title: Weight gain after lung reduction surgery is related to improved lung function and ventilatory efficiency.
abstract: BACKGROUND
  Lung volume reduction surgery (LVRS) is associated with weight gain in some patients, but the group that gains weight after LVRS and the mechanisms underlying this phenomenon have not been well characterized.
  
  
  OBJECTIVE
  To describe the weight change profiles of LVRS patients enrolled in the National Emphysema Treatment Trial (NETT) and to correlate alterations in lung physiological parameters with changes in weight.
  
  
  METHODS
  We divided 1,077 non-high-risk patients in the NETT into groups according to baseline body mass index (BMI): underweight (<21 kg/m(2)), normal weight (21-25 kg/m(2)), overweight (25-30 kg/m(2)), and obese (>30 kg/m(2)). We compared BMI groups and LVRS and medical groups within each BMI stratum with respect to baseline characteristics and percent change in BMI (%ΔBMI) from baseline. We examined patients with (ΔBMI ≥ 5%) and without (ΔBMI < 5%) significant weight gain at 6 months and assessed changes in lung function and ventilatory efficiency (Ve/Vco(2)).
  
  
  RESULTS
  The percent change in BMI was greater in the LVRS arm than in the medical arm in the underweight and normal weight groups at all follow-up time points, and at 12 and 24 months in the overweight group. In the LVRS group, patients with ΔBMI ≥ 5% at 6 months had greater improvements in FEV(1) (11.53 ± 9.31 vs. 6.58 ± 8.68%; P < 0.0001), FVC (17.51 ± 15.20 vs. 7.55 ± 14.88%; P < 0.0001), residual volume (-66.20 ± 40.26 vs. -47.06 ± 39.87%; P < 0.0001), 6-minute walk distance (38.70 ± 69.57 vs. 7.57 ± 73.37 m; P < 0.0001), maximal expiratory pressures (12.73 ± 49.08 vs. 3.54 ± 32.22; P = 0.0205), and Ve/Vco(2) (-1.58 ± 6.20 vs. 0.22 ± 8.20; P = 0.0306) at 6 months than patients with ΔBMI < 5% at 6 months.
  
  
  CONCLUSIONS
  LVRS leads to weight gain in nonobese patients, which is associated with improvement in lung function, exercise capacity, respiratory muscle strength, and ventilatory efficiency. These physiological changes may be partially responsible for weight gain in patients who undergo LVRS.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Temple University School of Medicine, 785 Parkinson Pavilion, 3401 North Broad Street, Philadelphia, PA 19140, USA. victor.kim@tuhs.temple.edu
authors.forename: Victor
authors.initials: V
authors.lastname: Kim
authors.forename: Dana M
authors.initials: DM
authors.lastname: Kretschman
authors.forename: Alice L
authors.initials: AL
authors.lastname: Sternberg
authors.forename: Malcolm M
authors.initials: MM
authors.lastname: DeCamp
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Criner
mesh_terms: D000368:Aged; D015992:Body Mass Index; D001835:Body Weight; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D015999:Multivariate Analysis; D016017:Odds Ratio; D011013:Pneumonectomy / Q000379:methods*; D011182:Postoperative Care / Q000379:methods; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D011788:Quality of Life; D012016:Reference Values; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D015996:Survival Rate; D014109:Total Lung Capacity / Q000502:physiology*; D016896:Treatment Outcome; D015430:Weight Gain / Q000502:physiology*