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

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

Author information

1
Henri Mondor Teaching Hospital, Paris XII University, Créteil, France. arnaud.thille@hmn.aphp.fr

Abstract

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.

PMID:
18437356
DOI:
10.1007/s00134-008-1121-9
[Indexed for MEDLINE]

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