Extrathoracic obstruction and hypoxemia occurring during exercise in a competitive female cyclist

A 22-year-old competitive female cyclist complained of cough, chest tightness, and wheeze during high-intensity exercise that had previously been diagnosed as exercise-induced bronchospasm (EIB). A loud stridor, a sensation of her "throat closing," and severe dyspnea developed during maximal cycling exercise with concomitant reductions in both inspiratory and expiratory flow rates. A decrease of 25 L/min (26%) in minute ventilation and arterial hypoxemia (PaO(2) decrease, 93 to 76.5 mm Hg) resulted from this obstruction. Spontaneous tidal flow-volume loops (FVLs) during exercise exhibited a sawtooth pattern during inspiration, and substantial drops in flow rates after the stridor developed. However, maximal FVLs were unchanged from baseline following exercise, indicating that the obstruction was not EIB. We suggest that the continuous measurement of spontaneous breath-by-breath tidal FVLs may be a useful diagnostic tool for the identification of exercise-induced extrathoracic obstruction. Additionally, extrathoracic obstruction should be considered as an uncommon but potential cause of inadequate ventilation and arterial hypoxemia during exercise.