Table 1.

Methods of Predicting In-Flight Hypoxemia

Method	Pros	Cons
Resting oxygen assessment
Pulse oximetry	Noninvasive, inexpensive, accessible	Single point value may miss significant hypoxemia with exertion
Arterial blood gas	Inexpensive	Uncomfortable
Exercise testing
6-Minute Walk	Minimal equipment required, widely used measurement in other pulmonary disease	Poor ability to predict inflight hypoxemia
50-Meter Walk	Assesses patient during exercise, not just at rest	Poor ability to predict inflight hypoxemia
Cardiopulmonary exercise test	Provides thorough evaluation of cardiopulmonary system	Time consuming, limited availability, expensive
Pulmonary function testing
Spirometry, lung volumes, and diffusion capacity	Widely available, gives additional information on pulmonary disease	Poor ability to predict inflight hypoxemia
Predictive equations
Calculation from point oxygen saturation determined by pulse oximetry or oxygen saturation	Inexpensive, quick, simple to use	Lack of agreement between equations, poor predictive ability
Altitude simulation
Hypoxic challenge test	Good ability to predict inflight hypoxemia	Time consuming, may not be readily available at all centers
Hypobaric chamber	Most closely mimics inflight environment	Very limited clinical availability, primarily used for research, expensive, time consuming