A NEW DEVICE FOR AMBULATORY COUGH RECORDING

Nocturnal cough reporting on diary cards has been shown to be unreliab le and inconsistent. Whether subjective reporting of daytime cough is equally unreliable remains unknown. We have, therefore, developed a ne w and easily portable device (RBC-7) that records electromyographic (E MG) and audio cough signals for at least a 24-hr period, with a capaci ty of over 48 hr. Additional information is obtained from electrocardi ographic (ECG) signals, and from an accelerometer indicating the level of the subject's activity. The RBC-7 can be set up with the aid of a notebook computer at the subjects home, school or workplace. Initial s tudies utilizing a prototype device were performed to determine the op timal position of the EMG leads and the microphone. The optimal positi on for the EMG leads was determined as the positive electrode in the s ixth intercostal space (ICS) in the midclavicular line on the left, th e negative electrode in the same position on the right, and the refere nce electrode in the midline over the abdomen. This position was shown to give the highest EMG voltages and the greatest difference in volta ges between cough and other signals. The optimal microphone position f or signal strength and comfort was over the first ICS, either right or left, close to the sternum. Recordings were performed simultaneously in 20 subjects with conventional tape recorders and the multiparametri c cough monitoring system (RBC-7). Conventional tape recordings limite d the duration of the studies due to the inherent restrictions. No sig nificant difference in the number of single coughs recorded by each sy stem was detected (correlation coefficient = 0.996). The RBC-7 offers a unique opportunity to obtain objective information on cough in ambul atory subjects over at least a 24-hr period, and to relate cough to ti me, activity and heart rate, while normal activities are pursued. (C) 1994 Wiley-Liss, Inc.