Reduction of patient-ventilator asynchrony by reducing tidal volume during pressure-support ventilation
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.
Full Text Links
Find Full Text Links for this Article
You are not logged in. Sign Up or Log In to join the discussion.