Cough variant asthma (CVA) is one of the most common causes of chronic persistent cough, and early treatment with inhaled corticosteroids (ICSs) is recommended to attenuate the inflammation and remodeling. The impulse oscillometry system (IOS) is a novel device for respiratory functional assessment that has not yet been assessed in terms of CVA. Therefore, we investigated the relationship between CVA and IOS, and the difference in therapeutic effects of ICSs among the subtype classifications by IOS. The following ICSs were randomly prescribed in daily medical care: coarse-particle ICS (fluticasone propionate [FP]), fine-particle ICS (mometasone furoate [MF]), and moderate-particle ICS (budesonide [BUD]). Treatment effects were assessed by the Leicester cough questionnaire (LCQ) and were compared among three separated subtypes based on IOS measurements: central, peripheral, and resistless. Regarding LCQ scores, in the central type, the LCQ of the MF group was significantly lower than FP and BUD. In the peripheral type, the LCQ of the FP group was significantly lower than MF and BUD. In the resistless type, the LCQ of the MF group was significantly lower than BUD. Also, IOS factors were improved by 4 weeks of therapy with ICS. Thus, there was strong relationship between subtypes and particle size in terms of effectiveness. There is a strong relationship between IOS subtype classification and ICS particle size in terms of therapeutic efficiency in CVA. It appears important to determine the ICS particle size, based on the IOS subtype classification, before treatment.

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Comparison of therapeutic effects of inhaled corticosteroids on three subtypes of cough variant asthma as classified by the impulse oscillometry system.

As mentioned previously in the chapter on the ‘mechanism of cough’, cough is an important host defence mechanism to clear sputum and foreign bodies from the airway. With the exception of psychogenic cough, cough receptors in the airway are stimulated, the impulse is transmitted to the cough centre, then cough is elicited through efferent nerves. Antitussives are classified depending on where they act in the cough reflex pathway: central antitussives that act on the cough centre, and peripheral antitussives that act on cough receptors. At present, agents classified as peripheral antitussives, including local anaesthetics, expectorants and mouthwashes, primarily have other effects and are broadly classified as antitussives only because of their secondary effects on cough receptors. Those classified more narrowly as antitussives are central cough suppressants. Central cough suppressants are classified as narcotic (e.g. Codeine Phosphate ) or non-narcotic (e.g. Asverin, Medicon, Toclase). Side-effects commonly seen with narcotic cough suppressants include constipation, drowsiness and difficulty in micturition. These side-effects, albeit mild, may also occur with non-narcotic cough suppressants. Cough suppressants are not specific therapy for cough, and their use should be limited to cough associated with other symptoms such as chest pain, headache, or rib fractures, where patient QOL is significantly affected. In patients with a productive cough, antitussives are contraindicated because they suppress sputum production and may worsen infection. 2. BRONCHODILATORS

B Volpari

Papers

Treatment of cough