Development of a Novel Wireless Multi-Channel Stethograph System for Monitoring Cardiovascular and Cardiopulmonary Diseases

Abstract

A multi-channel stethograph system was designed and developed as an electronic auscultation system for graphic recording of heart, lung and trachea (HLT) sounds non-invasively through a set of 16 acoustic sensors. The multi-channel stethograph system was fabricated by placing 16 microphone based acoustic sensor in a CNC machined Delrin® housing cases that are covered using diaphragms. Among the 16 acoustic sensors, 14 were positioned in a memory foam pad and 2 were placed directly on the heart and trachea to acquire sounds simultaneously from the lungs, heart and trachea. The sounds acquired from the 16 acoustic sensors were processed through a custom designed and fabricated 16-channel PCB for signal conditioning. A National Instruments (NI) 9205 data acquisition device (DAQ) along with a NI 9191 wireless chassis was used to acquire and wirelessly transmit the data from the 16-channel PCB to a Wi-Fi enabled device such as a PC/tablet. A custom LabVIEW program was developed on a Wi-Fi enabled PC/tablet to record the data from the DAQ. In addition, a MATLAB program was developed to convert the recorded data from the acoustic sensors into 16 audio files (for audio playback) and plot the waveforms in time and frequency domain as well as spectrogram for visual examination of any abnormal patterns in inhalation and exhalation. This provides critical information on the presence of wheezes, crackles and rhonchi sounds as well as abnormal heartbeat and respiration rate which helps in analyzing the condition of heart and lungs. The graphically displayed HLT sounds will help physicians in the clinical diagnosis and monitoring of lung and heart disorders, particularly chronic obstructive pulmonary disease (COPD), asthma, pneumonia, and congestive heart failure by providing objective evidence.