© 2002 American Thoracic Society
Response of Ventilator-Dependent Patients to Delayed Opening of Exhalation ValveSections of Respiratory and Critical Care Medicine, Department of Medicine, University of Manitoba, Winnipeg, Canada Correspondence and requests for reprints should be addressed to Dr. M. Younes, 3611-55 Harbour Square, Toronto, ON, M5J 2L1 Canada. E-mail: mkyounes{at}sympatico.ca
In conventional mechanical ventilation, the inflation cycle often extends into neural expiration (TEN), potentially exacerbating dynamic hyperinflation (DH). We wished to determine the extent to which patients defend against DH when this happens. Such defense may include prolongation of TEN (timing response) and/or expiratory muscle recruitment (neuromuscular response). Fifty patients were ventilated in the Proportional Assist mode, allowing us to infer these responses noninvasively. At random intervals, exhalation of single breaths was delayed by briefly delaying the opening of exhalation valve (occlusion) (Tocc = 0.78 ± 0.34 seconds). Timing response was assessed from the change in TEN. Neuromuscular response was assessed from the difference between volume exhaled after release of occlusion and volume exhaled in unoccluded breaths over a similar expiratory flow duration (
Key Words: Hering–Breuer reflex • control of breathing • patient–ventilator interactions • dynamic hyperinflation • ineffective efforts This article has been cited by other articles:
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Viso-time). There was no evidence of an acute neuromuscular response; 
