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Lung epithelial permeability to aerosolized solutes: relation to position
Journal of Applied Physiology (Bethesda, Md. : 1985)
|March 1, 1987
Summary
Lung epithelial permeability to inhaled solutes, measured using technetium-99m-labeled diethylenetriamine pentaacetate (99mTc-DTPA), is influenced by alveolar volume. Gravity affects solute clearance independent of deposition, indicating alveolar distension impacts lung permeability.
Area of Science:
- Pulmonary Physiology
- Respiratory Medicine
- Nuclear Medicine
Background:
- Lung epithelial permeability is crucial for gas exchange and defense against inhaled substances.
- The degree of interepithelial junction distension and alveolar volume are hypothesized to be primary determinants of permeability to inhaled solutes.
Purpose of the Study:
- To investigate the relationship between alveolar volume and lung epithelial permeability.
- To assess if gravity-dependent gradients in alveolar distension influence the clearance of inhaled solutes.
Main Methods:
- Eight healthy subjects inhaled a submicronic aerosol of 99mTc-DTPA.
- Regional lung clearance of 99mTc-DTPA was measured in left lateral decubitus (LLD) and right lateral decubitus (RLD) positions.
- Clearance rates were compared between dependent and nondependent lung regions in each position.
Main Results:
- Despite greater aerosol deposition in dependent regions in LLD, clearance was significantly lower (0.7%/min) compared to nondependent regions (2%/min).
- Reversing body position to RLD significantly reversed these clearance gradients (1.6%/min vs. 0.6%/min).
- A gravity gradient in 99mTc-DTPA clearance was observed, independent of aerosol deposition patterns.
Conclusions:
- Lung epithelial permeability to solutes exhibits a gravity-dependent gradient in lateral decubitus positions.
- This gradient appears to be influenced by the gradient of alveolar volume, suggesting alveolar distension plays a key role in regulating epithelial permeability.