title: Gas diffusion and alveolar-capillary unit in chronic heart failure.
abstract: OBJECTIVE
  Alveolar gas diffusion (DLCO) is impaired in chronic heart failure (CHF). Diffusion depends on membrane diffusion (DM) and the amount of blood participating in gas exchange (VC). How DM, VC, and the alveolar-capillary unit behave in relationship to CHF severity is unknown.
  
  
  RESULTS
  We measured pulmonary function, including DLCO, DM, VC, and alveolar volume (VA), in 191 CHF patients in NYHA class I-III. CHF patients were grouped accordingly to peak exercise oxygen uptake (pVO(2)): group <12 mL/min/kg (n=24), group 12-16 (n=76), group 16-20 (n=64), and group >20 (n=27). DLCO, DM, VC, and VA were lowest in severe CHF and were linearly related to pVO(2) (DLCO, r=0.577, P<0.001; DM, r=0.490, P<0.001; VC, r=0.216, P<0.01; VA, r=0.565, P<0.01). DM/VC ratio, an index of the alveolar-capillary unit efficiency, was higher in group <12 (0.49+/-0.39 mL/min/mmHg/mL) and >20 (0.46+/-0.29), compared with 12-16 (0.34+/-0.19) and 16-20 (0.35+/-0.17).
  
  
  CONCLUSIONS
  DLCO progressively worsens as CHF severity increases due to reduction in lung tissue participating to gas exchange (low VC and VA). In severe CHF, the few working alveolar-capillary units are the most efficient as shown by the high DM/VC. This is useful for maintaining gas exchange efficiency in severe CHF.
authors.affiliation: Centro Cardiologico Monzino, IRCCS, Istituto di Cardiologia, Università di Milano, via Parea 4, 20138 Milan, Italy. piergiuseppe.agostoni@ccfm.it
authors.forename: Piergiuseppe
authors.initials: P
authors.lastname: Agostoni
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bussotti
authors.forename: Gaia
authors.initials: G
authors.lastname: Cattadori
authors.forename: Eliana
authors.initials: E
authors.lastname: Margutti
authors.forename: Mauro
authors.initials: M
authors.lastname: Contini
authors.forename: Manuela
authors.initials: M
authors.lastname: Muratori
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Marenzi
authors.forename: Cesare
authors.initials: C
authors.lastname: Fiorentini
mesh_terms: D002196:Capillaries / Q000502:physiology*; D002908:Chronic Disease; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000502:physiology*; D011653:Pulmonary Diffusing Capacity / Q000502:physiology*; D012129:Respiratory Function Tests