Methods: Ten patients, undergoing general anesthesia, were studied while they were breathing (1) pure oxygen and (2) a gas mixture of 70% Xenon - 30% Oxygen. To calculate the true Rrs, (i.e. Rrs,tot minus the tube resistance), an in vitro experiment was conducted to obtain the K1 and K2 values of the Roher’s equation for different tube size.

Results: Using Xenon the K2 values were higher than those obtained for a gas mixture of 70% Nitrous Oxide or Oxygen. The true Rrs increased during Xenon anesthesia due to an increase of lung resistance. The high Rrs,tot promoted the development of PEEPi when a tidal volume higher than 0.7 l was used.

Conclusion: The ventilatory strategy during Xenon anesthesia to minimize PEEPi should promote the use of a long expiratory time and of an endotracheal tube with a large inner diameter.

Keywords: Intrinsic positive end expiratory pressure, lung elastance, lung resistance, xenon anesthesia

Applied Cardiopulmonary Pathophysiology 7: 201-207, 1998

Carlo Alberto Volta, M.D.
Dipartimento di Scienze Biomediche e Terapie Avanzate
Sezione di Anestesia e Rianimazione Arcispedale S. Anna
University of Ferrara
Corso Giovecca n. 203
I-44100 Ferrara
Italy
Phone: (532) 206570
Fax: (532) 206570
E-mail: vlc@dns.unife.it