title: Effects of emphysema and lung volume reduction surgery on transdiaphragmatic pressure and diaphragm length.
abstract: OBJECTIVE
  To determine the effect of emphysema and lung volume reduction surgery (LVRS) on diaphragm length (Ldi) and its capacity to generate transdiaphragmatic pressure (Pdi).
  
  
  METHODS
  Prospective clinical trial with a parallel group design.
  
  
  METHODS
  Laboratory investigations in normal volunteers recruited by advertisement and in emphysema outpatients being evaluated for elective LVRS.
  
  
  METHODS
  Thirteen normal subjects and 13 emphysema patients matched for age and sex. Six emphysema patients underwent LVRS.
  
  
  METHODS
  Ldi and maximal Pdi during static inspiratory efforts (PdiMax) were measured at three different lung volumes (LVs). Pdi during maximal bilateral phrenic nerve twitch stimulation (PdiTw) was measured at functional residual capacity (FRC). All measurements were repeated at 3, 6, and 12 months postoperatively.
  
  
  RESULTS
  Ldi, PdiMax, and PdiTw were lower in emphysema patients than in normal subjects at their respective LVs. PdiMax and PdiTw at FRC returned within the normal range after LVRS in emphysema patients. The relationships between PdiMax and LV or Ldi were shifted respectively to higher LV and shorter Ldi in emphysema patients relative to normal subjects, both before and after LVRS. LVRS effected craniad displacement of the diaphragm but no change in rib cage dimensions. Improvements in dyspnea and quality of life after LVRS correlated with changes in LV and Ldi but not with changes in airway caliber.
  
  
  CONCLUSIONS
  Adaptive mechanisms, consistent with sarcomere deletion, tend to restore diaphragm strength in emphysema patients at FRC, which are fully expressed after LVRS. Lung remodeling by LVRS may alter pleural surface pressure distribution, causing a sustained change in chest wall shape.
authors.affiliation: Research Center, University of Montreal Health Center, Hôtel-Dieu, Montréal, PQ, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Bellemare
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Cordeau
authors.forename: Jacques
authors.initials: J
authors.lastname: Couture
authors.forename: Edwin
authors.initials: E
authors.lastname: Lafontaine
authors.forename: Pierre
authors.initials: P
authors.lastname: Leblanc
authors.forename: Louise
authors.initials: L
authors.lastname: Passerini
mesh_terms: D003964:Diaphragm / Q000033:anatomy & histology* / Q000502:physiology*; D004646:Emphysema / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011013:Pneumonectomy; D011312:Pressure; D011446:Prospective Studies; D012129:Respiratory Function Tests