airway adjuncts and oxygen therapy
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BASICS OF OXYGEN THERAPY
OXYGEN THERAPY Dr.Gagan
Oxygen:ColourlessOdourlessTastelessTransparent gasSlightly heavier than airConstitutes 20-21% of atmospheric airEssential for life
What is O2 Therapy ? Oxygen therapy is the administration of oxygen at concentrations greater than that in room air to treat or prevent hypoxia.
Oxygen is available to us Medical grade oxygen (99% or 99.5% pure) is manufactured by fractional distillation of liquid air.Oxygen can be stored as compressed gas at room temperature or as liquid when refrigerated.Oxygen cylinder
Delivery system : Hose drops, Gas columns, Articulating arms E-cylinder capacityH-cylinder Capacity Pressure (psig at 20oC)Color PIN index 625-700 liters6000-8000 liters1800-2000 Black body with white shoulder 2, 5
Anoxia No oxygen availability in tissuesHypoxia Lack of oxygen availability in tissuesHypoxemia Lack of oxygen in the bloodBasics
6Indications for Oxygen TherapyHypoxemiaInadequate amount of oxygen in the bloodSPO2 < 90%PaO2 < 60 mmHgExcessive work of breathingExcessive myocardial workload
7Causes of HypoxemiaShuntHypoventilationAs carbon dioxide increases oxygen fallsV/Q mismatching (ventilation/perfusion)PneumoniaPulmonary edemaARDSIncreased diffusion gradientasbestosisEarly pulmonary edema
Types of hypoxiaHypoxic hypoxia PaO2
Anaemic hypoxia O2 content , PaO2 normal
Stagnant hypoxia Histotoxic hypoxia
Hypoxic hypoxiaCausesO2 poor air, hypoxic gas mixtureHigh altitude HypoventilationShunts Septal defects Diffusion defects - pneumonia, lobar collapse
1010ASD VSD have a L-R shunt, only when PAH sets in shunt is R L Portal hypertension
Anaemic hypoxiaOxygen carrying capacity of blood is decreased. Anemia : haemoglobinAltered haemoglobin CO poisoning meth / sulph-haemoglobin
1111Aniline dyes, nitrates in paints or medicines (GTN), Prilocaine Methylene blue (1%) 1-2 mg kg over 5 mins
Stagnant hypoxiaInadequate tissue perfusionGeneralized:- Hypovolemia- Mitral stenosis- Constrictive pericerditis- Myocardial ischaemiaLocalized hypo perfusion: - Arterial obstruction, thrombus, oedema
Cells can not utilize the oxygen .Electron transfer system of cytochrome oxidase is paralysed.e.g. cyanide poisoning
Benefit of O2 therapy in HypoxiaHypoxic hypoxia + + +Anaemic hypoxia +Stagnant hypoxia +Histotoxic hypoxia -
Effects of hypoxiaAcute hypoxia :- Restlessness- Disorientation, confusion- In-coordination, Impaired judgment- Hyperventilation air hunger-Circulatory changes (tachycardiabrady )Chronic hypoxia :- fatigue, drowsiness, work capacity- inattentiveness ,apathy, delayed reaction time
Assessment of needPresence of clinical indicators Measurement of inadequate oxygen saturationsby invasive or noninvasive methods,Arterial blood gasPulse oximetry
Errors in pulse oximetryArtificial fingernailsDark pigmentation Electrical interference Intravenous dyes MovementNail Polish Pulsatile venous systemRadiated light
Types of Oxygen TherapyGiving Oxygen more than 21% at ambient atm pressure Giving Oxygen more than 21% at high atm pressure ( >1 atm)
Three clinical goals of O2 therapy 1. Treat hypoxia
2. Decrease work of breathing
3. Decrease myocardial Work
20COPD , asthma ptPt with acute MI
Correcting HypoxemiaBy raising Alveolar & Blood levels of OxygenEasiest objective to measureDecreasing symptoms of HypoxemiaSupplemental O2 can help relieve symptoms of hypoxiaLessen dyspnoea/work of breathingImprove mental function
Minimizing Cardiopulmonary workloadCardiopulmonary system will compensate for Hypoxemia by:Increasing ventilation to get more O2 in the lungs & to the BloodIncreased work of breathing Increasing Cardiac Output to get more oxygenated blood to tissuesHard on the heart, especially if diseasedHypoxia causes Pulmonary vasoconstritcion & Pulmonary HypertensionThese cause an increased workload on the right side of heartOver time the right heart will become more muscular & then eventually fail (Cor Pulmonale)
Supplemental o2 can relieve hypoxemia & relieve pulmonary vasoconstriction & Hypertension, reducing right ventricular workload!!
