The course of lung inflation alters the central pattern of tracheobronchial cough in cat—The evidence for volume feedback during cough

Abstract

The effect of volume-related feedback and output airflow resistance on the cough motor pattern was studied in 17 pentobarbital anesthetized spontaneously-breathing cats. Lung inflation during tracheobronchial cough was ventilator controlled and triggered by the diaphragm electromyographic (EMG) signal. Altered lung inflations during cough resulted in modified cough motor drive and temporal features of coughing. When tidal volume was delivered (via the ventilator) there was a significant increase in the inspiratory and expiratory cough drive (esophageal pressures and EMG amplitudes), inspiratory phase duration (CTI), total cough cycle duration, and the duration of all cough related EMGs (Tactive). When the cough volume was delivered (via the ventilator) during the first half of inspiratory period (at CTI/2 - early over inflation), there was a significant reduction in the inspiratory and expiratory EMG amplitude, peak inspiratory esophageal pressure, CTI, and the overlap between inspiratory and expiratory EMG activity. Additionally, there was significant increase in the interval between the maximum inspiratory and expiratory EMG activity and the active portion of the expiratory phase (CTE1). Control inflations coughs and control coughs with additional expiratory resistance had increased maximum expiratory esophageal pressure and prolonged CTE1, the duration of cough abdominal activity, and Tactive. There was no significant difference in control coughing and/or control coughing when sham ventilation was employed. In conclusion, modified lung inflations during coughing and/or additional expiratory airflow resistance altered the spatio-temporal features of cough motor pattern via the volume related feedback mechanism similar to that in breathing.

Brainstem mechanisms underlying the cough reflex and its regulation

“…The role of pulmonary stretch receptors and, in particular, of volume-related feedback in the regulation of the cough reflex is controversial (Nishino et al, 1989b;Javorka et al, 1994;Romaniuk et al, 1997;Bolser and Davenport 2000). In a recent study, Poliacek et al (2016) found that modified lung inflations during coughing and/or additional expiratory airflow resistances altered the spatio-temporal characteristics of the cough motor pattern through volume-related feedback mechanisms similar to those operating during eupneic breathing. In the same report, an interesting discussion on lung volume feedback during coughing and the related contribution of both SARs and RARs has also been provided.…”

GABA-ergic neurotransmission in the nucleus of the solitary tract modulates cough in the cat

“…Another potential mechanism of CTI prolongation represents the activity of P cells which are 2nd order neurons from slowly-adapting pulmonary stretch receptors. We have shown that this afferent pathway may modulate cough, in particular reduced afferent drive from pulmonary stretch receptors prolonged CTI (Poliacek et al, 2016). It is likely that the rNTS microinjections inhibited the activity of P cells.…”

“…In the temporal analysis (Poliacek et al, 2016, 2017a), the duration of cough-related DIA (TDIA) and ABD (TABD) activations, augmenting part of DIA (CTI =inspiratory cough phase), the time from the maximum of DIA activity to the end of cough-related ABD activity (CTE1 = active expiratory cough phase), the time from the maximum of DIA activity to the end of the cough cycle (CTE =cough expiratory phase) were measured. Further, the time between maxima of DIA and ABD activity (peaks), the quiescent period of the cough cycle (cough TE2 phase =CTE2), the duration of all cough-related EMG activity (CTactive), and the whole cough cycle duration were analysed in each stimulation period (CTtot).…”

Cough Modulation by Upper Airway Stimuli in Cat—Potential Clinical Application?

“…pulmonary stretch receptor activation) can increase the excitability for cough [8]. However, there is no relationship of volume-timing during cough [24], there are limited correlations between I and E efforts/durations during cough [25], and the reduction of volume feedback increased I and E drive [26]. …”

“…Upper airways inflammatory diseases and gastro-esophageal reflux disease can up regulate cough [33,34], while bronchopulmonary C-fiber activation [35], BP alterations [36] and perhaps irregular cough volumes stretch receptor activation [26] can decrease cough excitability and/or cough motor drive. We focused on those, which are easily applicable and inducible due to their potential employment for cough modulation in correction of excessive or insufficient coughing.…”