Bioamp modules

Clinical tests at Camp Lowell Cardiology involved eight elderly patients as volunteers, all providing informed consent. Optimal sensor placement sites at traditional aortic, pulmonary, tricuspid, and mitral locations were determined by ultrasound probes, with verification of heart murmurs by echocardiogram (GE Healthcare). A three-lead setup enabled simultaneous recording of ECG using the same device platform. PowerLab system (8/35, ADInstruments) with BioAmp modules served as the hardware for data acquisition and analysis. During measurement, the subject was asked to “stop breathing” for 3 s and then to “breathe normally” after a verbal countdown to eliminate the respiratory effect on the baseline and amplitude of the SCG data. Passing the output of the accelerometer through a 20-Hz low-pass digital filter followed by an analog-to-digital converter in the PowerLab system yielded processed data at a sampling rate of 1 kHz. A band-pass digital filter with a low cutoff and a high cutoff frequency of 1 and 30 Hz, respectively, was used with the ECG signal. All vibration signals were converted from output voltage to “mechano-acoustic response (arbitrary units).”