Sensors · 2014 · 100 citations · 15 references
Medical UltrasoundEngineeringWearable TechnologyUltrasonic SensorsAcoustic SensorSleep-related Breathing DisorderKinesiologyPower UltrasoundPatient MonitoringHuman Breathing ActivitySleepUltrasonic Contactless SensorUltrasoundSleep Disordered BreathingNon-contact SensingBreathing ActivityPhysiologyHealth MonitoringSleep ApneaMedicineLong PeriodMicromachined Ultrasonic Transducer
Monitoring breathing over long periods is crucial for medical applications, yet standard polysomnography relies on contact sensors that disturb sleep and can produce artifacts, especially in diagnosing apnea. This study evaluates the feasibility of a contactless ultrasonic device to quantify breathing activity without disturbing the subject. The device uses a low‑power ultrasonic source and transducer to detect Doppler frequency shifts from exhaled airflow, then applies signal processing to isolate breathing from movement artifacts. At a 50 cm distance and 40 kHz ultrasound, the system can monitor breathing without perceptible disturbance, preserving sleep quality—an important advantage for sleep‑disorder diagnostics. The work is patented (patent pending 2013‑7‑31, FR.13/57569).
The monitoring of human breathing activity during a long period has multiple fundamental applications in medicine. In breathing sleep disorders such as apnea, the diagnosis is based on events during which the person stops breathing for several periods during sleep. In polysomnography, the standard for sleep disordered breathing analysis, chest movement and airflow are used to monitor the respiratory activity. However, this method has serious drawbacks. Indeed, as the subject should sleep overnight in a laboratory and because of sensors being in direct contact with him, artifacts modifying sleep quality are often observed. This work investigates an analysis of the viability of an ultrasonic device to quantify the breathing activity, without contact and without any perception by the subject. Based on a low power ultrasonic active source and transducer, the device measures the frequency shift produced by the velocity difference between the exhaled air flow and the ambient environment, i.e., the Doppler effect. After acquisition and digitization, a specific signal processing is applied to separate the effects of breath from those due to subject movements from the Doppler signal. The distance between the source and the sensor, about 50 cm, and the use of ultrasound frequency well above audible frequencies, 40 kHz, allow monitoring the breathing activity without any perception by the subject, and therefore without any modification of the sleep quality which is very important for sleep disorders diagnostic applications. This work is patented (patent pending 2013-7-31 number FR.13/57569).
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Noncontact Respiration Rate Measurement System Using an Ultrasonic Proximity Sensor
Se Dong Min, Jin Kwon Kim, Hang‐Sik Shin et al. · IEEE Sensors Journal · 2010 · 170 citations