[Pulmonary diffusing capacity in normal aged subjects of both sexes: the effect of smoking habit]

The diffusing capacity of the lung (DL) or transfer factor for the lung (T1) for carbon monoxide (DLCO) was determined, at rest, by single-breath method in 65 normal subjects ranging in age from 60 to 84 years. The subjects were divided into four groups: 15 male smokers (MS); 20 male non-smokers (MNS); 10 female smokers (FS); 20 female non-smokers (FNS). The DLCO was determined using the "Collins Computerized Modular Lung Analyser". The inspired mixture consisted of 0.3 per cent carbon monoxide, 10.0 per cent helium, 21.0 per cent oxygen and 68.7 per cent nitrogen. The mean values and the standard derivations for DLCO (ml/min/mmHg) were: 23.31 +/- 6.48 in MS; 29.33 +/- 6.27 in MNS; 19.74 +/- 5.87 in FS; 19.55 +/- 4.86 in FNS. The DLCO was found to be dependent upon age and body surface area (BSA). Regression equations for predicting normal DLCO have been determined for every one of the four groups (MS, MNS, FS, FNE). Difference, statistically significant was found for MS as compared to MNS, FS and FNS. Therefore two regression equations for predicting normal DLCO have been determined; one for male smokers (MS) and other for male non-smokers (MNS), female smokers (FS) and female non-smokers (FNS). The regression equation for predicting normal DLCO for male smokers (MS) was: DLCO (ML/min/mmHg) = 9.37 - 0.22 Age (Years) + 19.99 BSA (M2). The regression equation for predicting normal DLCO for male non-smokers (MNS), female smokers (FS) and female non-smokers (FNS) was: DLCO (ml/min/mmHg) = 25.05 - 0.27 Age (Years) + 8.41 BSA (m2).(ABSTRACT TRUNCATED AT 250 WORDS)