Page 377 - Clinical Application of Mechanical Ventilation

Ventilator Waveform Analysis 343

V (L/min) 100

2 4 6 8 10 12 14

260
P (cm H 2 O)

40 a b c d e
© Cengage Learning 2014

22
2 4 6 8 10 12 14
Time (sec)
Figure 11-25 SIMV and PSV during descending ramp flow ventilation. Mandatory breath (a);
pressure support breaths (b, c, and e); assist breath (d).

breaths, the first mandatory and the other an assist breath. Three pressure-supported
breaths, b, c, and e, show variable DRFWs, patient-triggered, pressure-controlled
(20 cm H O) breaths of varied flow, volume, and inspiratory time.
2
SIMV (DRFW) and PSV

Figure 11-25 depicts the combination mode, SIMV 1 PSV, except that DRFWs with
end-flows at 5 L/min have replaced the CFW used in Figure 11-24. The DRFWs for
the SIMV breaths show that initial flow was set relatively high (80 L/min), resulting
in PIP for pressure patterns a and d being created at the beginning of inspiration.
Three pressure-supported breaths, b, c, and e, are displayed again for this example.

EFFECTS OF LUNG CHARACTERISTICS ON
PRESSURE-CONTROLLED VENTILATION WAVEFORMS

Figure 11-26 exemplifies the effect that changes in circuit/airway resistance and
C can have on waveforms, flow, and volume delivered during pressure-controlled
LT
ventilation. During CMV VCV, volume delivery is sustained and the pressures
(P , P ALV , or both) vary when there are changes in pulmonary mechanics. During
TA
During pressure- pressure-controlled ventilation, in either the CMV or spontaneous modes, the pres-
controlled ventilation, the
pressure target is sustained sure target is sustained while the flow and volume vary when there are changes
while the flow and volume in pulmonary mechanics. For each pressure-controlled breath under the dashed
vary when there are changes
in pulmonary mechanics. lines labeled A and B (Figure 11-26) characterize different lung conditions during
PCV. The peak flow and area under the inspiratory curve of the flow waveforms

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.