HISTORY: A healthy 22 year-old female volunteered for an exercise provocation test involving repeated forced expiratory volume maneuvers (FEVs) as part of an Institutional Review Board approved research study. The subject was a non-smoker with no history of lung or heart disease and was not taking any medications at the time of the test. The physical examination and vital signs were normal prior to testing. She had recently been accepted to medical school, was eager to cooperate, and performed the FEV maneuvers with great vigor. After an initial FEV, she felt pain across her anterior chest, but did not report this to the supervising staff. She then ran on a treadmill for 10-min at a work rate equivalent to about 60% of maximal heart rate, and, upon completion, repeated the FEV maneuver twice more. The results of all of the FEV maneuvers were normal with no indication of bronchoconstriction. The subject subsequently reported that her chest pain had steadily increased and had begun to radiate to the neck. After the treadmill exercise and the FEV maneuvers were completed, the subject reported her pain to the staff and complained of worsening anterior chest tightness and a sensation of her “neck closing off”. PHYSICAL EXAMINATION: She appeared uncomfortable, but was not in distress. Her temperature was normal; pulse was 86 beats/min; respiratory rate was 20 breath/min, and pulse oximetry showed 97–100% saturation on room air. Palpation revealed crepitance in the anterior neck without tracheal deviation. Examination of the lungs revealed good gas exchange bilaterally and normal breath sounds. The heart sounds were normal–no murmurs or gallop were heard. An electrocardiogram was normal. The patient was escorted to the emergency room, where one of the emergency room physicians noted an unusual systolic crunch heard over the cardiac apex and the left sternal border. DIFFERENTIAL DIAGNOSIS: Subcutaneous emphysema, pneumomediastinum, pneumothorax, musculoskeletal pain, reactive airways disease. TEST AND RESULTS: Posterior-anterior and lateral chest radiographs were obtained, demonstrating pneumome-diastinum with tracking of air into the subcutaneous tissues of the neck, there was also air adjacent to the pericardium. Inspiratory and expiratory radiographs did not demonstrate pneumothorax. TREATMENT AND OUTCOME: The patient was admitted to the hospital and treated with supplemental oxygen to hasten resorption of the pneumomediastinum. By the following day, the pain had completely subsided, anterior neck crepitance had resolved, radiographic improvement occurred, and the patient was discharged. At a follow-up appointment 2 weeks after discharge, repeat chest radiographs were normal, and no sequelas from this incident were noted. COMMENTS: To our knowledge, this is only the second reported case of documented pneumomediastinum occurring in association with FEV maneuvers in a healthy subject. Pneumomediastinum associated with drug use that involves vigorous straining against closed glottis are regularly observed in emergency rooms. But pneumomediastinum has also been reported in healthy subjects who were engaged in physical exertion, dancing, singing and yelling, glass blowing, playing the trumpet, inflating balloons, and mountain climbing. Given the frequent routine use of FEV maneuvers, the presumed safety of these maneuvers in both healthy subjects and patients with lung disease, and the paucity of case reports of pneumomediastinum (or, for that matter, any complications) associated with pulmonary function testing, our case likely represents a very rare complication.