Page 727 - Clinical Application of Mechanical Ventilation

Appendix 1 693

Calculate the V /V ratio.
D
T
V D (P CO - P CO )
2
E
a
2
V = P CO 2
T
a
40 - 30
=
40
10
=
40
= 0.25 or 25%
H. I:E RATIO
EXAMPLE 1
When the I time and E time are known:
What is the I:E ratio if the inspiratory time is 0.4 sec and the expiratory time is 1.2 sec?

I time E time
I:E = a b : a b
I time I time
0.4 1.2
= a b : a b
0.4 0.4
= 1 : 3

EXAMPLE 2
When the I time % is known:
What is the I:E ratio if the inspiratory time ratio is 25% or 0.25?

I time, 1-I time,
I:E = a b : a b
I time, I time,
0.25 1-0.25
= a b : a b
0.25 0.25
0.75
= 1 : a b
0.25
:
= 1
EXAMPLE 3
When the I time and f are known:
What is the I:E ratio if the inspiratory time is 1.5 sec and the frequency is 15/min?
I time 5 1.5 sec
60
I
E time = - time
f
60
= -1.5
15
= 4 - 1.5
= 2.5 sec
I:E = I time: E time
= 1.5 : 2.5

Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.