Laboratory assessment of fitness to fly in patients with lung disease: a practical approach

To identify patients with respiratory disease, who may be at risk of develo ping respiratory distress during commercial air travel, a hypoxia inhalatio n test (HIT) can be performed. This paper reports our experience of using s uch a test combined with an interpretation algorithm in a routine respirato ry function laboratory. Twenty-eight patients were studied. Baseline oxygen saturation (Sa,O-2) was measured using a pulse oximeter. If Sa,O-2 was <90% no HIT was performed a nd the patient was assessed as unfit for air travel. If baseline Sa,O-2 was greater than or equal to 90% an HIT was performed by the patient breathing through a 35% Venturi mask supplied with 100% nitrogen which reduced inspi ratory oxygen fraction to 15.1+/-0.2%. Results were interpreted using a loc ally derived algorithm, and validation was attempted using a questionnaire to investigate subsequent symptoms during travel. All patients tolerated the assessment well. Twenty-two patients were assess ed as "fit to fly" with a further two patients "fit to fly with supplementa l O-2". Four patients were considered unfit to fly. Hypoxic response could not be predicted from either forced expiratory volume in one second, or pre test saturation. Validation of such protocols is difficult, but the hypoxia inhalation test may be a useful tool for predicting hypoxia during air travel in patients w ith chronic respiratory disease.