Patient-ventilator asynchrony during assisted mechanical ventilation.
OBJECTIVE
The incidence, pathophysiology, and consequences of patient-ventilator asynchrony are poorly known. We assessed the incidence of patient-ventilator asynchrony during assisted mechanical ventilation and we identified associated factors.


METHODS
Sixty-two consecutive patients requiring mechanical ventilation for more than 24 h were included prospectively as soon as they triggered all ventilator breaths: assist-control ventilation (ACV) in 11 and pressure-support ventilation (PSV) in 51.


METHODS
Gross asynchrony detected visually on 30-min recordings of flow and airway pressure was quantified using an asynchrony index.


RESULTS
Fifteen patients (24%) had an asynchrony index greater than 10% of respiratory efforts. Ineffective triggering and double-triggering were the two main asynchrony patterns. Asynchrony existed during both ACV and PSV, with a median number of episodes per patient of 72 (range 13-215) vs. 16 (4-47) in 30 min, respectively (p=0.04). Double-triggering was more common during ACV than during PSV, but no difference was found for ineffective triggering. Ineffective triggering was associated with a less sensitive inspiratory trigger, higher level of pressure support (15 cmH(2)O, IQR 12-16, vs. 17.5, IQR 16-20), higher tidal volume, and higher pH. A high incidence of asynchrony was also associated with a longer duration of mechanical ventilation (7.5 days, IQR 3-20, vs. 25.5, IQR 9.5-42.5).


CONCLUSIONS
One-fourth of patients exhibit a high incidence of asynchrony during assisted ventilation. Such a high incidence is associated with a prolonged duration of mechanical ventilation. Patients with frequent ineffective triggering may receive excessive levels of ventilatory support.
Thille
Arnaud W
AW
Université Paris XII, INSERM U651, Réanimation Médicale, AP-HP Hôpital Henri Mondor, Faculté de Médecine, 51 avenue du Maréchal de Lattre de Tassigny, 94000 Créteil, France. arnaud.thille@wanadoo.fr
Rodriguez
Pablo
P
Cabello
Belen
B
Lellouche
François
F
Brochard
Laurent
L
D000368:Aged; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods* / Q000706:statistics & numerical data; D012815:Signal Processing, Computer-Assisted; D018709:Statistics, Nonparametric