Journal of Applied Physiology, Vol 55, Issue 1 258-262, Copyright © 1983 by American Physiological Society
A computerized timing algorithm for determination of pulmonary tissue volume
M. F. Petrini, T. M. Dwyer and M. S. Phillips
We developed a computerized method to measure pulmonary tissue volume (Vt)
and capillary blood flow (Qc) that requires only a single interface for
measurement of a soluble and an insoluble gas. The method uses a timing
algorithm that replaces either a marker gas (C18O) or a volume signal. Gas
concentrations are stored in digitized form. The data analysis consists of
three parts: 1) initial and end-tidal samples found by using minima and
maxima; 2) a timing algorithm derived from the end-tidal dead space method
(ETDS, J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 782-795,
1978); and 3) calculations of Vt and Qc, also by the ETDS method. Both the
timing and Vt and Qc agree well with the hand-calculated values, but the
coefficient of variation of Vt is slightly improved (6 vs. 7% manually). We
conclude that our computerized method is equivalent to the manual ETDS
method, but it is faster and more accurate; in addition, it has the
advantage of requiring only one interface without the use of expensive
gases.
