title: The Intensity of Voluntary, Induced, and Spontaneous Cough.
abstract: BACKGROUND
  The intensity of cough is an important determinant of cough severity. Few studies have quantified cough intensity in patients with chronic cough with objective measures. We investigated the intensity of voluntary, induced, and spontaneous cough in patients with chronic cough and healthy control subjects.
  
  
  METHODS
  Patients with chronic cough and control subjects underwent physiologic assessment of the intensity of maximum voluntary, capsaicin-induced, and spontaneous cough. Assessments included measurement of gastric pressure (Pga) and esophageal pressure (Pes) during cough, peak cough flow (PCF), expiratory muscle strength (twitch gastric pressure [TwPga]), and cough compression phase duration (CPD). Subjective perception of cough intensity was assessed using a visual analog scale (VAS).
  
  
  RESULTS
  Pes, Pga, and PCF during maximum voluntary cough were significantly greater in patients with chronic cough compared with control subjects (P = .003-.042). There was no difference in TwPga between patients and control subjects. CPD was increased in female patients compared with control subjects (mean ± SD, 0.50 ± 0.22 s vs 0.28 ± 0.17 s; P = .007). Mean ± SD Pes during spontaneous cough was comparable to induced cough (128 ± 28 cm H2O vs 122 ± 37 cm H2O, P = .686) but less than maximum voluntary cough (170 ± 46 cm H2O, P = .020). Median within-subject correlation coefficients between cough intensity VAS and Pes, Pga, and PCF were r = 0.82 to 0.86.
  
  
  CONCLUSIONS
  Maximum voluntary cough intensity was increased in patients with chronic cough compared with control subjects. There was no significant difference in expiratory muscle contractility. Further studies should evaluate the compressive phase of cough in more detail. Physiologic measures of cough intensity correlated strongly with subjective perception of intensity in patients with chronic cough and may be relevant objective outcome measures for clinical studies.
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, King's Health Partners, London, England.
authors.forename: Kai K
authors.initials: KK
authors.lastname: Lee
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, King's Health Partners, London, England.
authors.forename: Katie
authors.initials: K
authors.lastname: Ward
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, King's Health Partners, London, England.
authors.forename: Gerrard F
authors.initials: GF
authors.lastname: Rafferty
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, King's Health Partners, London, England.
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.affiliation: Division of Asthma, Allergy and Lung Biology, King's College London, King's Health Partners, London, England. Electronic address: surinder.birring@nhs.net.
authors.forename: Surinder S
authors.initials: SS
authors.lastname: Birring
mesh_terms: D002908:Chronic Disease; D003371:Cough / Q000175:diagnosis / Q000503:physiopathology*; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D010366:Peak Expiratory Flow Rate; D011312:Pressure; D012132:Respiratory Muscles / Q000503:physiopathology*; D012720:Severity of Illness Index