title: Effect of heliox breathing on dynamic hyperinflation in COPD patients.
abstract: BACKGROUND
  and objective: Patients with COPD exhibit increased inspiratory work and dyspnea due to dynamic hyperinflation caused by expiratory flow limitation. Helium-oxygen mixtures (ie, heliox) have been used in treating these patients on the assumption that, by lowering airway resistance, they might be beneficial.
  
  
  METHODS
  In 22 patients with COPD, the presence of expiratory flow limitation was assessed with patients in the sitting and supine positions using the negative expiratory pressure technique, and the effects of heliox (80% He, 20% O2) on breathing pattern, expiratory flow limitation, and dynamic hyperinflation, evaluated from the change in inspiratory capacity (IC), were measured at rest and were compared with those due to inhaled salbutamol.
  
  
  RESULTS
  During air breathing, 13 patients experienced flow limitation while in the sitting position and 18 experienced flow limitation while in the supine position. Neither heliox nor salbutamol therapy changed the breathing pattern in any of the patients, regardless of posture and the presence or absence of expiratory flow limitation. However, in both positions IC increased significantly in most flow-limited patients after bronchodilator administration, but not after heliox administration.
  
  
  CONCLUSIONS
  Since heliox had no effect on dynamic hyperinflation, the use of this gas mixture, which is costly and cumbersome, does not appear to be beneficial in stable patients with COPD breathing at rest.
authors.affiliation: Istituto di Fisiologia Umana I, Università di Milano, Milan, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Pecchiari
authors.forename: Andrea
authors.initials: A
authors.lastname: Pelucchi
authors.forename: Emanuela
authors.initials: E
authors.lastname: D'Angelo
authors.forename: Antonio
authors.initials: A
authors.lastname: Foresi
authors.forename: Joseph
authors.initials: J
authors.lastname: Milic-Emili
authors.forename: Edgardo
authors.initials: E
authors.lastname: D'Angelo
mesh_terms: D000368:Aged; D000403:Airway Resistance / Q000187:drug effects*; D000420:Albuterol / Q000008:administration & dosage*; D001993:Bronchodilator Agents / Q000008:administration & dosage; D005260:Female; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D007320:Inspiratory Capacity / Q000187:drug effects*; D008297:Male; D010100:Oxygen / Q000008:administration & dosage*; D011187:Posture; D011336:Probability; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000628:therapy*; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013147:Spirometry; D013990:Tidal Volume
chemical_list: D001993:Bronchodilator Agents; D006371:Helium; C038949:heliox; D000420:Albuterol; D010100:Oxygen