title: Effect of Weight Loss on Postural Changes in Pulmonary Function in Obese Subjects: A Longitudinal Study.
abstract: BACKGROUND
  Postural changes are known to affect normal lung volumes. A reduction in sitting to supine functional residual capacity (FRC) is well-described in non-obese subjects adopting a supine position. However, postural changes in lung volumes in the obese require further exploration. We aimed to longitudinally address the effects of weight loss on postural changes in lung volumes and pulmonary function in obese subjects. We tested the hypothesis that supine reduction in FRC would be absent in morbid obesity and recovered upon weight loss.
  
  
  METHODS
  This was a prospective, observational, longitudinal study. Consecutive morbidly obese adults (N = 12, age: 44 ± 14 y, body mass index: 45 ± 5 kg/m(2)) enrolled in a bariatric surgery program were included. Standard pulmonary function tests and blood gas analysis were performed both before and 1 y after surgery. Pulmonary function was assessed in both the sitting and supine position using spirometry and multi-breath helium dilution. Parameters recorded before and after weight loss were compared. The main outcome measure was FRC.
  
  
  RESULTS
  Ten subjects were retested 1 y after surgery (body mass index: 31 ± 5 kg/m(2)). FRC was not affected by change in posture before surgery. Supine reduction in FRC was observed after weight loss (ΔFRC: -0.6 ± 0.4 L, sitting vs supine, P = .002). Pulmonary gas exchange improved (alveolar-to-arterial oxygen partial pressure difference: -8 ± 11 mm Hg, P = .035).
  
  
  CONCLUSIONS
  Although postural change in FRC is absent when the morbidly obese adopt a supine position, supine reduction in FRC can be recovered following gastroplasty-induced weight loss, despite residual mild to moderate obesity. This also shows that mild to moderate obesity may affect supine FRC more than morbid obesity. (ClinicalTrials.gov registration NCT02207192.).
authors: Département des Urgences, Hôpital Lapeyronie m-sebbane@chu-montpellier.fr.
authors: Mustapha
authors: M
authors: Sebbane
authors: Département d'Anesthésie-Réanimation B, Hôpital St Eloi.
authors: Moez
authors: M
authors: El Kamel
authors: Département d'Anesthésie-Réanimation B, Hôpital St Eloi.
authors: Alice
authors: A
authors: Millot
authors: Département d'Anesthésie-Réanimation B, Hôpital St Eloi PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, CHRU de Montpellier, Montpellier, France.
authors: Boris
authors: B
authors: Jung
authors: Département des Urgences, Hôpital Lapeyronie.
authors: Sophie
authors: S
authors: Lefebvre
authors: Département des Urgences, Hôpital Lapeyronie.
authors: Josh
authors: J
authors: Rubenovitch
authors: Département d'Information Médicale, Hôpital Lapeyronie.
authors: Grégoire
authors: G
authors: Mercier
authors: Département des Urgences, Hôpital Lapeyronie.
authors: Jean-Jacques
authors: JJ
authors: Eledjam
authors: Département d'Anesthésie-Réanimation B, Hôpital St Eloi PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, CHRU de Montpellier, Montpellier, France.
authors: Samir
authors: S
authors: Jaber
authors: PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, CHRU de Montpellier, Montpellier, France.
authors: Maurice
authors: M
authors: Hayot
mesh_terms: D000293:Adolescent; D000328:Adult; D050110:Bariatric Surgery; D001784:Blood Gas Analysis; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000097:blood / Q000503:physiopathology* / Q000601:surgery; D011184:Postoperative Period; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D013147:Spirometry; D015431:Weight Loss / Q000502:physiology*; D055815:Young Adult
keywords: bariatric surgery; functional residual capacity; lung function; obesity; postural change; pulmonary function test; weight loss