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.


METHODS
Prospective physiological study in a 13-bed medical intensive care unit in a university hospital.


METHODS
Twelve intubated patients with more than 10% of ineffective breaths while receiving pressure-support ventilation.


METHODS
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.


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.
Thille
Arnaud W
AW
Henri Mondor Teaching Hospital, Paris XII University, Créteil, France. arnaud.thille@hmn.aphp.fr
Cabello
Belen
B
Galia
Fabrice
F
Lyazidi
Aissam
A
Brochard
Laurent
L
D018806:APACHE; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000145:classification / Q000401:mortality / Q000628:therapy*; D012119:Respiration; D013990:Tidal Volume / Q000502:physiology; D015300:Ventilator Weaning; D014939:Work of Breathing / Q000502:physiology*