Oxygen Delivery Devices they’re not what you think

Oxygen Delivery Devices they’re not what you think

Indications for oxygen use Low ambient O2 Hypoxemia Suspected hypoxemia Increased work-of-breathing Flaring Tachypnea Increased myocardial work Acute head injury

O2 delivery systems High-flow Venti-masks (air entrainment masks) Mechanical aerosol systems High-flow humidifier systems Low-flow Nasal cannula Simple masks Partial rebreathing masks Non-rebreathing masks

Entrainment ratios Entrainment ratio FiO2 Minimal flow to operate Total flow (L/min) 1/25 0.24 4 104 1/10 1/7 1/5 0.28 0.31 0.35 4 6 8 44 48 48 1/3 0.40 8 32 1/1.7 0.50 12 32 1/1 1/0.6 0.60 0.70 12 12 24 19

Delivered FiO2 with low-flow

What’s my PaO2? a: b: On room air? On 0.50 FiO2? c: On 0.80 FiO2?

The answers: PaO2 FiO2 x (barometric pressure water vapor pressure) - PaCO2/RQ PaO2 FiO2 X (760 - 43) - PaCO2/0.8 a: PaO2 .21 X 713 - 40/0.8 100 b: PaO2 .50 X 713 - 40/0.8 306 c: PaO2 .80 X 713 - 40/0.8 520

O2Hgb dissociation curve 100 % Sat 80 60 40 20 0 0 20 40 60 80 100 PO2 mmHg 120 140 160

Resorption atelectasis 100% O2 nitrogen oxygen A A B A B PO2 673 PCO2 40 PH2O 47 B After 15 minutes, blood N2 is depleted. Poorly ventilated & well perfused units (A) become atelectactic.

Non-rebreathing system Room air Gas source Expiratory gas Reservoir To patient One way valves

Air entrainment devices exhaled gas oxygen room air

O2Hgb dissociation curve shift 100 % Sat 80 pH CO2 60 temp 40 20 0 0 20 40 60 80 100 PO2 mmHg 120 140 160

What happens to your pO2 and sats when your pH changes? ph 7.4, pO2 100, sat 96% ph 7.0, pO2 ?, sat ?

Oxygen delivery # trucks X how full they are loaded X how fast they go DO2 1.38(hgb X sat X CI) (pO2 X 0.003)

Entrainment ratios System Ventimasks Aerosol Flow Total Entrainment rate flow FiO2 ratio (O2/air) (L/min) (L/min) 0.24 1-25 4 104 0.28 1-10 4 44 0.31 1-7 6 48 0.35 1-5 8 48 0.4 1-3 8 32 0.5 1-1.7 12 32 0.6 1-1 12 24 0.7 1-0.6 12 19

Estimating FiO2 O2 Flow rate FiO2 Nasal cannula 1 0.24 2 0.28 3 0.32 4 0.36 5 0.4 6 0.44 O2 Flow rate FiO2 Oxygen mask 5-6 0.4 6-7 0.5 7-8 0.6 O2 Flow rate FiO2 Mask with reservoir 6 0.6 7 0.7 8 0.8 9 0.80 10 0.80

Simple mask Exhalation ports O2 inlet Open ports for exhaled gas Air entrained through ports if O2 flow through does not meet peak insp flow 35-55% O2 at 6-10 L/min

Partial rebreather mask Exhalation ports O2 Reservoir O2 directed into reservoir Insp: draw gas from bag & ? room air Exp: first 1/3 of exhaled gas goes into bag (dead space) Dead space gas mixes with ‘new’ O2 going into bag Deliver 60% O2

Non-rebreathing mask One-way valves O2 Reservoir Valve prevents exhaled gas flow into reservoir bag Valve over exhalation ports prevents air entrainment Delivers 100% O2, if bag does not completely collapse during inhalation