Methods of recording and analysing cough sounds.

Efforts have been directed to evolve a computerized system for acquisition and multi-dimensional analysis of the cough sound. The system consists of a PC-AT486 computer with an ADC board having 12 bit resolution. The audio cough sound is acquired using a sensitive miniature microphone at a sampling rate of 8 kHz in the computer and simultaneously recorded in real time using a digital audio tape recorder which also serves as a back up. Analysis of the cough sound is done in time and frequency domains using the digitized data which provide numerical values for key parameters like cough counts, bouts, their intensity and latency. In addition, the duration of each event and cough patterns provide a unique tool which allows objective evaluation of antitussive and expectorant drugs. Both on-line and off-line checks ensure error-free performance over long periods of time. The entire system has been evaluated for sensitivity, accuracy, precision and reliability. Successful use of this system in clinical studies has established what perhaps is the first integrated approach for the objective evaluation of cough.

Quantitative assay of maprotiline in biological fluids by gas-liquid chromatography.

A specific and sensitive gas-liquid chromatographic method has been developed for the assay of maprotiline in biological fluids. Maprotiline is isolated from the biological sample by base-specific extraction followed by conversion into the heptafluorobutyramide. The derivative is determined quantitatively by gas-liquid chromatography with an electron capture detector, nortriptyline being used as the internal standard. Amounts below 10 ng per biological sample can be measured.

Evaluation of antitussive agents in man.

Methodology to evaluate the efficacy of antitussive drugs rely largely on subjective methods and cough counts. There are few studies in cough due to natural disease especially using objective techniques. This paper presents data from a series of randomized, double blind, placebo controlled clinical trials in cough due to both chronic bronchopulmonary disease and acute upper respiratory tract infections. In these studies, cough was quantified using a standardized and validated computerized system for the acquisition and multidimensional analysis of the cough sound. Key objective parameters like cough counts, intensity, latency and total effort expended were studied. Guaiphenesin and bromhexine showed significant expectorant effects in patients with productive cough due to chronic bronchopulmonary disease. Differences were observed in speed of action, and objective and subjective measures, that probably indicate differences in drug action. More recently, three studies evaluated the antitussive drug dextromethorphan in non-productive cough due to uncomplicated upper respiratory tract infections. Reproducible cough suppressant effects were demonstrated after a single 30 mg dose using objective measures of cough counts, latency and total effort. These results establish the sensitivity and robustness of the cough quantitation methodology in the objective evaluation of cough treatments.