title: Lung structure and gas exchange in mild chronic obstructive pulmonary disease.
abstract: To investigate the influence of pulmonary emphysema and small airways abnormalities on ventilation-perfusion (VA/Q) mismatching in mild chronic obstructive pulmonary disease (COPD), we studied 23 patients (mean predicted FEV1, 76 +/- 15%) before lung resection because of a localized neoplasm. Respiratory gas exchange and VA/Q distributions were measured while the patients breathed room air and 100% O2. Breathing room air, the AaPO2 was moderately increased (25 +/- 12 mm Hg) as was VA/Q mismatching, indicated by the dispersion (log SD) of both blood flow (Q) and ventilation (V) distributions (log SD Q, 0.78 +/- 0.3; and log SD V, 0.66 +/- 0.28, respectively) (normal range, 0.3-0.6). AaPO2, log SD Q, and log SD V all significantly correlated with the emphysema severity assessed morphologically from the resected lung specimens (r = 0.57, r = 0.62, and r = 0.45, respectively). Log SD V also significantly correlated with the severity of the inflammatory infiltrate of membranous bronchioles (r = 0.62). During 100% O2 breathing there was an increase in VA/Q mismatching (log SD Q rose to 1.12 +/- 0.08, p less than 0.001), suggesting release of hypoxic pulmonary vasoconstriction. This increase in VA/Q inequality was not significantly related to the severity of lung pathologic findings. We conclude that, in mild COPD, both pulmonary emphysema and small airways abnormalities contribute to VA/Q mismatch, the severity of emphysema being the major morphologic correlate of the increase in AaPO2.
authors.affiliation: Department of Medicine, Hospital Clínic, Facultat de Medicina, Universitat de Barcelona, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Barbera
authors.forename: J
authors.initials: J
authors.lastname: Ramirez
authors.forename: J
authors.initials: J
authors.lastname: Roca
authors.forename: P D
authors.initials: PD
authors.lastname: Wagner
authors.forename: J
authors.initials: J
authors.lastname: Sanchez-Lloret
authors.forename: R
authors.initials: R
authors.lastname: Rodriguez-Roisin
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008168:Lung / Q000473:pathology*; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood / Q000502:physiology; D011656:Pulmonary Emphysema / Q000473:pathology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012129:Respiratory Function Tests
chemical_list: D010100:Oxygen