A proposal of a novel cardiorespiratory long-term monitoring device

Monitoring of respiratory movements is an important feature in planning of medical care. We present here a simple, portable, accelerometer-based device suitable for long term-monitoring of the breathing and heart rates, along with postural changes, during sleep and wakefulness. Recordings of respiratory frequency, heart rate, posture and voluntary cough were obtained from a group of volunteers who also participated in sleep studies (6-8 hrs). A pair of capacitive MEMS tri-axial accelerometers was positioned at the level of the 10th rib along the mid-axillary line bilaterally; simultaneous recordings of respiratory movements, heart rate and body position could be easily performed. The signal were digitized and used to detect body position and relative movement between accelerometers. Conventional spirometry was performed in parallel when appropriate. During resting breathing, qualitative analysis revealed that the accelerometric assessment of respiratory pattern correlated well with that obtained by spirometry. Values of respiratory rates were identical with the two techniques. Recordings of respiratory and cardiac activity during sleep were satisfactorily obtained except for short lasting episodes corresponding to changes in body position. These devices seem to be also suitable for detecting the motor pattern of cough.