Regulation of ventilatory capacity during exercise in asthmatics

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

In asthmatic and control subjects, we examined the changes in ventilatory capacity (V̇(Cap)), end-expiratory lung volume (EELV), and degree of flow limitation during three types of exercise: 1) incremental, 2) constant load (50% of maximal exercise capacity; 36 min), and 3) interval (alternating between 60 and 40% of maximal exercise capacity; 6-min workloads for 36 min). The V̇(Cap) and degree of flow limitation at rest and during the various stages of exercise were estimated by aligning the tidal breathing flow- volume (F-V) loops within the maximal expiratory F-V (MEFV) envelope using the measured EELV. In contrast to more usual estimates of V̇(Cap) (i.e., maximal voluntary ventilation and forced expiratory volume in 1 s x 40), the calculated V̇(Cap) depended on the existing bronchomotor tone, the lung volume at which the subjects breathed (i.e., EELV), and the tidal volume. During interval and constant-load exercise, asthmatic subjects experienced reduced ventilatory reserve, higher degrees of flow limitation, and had higher EELVs compared with nonasthmatic subjects. During interval exercise, the V̇(Cap) of the asthmatic subjects increased and decreased with variations in minute ventilation, due in part to alterations in their MEFV curve as exercise intensity varied between 60 and 49% of maximal capacity. In conclusion, asthmatic subjects have a more variable V̇(Cap) and reduced ventilatory reserve during exercise compared with nonasthmatic subjects. The variations in V̇(Cap) are due in part to a more labile MEFV curve secondary to changes in bronchomotor tone. Asthmatics defend V̇(Cap) and minimize flow limitation by increasing EELV.

Original languageEnglish (US)
Pages (from-to)892-901
Number of pages10
JournalJournal of Applied Physiology
Volume79
Issue number3
StatePublished - 1995

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Lung
Maximal Voluntary Ventilation
Tidal Volume
Forced Expiratory Volume
Workload
Ventilation
Respiration

Keywords

  • airway caliber
  • end-expiratory lung volume
  • exercise-induced asthma
  • flow limitation

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Regulation of ventilatory capacity during exercise in asthmatics. / Johnson, Bruce David; Scanlon, Paul D; Beck, K. C.

In: Journal of Applied Physiology, Vol. 79, No. 3, 1995, p. 892-901.

Research output: Contribution to journalArticle

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