[The importance of diffusing capacity as a complementary study to plethysmography in smokers].
This study comprised 194 male and female heavy smokers or ex-smokers (>or= 1 pack-year) aged between 20 and 82, whose symptoms varied. Cases were only selected from patients with normal whole-body plethysmography. Subjects with any significant pathology and occupational risk factors were excluded from the study. Varying degrees of symptoms were found and a range of results from normal plethysmography examination, with abnormal levels of alveolar-capillary transfer, determined by the single-breath method to analyse CO (TLCO and TLCO-VA) coefficients. Using the chi-square test for statistical analysis of the sample revealed a significant variation in sensitivity between both parameters (p=0.0001). Possible limitations of using the single-breath method, of were reduced in this study (ventilatory restriction with Vital Capacity <1.5 litres) by the routine plethysmography results seen. Likewise, the presence of alterations in ventilatory distribution was, in principle, minimised by the absence of TLCsb/TLCplet values below 0.85%


CONCLUSIONS
Normal plethysmography results in heavy or ex-smokers are not enough to confirm normal respiratory function, as a large percentage of cases present abnormalities in the alveolar-capillary transfer factor for CO. Alveolar limitation was considered not only anatomically, but also from a functional perspective.
Paes Cardoso
António
A
Human Physiology, Porto University, Instituto de Ciências Biomédicas de Abel Salazar, Santo António Hospital.
Reis Ferreira
José Manuel
JM
Moreira da Silva
Alvaro
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D011653:Pulmonary Diffusing Capacity; D012907:Smoking / Q000503:physiopathology*