Normal Predicted Values of Pulmonary Carbon Monoxide Diffusing Capacity at Rest by Steady State Method for the Elderly Subjects

Abstract

The pulmonary carbon monoxide diffusing capacity (D_LCO) by endtidal air sampling method in steady state has been studied in our pulmonary laboratory of Tokyo Metropolitan Geriatric Hospital for elderly subjects, including 19 males and 11 females (mean age 67.7 y.o. and 71.6 y.o., respectively). They were considered and selected as the normal in the findings of chest X-ray, spirometry, blood gas and others. Their D_LCO were compared with those of young male volunteers (mean age 22.3 y.o.). D_LCO was tested statistically on its dependency with expired minute volume (V_E) and their significant correlation (P<0.01) was ascertained in regression formulae for both groups as was reported previously:
normal esderly subjects:
D_LCO=1.19V_E+0.13 (r: 0.71)
and
young volunteers:
D_LCO=1.18V_E+9.33 (r: 0.69)
There is no statistical significance in difference between male and female regressions of the elderly subjects. Then we can predict the normal value of D_LCO for the elderly over 60 years at resting V_E with the above regression formula, D_LCO=1.19V_E+0.13, and we can estimate %D_LCO of the measured to the predicted value for the elderly subjects.