Journal of Applied Physiology, Vol 52, Issue 3 786-791, Copyright © 1982 by American Physiological Society
Instrumentation simultaneously measuring VCO2 and VO2 in humans using titration methods
C. M. Tsoi, D. B. Raemer and D. R. Westenskow
An instrument has been developed for the simultaneous measurement of carbon
dioxide excretion (VCO2) and oxygen uptake (VO2). This instrument, the
Nutrimeter, gives these breath-averaged measurements continuously without
having to determine respiratory flow rate, perform timed spirometric gas
collections, or determine absolute CO2 or O2 concentrations. It can be used
on ventilated or nonventilated patients in long- and short-term studies.
VO2 is determined via the replenishment technique. VCO2 is determined via a
new technique, absorption-titration, described here. Bench test results of
VCO2 measurements show a standard error of the estimate (SEE) +/- 0.591% of
full scale (500 ml/min) and maximum single point error (MSPE) of +/- 3.54%
over a 100--350 ml/min range. VO2 measurements show SEE +/- 0.518% of full
scale (1,000 ml/min) and MSPE +/- 2.42% over a 100--450 ml/min range. In 31
human clinical trials the Nutrimeter was compared with the open-circuit
spirometric collection and micro-Scholander analysis technique. VCO2
measurements show SEE +/- 2.208% and MSPE +/- 10.57% over 135--315 ml/min.
VO2 measurements show SEE +/- 1.134% of full scale and MSPE +/- 9.54% over
170--360 ml/min. Response time is 60 s optimally for step changes in VO2
(0--90% of steady-state value), 90 s for VCO2.
