Page 357 - Clinical Application of Mechanical Ventilation

Ventilator Waveform Analysis 323

TABLE 11-4 Calculations to Determine the P ALV Pattern that Develops during Constant Flow Ventilation
(See Figure 11-8)

C 5 V /(P 2 PEEP) C 5 V /(P 2 PEEP)
T
ALV
ALV
LT
T
LT
C 5 0.833 L/(30 cm H O 2 10 cm H O) P 5 V /C 1 PEEP
2
LT
ALV
2
T
LT
C 5 0.833 L/20 cm H O
2
LT
C 5 0.4166 L/cm H O
2
LT
P 5 0.8333 L/0.04166 L/cm H O 1 10 cm H O 5 30 cm H O
2
ALV
2
2
P 5 0.6249 L/0.04166 L/cm H O 1 10 cm H O 5 25 cm H O
2
2
2
ALV
P 5 0.4166 L/0.04166 L/cm H O 1 10 cm H O 5 20 cm H O
2
2
2
ALV
P 5 0.2083 L/0.04166 L/cm H O 1 10 cm H O 5 15 cm H O
2
2
2
ALV
40
30 P ALV
25
P (cm H 2 O) 20
15
© Cengage Learning 2014
0 0.25 0.5 0.75 1.0
Time (sec)
© Cengage Learning 2014
Figure 11-8 demonstrates drawing a line (dashed line) through the values plotted for
the volume delivered and the P ALV developed over time. This demonstrates also that
P ALV rises linearly and in parallel to the P throughout inspiration.
TA
SPONTANEOUS VENTILATION DURING
MECHANICAL VENTILATION

Synchronized Intermittent Mandatory Ventilation

synchronized intermittent Figure 11-9 shows the three types of breaths (controlled, spontaneous, and assist) of-
mandatory ventilation (SIMV): fered during synchronized intermittent mandatory ventilation (SIMV). The first set
A mode of ventilation in which
mechanical breaths are delivered of waveforms (Figure 11-9, left) is ideal flow- and pressure-time patterns for a volume-
without overlapping spontaneous or flow-controlled mandatory breath. Letter a (arrow) beneath the first pressure wave-
breaths.
form indicates that the breath is ventilator-initiated (time-triggered and controlled).

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