The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Ashutosh N. Aggarwal1, Ritesh Agarwal1, Dheeraj Gupta1

Background: Information on utility of automatic tube compensation (ATC) as an adjunct in facilitating weaning from mechanical ventilation is rather limited. This study aimed to evaluate if combination of pressure support ventilation (PSV) with ATC is superior to PSV alone in weaning patients of severe neuroparalytic snake envenomation receiving mechanical ventilation.

Methods: 41 patients on assist control ventilation (Evita 2 Dura vetntilator, Draeger Medical, Germany) at our Respiratory Intensive Care Unit (RICU) were randomized to weaning with PSV alone (Group I, 18 patients) or PSV plus ATC (Group II, 23 patients) when considered fit to undergo weaning trial. In both groups, PSV was initially set at 15 cm H2O, and CPAP at 5 cm H2O, with progressive downward titration to maintain respiratory rate below 30 breaths/minute and tidal volume 6-8 mL/kg of ideal body weight. In addition, Group II patients breathed through ventilator circuit with inspiratory ATC set at 100% based on size of their endotracheal tube and a ventilator software-driven algorithm. The primary outcome measure was weaning duration (time needed for successful extubation after initiation of weaning). Secondary outcomes studied included reintubation rate, occurrence of pneumonia, length of RICU stay, and hospital mortality. Considering a non-normal distribution, time variables are described as medians and interquartile range (IQR).

Results: Median time to presentation to hospital after snake bite was five hours (IQR 4-9.5 hours). Median time spent on manual assisted ventilation before transfer to RICU, and on mechanical ventilation in RICU, were similar in Group I and II patients (5.75 [IQR 3-10] vs. 5.0 [IQR 4-6.75], and 36 [IQR 23-52] vs. 41 [IQR 25.5-48], hours respectively). Median duration of weaning was significantly shorter in Group II, than in Group I, patients (8 [IQR 7-12] hours vs. 12 [IQR 7-17] hours, p 0.031 by log rank test; see accompanying figure). Median duration of RICU stay was similar between Group I and II patients (3.5 [IQR 2-4] vs. 3 [IQR 2-4] days). Three patients in Group I, and none in Group II, developed ventilator-associated pneumonia (p 0.07). No patient in either group needed reintubation or died in hospital.

Conclusion: Addition of ATC to a standard PSV-based weaning protocol significantly shortened time needed to wean patients of severe neuroparalytic snake envenomation, without much influence on duration of medical care, morbidity or mortality.