Page 730 - Clinical Application of Mechanical Ventilation

696 Appendix 1

EXAMPLE
Given: Hb 5 15 g%
S O 5 98%
2
a
P O 5 100 mm Hg
2
a
Calculate the arterial oxygen content.
C O 5 (Hb 3 1.34 3 S O ) 1 (P O 3 0.003)
a
2
a
2
2
a
5 (15 3 1.34 3 98%) 1 (100 3 0.003)
5 19.70 1 0.3
5 20 vol%
L. OXYGEN INDEX (OI)
EQUATION
(mPaw * F O )
OI = I 2
PaO 2
OI : Oxygen index
mPaw : Mean airway pressure
F O : Inspired oxygen concentration in %
I
2
P O : Arterial oxygen tension in mm Hg
a
2
NORMAL VALUE
,30%
An oxygen index of 0.35 to 0.6 for 0.5 to 6 hours is inclusive for ECMO therapy.

EXAMPLE
Given : mPaw 5 20 mm Hg, F O 5 60%, PaO 5 50 mm Hg

2
2
I
mPaw * F O 2
I
OI = a b
PaO 2
20 mm Hg * 0.6
= a b
50 mm Hg
12 mm Hg
=
50 mm Hg
= 0.24 or 24 %
m. SHuNT EQuATION (Q /Q ): CLASSIC PHYSIOLOGIC
sp
T
EQUATION
Q SP = C O - C O 2
c
a
2
Q T C O - C O 2
2
c-
v
Q /Q : Physiologic shunt to total perfusion ratio in %
sp
T
C O : End-capillary oxygen content in vol %
2
c
C O : Arterial oxygen content in vol %
a
2
C O : Mixed venous oxygen content in vol %
2
v
NORMAL VALUE
Less than 10%
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