Capillary recruitment and transit time in the rat lung

Robert G. Presson, Thomas M. Todoran, Bracken J. De Witt, Ivan F. McMurtry, Wiltz W. Wagner

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Increasing pulmonary blood flow and the associated rise in capillary perfusion pressure cause capillary recruitment. The resulting increase in capillary volume limits the decrease in capillary transit time. We hypothesize that small species with relatively high resting metabolic rates are more likely to utilize a larger fraction of gas-exchange reserve at rest. Without reserve, we anticipate that capillary transit time will decrease rapidly as pulmonary blood flow rises. To test this hypothesis, was measured capillary recruitment and transit time in isolated rat lungs. As flow increased, transit time decreased, and capillaries were recruited. The decrease in transit time was limited by an increased capillary volume due, in part, to recruitment. The recruitable capillaries, however, were nearly completely perfused at flow rates and pressures that were less than basal for the intact animal. This suggests that a limited reserve recruitable capillaries in the lungs of species with high resting metabolic rates may contribute to their inability to raise O2 consumption manyfold above basal values.

Original languageEnglish (US)
Pages (from-to)543-549
Number of pages7
JournalJournal of Applied Physiology
Issue number2
StatePublished - Aug 1997


  • Digital image analysis
  • Indicator dilution
  • Isolated rat lungs
  • Pulmonary microcirculation
  • Video microscopy

ASJC Scopus subject areas

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

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