There is a study in the Journal of Clinical Sleep Medicine where researchers investigated which patients with OSA would respond to a new treatment device. The treatment is Provent which is a one-way valve worn in the nostrils during sleep. The valve allows you to inhale normally, but makes it difficult to exhale through the nose. This exhalation difficulty increases the pressure inside the upper airway at a time when some patients with OSA are prone to collapse their throat, usually due to decreased airway pressure.
The way Provent works to reduce OSA is not known entirely. It is postulated that the device increases pressure duing expiration, which would make it harder for the airway to collapse. The device might also increase CO2 levels during sleep, which could incresae muscle tone in the airway and make it more difficult to collapse. Finally, the device could increase lung volumes while asleep, which would "tug" on the upper airway and reduce collapsibility.
The researchers studied 20 patients and ten of them demonstrated an objective response during polysmongraphy. Four patients had a partial response and five patients were considered non-responders to Provent. Neither baseline OSA severity nor obesity level predicted who would respond to Provent. However, there was a trend with the resonders if they had more severe OSA on their back than on their sides.
There could be a few reasons why the Provent did not work in all patients. Some were mouth breathers, so a nose device would not help. Also, in some patients with OSA, their airway collapses during inspiration, but not expiration. As this device works only during the expiratory phase of breathing, it would not work in those particular patients.