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Heterogeneous capillary recruitment among adjoining alveoli
William A Baumgartner1, Eric M Jaryszak, Amanda J Peterson
1Department of Anesthesis, Indiana University School of Medicine, Indianapolis, IN 46202-5120, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 10, 2003
Summary
Pulmonary capillaries exhibit complex recruitment patterns. Alveolar capillary networks show gradual, sudden, and paradoxical derecruitment, rarely reaching full capacity even at high pressures.
Area of Science:
- Pulmonary Physiology
- Cardiovascular Research
- Microcirculation Dynamics
Background:
- Pulmonary capillary recruitment is pressure-dependent, but the precise mechanisms remain debated.
- Existing models include gradual homogeneous, sudden complete, and heterogeneous recruitment patterns.
Purpose of the Study:
- To investigate the heterogeneity and patterns of alveolar capillary recruitment under increasing pulmonary venous pressure.
- To determine if a predominant recruitment model exists or if multiple patterns coexist.
Main Methods:
- Isolated, pump-perfused canine lung lobes were used for experiments.
- Video microscopy recorded alveolar fields as pulmonary venous pressure increased incrementally (0-40 mmHg).
- Analysis focused on recruitment patterns in neighboring alveoli.
Main Results:
- The majority of alveoli (42%) showed gradual recruitment.
- A significant portion (33%) exhibited sudden recruitment, characteristic of sheet flow.
- Paradoxical derecruitment was observed in half of the neighborhoods, even as neighbors recruited.
- At 40 mmHg, 86% of alveolar-capillary networks remained incompletely recruited.
Conclusions:
- Alveolar capillary recruitment is a complex process, not conforming to a single homogeneous model.
- Recruitment patterns are heterogeneous, involving both gradual and sudden changes.
- Complete recruitment of alveolar-capillary networks may not occur even under supra-maximal pressures.