Page 344 - Clinical Application of Mechanical Ventilation

310 Chapter 11

To develop expertise in waveform analysis requires an in-depth understanding
of the principles that govern the shape of waveforms and the characteristics of the
scalars measured: flow, pressure, and volume over time, and the dynamics of the
ventilator-patient interface. Skill is enhanced through mathematical analysis and
laboratory exercises. Prior to clinical practice, it is essential to analyze graphics
during simulations of different patient-ventilator interactions in the laboratory. Test
lungs should be used to simulate changing airflow resistance, compliance and I:E
ratios; and to create conditions such as gas leak, air trapping, and auto-PEEP.
In clinics, graphics should always be displayed during mechanical ventilation
and analyzed before and after implementing ventilator adjustments and therapy.
This chapter provides the students and clinicians the basic knowledge to improve
ventilator-patient management using waveform analysis. Refer to Table 11-1 as a
reference for key abbreviations used within this chapter.

TABLE 11-1 Key Abbreviations

C LT Lung-thorax compliance (static compliance)

CFW Constant flow waveform

CMV Controlled mandatory ventilation
DRFW Descending ramp flow waveform

FVL Flow-volume loop
IRPCV Inverse ratio pressure-controlled ventilation

P ALV Alveolar pressure

P AO Airway opening pressure
P TA Transairway pressure

PCV Pressure-controlled ventilation
Peak P ALV Peak alveolar pressure; plateau pressure

PIP Peak inspiratory pressure
PVL Pressure-volume loop

SIMV Synchronized intermittent mandatory ventilation

T E Expiratory time
T I Inspiratory time

TCT Total cycle time

VCV Volume-controlled ventilation
V T Tidal volume
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