Cough reflex is additively potentiated by inputs from the laryngeal and tracheobronchial [corrected] receptors and enhanced by stimulation of the central respiratory neurons

Cough modulation by upper airway stimuli in cat - potential clinical application?

The modulation of mechanically induced tracheobronchial cough was tested by applying various stimuli and the elicitation of other airway protective behaviors in pentobarbital anesthetized cats. Capsaicin and histamine were injected in the nose, and mechanical nylon fiber and / or air puff stimulation was applied to the nose and nasopharynx. Reflex responses of cough, sneeze, aspiration reflex and expiration reflex were induced mechanically. Swallow was initiated by the injection of water into oropharynx. Subthreshold mechanical stimulation of nasopharyngeal and nasal mucosa, as well as water stimulation in the oropharynx and larynx, with no motor response, had no effect on rhythmic coughing. Cough responsiveness and excitability increased with capsaicin and air puff stimuli delivered to the nose. Vice versa, the number of cough responses was reduced and cough latency increased when aspiration reflexes (>1) occurred before the cough stimulus or within inter-cough intervals (passive E2 cough phase). The occurrence of swallows increased the cough latency as well. Cough inspiratory and / or expiratory motor drive was enhanced by the occurrence of expiration reflexes, swallows, and sneezes and also by aspiration reflex within the inspiratory phase of cough and by nasal air puff stimuli. Complex central interactions, ordering and sequencing of motor acts from the airways may result in the disruption of cough rhythmic sequence but also in the enhancement of cough. Our data confirm that number of peripheral stimuli and respiratory motor responses significantly alters cough performance. We propose developing and testing stimulation paradigms that modify coughing and could be employed in correcting of inappropriate or excessive coughing.

What is chronic cough in children?

The cough reflex is modulated throughout growth and development. Cough—but not expiration reflex—appears to be absent at birth, but increases with maturation. Thus, acute cough is the most frequent respiratory symptom during the first few years of life. Later on, the pubertal development seems to play a significant role in changing of the cough threshold during childhood and adolescence resulting in sex-related differences in cough reflex sensitivity in adulthood. Asthma is the major cause of chronic cough in children. Prolonged acute cough is usually related to the long-lasting effects of a previous viral airway infection or to the particular entity called protracted bacterial bronchitis. Cough pointers and type may orient toward specific etiologies, such as barking cough in croup or tracheomalacia, paroxystic whooping cough in Pertussis. Cough is productive in protracted bacterial bronchitis, sinusitis or bronchiectasis. Cough is usually associated with wheeze or dyspnea on exertion in asthma; however, it may be the sole symptom in cough variant asthma. Thus, pediatric cough has particularities differentiating it from adult cough, so the approach and management should be developmentally specific.

Spirometric and flow-volume curve analysis in rats, and optimal parameters for estimating obstructive impairment

We obtained flow-volume (F-V) curves in anesthetized rats by applying positive pressure on the body surface. To obtain the best curve, tracheal intubation with either a 12 or 13 gauge catheter and a surface pressure greater than 56 cmH(2)O was necessary. Peak expiratory flow rate (PEFR) and forced vital capacity (FVC) were shown to be optimal parameters for estimation of bronchoconstriction induced by methacholine inhalation while FEV(0.05) (forced expiratory volume at 0.05 s) and FEV(0.10) were of limited usefulness for this purpose. The descending segment of the F-V curve consisted of two or three phases, with later phases shortened during bronchoconstriction. In conclusion, PEFR and FVC are optimal parameters for estimation of bronchoconstriction in rats. The decreases in PEFR and FVC may reflect constriction in large and smaller airways, respectively.