Refractory period after exercise-induced asthma unexplained by respiratory heat loss

I. Ben-Dov, E. Bar-Yishay, S. Godfrey

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45 Scopus citations

Abstract

Fifteen asthmatic children and young adults each exercised for 6 min by cycling on a cycle ergometer while breathing either cold (4.1°C ± 0.5 SEM) and dry (2.05 mg/L ± 0.05) air or warm (37.2°C ± 0.3) fully saturated air. Each subject performed 4 tests arranged in pairs. Test pair A consisted of cold dry exercise followed by another cold dry exercise, and test pair B consisted of a warm humid exercise followed by a cold dry exercise. Ventilation, heart rate, and gas exchange were closely matched in all 4 tests in each subject with a mean oxygen consumption of 34.8 ± 0.8 ml/min/kg. In test pair A, all subjects were rendered refractory by the first cold dry exercise as manifested by a significant attenuation of their exercise-induced asthma (EIA) after the second cold dry test (per cent decrease in FEV1, ΔFEV1=16 ± 4 compared with 38 ± 4). In 3 subjects, the warm humid exercise did not cause EIA and did not render them refractory to the second cold exercise. The 12 remaining subjects exhibited a refractory period similar to that shown in test pair A. They did not develop EIA after the warm humid test (ΔFEV1=1 ±2), but after the subsequent cold dry exercise the per cent decrease in FEV1 was 19 ± 3, similar to that in the second of the 2 cold dry exercise tests. These experiments suggest that in the majority of subjects exercise per se appears to be the cause for refractoriness and not airway cooling or bronchoconstriction.

Original languageEnglish
Pages (from-to)530-534
Number of pages5
JournalAmerican Review of Respiratory Disease
Volume125
Issue number5
DOIs
StatePublished - 1 Jan 1982
Externally publishedYes

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