Novel Technique for the Measurement of Chest Wall Kinematics Using Low Cost Stretch Sensors

Measurement of breathing patterns and thoracoabdominal movement (chest wall kinematics) is essential in studying patients with chronic obstructive pulmonary diseases (COPD), patients with neuromuscular diseases, critical patients in intensive care units and in healthy subjects during exercise. Currently, these measurements are being performed using optoelectronic plethysmography, which requires a number of motion detection cameras and large amount of three-dimensional vector field computation. In this study we have designed and implemented a novel method of measuring breathing patterns using low-cost stretch sensors. For this purpose, three stretch sensors were attached to belts around torsos. Each sensor was calibrated by stretching it for different lengths and measuring the change in resistance and voltage caused by this change in length of the sensor. An equation of voltage was calculated for each belt as function of length of the belt. 20 healthy subjects of both genders aged 23 ± 1.5 years participated in this study. Belts were tied around all subjects at pulmonary rib cage (RCp), abdominal rib cage (RCa) and the abdomen (AB). Data was collected during normal breathing for 1 minute i.e. 60 seconds for each subject. The sensors were analyzed using MATLAB to distinguish between thoracoabdominal and abdominothoracic breathing patterns and correlation between signals was computed. Results showed that the correlation values indicate a delay of 0.5 ± 0.1 ms between pulmonary rib cage RCp and abdomen AB signals. For the subjects with abdominothoracic breathing patters the delay was 0.3 ± 0.09 ms between abdomen AB and pulmonary rib cage RCp signals. The simplicity and affordability of this approach offer a promising alternative to current complex methodologies, making it a valuable tool for studying respiratory dynamics in various clinical scenarios and healthy subjects during exercise.