title: Inspiratory drive is related to dynamic pulmonary hyperinflation in COPD patients.
abstract: BACKGROUND
  Baseline high neuromuscular drive is present in chronic obstructive pulmonary disease (COPD). In moderate-to-very severe COPD patients, both static and/or dynamic pulmonary hyperinflation have been demonstrated at rest.
  
  
  OBJECTIVE
  To assess the influence of dynamic hyperinflation on neuromuscular drive at rest.
  
  
  METHODS
  We recruited 22 patients with severe-to-very severe COPD showing resting dynamic pulmonary hyperinflation, as assessed by the baseline reduction of inspiratory capacity (IC) (<80% of predicted). IC, occlusion pressure (P₀.₁), maximal inspiratory pressure (MIP), and their ratio were measured at end-expiratory lung volume (EELV) before and after acute inhalation of 400 mcg of albuterol (metered-dose inhaler plus spacer). In these patients the bronchodilator response was assessed also as lung volume changes.
  
  
  RESULTS
  Only in COPD patients with a marked increase in IC (>12% of baseline and at least 200 mL) after bronchodilator, resting P0.1 showed a clinically significant decrease, despite the EELV diminution (P < 0.001). MIP was augmented following EELV reduction and therefore the P₀.₁/MIP ratio was markedly decreased (P < 0.001). In contrast, no changes in these indices were found after bronchodilator in COPD patients with insignificant variations of IC. Breathing pattern parameters did not vary in both sub-groups after albuterol.
  
  
  CONCLUSIONS
  Following bronchodilator, significant P₀.₁ decrease, MIP increase, and reduction of the P₀.₁/MIP ratio were found only in COPD patients with a marked IC increase and these changes were closely related. These findings suggest that bronchodilators, by decreasing dynamic hyperinflation, may control exertional and/or chronic dyspnea partly through a reduction of central neuromuscular drive.
authors.affiliation: Respiratory Medicine Unit, Department of Medical and Surgical Sciences, University of Brescia, Brescia, Italy.
authors.forename: Diego
authors.initials: D
authors.lastname: Gatta
authors.forename: Marco
authors.initials: M
authors.lastname: Fredi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Aliprandi
authors.forename: Laura
authors.initials: L
authors.lastname: Pini
authors.forename: Claudio
authors.initials: C
authors.lastname: Tantucci
mesh_terms: D000368:Aged; D000420:Albuterol / Q000627:therapeutic use; D001993:Bronchodilator Agents / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D036501:Metered Dose Inhalers; D009469:Neuromuscular Junction / Q000502:physiology; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy / Q000503:physiopathology*; D012132:Respiratory Muscles / Q000502:physiology; D012720:Severity of Illness Index
chemical_list: D001993:Bronchodilator Agents; D000420:Albuterol
keywords: bronchodilators; chronic obstructive pulmonary disease; control of breathing; dynamic hyperinflation; inspiratory muscles