title: Defining hyperinflation as 'dynamic': moving toward the slope.
abstract: Measuring the severity of dynamic hyperinflation is a useful clinical approach to assess the effect of therapeutic interventions and explain their impact on exercise tolerance. Dynamic hyperinflation is typically quantified by the change in end expiratory lung volume from rest to the end of exercise. The result may be inconsistent with disease severity and does not clearly explain how exercise tolerance improves with therapy. Using a re-examination of selected studies, we suggest an operational definition of dynamic hyperinflation using the slope derived from serial measures of inspiratory capacity expressed as a linear function of ventilation that clearly differentiates whether therapies affect static or dynamic hyperinflation or affect lung volume only as a consequence of reducing ventilation. With this approach, the magnitude of the result is consistent with disease severity and is a more reliable outcome as it uses serial measures rather than a single time point estimate. The therapies re-evaluated are breathing helium or hyperoxic gas mixtures, bronchodilation and exercise training. A clear definition of dynamic hyperinflation will assist clinicians in assessing the impact of therapeutic interventions.
authors.affiliation: Department of Respiratory Medicine, West Park Healthcare Centre, Toronto M6M 2J5, Canada.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Dolmage
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Evans
authors.forename: Roger S
authors.initials: RS
authors.lastname: Goldstein
mesh_terms: D001993:Bronchodilator Agents / Q000627:therapeutic use; D005081:Exercise Therapy; D017079:Exercise Tolerance / Q000502:physiology; D006371:Helium / Q000627:therapeutic use; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology; D008173:Lung Diseases, Obstructive / Q000503:physiopathology* / Q000628:therapy*; D008176:Lung Volume Measurements / Q000379:methods; D010102:Oxygen Inhalation Therapy; D015656:Respiratory Mechanics / Q000502:physiology*; D009626:Terminology as Topic; D016896:Treatment Outcome
chemical_list: D001993:Bronchodilator Agents; D006371:Helium