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Updated: Aug 20, 2026
In vivo Measurement of the Mouse Pulmonary Endothelial Surface Layer
Published on: February 22, 2013
Pulmonary microvascular reflection coefficients estimated with modified lymphatic washdown technique
R E Drake1, S Dhother, J C Gabel
1Department of Anesthesiology, University of Texas Medical School, Houston 77030, USA.
Abstract:
Many investigators have used the lymphatic protein washdown technique to estimate the pulmonary microvascular membrane reflection coefficient to protein (sigma d). With that technique, the investigator causes a high microvascular filtration rate then estimates sigma d from the lymph and plasma protein concentrations. However the lymph may contain protein washed from the lung tissue, and the tissue protein may cause investigators to underestimate sigma d. Plasma protein osmotic pressure (IIc) may cause investigators to underestimate sigma d because IIc opposes fluid filtration. To minimize the effect of IIc, we decreased IIc to 5.6 +/- 1.1 mmHg in five anesthetized sheep. We increased the microvascular filtration rate by increasing pulmonary microvascular pressure to 22 +/- 3 mmHg. Then we tagged plasma protein with Evans blue dye and estimated sigma d from the lymph and plasma dye concentrations. Because tissue protein was not tagged, it did not interfere with our sigma d estimate. Our sigma d estimate (0.79 +/- 0.08) was much higher than previous estimates in anesthetized animals.
Insights
This study refined the lymphatic protein washdown technique to better estimate the pulmonary microvascular reflection coefficient (sigma d). New methods yielded a significantly higher sigma d estimate, improving accuracy in lung research.
Area of Science:
- Pulmonary physiology
- Cardiovascular research
- Microvascular function
Background:
- The lymphatic protein washdown technique is commonly used to estimate the pulmonary microvascular reflection coefficient to protein (sigma d).
- Previous methods may underestimate sigma d due to protein contamination from lung tissue and the opposing effect of plasma protein osmotic pressure (IIc).
Purpose of the Study:
- To develop a more accurate method for estimating sigma d by minimizing confounding factors.
- To re-evaluate sigma d in anesthetized sheep using an improved technique.
Main Methods:
- Reduced IIc to 5.6 +/- 1.1 mmHg and increased pulmonary microvascular pressure to 22 +/- 3 mmHg in five anesthetized sheep.
- Utilized Evans blue dye to tag plasma protein for estimating sigma d from lymph and plasma concentrations.
- Avoided interference from tissue protein by not tagging it.
Main Results:
- The estimated sigma d was 0.79 +/- 0.08.
- This estimate is significantly higher than previously reported values in anesthetized animals.
Conclusions:
- The refined technique provides a more accurate estimation of sigma d.
- Higher sigma d values suggest tighter pulmonary microvascular barrier integrity than previously thought.
