patient Data Modules) destroyed old BWH hosesGE replaced all BWH hoses freeNew hoses are compatible with TRAM Brick and PDMHoses should last several years

SUMMARYBWH has all new hoses and cuffsIf you find an old or soiled cuff, trhow it in the trash and get another

Noninvasive Blood Pressure problems at BWH in 2008

PDM Problems in ORNIBP Measurement Problems - cuff stopped cycling if

readings were exactly 1 minute apartreadings were exactly 2 minutes apart

Temperature value changed dramatically with ESU use

BWH OR SOLUTIONWe are not using PDMs in OR yetGE is making software and temperature cable changesWe in OR will use PDMs when they are OR-ready

Noninvasive Blood Pressure Measurement at BWH today

Noninvasive and Non Invasive are both used in the literatureNIBP and NBP are both used in the literatureGE calls it NBP

Methods of Noninvasive Blood Pressure Measurement

Blood Pressure Measurement History1773 Stephen Hales - Mean intra-arterial pressure (in horse carotid artery)1859 Etinne Marey - Sphygmograph1896 Riva-Rocci - Sphygmomanometer1901 Von Recklinghausen - Increased cuff width1904 Von Ricklinghausen and Erlanger - Oscillometer, Oscillotonometer1905 Korotkov - Auscultation1934 Hamilton - Intra-arterial recording1961 Franklin, Rushmer - Doppler blood flow,then wall motion for S, D NIBP1976 Ramsey - Dinamap® automated oscillometer1992 Friedman - Dinamap® advances2000 GE Acquired Critikon Corporation and Dinamap ® and technology

Sphygmomanometer Flow Detection Techniques

1. Distal pulse - plethysmograph, including pulse oximeter2. Cuff pulsations - oscillometer, AKA oscillotonometer3. Auscultation - Korotkoff sounds4. Doppler - ultrasound

Sphygmomanometer Cuff

1987 AAMI Standard, later Am Col CardiologistsCuff width > 0.4 Circumference = 1.3 Diameter of the extremity

Wrap evenlyTrapazoidal arms are a problem Wrist NIBP = Brachial NIBP + 10 mmHg*

* Emerick DR. An evaluation of non-invasive blood pressure (NIBP) monitoring on the wrist: comparison with upper arm NIBP measurement. Anaesth Intensive Care. 2002: 30(1):43-7

NIBP Monitors - How they work

Auscultatory NIBP

Korotkoff Sounds

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Auscultatory NIBP

Korotkoff Sounds

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Completed with cuff, aneroid manometer or mercury column, stethoscope,ear,brain,training

Auscultatory NIBP

Korotkoff Sounds

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Completed with cuff, aneroid manometer or mercury column, stethoscope,ear,brain,training

Five Korotkoff sounds:

K1. Snapping sound at systolic pressure. A clear tapping sound; onset of the sound for two consecutive beats is considered systolic.K2. Thud sounds between the systolic and diastolic pressures.K3. Loud, crisp tapping sound of unknown etiology.K4. Muffled sound, at pressures within 10 mmHg above the diastolic blood pressure.K5. Silence below diastolic blood pressure. Diastolic blood pressure = two mmHg below the last sound heard.

Auscultatory NIBP

Korotkoff Sounds

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Approximate Mean

= 1/3 of the way from diastolic up to systolic

= Diastolic + (Systolic - Diastolic) / 3

= 83 + (135 - 83) / 3

= 83 + 52 / 3

= 83 + 17.3 =

= 100.3

Auscultatory NIBP

Korotkoff Sounds

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Approximate Mean (of an arterial wave)

= Diastolic + (Systolic - Diastolic) / 3

Exact Mean (of a triangle wave)

= Diastolic / (Systolic - Diastolic) / 2

Origin of the 1/3 rule

Auscultatory NIBP

Korotkoff Sounds

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Approximate Mean (of an arterial wave)

= Diastolic / (Systolic - Diastolic) / 3

Exact Mean (of an arterial wave)

= { Integral (BP) / one beat period} Averaged over several beats

Oscillometric NIBP

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Pulse-Wave Oscillations in Cuff Pressure

Mean = 100

Oscillometric NIBP

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Pulse-Wave Oscillations in Cuff Pressure

Mean = 100

Best estimate of Mean*

= pressure of maximum oscillation

= 100 mmHg

* Yelderman M, Ream AK. Anesthesiology 50: 1979

Oscillometric NIBP

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Pulse-Wave Oscillations in Cuff Pressure

Mean = 100

ACCURACY OF ESTIMATE*

{Cuff Peak Oscillations - Mean Direct BP}

Mean = 1.4 mmHg, SD = 6.2 mmHg, 95% within 14 mmHg

Best estimate of Mean*

= pressure of maximum oscillation

= 100 mmHg

* Yelderman M, Ream AK. Anesthesiology 50: 1979

Oscillometric NIBPGE Dinamap®

A closer look at the cuff pressure and the oscillations

Oscillometric NIBPGE Dinamap®

Two hoses, One for inflation and deflationOther for measuring the small pressure pulsations

Cuff is inflated to up above SystolicCuff is deflated in small stepsMonitor waits for two pulsations of similar amplitude before stepping downMonitor uses information from earlier readings as best it canMonitor tries to read in the presence of abnormal pulsationsMonitor reports (publishes) BP if it is sure its results are correctIn not, “NO DETERMINATION” is displayed

Realities of NIBP Measurement

NIBP will fail in many waysAnything that causes artefact or blocks real

pulsationsSurgeon leaning on cuff

Thyroid surgeryCarotid Surgery

Patient movementPurposefulmovementTremorReaction to surgery

Oscillometric NIBP

Raw Cuff Pressure Signal

Systole = 135

Diastole = 83

Pulse-Wave Oscillations in Cuff Pressure

Mean = 100

What causes these pressure pulsations?

