Page 376 - Clinical Application of Mechanical Ventilation
P. 376
342 Chapter 11
80 a b
V (L/min)
2 4 6 8 10 12 14
260
P (cm H 2 O) x
20
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2 4 6 8 10 12 14
Time (sec)
Figure 11-23 PSV at 10 cm H 2 O of pressure support over 5 cm H 2 O of PEEP. Arrow x shows
a rapid rise in initial inspiratory flow generated by the patient causes a spike in the initial pressure
that overshoots the pressure support level. Letters a and b show two different rise time percents.
A slower rise time percent (b) causes a more gradual rise to the pressure support level and it
provides more patient comfort.
V (L/min) 80
2 4 6 8 10 12 14
260
P (cm H 2 O)
40 a b c d e
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22 2 4 6 8 10 12 14
Time (sec)
Figure 11-24 SIMV and PSV during constant flow ventilation. Mandatory breath (a); pressure
support breaths (b, c, and e); assist breath (d).
SIMV (CFW) and PSV
Figure 11-24 exemplifies the combination mode, SIMV 1 PSV. Two ideal CFWs and
corresponding step ascending ramp pressure patterns, a and d, depict volume-controlled
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