Oxygen Delivery Devices they’re not what you think

Indications for oxygen use  Low ambient O 2  Hypoxemia  Suspected hypoxemia  Increased work-of-breathing  Flaring  Tachypnea  Increased myocardial work  Acute head injury

O 2 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

Delivered FiO 2 with low-flow

What’s my PaO 2 ?  a: On room air?  b: On 0.50 FiO 2 ?  c: On 0.80 FiO 2 ?

The answers: PaO 2 = FiO 2 x (barometric pressure - water vapor pressure) - PaCO 2 /RQ PaO 2 = FiO 2 X ( ) - PaCO 2 /0.8 a: PaO 2 =.21 X /0.8 = 100 b: PaO 2 =.50 X /0.8 = 306 c: PaO 2 =.80 X /0.8 = 520

O 2 Hgb dissociation curve % Sat PO 2 mmHg

Resorption atelectasis 100% O 2 oxygen nitrogen P O 2 =673 P CO 2 = 40 P H 2 O = 47 A B After ~15 minutes, blood N 2 is depleted. Poorly ventilated & well perfused units (A) become atelectactic.

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

Air entrainment devices oxygen room air exhaled gas

O 2 Hgb dissociation curve shift % Sat PO 2 mmHg   pH  CO 2  temp

What happens to your pO 2 and sats when your pH changes? ph = 7.4, pO 2 = 100, sat 96% ph = 7.0, pO 2 = ?, sat = ?

Oxygen delivery = # trucks X how full they are loaded X how fast they go DO 2 = 1.38(hgb X sat X CI) + (pO 2 X 0.003)

Entrainment ratios

Estimating FiO 2

Simple mask O 2 inlet Exhalation ports  Open ports for exhaled gas  Air entrained through ports if O 2 flow through does not meet peak insp flow  35-55% O 2 at 6-10 L/min

Partial rebreather mask Exhalation ports O2O2 Reservoir  O 2 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’ O 2 going into bag  Deliver ~60% O 2

Non-rebreathing mask  Valve prevents exhaled gas flow into reservoir bag  Valve over exhalation ports prevents air entrainment  Delivers ~100% O 2, if bag does not completely collapse during inhalation O2O2 Reservoir One-way valves