[Factors affecting upper airway patency].

We studied the following functional factors which affect upper airway patency. First, the effects of inspiratory resistive loading, increased pulmonary resistance, hypercapnic gas or hypoxic gas loading on the upper airway pressure-flow (P-F) relationship were studied. The upper airway P-F curves under these loading conditions shifted upward with load dependency. Secondly, effects of limb muscle contraction on upper airway resistance (Rua) were studied. Rua decreased reflexly during limb muscle contraction. Thirdly, effects of body position on the stability of the upper airway were studied. The upper airway was kept patent in the lateral position. Fourthly, effects of electrical stimulation of the genioglossus muscle on P-F relationship of upper airway were studied. P-F curves of upper airway shifted upward with increase in stimulation frequency. Fifthly, effects of nasal or oropharyngeal lubrication by artificial surfactant on the critical stimulation frequency (CSF) for upper airway opening were studied. Nasal or oropharyngeal lubrication decreased CSF. Based on these fundamental studies, we applied constrained lateral position, submental stimulation due to demand-type stimulator and nasal or oropharyngeal lubrication for treatment of patients with obstructive sleep apnea syndrome (OSAS). We found these three methods were effective in treatment of OSAS patients.