An electromyographic method of objectively assessing cough intensity and use of the method to assess effects of codeine on the dose‐response curve to citric acid.

Cox, ID; Wallis, PJ; Apps, MC; Hughes, David J.; Empey, D. W.; Osman, RC; Ca, Burke

doi:10.1111/j.1365-2125.1984.tb02479.x

Cited by 44 publications

(37 citation statements)

References 8 publications

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“…This has also been reported with citric acid [18] and fog [19] in humans. The shape of the dose/response curve is equivocal.…”

Section: Motor Neural Activationsupporting

confidence: 78%

“…In cats, the RA plays a major role in the expulsive phase [7,24], whereas in humans the EO is thought to be the major abdominal muscle [18,19,25]. We did not compare the degree of activation of the IC8, EO or RA, but we do show that the relative increase in activation of these muscle groups was the same with increasing capsaicin concentration.…”

Section: Motor Neural Activationmentioning

confidence: 76%

“…The shape of the dose/response curve is equivocal. Fontana et al [19] report a linear relationship between EO EMG and fog, while Cox et al [18] show an exponential rise in EO EMG with citric acid. Redrawn and modelled with a line of best fit, the data sets, including ours, demonstrate a curvilinear relationship (data not shown).…”

Section: Motor Neural Activationmentioning

confidence: 99%

“…Therefore airflow relates to abdominal muscle activity in health and disease, and both can be used to measure strength of airway defensive behaviours such as cough. However, the correlation between peak airflow and integrated or peak EMG is weak in response to citric acid [18], and negative in response to tartaric acid [10]. Fontana et al [17] show a stronger correlation between rate of rise of EMG to peak airflow compared to peak EMG, suggesting the parameter used to assess EMG activity (i.e.…”

Section: Airway Mechanicsmentioning

confidence: 99%

“…While EMG activity has been recorded in response to citric acid [18], ultrasonically nebulized distilled water [19,20] and tartaric acid [10], and airflow has been assessed in bronchitis [9], the EMG and airflow response has not been evaluated simultaneously in the same subject pool and to the same tussive agent. Thus, direct comparisons of respiratory muscle activation and airway mechanics have not been made.…”

Section: Introductionmentioning

confidence: 99%

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Capsaicin exposure elicits complex airway defensive motor patterns in normal humans in a concentration-dependent manner

Vovk

Bolser

Hey³

et al. 2007

Pulmonary Pharmacology & Therapeutics

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The airway defensive response to tussive agents, such as capsaicin, is frequently assessed by counting the number of cough sounds, or expulsive events. This method does not identify or differentiate important respiratory events that occur in the respiratory muscles and lungs, which are critical in assessing airway defensive responses. The purpose of this study was to characterize the airway defensive behaviours (cough and expiration reflex) to capsaicin exposure in humans. We observed complex motor behaviours in response to capsaicin exposure. These behaviours were defined as cough reacceleration (CRn) and expiration reflex (ERn), where n is the number of expulsive events with and without a preceding inspiratory phase, respectively. Airway defensive responses were defined in terms of frequency (number of expulsive events), strength (activation of abdominal muscles) and behaviour type (CRn vs. ERn). Thirty-six subjects (15 females, 24±4 yr) were instrumented with EMG electrodes placed over the rectus abdominis (RA), external abdominal oblique (EO) and the 8th intercostal space (IC8). A custom-designed mouth pneumotachograph was used to assess the airflow acceleration, plateau velocity and phase duration of the expulsive phase. Subjects inhaled seven concentrations of capsaicin (5-200 μM) in a randomized block order. The total number of expulsive events (frequency) and the sum of integrated EMG for the IC8, RA and EO (strength) increased in a curvilinear fashion. Differentiating the airway defense responses into type demonstrated predominately CR1 and CR2 (i.e. inspiration followed by one and two expulsive events, respectively) with very few ER's at <50 μM capsaicin. At higher concentrations (>50 μM) ER's with one or more expulsive events (≥ER1) appeared, and the number of CR's with three or more expulsive events (≥CR3) increased. The decrease in EMG activation and airflow measurements with each successive expulsive event suggests a decline in power and shear force as the number of expulsive events increased. Therefore, the airway defensive response to capsaicin is a complex motor pattern that functions to coordinate ER's and CR's with differing numbers of expulsive events possibly to prevent aspirations and keep air moving to promote clearance.

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“…This has also been reported with citric acid [18] and fog [19] in humans. The shape of the dose/response curve is equivocal.…”

Section: Motor Neural Activationsupporting

confidence: 78%