The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

EFFECT OF POSITION ON VENTILATOR-INDUCED LUNG INJURY IN RABBITS.

Masaji Nishimura MD, Akitoshi Ohara MD, Yhuji Fujino MD, Nariaki Matsuura MD. Intensive Care Unit, Hyogo College of Medicine, and Departments of Anesthesiology, ICU and Pathology, Osaka University Medical School

Tidal recruitment and collapse are considered to be important in ventilator-induced lung injury. In the prone position, pleural pressure and ventilation distribution are more uniform than in the supine position. We therefore hypothesized that ventilator-induced lung injury due to tidal recruitment and collapse was less in the prone position than in the supine.

Methods: Ten anesthetized, paralyzed and tracheostomized rabbits were randomized to either the supine or prone position. The internal carotid artery was cannulated to monitor arterial pressure and to aspirate blood for respiratory gas measurements. Respiratory gases were measured every hour after starting mechanical ventilation. The animals were all ventilated with an infant ventilator (V.I.P. Bird) at a rate of 30/min, T_{1} 0.6 sec, peak inspiratory pressure (PIP) 30 cmH_{2}O, inspiratory flow 15 L/min and no applied PEEP in CMV mode. All animals were ventilated for 5 hours or until the PaO_{2} value was below 100 mmHg. At the end of the protocol, the lungs were removed.

Results: In the supine group, PaO_{2} was below 100 mmHg within 2 hours in o animal, and within 3 hours in 3 animals. The lungs were reddish, especially in the dependent regions. PaO_{2} remained above 200 mmHg in all prone animals. The lungs of this group revealed a normal appearance at the end of the protocol.

Conclusions: In the setting of the study, the lungs were significantly injured by positive pressure ventilation in the supine position. Position has a great effect on lung injury during mechanical ventilation.

(See original for figure)

Reference: OF-96-108

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