Intensive Care Medicine

, Volume 34, Issue 8, pp 1477–1486 | Cite as

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

  • Arnaud W. ThilleEmail author
  • Belen Cabello
  • Fabrice Galia
  • Aissam Lyazidi
  • Laurent Brochard



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.


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 H2O (IQR 19.5–20) to 13.0 (12.0–14.0) reduced tidal volume [10.2 ml/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 PCO2. Shortening the insufflation time reduced ineffective triggering events and patient effort, while applying positive end-expiratory pressure had no influence on asynchrony.


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.


Patient-ventilator asynchrony Patient-ventilator interaction Assisted mechanical ventilation Pressure-support ventilation Work of breathing 



This study was supported by VIASYS Healthcare.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Arnaud W. Thille
    • 1
    Email author
  • Belen Cabello
    • 1
  • Fabrice Galia
    • 1
  • Aissam Lyazidi
    • 1
  • Laurent Brochard
    • 1
  1. 1.Medical Intensive Care Unit, Henri Mondor Teaching Hospital, AP-HP, INSERM U841Paris XII UniversityCréteilFrance

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