Page 732 - Clinical Application of Mechanical Ventilation

698 Appendix 1

EXAMPLE 2
Given: A patient on mechanical ventilation
C O 5 20.4 vol %
2
c
C O 5 19.8 vol % #
2
a
Use 3.5 vol % as the estimated C(a2v )O and calculate Q Q .
2
sp
T
Q . SP = C O - C O 2
2
c
a
Q T 3.5 + (C O C O )
2
a
2
c
20.4 - 19.8
=
3.5 + (20.4-19.8)
0.6
=
3.5 + 0.6
0.6
=
4.1
5 0.146 or 14.6%
O. VAsCulAr resistAnCe: PulmOnAry
EQUATION
80
PVR = (P A - PCWP) *
CO
PVR : Pulmonary vascular resistance in dyne sec/cm 5
P A : Mean pulmonary artery pressure in mm Hg
PCWP : Pulmonary capillary wedge pressure in mm Hg
80 : Conversion factor from mm Hg/L/min to dynes sec/cm 5
#
CO : Cardiac output in L/min(Q )
T
NORMAL VALUE
PVR 5 50 to 150 dyne sec/cm 5
EXAMPLE
A patient with pulmonary hypertension has the following measurements. What is
the calculated pulmonary vascular resistance (PVR)?
P A 5 22 mm Hg
PCWP 5 6 mm Hg
CO 5 4.0 L/min
80
PVR = (PA - PCWP) *
CO
80
= (22 - 6) *
4.0
80
= 16 *
4.0
1280
=
4
= 320 dyne sec/cm 5

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