Page 729 - Clinical Application of Mechanical Ventilation

Appendix 1 695

22.5
= J R * 30 + 5
60
= {0.375} * 30 + 5
= 11.25 + 5
= 16.25 or 16 cm H O
2
J. mINuTE VENTILATION: EXPIRED AND ALVEOLAR

EQUATION 1
#
V = V * f
T
E
EQUATION 2
#
V = (V - V ) * f
A
T
D
#
V : Expired minute ventilation in L/min
E
#
V : Alveolar minute ventilation in L/min
A
V : Tidal volume in mL
T
V : Deadspace volume in mL
D
f : Respiratory frequency per minute
EXAMPLE
Given: V 5 600 mL
T
V 5 150 mL
D
f 5 12/min #
Calculate the expired minute ventilation (V ) and the alveolar minute ventilation
# E
(V ).
A
#
V 5 V 3 f
E
T
5 600 3 12
5 7200 mL/min or 7.2 L/min
#
V 5 (V – V ) 3 f
D
A
T
5 (600 – 150) 3 12
5 450 3 12
5 5400 mL/min or 5.4 L/min
K. Oxygen COntent: ArteriAl (C O )
a
2
EQUATION
C O 5 (Hb 3 1.34 3 S O ) 1 (P O 3 0.003)
a
2
a
2
2
a
C O : Arterial oxygen content in vol %
2
a
Hb : Hemoglobin content in g %
1.34 : Amount of oxygen that fully saturated hemoglobin can hold in g
S O : Arterial oxygen saturation in %
2
a
P O : Arterial oxygen tension in mm Hg
a
2
0.003 : Amount of dissolved oxygen for 1 mm Hg of P O 2
a
NORMAL VALUE
16 to 20 vol %
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