[Preflight assessment by hypoxic inhalation test in cardiopulmonary patients]

Flying may expose passengers to hypoxic conditions, which may induce hypoxemia, particularly in those with chronic heart and/or lung disease. Onset of dyspnea, wheezing, chest pain, cyanosis and right heart failure can lead to urgent need for oxygen during flight. The hypoxia inhalation test (HIT) provides a safe and simple means of identifying those who may develop hypoxemia during flight. We report our experience with 48 self-reporting patients who underwent HIT prior to pre-planned air travel. They inhaled for 15-minute periods a reduced oxygen concentration (F1O2 15%) under normobaric conditions, during which O2 saturation was monitored by pulse oximeter; electrocardiogram, blood pressure and symptoms were also monitored. O2 saturation of < 85% (PaO2 50 mm Hg) was considered a positive test. In the 8 cases (17%) with a positive test, 5 had chronic obstructive pulmonary disease and 3 had cardiovascular and/or combined heart-lung disease. We calculated predicted O2 partial pressure in altitude (PaO2ALT) and compared it to actual results in the 8 patients with a positive HIT. In 5, use of the predicted formula would have under-diagnosed the hypoxemia that developed during the HIT. Thus, the results of the HIT changed treatment strategy in these patients. We recommend that patients with positive tests use O2 (2LPM or 4LPM) during flight. HIT is practical and of potential benefit in the objective assessment of patients with various degrees of heart, lung or combined heart-lung disease. Clinicians should be aware of the relative risk of hypoxia during flight in such patients, and of the value of HIT in identifying them, leading to increase in its use.