title: Hypoxemia in inferior pulmonary veins in supine position is dependent on obesity.
abstract: BACKGROUND
  Although arterial oxygen concentration decreases in obese subjects, the mechanism for this remains to be determined.
  
  
  OBJECTIVE
  The blood gas level in each pulmonary vein (PV) was measured in supine subjects with diverse body mass index (BMI) values, to determine whether there was a regional insufficiency in gas exchange depending on the subject's BMI.
  
  
  METHODS
  Forty subjects with normal cardiopulmonary function who underwent a catheter ablation for atrial fibrillation were included. Before delivering any radiofrequency energy application, blood samples were obtained from each of the four PVs during physiologic breathing in a supine position to measure the PO2 and PCO2 values. Spirometry and ventilation/perfusion lung scintigraphy were also performed.
  
  
  RESULTS
  The PO2 value was significantly higher in superior veins than inferior veins (91.8 +/- 13.5, 70.8 +/- 16.3, 92.2 +/- 11.1, and 73.6 +/- 13.7 mm Hg, in the left superior, left inferior, right superior, and right inferior PV, respectively). There was a significant inverse relationship between the PO2 and PCO2 values. Neither the spirometry nor lung scintigraphy could detect any remarkable findings corresponding to the low PO2 values. Among the various clinical characteristics, only the BMI was significantly associated with the decreased PO2 value in the inferior veins.
  
  
  CONCLUSIONS
  Hypoxia in obese subjects in a supine position is thus considered to be primarily caused by insufficient gas exchange in the regions of lung linked to the inferior PVs. The inverse relationship between the BMI and PO2 value in the inferior PVs suggests a possible subclinical manifestation of obesity-related respiratory insufficiency.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan. yamanet1@aol.com
authors.forename: Teiichi
authors.initials: T
authors.lastname: Yamane
authors.forename: Taro
authors.initials: T
authors.lastname: Date
authors.forename: Michifumi
authors.initials: M
authors.lastname: Tokuda
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Aramaki
authors.forename: Keiichi
authors.initials: K
authors.lastname: Inada
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Matsuo
authors.forename: Kenri
authors.initials: K
authors.lastname: Shibayama
authors.forename: Satoru
authors.initials: S
authors.lastname: Miyanaga
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Miyazaki
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Michihiro
authors.initials: M
authors.lastname: Yoshimura
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000628:therapy; D001784:Blood Gas Analysis; D015992:Body Mass Index; D017115:Catheter Ablation; D015331:Cohort Studies; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D011667:Pulmonary Veins / Q000503:physiopathology*; D016683:Supine Position