Reduction of patient-ventilator asynchrony by reducing tidal volume during pressure-support ventilation

Intensive Care Med. 2008 Aug;34(8):1477-86. doi: 10.1007/s00134-008-1121-9. Epub 2008 Apr 24.


Objective: To identify ventilatory setting adjustments that improve patient-ventilator synchrony during pressure-support ventilation in ventilator-dependent patients by reducing ineffective triggering events without decreasing tolerance.

Design and setting: Prospective physiological study in a 13-bed medical intensive care unit in a university hospital.

Patients and participants: Twelve intubated patients with more than 10% of ineffective breaths while receiving pressure-support ventilation.

Interventions: Flow, airway-pressure, esophageal-pressure, and gastric-pressure signals were used to measure patient inspiratory effort. To decrease ineffective triggering the following ventilator setting adjustments were randomly adjusted: pressure support reduction, insufflation time reduction, and change in end-expiratory pressure.

Measurements and results: Reducing pressure support from 20.0 cm H(2)O (IQR 19.5-20) to 13.0 (12.0-14.0) reduced tidal volume [10.2ml /kg predicted body weight (7.2-11.5) to 5.9 (4.9-6.7)] and minimized ineffective triggering events [45% of respiratory efforts (36-52) to 0% (0-7)], completely abolishing ineffective triggering in two-thirds of patients. The ventilator respiratory rate increased due to unmasked wasted efforts, with no changes in patient respiratory rate [26.5 breaths/min (23.1-31.9) vs. 29.4 (24.6-34.5)], patient effort, or arterial PCO(2). Shortening the insufflation time reduced ineffective triggering events and patient effort, while applying positive end-expiratory pressure had no influence on asynchrony.

Conclusions: Markedly reducing pressure support or inspiratory duration to reach a tidal volume of about 6 ml/kg predicted body weight eliminated ineffective triggering in two-thirds of patients with weaning difficulties and a high percentage of ineffective efforts without inducing excessive work of breathing or modifying patient respiratory rate.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Intensive Care Units
  • Male
  • Middle Aged
  • Positive-Pressure Respiration / methods*
  • Pulmonary Disease, Chronic Obstructive / classification
  • Pulmonary Disease, Chronic Obstructive / mortality
  • Pulmonary Disease, Chronic Obstructive / therapy*
  • Respiration
  • Tidal Volume / physiology
  • Ventilator Weaning
  • Work of Breathing / physiology*