# A Novel mHealth Approach for the Monitoring and Assisted Therapeutics of Obstructive Sleep Apnea
## 2 Related Work
Detecting and Treating Sleep ApneaThe diagnosis of obstructive sleep apnea syndrome requires the combined evaluation of relevant clinical features, as well as the objective demonstration of abnormal breathing during sleep. Currently, among all the tests for this disease, the standard test is the complete polysomnography, which provides detailed information about sleep status and respiratory abnormalities through electrophysiological signals [24]. Polysomnography (PSG), or nocturnal sleep study, is a diagnostic method that consists of continuously and simultaneously recording sleep by means of electrophysiological signals. Generally, this means of diagnosis involves electroencephalogram (EEG), electromyogram (EMG), electrooculogram (EOG), and electrocardiogram (ECG), among others. However, the human respiratory act does not generate any readily detectable electrical signal, which makes the use of sensors necessary so that these data can be read and analyzed in light of current technologies. These sensors take different forms and functions and can be directly in contact with the upper airways or in contact with other parts of the body, such as the fingers and thorax, among others [31,32]. Similar to the methods used for the detection of this disease, there are also a fairly large number of techniques and devices for its treatment [33]. Examples include the following: surgical treatments [34], oral appliances [35], and weight reduction and lifestyle changes [36]. However, treatment using continuous positive airway pressure (CPAP) is considered the gold standard for the therapy of moderate to severe obstructive sleep apnea. This consists of a device that is used at night and that allows air to pass through the airways by applying constant positive pressure to the upper airways through an oral or nasal mask, using a tubing system [37,38]. However, although it is a non-invasive treatment and its effectiveness in treating OSAS is proven, the rate of adherence to this treatment is relatively low. Nasal congestion and mask intolerance are the most common complaints and the main reasons that reduce CPAP compliance [39]. When more conventional treatment techniques are not well accepted by the patient or are insufficient, nerve stimulation devices can be used. Three upper airway stimulation devices are currently available for the treatment of obstructive sleep apnea. Although slightly different in design, each of these implants electrically stimulates the hypoglossal nerve. This stimulation causes a contraction of the genioglossus muscle, pulling the tongue forward in order to open the airway. The _Inspire_ system [40,41] and the _Aura 6000_ system [42,43] operate identically, by directly stimulating the hypoglossal nerve via electrodes implanted in it and that are controlled by a battery-powered pulse generator, which is implanted in the chest. The major drawback of these two devices is that they require surgery for them to be implanted, as well as to change the battery when it runs low. The _Genio_ system is the latest and most innovative implantable device for treating OSA to receive FDA approval [44,45]. This system consists of an implantable stimulator that comprises two electrodes, which are placed on the patient through medical surgery in the submental region (under the chin), with the stimulating electrodes close to the right and left branches of the hypoglossal nerve. This is the only part of the whole system that needs to be implanted with surgery and it is controlled by a pre-programmed activation chip, with patient-specific stimulation parameters, and is placed externally, under the chin. Despite being the most advantageous device of the three, the main disadvantage is still the fact that it is an invasive solution and that it is a pre-programmed therapy, which does not act optimally if some of the patient's physical or physiological parameters change.