Short reflex expirations (expiration reflexes) induced by mechanical stimulation of the trachea in anesthetized cats

Abstract

Fifty spontaneously breathing pentobarbital-anesthetized cats were used to determine the incidence rate and parameters of short reflex expirations induced by mechanical stimulation of the tracheal mucosa (ERt). The mechanical stimuli evoked coughs; in addition, 67.6% of the stimulation trials began with ERt. The expiration reflex mechanically induced from the glottis (ERg) was also analyzed (99.5% incidence, p < 0.001 compared to the incidence of ERt). We found that the amplitudes of abdominal, laryngeal abductor posterior cricoarytenoid, and laryngeal adductor thyroarytenoid electromyograms (EMG) were significantly enhanced in ERg relative to ERt. Peak intrathoracic pressure (esophageal or intra-pleural pressure) was higher during ERg than ERt. The interval between the peak in EMG activity of the posterior cricoarytenoid muscle and that of the EMG of abdominal muscles was lower in ERt compared to ERg. The duration of thyroarytenoid EMG activity associated with ERt was shorter than that in ERg. All other temporal features of the pattern of abdominal, posterior cricoarytenoid, and thyroarytenoid muscles EMGs were equivalent in ERt and ERg.In an additional 8 cats, the effect of codeine administered via the vertebral artery was tested. Codeine, in a dose (0.03 mg/kg) that markedly suppressed cough did not significantly alter either the incidence rate or magnitudes of ERt.In the anesthetized cat the ERt induced by mechanical stimulation of the trachea was similar to the ERg from the glottis. These two reflex responses differ substantially only in the frequency of occurrence in response to mechanical stimulus and in the intensity of motor output.

Brainstem mechanisms underlying the cough reflex and its regulation

“…These features separated cough from other airway defensive reflexes such as the expiration reflex (e.g. Poliacek et al, 2008b). This topic along with the techniques employed and, in particular, recordings from medullary neurons and drug microinjections have been fully described in our reports (see e.g.…”

“…The expiration reflex closely resembles cough responses, but it consists of a pure expiratory effort evoked by the mechanical stimulation of the vocal fold mucosa in the absence of a preparatory inspiratory phase (Korpáš and Tomori, 1979;Korpas and Jakus, 2000;Sant'Ambrogio and Widdicombe, 2001). The expiration reflex can be also evoked by the stimulation of the tracheobronchial tree (Widdicombe 1954;Tatar et al, 2008;Poliacek et al, 2008b). Glottal closure and the expiration reflex may be regarded as the first level of airway defense since they prevent penetration of foreign bodies into the airways.…”

Role of the dorsomedial medulla in suppression of cough by codeine in cats

“…These criteria separate cough from other defensive airway behaviors such as expiration reflex (Poliacek et al, 2008) or swallow (Pitts et al, 2013). …”

Voluntary and reflex cough and the expiration reflex; implications for aspiration after stroke

“…There is no preliminary inspiration before the ER; this would invalidate its function which is to prevent solid or liquid material from entering the lungs, although after the bout of expiratory efforts there will be a compensatory inspiration. The ER can be elicited from the trachea (TER) [30,31], but here we will consider only the laryngeal ER (LER) which has an anti-aspiration effect.…”