Reference values for lung function tests. III. Carbon monoxide diffusing capacity (transfer factor)

Carbon monoxide diffusing capacity (DLCO) Or transfer factor (TLCO) is a pa rticularly useful test of the appropriateness of gas exchange across the lu ng alveolocapillary membrane. With the purpose of establishing predictive e quations for DLCO using a non-smoking sample of the adult Brazilian populat ion, we prospectively evaluated 100 subjects (50 males and 50 females aged 20 to 80 years), randomly selected from more than 8,000 individuals. Gender -specific linear prediction equations were developed by multiple regression analysis with single breath (SB) absolute and volume-corrected (VA) DLCO v alues as dependent variables. In the prediction equations, age (years) and height (cm) had opposite effects on DLCOSB (ml min(-1) mmHg(-1)), independe nt of gender (-0.13 (age) + 0.32 (height) - 13.07 in males and -0.075 (age) + 0.18 (height) + 0.20 in females). On the other hand, height had a positi ve effect on DLCOSB but a negative one on DLCOSB/ VA (P<0.01). We found tha t the predictive values from the most cited studies using predominantly Cau casian samples were significantly different from the actually measured valu es (P<0.05). Furthermore, oxygen uptake at maximal exercise (VO(2)max) corr elated highly to DLCOSB (R = 0.71, P<0.001); this variable, however, did no t maintain an independent role to explain the VO(2)max variability in the m ultiple regression analysis (P>0.05). Our results therefore provide an orig inal frame of reference for either DLCOSB or DLCOSB/VA in Brazilian males a nd females aged 20 to 80 years, obtained from the standardized single-breat h technique.