Transcript Oxygen Delivery Devices they’re not what you think Indications for oxygen use  Low ambient O2  Hypoxemia  Suspected hypoxemia  Increased work-of-breathing  Flaring 

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
0.28
4
44
1/7
1/5
0.31
0.35
6
8
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: On room air?
 b: 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
60
CO2
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
 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
O2
Reservoir