Oxygen Delivery DevicesOxygen Delivery Devices

they’re not what you thinkthey’re not what you think

Indications for oxygen useIndications for oxygen use

Low ambient OLow ambient O22

HypoxemiaHypoxemia Suspected hypoxemiaSuspected hypoxemia

Increased work-of-breathingIncreased work-of-breathing FlaringFlaring TachypneaTachypnea

Increased myocardial workIncreased myocardial work Acute head injuryAcute head injury

OO22 delivery systems delivery systems

High-flowHigh-flow Venti-masks (air entrainment masks)Venti-masks (air entrainment masks) Mechanical aerosol systemsMechanical aerosol systems High-flow humidifier systemsHigh-flow humidifier systems

Low-flowLow-flow Nasal cannulaNasal cannula Simple masksSimple masks Partial rebreathing masksPartial rebreathing masks Non-rebreathing masksNon-rebreathing masks

Entrainment ratiosEntrainment ratios

Entrainment ratio

FiO2 Minimal flow to operate

Total flow (L/min)

1/25 0.24 4 104

1/10 0.28 4 44

1/7 0.31 6 48

1/5 0.35 8 48

1/3 0.40 8 32

1/1.7 0.50 12 32

1/1 0.60 12 24

1/0.6 0.70 12 19

Delivered FiODelivered FiO22 with low-flow with low-flow

What’s my PaOWhat’s my PaO22??

a: On room air?a: On room air? b: On 0.50 FiOb: On 0.50 FiO22??

c: On 0.80 FiOc: On 0.80 FiO22??

The answers:The answers:

PaOPaO22 = FiO = FiO22 x (barometric pressure - x (barometric pressure - water vapor pressure) - PaCOwater vapor pressure) - PaCO22/RQ/RQ

PaOPaO22 = FiO = FiO22 X (760 - 43) - PaCO X (760 - 43) - PaCO22/0.8/0.8

a: PaOa: PaO22 = .21 X 713 - 40/0.8 = 100 = .21 X 713 - 40/0.8 = 100

b: PaOb: PaO22 = .50 X 713 - 40/0.8 = 306 = .50 X 713 - 40/0.8 = 306

c: PaOc: PaO22 = .80 X 713 - 40/0.8 = 520 = .80 X 713 - 40/0.8 = 520

OO22Hgb dissociation curveHgb dissociation curve

0 20 40 60 80 100 120 140 1600

20

40

60

80

100

% S

at

PO2 mmHg

Resorption atelectasisResorption atelectasis

A B A B

100% O2

oxygennitrogen

PO2 =673PCO2 = 40PH2O = 47

A BAfter ~15 minutes,blood N2 is depleted.Poorly ventilated &well perfused units (A)become atelectactic.

Non-rebreathing systemNon-rebreathing system

Reservoir

Gas source

Room air

Expiratorygas

To patientOne way valves

Air entrainment devicesAir entrainment devices

oxygen

room air

exhaled gas

OO22Hgb dissociation curve shiftHgb dissociation curve shift

0 20 40 60 80 100 120 140 1600

20

40

60

80

100

% S

at

PO2 mmHg

pH CO2

temp

What happens to your pOWhat happens to your pO22 and and sats when your pH changes?sats when your pH changes?

ph = 7.4, pOph = 7.4, pO22 = 100, sat 96% = 100, sat 96%

ph = 7.0, pOph = 7.0, pO22 = = ??, sat = , sat = ??

Oxygen delivery Oxygen delivery = # trucks = # trucks XX how full they are loaded how full they are loaded XX

how fast they gohow fast they go

DODO22 = 1.38(hgb X sat X CI) = 1.38(hgb X sat X CI)

+ (pO+ (pO22 X 0.003) X 0.003)

Entrainment ratiosEntrainment ratios

System FiO2

Entrainment ratio (O2/air)

Flow rate

(L/min)

Total flow

(L/min)

Ventimasks 0.24 1-25 4 1040.28 1-10 4 440.31 1-7 6 480.35 1-5 8 480.4 1-3 8 320.5 1-1.7 12 320.6 1-1 12 24

Aerosol 0.7 1-0.6 12 19

Estimating FiOEstimating FiO22

O2 Flow rate FiO2 O2 Flow rate FiO2 O2 Flow rate FiO2

Nasal cannula Oxygen mask Mask with reservoir1 0.24 5-6 0.4 6 0.62 0.28 6-7 0.5 7 0.73 0.32 7-8 0.6 8 0.84 0.36 9 0.80+5 0.4 10 0.80+6 0.44

Simple maskSimple mask

O2 inlet

Exhalation ports

Open ports for Open ports for exhaled gas exhaled gas

Air entrained Air entrained through ports if Othrough ports if O22 flow through does flow through does not meet peak insp not meet peak insp flowflow

35-55% O35-55% O22 at 6-10 at 6-10 L/minL/min

Partial rebreather maskPartial rebreather mask

Exhalationports

O2

Reservoir

OO22 directed into directed into reservoirreservoir

Insp: draw gas from Insp: draw gas from bag & ? room airbag & ? room air

Exp: first 1/3 of Exp: first 1/3 of exhaled gas goes into exhaled gas goes into bag (dead space)bag (dead space)

Dead space gas mixes Dead space gas mixes with ‘new’ Owith ‘new’ O22 going going into baginto bag

Deliver ~60% ODeliver ~60% O22

Non-rebreathing maskNon-rebreathing mask

Valve prevents Valve prevents exhaled gas flow exhaled gas flow into reservoir baginto reservoir bag

Valve over Valve over exhalation ports exhalation ports prevents air prevents air entrainmententrainment

Delivers ~100% ODelivers ~100% O22, , ifif bag does not bag does not completely collapse completely collapse during inhalationduring inhalation

O2

Reservoir

One-way valves