Page 371 - Clinical Application of Mechanical Ventilation

Ventilator Waveform Analysis 337

WAVEFORMS DEVELOPED DURING
PRESSURE-CONTROLLED VENTILATION

Pressure-Controlled Ventilation (PCV)

Figure 11-19 is an example of pressure-controlled ventilation (PCV) in the
CMV mode. In PCV CMV, a set (operator) pressure is targeted and sustained
by the ventilator for a set T period. Also, the frequency, T or I:E ratio are set
I
I
by the operator. The V and flow rate delivered by the ventilator are variable,
T
and are dependent on the pressure level set and the patient’s lung characteris-
tics. The ventilator may be time- or patient-triggered and delivers a DRFW in
a manner that will reach and sustain the pressure level set. In Figure 11-19, the
pressure level set for ventilation is 30 cm H O. For the letters on the pressure-
2
time waveform, a marks the end of expiration and beginning of inspiration; b
indicates the PIP level set and sustained; c is the transition from inspiration to
expiration; and d is end of expiration with flow. Total cycle time (TCT) is 2
total cycle time (TCT): Time pe-
riod from beginning inspiration to seconds and frequency is 30/min (60s/2s/breath 5 30/min). T is twice T . The
I
E
the beginning of next inspiration. I:E ratio set is 1:2.

TCT TCT TCT
100 I E I E I E
V (L/min)

1 2 3 4 5 6 7

2100
P (cm H 2 O)

40
b c
20

d © Cengage Learning 2014
a 1 2 3 4 5 6 7
Time (sec)
Figure 11-19 Characteristics of pressure-controlled ventilation (PCV). The pressure control
level of 30 cm H 2 O is set and sustained at this level throughout the inspiratory phrase. The flow
patterns may vary according to the compliance and airflow characteristics.

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.