Journal of Applied Physiology, Vol 72, Issue 3 944-953, Copyright © 1992 by American Physiological Society
Application of respiratory heat exchange for the measurement of lung water
V. B. Serikov, M. S. Rumm, K. Kambara, M. I. Bootomo, A. R. Osmack and N. C. Staub
Cardiovascular Research Institute, University of California, San Francisco 94143.
A noninvasive method for measuring pulmonary blood flow and lung mass
(called airway thermal volume), based on the measurements of lung heat
exchange with environment, is described. The lungs function as a
steady-state heat exchange system, having an inner heat source (pulmonary
blood flow) and an external heat sink (ventilation). Sudden changes in the
steady-state condition, such as caused by hyperventilation of dry air, lead
to a new steady state after a few minutes. The expired air temperature
difference between the initial and final steady states is proportional to
pulmonary blood flow, whereas the rate at which the new steady state is
achieved is proportional to airway thermal volume. The method was tested in
20 isolated dogs lungs, 9 perfused goat lungs, and 27 anesthetized sheep.
The expired air temperature fall during hyperventilation was inversely
proportional to the perfusion rate of the isolated lungs, and half-time of
the temperature fall was proportional to the lung tissue mass. Experiments
in anesthetized sheep showed that the measured airway thermal volume is
close to the total mass of the excised lungs, including its residual blood
(r = 0.98). Pulmonary edema and fluid instillation into the bronchial tree
increased in the measured lung mass.
