Wirelessly Powered Device for Optical Measurement of Respiration Rate

The accurate measurement of respiration rate in sleeping patients requires the patients to be in a comfortable state. Current measurement systems usually require patients to wear tights because the sensors must be close to the body to enable the acquisition of high-quality measurements. However, tights are uncomfortable when worn for a long period, especially during sleep. Moreover, current systems are marred by poor battery life, which is a major problem for overnight monitoring processes; existing battery designs cannot be integrated into smart clothing, which must be waterproof to protect electronic components during laundry.To solve these problems, this study developed a wireless power– supplied optical respiratory measurement module (wireless-ORM), which can be integrated with cotton clothing for the optical, noncontact measurement of respiratory rate. This module is powered wirelessly, which eliminates the need for a battery and allows for an indefinite power supply. The wireless-ORM can also be easily covered with a waterproof membrane for waterproofing. We fabricated and tested a prototype of the wireless-ORM measuring 197 × 20 × 3 mm3 in volume and 2.8 g in weight. The sensor was determined to function at distances up to 40 mm from the body, meaning that respiration rate could be measured even with thick winter clothes. The wireless-ORM could also receive power wirelessly up to 70 cm from a base station. Due to its small size, the wireless-ORM can be wrapped in plastic for waterproofing to enable its use in smart clothing.