4 wires being tangled up during sleep. However, the number of wireless motes needs to be balanced as well, because the more parts a system contains the less easy it is to setup and use. Because of the expandability of the system, it is easy to incorporate many wireless nodes or stick to fewer nodes with more sensors attached to each one. Figure 1 shows one such conﬁguration. In addition to the nighttime sensor network, the daytime data collection must be quick and simple as well. By allowing the user multiple ways to enter information, she can choose the most convenient way and is therefore more likely to report throughout the day. 3.7. Portable Portability is the key aspect that draws users to our system. Besides the advantages of allowing a user to sleep in her own bed each night and not be bothered by traveling to and from a sleep center; the system is also readily portable to be taken to a diﬀerent sleeping location. For instance, when the user goes on vacation or temporarily is staying at another place, the system can be brought along; data collection does not have to stop. 3.8. Customizable For a system to be truly universal, it must be easy to customize for diﬀerent users. In our system, this is accom- plished in two ways. First, as explained in Section 3.6, our wireless sensor network allows nodes to be easily added and removed. Sensors that are not applicable to a certain users diagnosis can be left out, saving time and money. Further, if a doctor believes a patient needs more advanced monitoring, additional sensors can be added to the system to provide a more detailed report. Second, the main aspects of the system can be used in several diﬀerent ways to achieve the same end result. See Section 6B for an example of multiple input methods. Such a customizable system would lead to separate base conﬁguration for diﬀerent user groups, for example, divided by age. On the one hand, an elderly person may be techno- phobic, and would want a system that requires very little interaction on his part. His system could include a passive infrared video monitor that could be setup once and then used every night. Also, instead of entering data throughout the day, he could enter a simple phone survey once each night. All the data collected would be automatically sent to the doctor and analyzed without any interaction. A middle aged person, on the other hand, would perhaps want a great deal of control over his system. He would choose the most accurate sensors that attach directly to his body, such as the accelerometer and thermistors for airﬂow, even though for other people they may be more diﬃcult to setup. Although he does not use texting for cell phone data entrance, he periodically takes a quick survey from his work or home computer to enter daytime information. Every morning when he wakes up he checks out his sleeping and International Journal of Telemedicine and Applications daytime scores, and looks to see how he can improve his sleep by changing his habits. There is also the case of a younger person, who does not mind entering her data throughout the day via simple text messaging. At night however, she prefers a similar setup to the elderly person: easy to setup and quick to activate. Also like the elderly person, she prefers to have her doctor look at the data and thus has it sent directly to him. The preceding customizations are only a few ways by which the system could be conﬁgured. It is adaptable to any circumstances, and can be updated with new sensors just as easily as old ones can be removed. 4. OUR APPROACH We have focused on making PATHOS low cost, suitable for home use, and most importantly a continuous, long- term system. Our approach can be split into three major sections: nighttime data collection, daytime data collection, and analysis. 4.1. Nighttime data collection In order to make a sensor-based system that is user friendly and not too invasive during sleep, we will use a network of sensors and motes that communicate wirelessly using the Zigbee protocol. Figure 1 details a possible setup for the patient during nighttime monitoring. Three of the sensors are connected via wires to the main mote located on the person arm. The nasal and oral airﬂow sensors are thermistors that measure the patient’s breathing, a characteristic especially important when diagnosing sleep apnea. There is also a microphone near the base of the subject’s neck to record sound such as snoring. The pulse and blood oxygen sensor uses a simple ﬁnger clip-on, and is then connected to the main mote by a wire running up the arm. Because of their proximity to the main mote, it would have been more cumbersome for the sensors to communicate wirelessly via their own motes. The main mote itself contains an accelerometer to measure arm movement and a thermometer to measure the subject’s temperature. The leg movement sensor (accelerometer) is connected to its own mote and transmits data to the main mote wirelessly. Additional sensors could be added wirelessly to the network very easily. For example, a simple passive infrared camera could be setup to record nighttime sleep movement patterns with more detail than the accelerometers could. The setup that we have depicted is one of many. The system can be adapted to include more sensors in diﬀerent ways, depending on the age group of the user, and what and how they want their sleep to be monitored. Not pictured in the diagram is the receiving mote connected to the person’s personal computer. If the pc is in the same room, the mote connected to it could be used to record the ambient pressure and humidity of the sleeping environment. If not, another mote could easily be added to the network and placed on a bedside desk. The main mote on the patients arm cannot be used to measure ambient