Pulmonary Respiratory Dead Space for Carbon Monoxide with the Measurement of Diffusing Capacity by Steady State in Elderly Persons

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Pulmonary diffusing capacity (DLCOSS) and fractional CO uptake (COF) measured with endtidal air sampler in steady state were studied in normal elderly persons over 60 years old including 19 males and 11 females (mean; 67.7 and 71.6, respectively) and in normal young volunteers (mean age; 22.3 y.o.). By assuming endtidal CO fraction for the mean alveolar in this method, the respiratory dead space (VD) for carbon monoxide was easily calculated with Bohr's equation and was related to the tidal volume (VT) as follows: VD=0.289VT+0.012 (liter: 1 SE; 0.027, r; 0.860) in elderly persons, and VD=0.303VT+0.015 (liter: 1SE; 0.022, r; 0.903) in young volunteers. Thus obtained VD is considered as a kind of physiological dead space. Mathematical analysis of the parameters (VD/VT, DLCOSS and COF) in this method leads us to comparehend graphycally that DLCOSS (BP-47)/VE and COF are in hyperbolic relation, one of whose asymptotes is 1-VD/VT.
社団法人日本老年医学会の論文