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Repeat exercise normalizes the gas-exchange impairment induced by a previous exercise bout in asthmatic subjects

Departments of ¹Population Health Sciences and ²Pediatrics, University of Wisconsin-Madison, Madison, Wisconsin

Submitted 21 December 2004 ; accepted in final form 14 July 2005

Twenty-one subjects with asthma underwent treadmill exercise to exhaustion at a workload that elicited 90% of each subject's maximal O₂ uptake (EX1). After EX1, 12 subjects experienced significant exercise-induced bronchospasm [(EIB⁺), %decrease in forced expiratory volume in 1.0 s = –24.0 ± 11.5%; pulmonary resistance at rest vs. postexercise = 3.2 ± 1.5 vs. 8.1 ± 4.5 cmH₂O·l^–1·s^–1] and nine did not (EIB^–). The alveolar-to-arterial PO₂ difference (A-aDO₂) was widened from rest (9.1 ± 6.7 Torr) to 23.1 ± 10.4 and 18.1 ± 9.1 Torr at 35 min after EX1 in subjects with and without EIB, respectively (P < 0.05). Arterial PO₂ (Pa_O2) was reduced in both groups during recovery (EIB⁺, –16.0 ± –13.0 Torr vs. baseline; EIB^–, –11.0 ± 9.4 Torr vs. baseline, P 0.05). Forty minutes after EX1, a second exercise bout was completed at maximal O₂ uptake. During the second exercise bout, pulmonary resistance decreased to baseline levels in the EIB⁺ group and the A-aDO₂ and Pa_O2 returned to match the values seen during EX1 in both groups. Sputum histamine (34.6 ± 25.9 vs. 61.2 ± 42.0 ng/ml, pre- vs. postexercise) and urinary 9,11-prostaglandin F₂ (74.5 ± 38.6 vs. 164.6 ± 84.2 ng/mmol creatinine, pre- vs. postexercise) were increased after exercise only in the EIB⁺ group (P < 0.05), and postexercise sputum histamine was significantly correlated with the exercise Pa_O2 and A-aDO₂ in the EIB⁺ subjects. Thus exercise causes gas-exchange impairment during the postexercise period in asthmatic subjects independent of decreases in forced expiratory flow rates after the exercise; however, a subsequent exercise bout normalizes this impairment secondary in part to a fast acting, robust exercise-induced bronchodilatory response.

exercise-induced bronchospasm; pulmonary resistance; airway inflammation; bronchodilation; alveolar-to-arterial oxygen difference

This article has been cited by other articles:

				J. A. Dempsey, D. C. McKenzie, H. C. Haverkamp, and M. W. Eldridge Update in the Understanding of Respiratory Limitations to Exercise Performance in Fit, Active Adults Chest, September 1, 2008; 134(3): 613 - 622. [Abstract] [Full Text] [PDF]

				E. Simons Repeat Exercise Normalizes the Gas-Exchange Impairment Induced by a Previous Exercise Bout in Asthmatic Subjects Pediatrics, August 1, 2006; 118(Supplement_1): S28 - S29. [Abstract] [PDF]