The estimation of arterial pco2 in the elderly.
St, Claudette M., Croix, D. A. Cunningham, J. M. Kowalchuk, A. K
McConnell, A. S. Kirby, B. W. Scheuermann, R. J. Petrella, and D. H.
Paterson.
Centre for Activity and Ageing (affiliated with the Faculties of
Kinesiology and Medicine at the University of Western Ontario and The
Lawson Research Institute at the St. Joseph's Health Centre), the
Department of Physiology, University of Western Ontario, London,
Ontario, Canada and the Department of Human Sciences, Loughborough
University, Loughborough, Leicestershire, United Kingdom
APStracts 2:0331A, 1995.
Arterial PCO2, determined directly in the radial artery, was compared
to indirect estimates of PCO2 in six elderly men (mean age 73.8 yrs).
Estimates of arterial PCO2 included arterialized-venous (PavCO2);
end-tidal (PETCO2); mean alveolar PCO2, calculated using a
reconstruction of the alveolar oscillation in PCO2, and accounting
for the presence of deadspace (PADCO2); and values calculated using
the empirical formula developed by Jones et al. (J. Appl. Physiol.:
Respirat. Environ. Exercise Physiol. 47(5): 954-960, 1979) which
incorporates PETCO2 and tidal volume (PJCO2). Measurements were made
at rest and during cycle ergometry at 25 and 50 Watts, while
breathing various gas mixtures (euoxic/eucapnic; hypoxic/eucapnic;
hyperoxic/eucapnic; and hyperoxic/hypercapnic). The mean differences
between the estimates and the actual PaCO2 +/- standard deviations,
at rest and in 25 W and 50 W exercise were as follows: PavCO2, 0.3
+/- 0.7, -0.1 +/- 0.7, and 1.8 +/- 1.2 torr; PETCO2, 2.9 +/- 1.7, 4.0
+/- 3.1, and 3.7 +/- 3.2 torr; PADCO2, 2.6 +/- 1.9, 3.3 +/- 3.1, and
3.6 +/- 3.8 torr; and PJCO2, 2.4 +/- 1.3, 1.3 +/- 3.0, and 0.6 +/-
2.9 torr. It is concluded that mean PavCO2 agreed most closely with
mean PaCO2 both at rest and in exercise. All methods of deriving
PaCO2 using measurements from the respired gases overestimated
arterial values at rest. Of the noninvasive techniques, mean
estimates calculated using the regression equation developed by Jones
et al. (1979) corresponded most closely with PaCO2 in exercise.
Received 19 January 1995; accepted in final form 17 July 1995.
APS Manuscript Number A70-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.