Effect of high negative inspiratory pressure on single breath CO diffusing capacity

Respir Physiol. 1983 Oct;54(1):19-29. doi: 10.1016/0034-5687(83)90110-x.


We measured the single breath diffusing capacity for carbon monoxide (DLcoSB) using a three-equation method to describe CO uptake in 10 normal seated subjects who either voluntarily inhaled slowly (0.5 L/sec) to total lung capacity (TLC), or inhaled slowly to TLC with maximal effort through a high inspiratory resistance which created high negative inspiratory pressure. Subjects then immediately exhaled slowly at a voluntarily controlled exhaled flow. Single breath maneuvers were performed in duplicate both with and without high negative inspiratory pressure while subjects were seated upright at rest and during steady-state bicycle exercise. We found that high negative inspiratory pressure increased DLcoSB by 10.5 +/- 4.9% (mean +/- 1 SD) at rest (P less than 0.001). In 7 subjects low level exercise alone increased DLcoSB by a similar amount (12.1 +/- 7.3%; P = 0.005). In six of the subjects there was a significant correlation between the increase in DLcoSB during high negative inspiratory pressure at rest and the increase in DLcoSB during steady-state exercise (r = 0.89; P less than 0.01). During steady-state exercise, high negative inspiratory pressure further increased DLcoSB 6.4 +/- 6.3% compared to exercise alone (P = 0.05). We conclude that the increase in DLcoSB with high negative inspiratory pressure at rest is a simple reproducible method of assessing recruitment of the pulmonary capillary bed in man.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Carbon Monoxide / physiology*
  • Female
  • Heart Rate
  • Humans
  • Male
  • Middle Aged
  • Physical Exertion
  • Pressure
  • Pulmonary Diffusing Capacity*
  • Respiration*


  • Carbon Monoxide