Ubiquitous Health Monitoring System for Diagnosis of Sleep Apnea With Zigbee Network and Wireless LAN

The Greek word “apnea” literally means “without breath.” The three types of apnea are obstructive, central, and mixed. Obstructive is the most common type. Despite the difference in the root cause of the three types of apnea, people with untreated sleep apnea stop breathing repeatedly during their sleep, sometimes hundreds of times during the night and often for 1 min or longer. Sleep apnea can cause high blood pressure and other cardiovascular diseases, memory problems, weight gain, impotency, and headaches. Sleep apnea may be responsible for job impairment and motor vehicle accidents. Apart from the physical health risks, sleep apnea can lead to social problems when left undiagnosed or untreated such as a high amount of unnecessary health care cost. Sleep disorder is diagnosed with polysomnography, an overnight sleep study, by monitoring electrical activity of brain, heart, eye movement, muscle activity, breathing pattern, and other physiological signals. Because polysomnography requires overnight monitoring by a sleep technologist with full sleep staging, polysomnography is expensive, inconvenient, time consuming, and labor intensive. Although some systems provide home based diagnosis, most systems record the sleep data in a memory card. The patient must send the memory card to a medical center through the mail or internet. The real-time monitoring is not performed and a patient can experience life threatening episodes by not receiving proper feedback from a medical center or a physician. We propose a wireless health monitoring system to diagnose sleep apnea, which enables the global monitoring of biomedical signals. A patient does not need hospitalization and can be diagnosed and receive feedback at home. The system supports monitoring five different biomedical signals to diagnose sleep apnea: electrocardiogram with dry electrodes (no gel), body position, nasal airflow, abdomen/chest efforts and oxygen saturation. The system consists of three units: a wireless transmitter, a wireless receiver, and a monitoring unit. A wireless transmitter unit sends the measured signals from sensors to a receiver unit with Zigbee communication. The receiver unit, which has two wireless modules, Zigbee and Wi-Fi, receives signals from the transmitter unit and retransmits signals to the remote monitoring system with Zigbee and Wi-Fi communication, respectively. By using both the Zigbee network and wireless LAN, the system can achieve low power consumption in a local monitoring area with the feature of the Zigbee standard. The system also provides wide data coverage and easily extends its sensor network to the Internet with the Wi-Fi standard. The features of the system and the results of the continuous monitoring of vital signals are presented.