Page 723 - Clinical Application of Mechanical Ventilation

Appendix 1 689

Appendix 1:

Respiratory Care Calculations

A. ARTERIAL OXYGEN TENSION TO INSPIRED OXYGEN
CONCENTRATION (PaO /F O ) INDEX
2
2
I
EQUATION
Arterial Oxygen Tension to Inspired Oxygen Concentration Index 5 PaO /F O 2
2
I
PaO /F O Index : Arterial oxygen tension to inspired oxygen concentration index
I
2
2
PaO : Arterial oxygen tension in mm Hg
2
F O : Inspired Oxygen Concentration
I
2
NORMAL VALUE
(1) For weaning purpose with F O ,40%, 150 to 200 mm Hg or higher suggests
I
2
a successful weaning outcome.
(2) For patients with non-cardiogenic pulmonary edema, the thresholds are
,300 mm Hg for ALI and ,200 mm Hg for ARDS.
EXAMPLE
Given: PaO 5 50 mm Hg, F O 5 40% (0.4)
2
2
I
50 mm Hg
PaO /F O Index =
2
2
I
0.4
= 125 mm Hg
B. CARDIAC OuTPuT (CO): FICk’S ESTImATED mETHOD

EQUATION 1

O consumption
2
CO =
C O - C O 2
v
a
2
EQUATION 2
130 * BSA
CO =
C O - C O 2
a
2
v
CO : Cardiac output in L/min (Q ) #
T
O consumption : Estimated to be 130 3 BSA, in mL/min V O 2
2

C O : Arterial oxygen content in vol %
2
a
C O : Mixed venous oxygen content in vol %
2
v
130 : Estimated O consumption rate of an adult, in mL/min/m 2
2
BSA : Body surface area in m 2
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