Elisa Chellini

Desensitization of the cough reflex by exercise and voluntary isocapnic hyperpnea

Little is known about the effects of exercise on the sensory and cognitive aspects of coughing evoked by inhalation of tussigenic agents. The threshold for the cough reflex induced by inhalation of increasing nebulizer outputs of ultrasonically nebulized distilled water (fog), an index of cough reflex sensitivity, was assessed in twelve healthy humans in control conditions, during exercise and during voluntary isocapnic hyperpnea (VIH) at the same ventilatory level as the exercise. The intensity of the urge to cough (UTC), a cognitive component of coughing, was recorded throughout the trials on a linear scale. The relationships between inhaled fog nebulizer outputs and the correspondingly evoked UTC values, an index of the perceptual magnitude of the UTC sensitivity, were also calculated. Cough appearance was always assessed audiovisually. At an exercise level of 80% of anaerobic threshold, the median cough threshold was increased from a control value of 0.73 to 2.22 ml/min (P<0.01), i.e., cough sensitivity was downregulated. With VIH, the threshold increased from 0.73 to 2.22 ml/min (P<0.01), a similar downregulation. With exercise and VIH compared with control, mean UTC values at cough threshold were unchanged, i.e., control, 3.83 cm; exercise, 3.12 cm; VIH, 4.08 cm. The relationship of the fog nebulizer output/UTC value was linear in control conditions and logarithmic during both exercise and VIH. The perception of the magnitude of the UTC seems to be influenced by signals or sensations arising from exercising limb and thoracic muscles and/or by higher nervous (cortical) mechanisms. The results indicate that the adjustments brought into action by exercise-induced or voluntary hyperpnea exert inhibitory influences on the sensory and cognitive components of fog-induced cough.

Voluntary and reflex cough: Similarities and differences

Cough is defensive airway reflex subjected to a high degree of cortical control. Not surprisingly, all cough motor patterns can be mimicked and reflex cough be inhibited up to complete suppression, at least to a certain extent. Reflex cough differentiates from other airway reflex responses for its characteristic 3-phase motor pattern, and such pattern is maintained when coughing is produced voluntarily. Despite these and some other similarities, voluntary and reflex cough differ in many important respects, suggesting different neural control of the respiratory and non-respiratory musculature implicated in the generation of the cough modalities. This paper focuses the motor features that differentiate voluntary and reflex cough efforts, and highlights the importance of functional assessment of coughing in the diagnostic workup of respiratory and extra-respiratory diseases affecting the production of voluntary and reflex cough.

Cough variant asthma and atopic cough

Chronic cough has been reported to be the fifth most common complaint seen by primary care physicians in the world, the third in Italy. Chronic cough in non-smoking, non-treated with ACE-inhibitor adults with normal chest radiogram could be a symptom of asthma and can be sub-classified into: cough-variant asthma, atopic cough, and eosinophilic bronchitis. This review discusses the differential diagnosis of these three disorders.RiassuntoLa tosse cronica è la quinta causa che induce a consultare il proprio medico di famiglia nel mondo, in Italia è la terza. La tosse cronica in un adulto non fumatore che non assume ACEinibitori ed ha una Rx torace nella norma può essere un sintomo indicatore di asma in una delle sue tre varianti: asma variante con tosse, tosse atopica e bronchite eosinofila. La diagnosi differenziale di queste tre patologie è oggetto di questa rassegna.