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Understanding Patient-Ventilator Asychrony

People display normal variability in their breathing patterns even at rest. In contrast, although a necessary medical intervention, mechanical ventilation uses some sort of fixed parameter in almost all currently available modes.

What is asynchrony?

The best way to describe asynchrony is to call it poor patient-ventilator interaction. Patient-ventilator interaction is dependent upon many variables. Some of those are:

  • The patient’s pathophysiology
  • The ventilator settings
  • The patient-ventilator interface used

How often does asynchrony occur?

Asynchrony occurs at varying degrees depending on the patient population and the mechanical ventilation strategy employed. The most common types of asynchrony are ineffective efforts and double triggers.

Overview

Why is asynchrony important?

Patient-ventilator asynchrony is typically uncomfortable for the patient. In addition, it may have an impact on patient outcomes. Epstein1 put together a list of adverse effects associated with poor patient-ventilator interaction:

  • A higher or wasted work of breathing
  • Patient discomfort
  • An increased need for sedation
  • Confusion during the weaning process
  • Prolonged mechanical ventilation
  • A longer stay
  • The possibility of higher mortality

Investigators have examined the relationship between patient-ventilator asynchrony and outcomes. Thille et al2 found patients with an asynchrony index >10% had a longer duration of mechanical ventilation and were more likely to need a tracheostomy. de Wit et al3 found that those patients who had an ineffective trigger index of >10% had a longer duration of mechanical ventilation, a worse 28-day ventilator-free survival, and a longer ICU time and hospital stay. Patients in the ineffective trigger group were less likely to be discharged to home. Varon et al4 found that mortality was higher in patients with an asynchrony index >30%.

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  • 1. Sassoon C. Triggering of the ventilator in patient-ventilator interactions. Respiratory Care. 2011;56(1):39-51.
  • 2. Thille AW et al. Patient-ventilator asynchrony during assisted mechanical ventilation. Intensive Care Med. 2006;32(10):1515-1522.
  • 3. de Wit M. Monitoring of patient ventilator interaction at the bedside. Respiratory Care. 2011;56(1):61-68.
  • 4. Puritan Bennett™ 980 Ventilator Operator's Manual
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