Measurements of membrane diffusing capacity and pulmonary capillary blood volume in normal subjects and patients with mild emphysema.
OBJECTIVE
To establish predicted values of membrane diffusing capacity (Dm) and pulmonary capacity blood volume (Vc), to compare the predicted values from our equations with those for Caucasians, to determine whether there are changes initially in Dm or Vc in patients with mild emphysema.


METHODS
Diffusing capacity for carbon monoxide (DLco), Dm and Vc were determined in 86 normal subjects and 16 patients using the single-breath diffusing capacity for carbon monoxide (DLcosB) with two different alveolar concentrations of oxygen.


RESULTS
The predicted equations are as follows. For males, DLco (ml/min/mm Hg) = 0.37H-0.19A-27.8; Dm (ml/min/mm Hg) = 0.65H-0.24A-53.7; Vc(ml) = 0.88H-78.9. For females, DLco = 0.28H-22.7; Dm = 0.59H-53.6; Vc = 66.6-0.36A. DLco and Vc are lower in Chinese than Caucasians while Dm is similar in Chinese and Caucasians. Eleven of 16 patients had a low DLco (< 80% predicted value), 12 had a low Dm and 5 had a low Vc. Eight of 12 patients with a low Dm also had a low DLco, but in 4 the DLco was normal. Nine of 12 with low Dm had a normal Vc.


CONCLUSIONS
This study provides prediction equations of Dm and Vc. Chinese have a low DLco because their Vc is lower than Caucasians. The DLco and Dm are abnormal in a comparable percentage of patients. In patients with mild emphysema, the Dm becomes abnormal before the Vc.
Xie
C
C
Department of Pulmonary Medicine, First Affiliated Hospital of Sun Yat-sen University of Medical Sciences, Guangzhou.
Rong
Z
Z
Li
Z
Z
Yan
Y
Y
Light
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D000293:Adolescent; D000328:Adult; D000368:Aged; D044466:Asian People; D001810:Blood Volume; D001991:Bronchitis / Q000150:complications; D002196:Capillaries; D002908:Chronic Disease; D005260:Female; D006801:Humans; D008168:Lung / Q000098:blood supply* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011653:Pulmonary Diffusing Capacity; D011656:Pulmonary Emphysema / Q000209:etiology / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D044465:White People