Down-regulation of cough sensitivity after eucapnic dry air provocation in chronic idiopathic cough.
Down-regulation of cough sensitivity in humans is rarely discussed in terms other than pharmacological treatment of cough or hypersensitive cough reflex. Chronic cough and increased cough sensitivity could be due to a number of airway and other diseases. When such conditions are excluded, there still remains a group of patients with no evident medical explanation for persistent coughing; such patients are often described as having "chronic idiopathic cough". The aim of this study was to use a standardized eucapnic dry air provocation among patients with chronic idiopathic cough in order to study physiological parameters and measure their possible influence on capsaicin cough sensitivity. Fourteen female patients with chronic idiopathic cough and ten healthy controls underwent a capsaicin inhalation provocation on two occasions. In all patients, irritating environmental factors were known to induce cough and airway symptoms. One of the two capsaicin provocations was preceded by a eucapnic dry air provocation. Number of coughs, spirometry, respiratory rate, pulse rate, end-tidal CO(2), and oxygen saturation by pulse oximetry (PSaO(2)) were registered and compared. The patients showed increased capsaicin sensitivity compared with the control subjects. This sensitivity was decreased when the capsaicin test was preceded by a eucapnic dry air provocation. Before the dry air provocation and after the capsaicin provocations, end-tidal CO(2) was decreased among the patients in comparison with the controls. After dry air provocation, spirometry values remained unchanged. The results suggest that in patients with chronic idiopathic cough, physiological down-regulation of the cough sensitivity is possible with a eucapnic dry air provocation.
Johansson
Ewa-Lena
EL
Asthma and Allergy Research Group, Department of Respiratory Medicine and Allergology, The Sahlgrenska Academy, Gothenburg University, Sweden.
Ternesten-Hasséus
Ewa
E
Millqvist
Eva
E
D000328:Adult; D000388:Air; D016535:Bronchial Hyperreactivity / Q000503:physiopathology; D002211:Capsaicin / Q000494:pharmacology; D002245:Carbon Dioxide / Q000097:blood; D002908:Chronic Disease; D003371:Cough / Q000139:chemically induced* / Q000503:physiopathology*; D003890:Desiccation; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology; D008875:Middle Aged; D012129:Respiratory Function Tests; D013147:Spirometry
D002245:Carbon Dioxide; D002211:Capsaicin