Volume change in the artery in the arm

What affects volume change in the artery in the arm?

Pulse PressureStiffness of the artery

What effects stiffness of the artery?

Arteriosclerosis

Drugs that stiffen the arterial wall

Realities of NIBP Measurement

Pressure too low to create pulsationsArterial wall too stiff to create volume changes

Arterial wall is too stiff to create arm volume pulses and NIBP cuff pressure pulses

Myomal injection of Arginine Vasopressin reduces pulse oximeter wave size measured on the ear (62%) but not on the finger 1

Myomal injection of Arginine Vasopressin reduces pulse oximeter wave size measured on the ear and simultaneously reduces pulse wave amplitude measured in a NIBP Cuff on the arm dramatically 2

Myomal injection of Arginine Vasopressin has led to Cardiac Arrest 3,4

Myomal injection of Arginine Vasopressin has preceded NIBP drop-out in 10 patients at BWH in 16 months

1. Jablonka DH, Awad AA, Stoout RG, Silverman DG, Shelly KH. Comparing the effect of argininevasopressin on ear and finger photoplethysmography. Journal of Clinical Anesthesia (2008) 20, 90–93

2. Philip JH. Friedman B. Data collected at BWH; manuscript in preparation3. Hobo R, Netsu S, Koyasu Y, Tsutsumi O. Bradycardia and cardiac arrest caused by intramyometrial

injection of vasopressin during a laparoscopically assisted myomectomy. Obstet Gynecol2009;113:484–6.

4. Fishman, G. Vasopressin: If some Is Good, Is More Better? Obstet Gynecol 2009;113:476–478.

Why we seeNIBP Dropout on Solar but present on EagleEagle is very old GE-Marquette TechnologyIt was created by Marquette before Marquette was purchased by GE and

before Dinamap was purchased by GEEagle sometimes made false readings of blood pressureEntire case performed with BP Cuff under patient’s pillow.BPs were displayed and recorded every 1 - 5 minutesClinician adjusted the NIBP cuff was found under the patient’s pillow

BWH and other institutions complained to GEGE revised NIBP algorithms to remove artifact readingsMonitor must be sure of a reading before reporting itNow Dinamap is unable to measure NIBP after vasopressin injection

Observations ofNIBP Dropout after Vasopressin Injection

We have a series of 8 patients who experienced NIBP dropout with Solar-TRAM-Brick1 patient with A-Line showing no BP change while NIBP fell significantly on

Solar-TRAM-Brick but not on Eagle1 patient with lowered ETCO2, and lowered I-Eo2 transiently

BWH Reports ofNIBP Dropout after Vasopressin Injection

We observed 8We reported 3 to GE including the present case.GE opened an iTrack on eachiTrack is an FDA auditable complaint kept on file by GEFDA inspects iTracks periodically to see that GE is resolving complaints

We reported the present case as an injury to MedSunMedSun is the FDA report submission networkFDA proactively checks that GE is resolving MedSun Injury complaints

We believe GE is working on a solution already

GE Progress

Bruce Friedman, PhDPrincipal EngineerDinamap section of GE

Audio on line with us

DINAMAP Peak Matching acceptance criterion

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Two equal and sequential pulses are required for acceptance

DINAMAP Motion Artifact rejection

Step Deflation and Peak Matching help reject Artifacts

SuperSTAT™ NIBP algorithm

Cuff Pressure (mmHg)

Systolic ratio ~ 0.5

Diastolic ratio ~ 0.625

MAP Maximum oscillation amplitude

New criteria are under consideration

Reduce false positive detectionReduce false negative detectionImprove pulse artifact rejectionImprove pulse data retention and analysis

BWH Anesthesia Dept Policy 2009

If Vasopressin may be used, especially if Robot will be usedGE Eagle Monitor in the room and connected or connectableSwitch to Eagle if Solar-TRAM-Brick cannot measure NIBPObserve patient condition in as many ways as possibleCapnogramPulse plethysmogram, possibly downstream from cuffA-Line if situation warrantsRecognize that patient usually has normal or high blood pressureEnter Equipment Malfunction and description in EARS report

BWH GE Monitor names and pictures

Standard Solar 8000 monitorwith new, insensitive NIBP

Solar 8000 Monitor, mounted on ADSTRAM Brickdata collection module

PDMPatientDataModule(soon)

Brick or PDM

Portable Eagle Monitor with old, sensitive NIBP measurement

Portable Eagle Monitor Portable Eagle Monitor Screen

Portable Eagle Monitor with old, sensitive NIBP measurement

Portable Eagle Monitor Portable Eagle Monitor Screen

Portable Eagle Monitors have RFID Tags so they can be found electronically, quickly.