Am. J. Respir. Crit. Care Med., Vol 151, No. 4, 04 1995, 1211-1217.
Inulin as a marker of dilution of bronchoalveolar lavage in asthmatic and normal subjects
LJ Restrick, AP Sampson, PJ Piper and JF Costello
Department of Thoracic Medicine, King's College School of Medicine and Dentistry, London, United Kingdom.
Bronchoalveolar lavage (BAL) fluid is a variable mixture of instilled and
lung fluid, which makes interpretation of solute concentrations difficult.
We describe the use of inulin as a marker of dilution of BAL in human
subjects. BAL, using saline containing 0.1 mM inulin, was safely performed
in 13 subjects with mild asthma and 11 normal subjects. The dilution factor
(DF: inulin concentration in BAL fluid/inulin concentration in instilled
fluid) was measured spectrophotometrically, and it was used to calculate
the volume of lung fluid in BAL fluid. There was no significant difference
between the median (range) DF of 0.931 (0.825 to 0.952) in asthmatics and
0.907 (0.768 to 0.985) in control subjects (p = 0.77). There was wide
individual variation in, but no significant difference between, the lung
fluid volume of 8.1 ml (5.4 to 22.2) in asthmatics and 12.3 ml (1.9 to
30.6) in control subjects (p = 0.56), thus validating comparisons of
concentrations per ml of BAL fluid. Alternatively, concentrations can be
compared per ml of lung fluid. Inulin fulfilled the requirements for a
marker of dilution of BAL, enabling the validation and standardization of
comparisons of solute concentrations in BAL fluid.
