Preflight Evaluation-To the Editor: Patients and Methods

Abstract

Dr. Dillard and his colleagues have conferred in their article (CHEST 1995; 107:352-57) that a hypoxemic inhalation test at sea level and hypobaric chamber exposure are compatible predictors for altitude hypoxemia. The two groups of COPD patients were different in their spirometric status (FEV1 for group 1 is 41 ±14% and that of group 3 being 31 ±10%); moreover, the presence of normocapnoea (PaCO2-38.0±4.7 mm Hg) in group 3 with FEV1 ≥1 L (0.97±0.32) appears physiologically difficult to appreciate when a rise in PaCO2 is likely. 1 Snider GL Faling LJ Rennard SI Chronic bronchitis and emphysema. in: Murray JF Nadal JA Text book of respiratory medicine. 2nd ed. WB Saunders Co, Philadelphia1994: 1359 Google Scholar The authors have not mentioned how long group 3 patients were given hypobaric chamber exposure and have not qualified the reason for different periods of hypoxic inhalation/hypobaric exposure in subjects from groups 1 and 2 (15 and 30 min respectively). Furthermore, it is unclear that at what point of time the arterial blood gas analysis was done to see altitude hypoxemia. An exposure of 15/30 min may be quite short to see the hypoxemic effect to long air travel since this duration is an important determinant of hypoxemia. 2 California Thoracic Society. Travel at high altitude: informations for physicians. Oakland, Calif: American Lung Association of California, 1989 Google Scholar A subclassification of chronic obstructive airway disease patients into predominant bronchitis vs emphysema would have been better to understand the utility of such tests in these different classes of patients who, pathophysiologically, are distinct from each other.