title: Pulmonary Vascular Congestion: A Mechanism for Distal Lung Unit Dysfunction in Obesity.
abstract: BACKGROUND
  Obesity is characterized by increased systemic and pulmonary blood volumes (pulmonary vascular congestion). Concomitant abnormal alveolar membrane diffusion suggests subclinical interstitial edema. In this setting, functional abnormalities should encompass the entire distal lung including the airways.
  
  
  OBJECTIVE
  We hypothesize that in obesity: 1) pulmonary vascular congestion will affect the distal lung unit with concordant alveolar membrane and distal airway abnormalities; and 2) the degree of pulmonary congestion and membrane dysfunction will relate to the cardiac response.
  
  
  METHODS
  54 non-smoking obese subjects underwent spirometry, impulse oscillometry (IOS), diffusion capacity (DLCO) with partition into membrane diffusion (DM) and capillary blood volume (VC), and cardiac MRI (n = 24). Alveolar-capillary membrane efficiency was assessed by calculation of DM/VC.
  
  
  RESULTS
  Mean age was 45±12 years; mean BMI was 44.8±7 kg/m2. Vital capacity was 88±13% predicted with reduction in functional residual capacity (58±12% predicted). Despite normal DLCO (98±18% predicted), VC was elevated (135±31% predicted) while DM averaged 94±22% predicted. DM/VC varied from 0.4 to 1.4 with high values reflecting recruitment of alveolar membrane and low values indicating alveolar membrane dysfunction. The most abnormal IOS (R5 and X5) occurred in subjects with lowest DM/VC (r2 = 0.31, p<0.001; r2 = 0.34, p<0.001). Cardiac output and index (cardiac output / body surface area) were directly related to DM/VC (r2 = 0.41, p<0.001; r2 = 0.19, p = 0.03). Subjects with lower DM/VC demonstrated a cardiac output that remained in the normal range despite presence of obesity.
  
  
  CONCLUSIONS
  Global dysfunction of the distal lung (alveolar membrane and distal airway) is associated with pulmonary vascular congestion and failure to achieve the high output state of obesity. Pulmonary vascular congestion and consequent fluid transudation and/or alterations in the structure of the alveolar capillary membrane may be considered often unrecognized causes of airway dysfunction in obesity.
authors.affiliation: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Bellevue Hospital/New York University School of Medicine, New York, NY, United States of America.
authors.forename: Beno W
authors.initials: BW
authors.lastname: Oppenheimer
authors.affiliation: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Bellevue Hospital/New York University School of Medicine, New York, NY, United States of America.
authors.forename: Kenneth I
authors.initials: KI
authors.lastname: Berger
authors.affiliation: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Bellevue Hospital/New York University School of Medicine, New York, NY, United States of America.
authors.forename: Saleem
authors.initials: S
authors.lastname: Ali
authors.affiliation: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Bellevue Hospital/New York University School of Medicine, New York, NY, United States of America.
authors.forename: Leopoldo N
authors.initials: LN
authors.lastname: Segal
authors.affiliation: Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Donnino
authors.affiliation: Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY, United States of America.
authors.forename: Stuart
authors.initials: S
authors.lastname: Katz
authors.affiliation: Bellevue Hospital Bariatric Center, Department of Surgery, New York University School of Medicine, New York, NY, United States of America.
authors.forename: Manish
authors.initials: M
authors.lastname: Parikh
authors.affiliation: André Cournand Pulmonary Physiology Laboratory, Division of Pulmonary, Critical Care and Sleep, Bellevue Hospital/New York University School of Medicine, New York, NY, United States of America.
authors.forename: Roberta M
authors.initials: RM
authors.lastname: Goldring
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008168:Lung / Q000098:blood supply* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000503:physiopathology*