Determinants of transdiaphragmatic pressure in dogs

R. D. Hubmayr, J. Sprung, S. Nelson

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

We measured the transdiaphragmatic pressure (Pdi) during bilateral phrenic nerve stimulation and evaluated the determinants of its change with lung volume, chest wall geometry, and respiratory system impedance in supine dogs. Four rows of radiopaque markers were sewn onto muscle bundles of the costal and crural diaphragm between their origin on the central tendon and their insertion on the rib cage and spine. The length of the diaphragm (L) was determined from the projection images of marker rows using biplane fluoroscopy. Measurements were made at lung volumes between total lung capacity and functional residual capacity before and after the infusion of Ringer lactate solution into the abdominal cavity. In contrast to relaxation, during tetanic stimulation the active lengths of the muscle bundles were similar at all volumes, but the diaphragm assumed different shapes. Although the small differences in active muscle length with volume and liquid loads are consistent with only small changes in muscle force output, Pdi varied by a factor of ≥5. There was no single L/Pdi curve that fitted all data during 50-Hz stimulations. We conclude that under these experimental conditions Pdi is not a unique measure of the force produced by the diaphragm and that lung volume, chest wall geometry, and respiratory system impedance are important determinants of the mechanical efficiency of the diaphragm as a pressure generator.

Original languageEnglish (US)
Pages (from-to)2050-2056
Number of pages7
JournalJournal of applied physiology
Volume69
Issue number6
DOIs
StatePublished - 1990

Keywords

  • diaphragm
  • lung volume
  • phrenic nerve stimulation
  • respiratory system geometry

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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