Among the various phenotypes of obstructive sleep apnea, a typical case is one in which the severity of disease changes depending on body posture. The severity of OSA decreases with the change in posture to the lateral decubitus position. The posture at this time means mainly the posture of the trunk. On the other hand, there are also some cases in which OSA becomes milder by rotating the head laterally. This paper describes the research findings and future issues for such patients.

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Objective : The magnitude of the airflow passing through the upper airway is directly associated with the pressure difference across the upper airway and indirectly associated with upper airway resistance determined by upper airway structures when Ohm’s Law applies to the upper airway. We are clinically interested in how upper airway geometry changes during sleep, particularly in sleep-disordered breathing patients with abnormalities of the maxilla and/or mandibular structures. Specifically, surgical dilation of the small maxilla and mandible could improve the breathing during sleep in these patients. According to Ohm’s Law, upper airway resistance, that is, upper airway geometry, can be assessed by measuring the pressure across the upper airway during a constant airflow through the upper airway. Based on this simple principle, Cuff Leak Pressure （CLP） measurement was proposed by Ishikawa and Isono in anesthetized and intubated patients. In this study, we examined Ohm’s Law and CLP measurements in patients undergoing maxillo-mandibular surgeries under general anesthesia.
Methods : In the case of tracheal intubation under general anesthesia for orthognathic surgery, CLP values were measured in case of only maxilla advancement and in case of only mandible advancement, respectively. CLP was classified into skeletal types according to the horizontal classification of Sassouni and examined.
Results : The average value of skeletal type Class Ⅰ （Class Ⅰ） was 4.56 ± 3.18cm H₂O, skeletal type Class Ⅱ （Class Ⅱ） was 8.43 ± 3.6cm H₂O, and skeletal type Class Ⅲ （Class Ⅲ） was 4.24 ± 2.74cm H₂O. As a result of statistical tests, significant differences were found for Class I and Class Ⅱ （P＝0.021）, and for Class Ⅱ and Class Ⅲ （P＜0.001）, respectively. This suggests that skeletal morphology affects upper airway resistance. The CLP value decreased by pulling both the maxilla and mandible forward. In addition, the CLP value of the group with maxilla advancement decreased more than that of the group with mandible advancement, suggesting that the maxillary movement is more affected than the mandibular movement.
Conclusions : By measuring the CLP value it is possible to physiologically evaluate the changes of the upper airway in sleep surgery. It may also enable the magnitude and direction of movements to be confirmed during surgery for considering airway resistance and the effect of sleep-surgery treatment. In addition, it is considered possible to estimate the skeletal morphology that induces OSA and its factors, thus helping to elucidate the pathophysiology of OSA.

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Objective: We present a case of narcolepsy in a patient with obstructive sleep apnea （OSA） who complained of residual sleepiness without improvement in Epworth sleepiness scale （ESS） after oral appliance （OA） therapy, and who underwent the Multiple Sleep Latency Test （MSLT）.
Method: The patient was a 48-year-old male who had no significant past medical history and family history, and had been experiencing excessive daytime sleepiness. The initial interview at the Department of Sleep Medicine did not reveal any cataplexy, sleep paralysis, and hypnagogic hallucinations. He was diagnosed with mild OSA （apnea hypopnea index: AHI 10.5/h） based on polysomnography （PSG）, and was referred to our department for OA therapy. Excessive daytime sleepiness did not improve after the initiation of OA therapy. Thereafter, follow-up sleep study with PSG and the MSLT were performed.
Results: The PSG with OA showed an improvement of OSA in AHI from 10.5 to 3.6/h, and sleep-onset REM sleep period （SOREMP） was not observed. MSLT showed that the mean sleep latency was 4min 6s/five naps, and number of SOREMP was two times; therefore, the patient was diagnosed with narcolepsy type 2. Use of Modafinil 100 mg/day decreased the ESS score from 15 to 4 and improved daytime sleepiness.
Conclusion: In patients with OSA and narcolepsy, it is not possible to improve excessive daytime sleepiness by providing treatment for OSA only. Patients who complain of residual sleepiness even after OA treatment should be assessed further for other sleep disorders including hypersomnia.

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