title: A pilot study of expiratory flow limitation and lung volume reduction surgery.
abstract: OBJECTIVE
  To examine the relationships between changes in expiratory flow limitation (FL) during anesthesia and postoperative responses to lung volume reduction surgery (LVRS).
  
  
  METHODS
  Prospective consecutive case comparison.
  
  
  METHODS
  University medical center.
  
  
  METHODS
  Eight patients with severe emphysema.
  
  
  METHODS
  General anesthesia with muscle paralysis and thoracic epidural analgesia were provided for LVRS via median sternotomy.
  
  
  METHODS
  FEV(1), functional residual capacity (FRC), and total lung capacity (TLC) were measured preoperatively and 3 months postoperatively. Tidal volume (VT) flow/volume (F/V) curves were obtained with a Pitot-type spirometer. VT, expiratory flow rate at 0. 25 x VT (V'VT,25% ), and peak expiratory flow rate (V'VT,MAX) were obtained from VT F/V curves to derive V'VT,25%/V'VT,MAX ratio as a measure of FL.
  
  
  RESULTS
  Closed chest VT F/V curves during anesthesia pre-LVRS showed four patients with FL (group A) whose V'VT,25%/V'VT, MAX ratio was 0.38 +/- 0.06 (mean +/- SD) and four patients without FL (group B) whose V'VT,25%/V'VT,MAX ratio was 0.82 +/- 0.06 (p = 0. 0001). Closed chest post-LVRS V'VT,25%/V'VT,MAX ratio during anesthesia increased by 0.48 +/- 0.08 in group A, compared with a 0. 19 +/- 0.16 reduction in group B (p = 0.0001). Preoperative FEV(1) was 0.57 +/- 0.10 L for group A vs 0.82 +/- 0.13 L for group B (p = 0.02). Postoperative FEV(1) increased by 67 +/- 40% for group A (p = 0.03) vs 29 +/- 21% for group B (not significant). FRC decreased by 33 +/- 3% for group A vs 17 +/- 5% for group B (p = 0.0007), and FRC/TLC decreased by 0.14 +/- 0.05 for group A vs 0.01 +/- 0.07 for group B (p = 0.026). Post-LVRS V'VT,25%/V'VT,MAX ratio change during anesthesia correlated with postoperative reduction in FRC (r(2) = 0. 89, p = 0.0004) and FRC/TLC (r(2) = 0.52, p = 0.045).
  
  
  CONCLUSIONS
  Post-LVRS change in V'VT,25%/V'VT,MAX ratio during anesthesia showed a linear relationship with 3-month postoperative improvement in dynamic hyperinflation. Thus, V'VT,25%/V'VT,MAX ratio may help provide valuable insights into the interactions between chest wall recoil, dynamic hyperinflation, and VT flow rates in patients with severe COPD and LVRS.
authors.affiliation: Department of Anesthesiology, University of California, San Diego and Veterans Affairs Medical Center, San Diego, CA, USA. rdueck@ucsd.edu
authors.forename: R
authors.initials: R
authors.lastname: Dueck
authors.forename: S
authors.initials: S
authors.lastname: Cooper
authors.forename: D
authors.initials: D
authors.lastname: Kapelanski
authors.forename: H
authors.initials: H
authors.lastname: Colt
authors.forename: J
authors.initials: J
authors.lastname: Clausen
mesh_terms: D000368:Aged; D000767:Anesthesia, Epidural; D005260:Female; D005540:Forced Expiratory Flow Rates; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011013:Pneumonectomy; D011184:Postoperative Period; D011446:Prospective Studies; D011656:Pulmonary Emphysema / Q000601:surgery*; D012129:Respiratory Function Tests