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Alveolar vessel behavior in the zone 2 lung inferred from indicator-dilution data
D A Rickaby1, C A Dawson, J H Linehan
1Research Service, Clement J. Zablocki Veterans Administration Medical Center, Milwaukee 53295.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1987
Summary
Alveolar vessel changes were studied using serotonin uptake and extravascular volume (Qev) measurements. Vessel occlusion reduced both, while zone 2 conditions decreased serotonin uptake but not Qev, indicating distinct indicator behaviors in altered lung physiology.
Area of Science:
- Pulmonary Physiology
- Vascular Biology
- Respiratory Medicine
Background:
- Alveolar vessels undergo complex pressure dynamics, particularly when alveolar pressure exceeds venous pressure (zone 2).
- Understanding indicator distribution and uptake in these vessels is crucial for diagnosing lung conditions.
Purpose of the Study:
- To investigate changes in alveolar vessels under zone 2 conditions compared to zone 3.
- To assess the impact of pulmonary artery occlusion on serotonin uptake and extravascular volume (Qev).
Main Methods:
- Isolated dog lung lobes were used to compare serotonin uptake and Qev under zone 2 and zone 3 conditions.
- Pulmonary arteries were occluded with beads of varying sizes (58-548 microns) to examine effects on indicator uptake.
Main Results:
- Bead embolization reduced both serotonin uptake and Qev.
- Transitioning from zone 3 to zone 2 decreased serotonin uptake but did not alter Qev.
- These findings suggest beads occluded larger vessels, while zone 2 caused capillary collapse affecting serotonin diffusion.
Conclusions:
- Serotonin's limited diffusion hinders uptake in collapsed capillaries under zone 2 conditions.
- Highly diffusible 3HOH accessed the same extravascular volume (Qev) in both zone 2 and zone 3, highlighting differential indicator accessibility.