Key result
Negative intra-alveolar pressure during a 10-second breath hold increased alveolar capillary blood volume by nearly 100% in one of two subjects.
Why the study?
Does negative intra-alveolar pressure affect alveolar capillary blood volume and pulmonary diffusing capacity?
Does negative intra-alveolar pressure affect alveolar capillary blood volume and pulmonary diffusing capacity?
Effect estimate: nearly 100% increase
Negative intra-alveolar pressure increases alveolar capillary blood volume, suggesting the presence of stationary blood in some alveolar capillaries at rest.
May warrant caution in interpreting breath-hold effects clinically; leaves open generalizability to diffusing capacity or larger populations.
In one of two subjects studied in detail, using 0.1% carbon monoxide in the test gas and a 10-second breath-holding period, the alveolar capillary blood volume (Vc) was found to increase by nearly 100% when the intra-alveolar pressure was made negative during breath holding. This was accompanied by a reduction in venous pressure in the forearm. In both subjects Vc was increased on exercise. The diffusing capacity of the alveolar capillary membrane (Dm) remained relatively constant in spite of large changes in Vc. The findings suggest that stationary blood is present in some alveolar capillaries at rest. The implications of this finding and a likely mechanism for the increase in Vc with negative pressure are discussed. xsSubmitted on September 14, 1959
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Cotes et al. (1960) studied this question. Negative intra-alveolar pressure was evaluated on Alveolar capillary blood volume (Vc) (nearly 100% increase). Negative intra-alveolar pressure during a 10-second breath hold increased alveolar capillary blood volume by nearly 100% in one of two subjects.
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