Quantitative assessment fluid in the lung FRANCIS
of epithelial
lining
P. CHINARD
Departments of Medicine and Physiology, University of Medicine New Jersey Medical School, Newark, New Jersey 07103 Chinard, Francis P. Quantitative assessment of epithelial lining fluid in the lung. Am. J. Physiol. 263 (Lung Cell. Mol. Physiol. 7): L617-L618,1992.Current techniques for the measurement lung epithelial fluid (ELF) volume depend on the dilution by a known volume of wash fluid (bronchoalveolar lavage) of a resident solute, such as urea, in the ELF or of a foreign solute introduced at known concentration in the lavage fluid. Knowledge of the ELF volume allows calculation of solute ELF concentrations. Urea concentration in ELF is assumed to be the same as in plasma. Although epithelial permeability to urea is low, entry of urea from tissues to lavage fluid occurs during the procedure and may lead to erroneous estimates of ELF volume as may loss of foreign solutes. Ideally, the extent of urea entry or of foreign solute loss should be estimated in each lavage. Other cautions are 1) equal osmolality of wash fluid and plasma, 2) minimizing residence time of wash fluid, 3) minimizing wash fluid-to-ELF volume ratio, and 4) adequate analytic procedures. bronchoalveolar lavage; pulmonary epithelium; urea
as a diagnostic procedure has rapidly been gaining in importance. Originally, it served to provide data on the relative concentrations of certain solutes, such as proteins, on the types and relative abundance of recovered cells, and on the presence of various microorganisms such as Pneumocystis carinii and Mycobacterium tuberculosis. Quantitative assessment on an absolute scale has proved to be more difficult inasmuch as it depends on an accurate measure of the endothelial lining fluid (ELF) and the extent of its dilution by the wash fluid. An early proposal involved the use of methylene blue added to the wash fluid (1). A further major step forward was provided by Rennard et al. (5), who used the dilution of urea already residing in the ELF to calculate that dilution. The use of urea was based on several assumptions: 1) the concentration of urea in the ELF is same as in plasma, 2) the entry of urea from lung tissue during the lavage period is negligible, and 3) the sampled fluid recovered is identical in composition to all the fluid in the lung (ELF and wash fluid are well mixed). With these assumptions, the derivation of the expression used to calculate the volume of the ELF is based essentially on the relationship used in chemistry to obtain a solution of a known normality by dilution
BRONCHOALVEOLAR
entry or loss of solute during the procedure, follows. I have used urea as the indicator, although the approach can be applied to other indicators. Initially, the amount of urea in the ELF, nurea, is n ELF urea
1040-0605/92
$2.00
Copyright
=
CELF urea
. VELF
where cfJ$ is the concentration of urea in ELF water (i.e., the molal concentration of urea), and VELF is the volume of ELF water. In the lavage procedure, a volume Va of water containing no urea is introduced. The amount of urea in the total volume, ntufrea,is given by ntfurea = nfJ$ = c,“,“,f . VELF = ckLea(VELF+ Va)
On rearrangement,
this becomes
CELF tf urea /c urea
LAVAGE
WI = NJ, where N is normality, V is volume, and the subscripts denote the initial and final solutions. A more exact approach, with the assumption of no
and Dentistry,
=
(VELF
+
Va)/VELF
and if VELF
of epithelial
lining
P. CHINARD
Departments of Medicine and Physiology, University of Medicine New Jersey Medical School, Newark, New Jersey 07103 Chinard, Francis P. Quantitative assessment of epithelial lining fluid in the lung. Am. J. Physiol. 263 (Lung Cell. Mol. Physiol. 7): L617-L618,1992.Current techniques for the measurement lung epithelial fluid (ELF) volume depend on the dilution by a known volume of wash fluid (bronchoalveolar lavage) of a resident solute, such as urea, in the ELF or of a foreign solute introduced at known concentration in the lavage fluid. Knowledge of the ELF volume allows calculation of solute ELF concentrations. Urea concentration in ELF is assumed to be the same as in plasma. Although epithelial permeability to urea is low, entry of urea from tissues to lavage fluid occurs during the procedure and may lead to erroneous estimates of ELF volume as may loss of foreign solutes. Ideally, the extent of urea entry or of foreign solute loss should be estimated in each lavage. Other cautions are 1) equal osmolality of wash fluid and plasma, 2) minimizing residence time of wash fluid, 3) minimizing wash fluid-to-ELF volume ratio, and 4) adequate analytic procedures. bronchoalveolar lavage; pulmonary epithelium; urea
as a diagnostic procedure has rapidly been gaining in importance. Originally, it served to provide data on the relative concentrations of certain solutes, such as proteins, on the types and relative abundance of recovered cells, and on the presence of various microorganisms such as Pneumocystis carinii and Mycobacterium tuberculosis. Quantitative assessment on an absolute scale has proved to be more difficult inasmuch as it depends on an accurate measure of the endothelial lining fluid (ELF) and the extent of its dilution by the wash fluid. An early proposal involved the use of methylene blue added to the wash fluid (1). A further major step forward was provided by Rennard et al. (5), who used the dilution of urea already residing in the ELF to calculate that dilution. The use of urea was based on several assumptions: 1) the concentration of urea in the ELF is same as in plasma, 2) the entry of urea from lung tissue during the lavage period is negligible, and 3) the sampled fluid recovered is identical in composition to all the fluid in the lung (ELF and wash fluid are well mixed). With these assumptions, the derivation of the expression used to calculate the volume of the ELF is based essentially on the relationship used in chemistry to obtain a solution of a known normality by dilution
BRONCHOALVEOLAR
entry or loss of solute during the procedure, follows. I have used urea as the indicator, although the approach can be applied to other indicators. Initially, the amount of urea in the ELF, nurea, is n ELF urea
1040-0605/92
$2.00
Copyright
=
CELF urea
. VELF
where cfJ$ is the concentration of urea in ELF water (i.e., the molal concentration of urea), and VELF is the volume of ELF water. In the lavage procedure, a volume Va of water containing no urea is introduced. The amount of urea in the total volume, ntufrea,is given by ntfurea = nfJ$ = c,“,“,f . VELF = ckLea(VELF+ Va)
On rearrangement,
this becomes
CELF tf urea /c urea
LAVAGE
WI = NJ, where N is normality, V is volume, and the subscripts denote the initial and final solutions. A more exact approach, with the assumption of no
and Dentistry,
=
(VELF
+
Va)/VELF
and if VELF
