Journal of Applied Physiology, Vol 60, Issue 5 1680-1685, Copyright © 1986 by American Physiological Society
In vivo estimation of tracheal wall water: effects of histamine and carbachol
H. Baier, R. Moas, L. Yerger and A. Wanner
Based on double-indicator-dilution principles we developed and validated a
new method of measuring water content in the tracheal wall by inscribing
time-concentration curves with the inert gas, helium and the water-soluble
gas, dimethylether. In the trachea of conscious adult sheep the measurable
water volume of the wall over a 15-cm length ranged between 0.50 and 0.70
ml. The tracheal radius calculated from helium volume and known tracheal
length ranged between 7.4 and 9.3 mm. The corresponding measurable "water
depth" ranged between 63 and 82 microns. Changes in bronchial blood flow
had no consistent influence on tracheal water volume. The intravenous
injection of histamine (4 micrograms/kg) increased mean water depth to
between 122 and 134% of base line (P less than 0.001), whereas the
intravenous injection of carbachol (4 micrograms/kg) had no effect on water
depth. The production of large amounts of airway secretions produced by
carbachol were removed prior to inscription of the indicator-dilution
curves. These findings indicate that the double-gas-indicator technique is
capable of measuring in vivo the volume of a water compartment in the
tracheal wall and that this volume is increased by histamine. This method
may be applicable in human subjects.
