Page 728 - Clinical Application of Mechanical Ventilation

694 Appendix 1

1.5 2.5
= a b : a b
1.5 1.5
= 1 : 1.67

EXAMPLE 4 #
When the minute volume (V ) and flow rate are known:
E
Given: V 5 800 mL (0.8 L)
T
ƒ 5 12/min
Flow rate 5 40 L/min
What is the I:E ratio?
I:E ratio 5 (Minute volume) : (Flow rate – Minute volume)
5 (V 3 f ) : (Flow rate – V 3 f )
T
T
5 (0.8 3 12) : (40 – 0.8 3 12)
5 9.6 : (40 – 9.6)
5 9.6 : 30.4
[divide both sides of this ratio by 9.6]
5 1 : 3.2

I. mEAN AIRWAY PRESSuRE (mPaw)

EQUATION

f * I time
mPaw = J R * (PIP - PEEP) + PEEP
60

mPaw : Mean airway pressure in cm H O
2
f : Respiratory frequency per minute
I time : Inspiratory time in sec
PIP : Peak inspiratory pressure in cm H O
2
PEEP : Positive end-expiratory pressure in cm H O
2
NORMAL VALUE
Below 30 cm H O (adults).
2
EXAMPLE
When PEEP is used.
Given: f 5 45/min
I time 5 0.5 sec
PIP 5 35 cm H O
2
PEEP 5 5 cm H O
2
Calculate the mean airway pressure.

f * I time
mPaw = J R * (PIP - PEEP) + PEEP
60
45 * 0.5
= J R * (35 - 5) + 5
60

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