Exercise-induced dehydration alters pulmonary function but does not modify airway responsiveness to dry air in athletes with mild asthma.
Local airway water loss is the main physiological trigger for exercise-induced bronchoconstriction (EIB). Our aim was to investigate the effects of whole body water loss on airway responsiveness and pulmonary function in athletes with mild asthma and/or EIB. Ten recreational athletes with a medical diagnosis of mild asthma and/or EIB completed a randomized, crossover study. Pulmonary function tests, including spirometry, whole body plethysmography, and diffusing capacity of the lung for carbon monoxide (DlCO), were conducted before and after three conditions: 1) 2 h of exercise in the heat with no fluid intake (dehydration), 2) 2 h of exercise with ad libitum fluid intake (control), and 3) a time-matched rest period (rest). Airway responsiveness was assessed 2 h postexercise/rest via eucapnic voluntary hyperpnea (EVH) to dry air. Exercise in the heat with no fluid intake induced a state of mild dehydration, with a body mass loss of 2.3 ± 0.8% (SD). After EVH, airway narrowing was not different between conditions: median (interquartile range) maximum fall in forced expiratory volume in 1 s was 13 (7-15)%, 11 (9-24)%, and 12 (7-20)% in dehydration, control, and rest conditions, respectively. Dehydration caused a significant reduction in forced vital capacity (300 ± 190 ml, P = 0.001) and concomitant increases in residual volume (260 ± 180 ml, P = 0.001) and functional residual capacity (260 ± 250 ml, P = 0.011), with no change in DlCO Mild exercise-induced dehydration does not exaggerate airway responsiveness to dry air in athletes with mild asthma/EIB but may affect small airway function.NEW & NOTEWORTHY This study is the first to investigate the effect of whole body dehydration on airway responsiveness. Our data suggest that the airway response to dry air hyperpnea in athletes with mild asthma and/or exercise-induced bronchoconstriction is not exacerbated in a state of mild dehydration. On the basis of alterations in lung volumes, however, exercise-induced dehydration appears to compromise small airway function.
['Simpson|A J|AJ|', 'Romer|L M|LM|', 'Kippelen|P|P|http://orcid.org/0000-0002-8443-0248']
D000328:Adult D001249:Asthma D056352:Athletes D001985:Bronchial Provocation Tests D016084:Bronchoconstriction D002248:Carbon Monoxide D018592:Cross-Over Studies D003681:Dehydration D015444:Exercise D005260:Female D005541:Forced Expiratory Volume D006801:Humans D008168:Lung D008297:Male D014797:Vital Capacity D055815:Young Adult
exercise-induced bronchoconstriction eucapnic voluntary hyperpnea whole body dehydration airway hyperresponsiveness exercise-induced asthma