Page 343 - Clinical Application of Mechanical Ventilation

Ventilator Waveform Analysis 309

Learning Objectives

After studying this chapter and completing the review questions, the learner
should be able to:

Describe the waveform characteristics of constant flow during volume-
controlled ventilation to include flow-time, pressure-time, and controlled
mandatory ventilation.
Describe the waveform characteristics of spontaneous breathing during
mechanical ventilation.
Provide examples to show the effects of flow, circuit, and lung characteris-
tics on the pressure-time waveform.
Describe the effects of descending ramp flow during volume-controlled
ventilation.
Describe the waveform characteristics of pressure-controlled ventilation
(PCV) and contrast PCV with volume-controlled ventilation.
Describe the waveform characteristics of pressure-supported ventilation.
Explain the effects of changing lung characteristics on the PCV waveforms.
Analyze pertinent waveforms to identify and correct the following: patient-
ventilator dyssynchrony, increased airway resistance, loss of elastic
recoil, decreased lung-thorax compliance, gas trapping, lack of ventilator
response, and circuit leaks.
Analyze the pressure-volume loop and flow-volume loop to evaluate the
changes in compliance and airway resistance.
Identify the upper and lower inflection points and describe the respective
clinical application.

INTRODUCTION

The advent of waveform (graphic) analysis marked the beginning of a new and
exciting era in ventilator-patient management for respiratory care professionals.
Waveforms give us the capacity to observe and document real-time measurements
of patient-ventilator interactions. In the past, many problematic interactions between
the patient and ventilator that were suspected could not be confirmed without sophis-
ticated equipment and time-consuming effort. Now, someone skilled at analyzing
waveforms can evaluate patient-ventilator synchrony, ventilator function, pulmonary
status, and appropriateness of ventilator adjustments in a matter of seconds. Also,
hard copies of graphics depicting improvements in pulmonary function, ventila-
tor management, and respiratory care can be documented. It should be common
practice for practitioners to use waveforms to assist in ventilator-patient assessment
and management.

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