Hypoxemia during Air Travel in Patients with Chronic Obstructive Pulmonary Disease

Abstract

Study Objective: To quantitate and identify determinants of the severity of hypoxemia during air travel in patients with chronic obstructive pulmonary disease.

Design: Prospective study of physiologic variables before and during intervention.

Setting: Referral-based pulmonary disease clinic at a U.S. Army medical center.

Patients: Eighteen ambulatory retired servicemen (age 68 ± 6 [SD] years) with severe chronic obstructive pulmonary disease (forced expiratory volume in the first second [FEV₁] 31% ± 10% of predicted).

Intervention: Altitude simulation equivalent to 2438 meters (8000 feet) above sea level in a hypobaric chamber.

Measurements and Main Results: Radial artery catheter blood oxygen tension in the patients declined from a ground value (PaO₂G) at sea level of 72.4 ± 9 mm Hg to an altitude value (PaO₂Alt) of 47.4 ± 6 mm Hg after 45 minutes of steady state hypobaric exposure. The PaO₂G correlated with PaO₂Alt (r = 0.587; P < 0.01). Multiple regression analysis revealed that the preflight FEV₁ reduced the variability in PaO₂Alt not explained by PaO₂G in the equation: PaO₂Alt = 0.453 [PaO₂G] + 0.386 [FEV₁% predicted] + 2.440 (r = 0.847; P < 0.001). Residuals from two previously published formulas using PaO₂G also correlated with FEV₁ (r ≥ 0.765; P < 0.001).

Conclusions: Arterial blood oxygen tension declined to clinically significant levels in most patients during hypobaric exposure. When combined with the preflight arterial PO₂ at ground level (PaO₂G), the measurement of the preflight FEV₁ improved prediction of PaO₂ at altitude (PaO₂Alt) in patients with severe chronic obstructive pulmonary disease.