• Ronald S Litman, Jennifer A Kottra, Paul R Gallagher, and Denham S Ward.
• Department of Anesthesiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA. Litmanr@email.chop.edu
• J Clin Monit Comput. 2002 Jul 1; 17 (5): 279-85.

ObjectiveUpper airway obstruction is the most rapid and clinically relevant cause of hypoxia during sedation and anesthesia. This study was designed to determine if respiratory inductance plethysmography (RIP) could quantify the degree of upper airway obstruction caused by induction of general anesthesia.MethodsRIP tracings were obtained during induction of general anesthesia in healthy children. Three sets of measurements were obtained during: (1) a 3 minute control period without anesthetics, (2) 3 minutes of 50% nitrous oxide, and (3) halothane administration to complete the induction of general anesthesia. Clinical impression of upper airway obstruction (none, partial, or complete) was correlated with two separate RIP analysis techniques.ResultsThree hundred ninety-five breathing epochs from 20 children (ages 3-10 years) were analyzed by both phase shift and phase inversion techniques. Although both techniques had good general correlation with severity of airway obstruction, neither was sufficiently reliable for accurate prediction of severity of airway obstruction.ConclusionsWe investigated two methods for analyzing RIP tracings during varying degrees of upper airway obstruction in anesthetized children. We found that neither technique was sufficiently accurate for predicting the severity of upper airway obstruction and would not be useful as a predictor of upper airway obstruction in the clinical or research settings.

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