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GENERAL ARTICLES

Middle Ear Pressure Changes During Anesthesia With or Without Nitrous Oxide are Similar Among Airway Devices

Mathias Hohlrieder, MD^*, Christian Keller, MD, MSc^*, Joseph Brimacombe, MB, ChB, FRCA, MD, Stephan Eschertzhuber, MD^*, Günter Luckner, MD^*, Irene Abraham, MD, and Achim von Goedecke, MD^*

*Department of Anaesthesia and Intensive Care Medicine, Leopold-Franzens University, Innsbruck, Austria; James Cook University, Cairns Base Hospital, Australia; Department of Ear, Nose and Throat Surgery, Leopold-Franzens University, Innsbruck, Austria

Address correspondence to Prof. J. Brimacombe, Department of Anaesthesia and Intensive Care, Cairns Base Hospital, The Esplanade, Cairns 4870, Australia. Address e-mail to jbrimaco{at}bigpond.net.au.

We tested the hypothesis that middle ear pressure (MEP) is influenced by the choice of airway device during anesthesia with or without nitrous oxide (N₂O) in the gas mixture. Eighty consecutive anesthetized, paralyzed ventilated patients (ASA physical status I–II, 18–65 yr) were randomly allocated for airway management with the orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, or laryngeal tube suction with or without N₂O 66% in the gas mixture. MEP was measured from both ears in random order by a blinded observer before induction of anesthesia and every 10 min for 70 min. In the N₂O groups, N₂O was changed to air after 40 min. There were no differences in MEP among the airway devices in the N₂O or air groups. MEP was unchanged in the air groups but increased in the N₂O groups with N₂O (P < 0.0001) and decreased with air (P < 0.02). Baseline values for MEP were similar, but MEP was always higher for the N₂O groups (P < 0.001). We conclude that the choice of airway device does not influence MEP among orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, and laryngeal tube suction during anesthesia with or without N₂O in the gas mixture.