Minimal acceptable saturation for post surgical patients who are cared for in non critical setup is 92%
FACTORS THAT DETERMINE WHICH SYSTEM TO USE 1. Patient comfort / acceptance 2. The level of FiO2 that is needed3. The requirement that the FiO2 be controlled within a certain range4. The level of humidification and /or nebulization5. Minimal resistance to breathing6. Efficient & economical use of oxygen
Orthobaric Oxygen therapy
LOW FLOW DEVICES
HIGH FLOW DEVICES
LOW FLOW OXYGEN DELIVERY DEVICES
NASAL CANNULAHOW TO USE? disposable.
plastic devise with two protruding prongs for insertion into the nostrils, connected to an oxygen source.
The standard nasal cannula delivers an inspiratory oxygen fraction (FIO2) of 24-44% at supply flows ranging from 1-6 Lmin-1.
The formula is FIO2 = 20% + (4 oxygen litre flow). The FIO2 is influenced by breath rate, tidal volume and pathophysiology.
The slower the inspiratory flow the higher the FIO2.
Delivers24to44%oxygenat1to6 L/min1=24 %2=28 %3=32 %4=36 %5=40 %6=44 %
FACTSADVANTAGESPatients are able to talk and eat with oxygen in place
Easily used in home setting DISADVANTAGESmay cause irritation to the nasal and pharyngeal mucosa if oxygen flow rates are above 4 liters/minute Variable FIO2
SIMPLE OXYGEN MASKSimple mask is made of clear, flexible , plastic or rubber that can be molded to fit the face.
It is held to the head with elastic bands.
Some have a metal clip that can be bent over the bridge of the nose for a comfortable fit
O2 inletExhalation ports
Open ports for exhaled gas
Air entrained through ports if O2 flow through does not meet peak inspiratory flow
5 10 liters per minute < 5 liters will not flush CO2 from mask 40 60% FIO2 approximately depending on the pattern of breathing.
FACTSADVANTAGES Can provide increased delivery of oxygen for short period of time The face mask is indicated in patients with nasal irritation or epistaxis. It is also useful for patients who are strictly mouth breathers.
DISADVANTAGES-Tight seal required to deliver higher concentration- Difficult to keep mask in position over nose and mouthPotential for skin breakdown due(pressure, moisture)Uncomfortable for pt while eating or talking.Obtrusive, uncomfortable and confining. It muffles communication, obstructs coughing.
PARTIAL REBREATHING MASKMask is a simple mask with a reservoir bag.Same as the Non re-breathing bag but..without a one way valve.Low flow, medium concentration 50 70% 8 12 liters per minute Bag should remain at least 1/3 full during inspiration Allow the mixture or oxygen and carbon dioxide in the mask.
Partial Rebreather mask
O2 directed into reservoirInsp: draw gas from bag & room airExp: first 1/3 of exhaled gas goes into bag (dead space)Dead space gas mixes with new O2 going into bagDeliver ~60% O2
FACTSADVANTAGESCan inhale room air through openings in mask if oxygen supply is briefly interrupted.
Not as drying to mucous membranes
DISADVANTAGES- Requires tight seal
- Eating and talking difficult, uncomfortable
NON REBREATHING MASKthe one-way valve closes and all of the expired air is deposited into the atmosphere, not the reservoir bag. This mask provides the highest concentration of oxygen (95-100%) at a flow rate 8-15 L/min.
It is similar to the partial rebreather mask except two one-way valves prevent conservation of exhaled air.
Non-Rebreathing MaskValve prevents exhaled gas flow into reservoir bagValve over exhalation ports prevents air entrainmentDelivers ~100% O2, if bag does not completely collapse during inhalation
ReservoirGas sourceRoom airExpiratorygasTo patient
One way valves
FACTSADVANTAGESDelivers the highest possible oxygen concentration
Suitable for pt breathing spontaneous with sever hypoxemia
DISADVANTAGES- Impractical for long term Therapy- Malfunction can cause CO2 buildup - suffocationExpensive Feeling of suffocation Uncomfortable
DELIVERY DEVICESOr FIXEDDELIVERY SYSTEMS
AIR ENTRAINMENT DEVICESHigh flow device (o2 concentration)Entrains air through side ports to achieve high flows Variable entrainment ports and/or jets adjust FIO2 Air Entrainment or Venti Masks Manufacturer recommends liter flows for each FIO2
The Venturi System
Room air dilutes the oxygen entering the tubing to a certain concentration
The amount of air drawn in is determined by the size of the orifice (jet adapter).
Applying the Bernoulli principle
How does it work?
exhaled gasoxygenroom air
Oxygen from 24 - 50% At liters flow of 4 to 15 L/min.The mask is so constructed that there is a constant flow of room air blended with a fixed concentration of oxygenIs designed with wide- bore tubing and various color - coded jet adapters. Each color code corresponds to a precise It is high flow concentration of o