title: Dynamic laryngeal narrowing during exercise: a mechanism for generating intrinsic PEEP in COPD?
abstract: BACKGROUND
  Patients with COPD commonly exhibit pursed-lip breathing during exercise, a strategy that, by increasing intrinsic positive end-expiratory pressure, may optimise lung mechanics and exercise tolerance. A similar role for laryngeal narrowing in modulating exercise airways resistance and the respiratory cycle volume-time course is postulated, yet remains unstudied in COPD. The aim of this study was to assess the characteristics of laryngeal narrowing and its role in exercise intolerance and dynamic hyperinflation in COPD.
  
  
  METHODS
  We studied 19 patients (n=8 mild-moderate; n=11 severe COPD) and healthy age and sex matched controls (n=11). Baseline physiological characteristics and clinical status were assessed prior to an incremental maximal cardiopulmonary exercise test with continuous laryngoscopy. Laryngeal narrowing measures were calculated at the glottic and supra-glottic aperture at rest and peak exercise.
  
  
  RESULTS
  At rest, expiratory laryngeal narrowing was pronounced at the glottic level in patients and related to FEV1 in the whole cohort (r=-0.71, p<0.001) and patients alone (r=-0.53, p=0.018). During exercise, glottic narrowing was inversely related to peak ventilation in all subjects (r=-0.55, p=0.0015) and patients (r=-0.71, p<0.001) and peak exercise tidal volume (r=-0.58, p=0.0062 and r=-0.55, p=0.0076, respectively). Exercise glottic narrowing was also inversely related to peak oxygen uptake (% predicted) in all subjects (r=-0.65, p<0.001) and patients considered alone (r=-0.58, p=0.014). Exercise inspiratory duty cycle was related to exercise glottic narrowing for all subjects (r=-0.69, p<0.001) and patients (r=-0.62, p<0.001).
  
  
  CONCLUSIONS
  Dynamic laryngeal narrowing during expiration is prevalent in patients with COPD and is related to disease severity, respiratory duty cycle and exercise capacity.
authors.affiliation: Department of Respiratory Medicine, Royal Brompton Hospital, London, UK NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK Departamento Clinico de Medicina, Hospital de Clinicas, Facultad de Medicina, Universidad de la Republica, Montevideo, Uruguay.
authors.forename: M
authors.initials: M
authors.lastname: Baz
authors.affiliation: Department of Respiratory Medicine, Royal Brompton Hospital, London, UK NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: G S
authors.initials: GS
authors.lastname: Haji
authors.affiliation: Department of Respiratory Medicine, Royal Brompton Hospital, London, UK NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Menzies-Gow
authors.affiliation: Department of Respiratory Medicine, Royal Brompton Hospital, London, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Tanner
authors.affiliation: Department of Respiratory Medicine, Royal Brompton Hospital, London, UK NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: N S
authors.identifier: http://orcid.org/0000-0003-3235-0454
authors.initials: NS
authors.lastname: Hopkinson
authors.affiliation: Department of Respiratory Medicine, Royal Brompton Hospital, London, UK NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: M I
authors.initials: MI
authors.lastname: Polkey
authors.affiliation: Department of Respiratory Medicine, Royal Brompton Hospital, London, UK NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: J H
authors.initials: JH
authors.lastname: Hull
mesh_terms: D000403:Airway Resistance; D016022:Case-Control Studies; D005080:Exercise Test; D017079:Exercise Tolerance; D045853:Exhalation / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D005931:Glottis / Q000503:physiopathology*; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D018467:Positive-Pressure Respiration, Intrinsic / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012123:Pulmonary Ventilation; D013990:Tidal Volume
keywords: COPD ÀÜ Mechanisms; Exercise; Respiratory Measurement