Cardiac output and O2 consumption during inspiratory threshold loaded breathing

Richard J Coast, R. A. Jensen, S. S. Cassidy, M. Ramanathan, R. L. Johnson

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

In this study, noninvasive measurements of cardiac output and O2 consumption were performed to estimate the blood flow to and efficiency of the respiratory muscles that are used in elevated inspiratory work loads. Five subjects were studied for 4.5 min at a respiratory rate of 18 breaths/min and a duty cycle of 0.5. Studies were performed at rest without added respiratory loads and at elevated inspiratory work loads with the use of an inspiratory valve that permitted flow only when a threshold pressure was maintained. Cardiac output and O2 consumption were calculated using a rebreathing technique. Respiratory muscle blood flow and O2 consumption were estimated as the difference between resting and loaded breathing. Work of breathing was calculated by integrating the product of mouth pressure and volume. Increases in cardiac output and O2 consumption in response of 4.5 min laoded breathing averaged 1.84 l/min and 108 ml/min, respectively. No increases were seen in response to 20-s loaded breathing. In a separate series of experiments on four subjects, though, cardiac output increased for the first 2 min then leveled off. These results indicate that the increase in cardiac output was a metabolic effect of the increased work load and was not caused primarily by the influence of the highly negative intrathoracic pressure on venous return. Efficiency of the respiratory muscles during inspiratory threshold loading averaged 5.9%, which was similar to measurements of efficiency of respiratory muscles using whole-body O2 consumption that have been reported previously in humans and in dogs.

Original languageEnglish (US)
Pages (from-to)1624-1628
Number of pages5
JournalJournal of Applied Physiology
Volume64
Issue number4
StatePublished - 1988
Externally publishedYes

Fingerprint

Respiratory Muscles
Cardiac Output
Respiration
Workload
Work of Breathing
Pressure
Venous Pressure
Respiratory Rate
Mouth
Dogs

ASJC Scopus subject areas

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

Cite this

Coast, R. J., Jensen, R. A., Cassidy, S. S., Ramanathan, M., & Johnson, R. L. (1988). Cardiac output and O2 consumption during inspiratory threshold loaded breathing. Journal of Applied Physiology, 64(4), 1624-1628.

Cardiac output and O2 consumption during inspiratory threshold loaded breathing. / Coast, Richard J; Jensen, R. A.; Cassidy, S. S.; Ramanathan, M.; Johnson, R. L.

In: Journal of Applied Physiology, Vol. 64, No. 4, 1988, p. 1624-1628.

Research output: Contribution to journalArticle

Coast, RJ, Jensen, RA, Cassidy, SS, Ramanathan, M & Johnson, RL 1988, 'Cardiac output and O2 consumption during inspiratory threshold loaded breathing', Journal of Applied Physiology, vol. 64, no. 4, pp. 1624-1628.
Coast, Richard J ; Jensen, R. A. ; Cassidy, S. S. ; Ramanathan, M. ; Johnson, R. L. / Cardiac output and O2 consumption during inspiratory threshold loaded breathing. In: Journal of Applied Physiology. 1988 ; Vol. 64, No. 4. pp. 1624-1628.
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