Page 734 - Clinical Application of Mechanical Ventilation

700 Appendix 1

New V : New tidal volume
T
New V : New deadspace volume
D
NORMAL VALUE

Set rate to provide eucapnic (patient’s normal) ventilation.
EXAMPLE

The PaCO of a patient is 55 mm Hg at a ventilator rate of 10/min. What should be
2
the ventilator rate if a PaCO of 40 mm Hg is desired, assuming the ventilator tidal
2
volume and spontaneous ventilation are stable?
(Rate * P CO )
New Rate = a 2
Desired P CO 2
a
(10 * 55)
=
40
550
=
40
= 13.75 or 14/min

R. WEANING INDEX: RAPID SHALLOW BREATHING

EQUATION
f
Rapid Shallow Breathing Index 5
V T
f : Spontaneous respiratory frequency/min (without or with minimal pressure
support)
V : Spontaneous tidal volume (in liters)
T
NORMAL VALUE
,100 breaths/min/L is predictive of weaning success

EXAMPLE
Calculate the rapid shallow breathing index, given that the spontaneous respiratory
frequency and tidal volume are 14 breaths/min and 0.5 L (500 mL), respectively.
Does this index indicate a successful weaning outcome?

f
Rapid Shallow Breathing Index 5
V T
14
5
0.5
5 28 breaths/min/L
Since the rapid breathing index is less than 100, it indicates a successful weaning
outcome.

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