title: Perfused lung volume to thoracic gas volume ratio (perfused lung fraction) in patients with COPD and in controls.
abstract: BACKGROUND
  The deterioration of the ventilation-to-perfusion distribution in patients with chronic obstructive pulmonary disease (COPD) reflects structural changes affecting both the airways and the blood vessels. These changes result in lung perfusion abnormalities that may be quantified by lung perfusion single photon emission computed tomography (SPECT).
  
  
  OBJECTIVE
  To compare the perfused lung fraction (PLF) in patients with airflow obstruction and controls.
  
  
  METHODS
  Fourteen patients with COPD and 21 controls underwent spirometry, whole-body plethysmography, and lung perfusion SPECT. PLF was derived from the ratio of perfused lung volume (measured by SPECT) to thoracic gas volume (measured by whole-body plethysmography).
  
  
  RESULTS
  In the whole study sample, there were 18 (51%) women and 17 (49%) men, mean age was 46.2 (±20.3) years, range: 18-80 years). In the COPD group, PLF was 0.74 (±0.08), whereas in the control group PLF was 0.99 (±0.18) (P<0.001). PLF correlated directly with forced expiratory volume in 1 s to forced vital capacity (r=0.597, P<0.001). Perfused lung volume was 3.66 (±0.64) l in the COPD group compared with 2.71 (±0.70) l in the control group (P<0.001).
  
  
  CONCLUSIONS
  The fraction of lung volume receiving blood from the pulmonary artery is reduced in patients with COPD. The degree of underperfusion seems to correlate with the degree of airflow limitation.
authors.affiliation: Department of Nuclear Medicine and Pneumology, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. prmasiero@hotmail.com
authors.forename: Paulo Ricardo
authors.initials: PR
authors.lastname: Masiero
authors.forename: Sergio S
authors.initials: SS
authors.lastname: Menna-Barreto
authors.forename: Maria A F
authors.initials: MA
authors.lastname: Moreira
authors.forename: Marcos Pretto
authors.initials: MP
authors.lastname: Mosmann
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Mayer
authors.forename: Bernardo L
authors.initials: BL
authors.lastname: Spiro
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000402:Airway Obstruction / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology; D001775:Blood Circulation; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010993:Plethysmography, Whole Body; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D012189:Retrospective Studies; D013909:Thorax / Q000503:physiopathology*; D015899:Tomography, Emission-Computed, Single-Photon; D014692:Ventilation-Perfusion Ratio; D055815:Young Adult