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Pulmonary capillaries are recruited during pulsatile flow.
Robert G Presson1, William A Baumgartner, Amanda J Peterson
1Department of Anesthesiology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5200, USA. rpresson@iupui.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 14, 2002
Summary
Pulmonary capillaries recruit rapidly in response to brief increases in pressure during cardiac systole. Once open, these capillaries remain perfused throughout the cardiac cycle.
Area of Science:
- Pulmonary circulation
- Cardiovascular physiology
- Microcirculation
Background:
- Pulmonary arterial pressure increases can cause capillary recruitment.
- Previous studies showed recruitment in seconds, but the role of transient systolic pressure was unknown.
Purpose of the Study:
- To investigate if brief systolic pressure increases recruit pulmonary capillaries.
- To determine if recruitment is maintained during diastole.
Main Methods:
- Isolated dog lungs were perfused with steady and pulsatile flow.
- Mean arterial and left atrial pressures were kept constant.
- Videomicroscopy was used for direct measurement of capillary recruitment.
Main Results:
- Pulsatile flow significantly increased the number (94%) and length (105%) of perfused capillaries.
- 92% of newly recruited capillaries remained perfused by red blood cells throughout the cycle.
- Capillary recruitment occurred during systole and persisted into diastole.
Conclusions:
- Pulmonary capillaries demonstrate rapid recruitment in response to pulsatile flow.
- Recruitment during systole is maintained throughout the cardiac cycle.
- This study provides direct evidence of pulmonary capillary response to pulsatile hemodynamics.