睡眠による周期的な上気道狭窄といびき—下顎骨発育不全を伴つた症例にみられた高度のいびきの成因についての検討

PATHOPHYSIOLOGICAL EVALUATION OF MARKED SNORING IN PATIENTS WITH MIICROGNATHIA

　I．はじめに

　最近われわれは下顎骨の発育不全を伴い，高度のいびきを訴える2症例を経験した。小児の1例では夜間，仰臥位で眠ると呼吸困難のために睡眠障害が強く，日中うとうとしていると言う訴えがあつた。この2症例は上気道周囲組織の器質的異常がいびきの明らかな原因となつている極端な例であるが，多くのいびき症例においても，程度の差こそあれ睡眠による上気道の形態の変化が局所の気流の空気力学的性状をかえて軟口蓋，その他の口腔軟部組織の振動を起こすと考えられる。1症例で睡眠による上気道の形態の変化と局所気流の空気力学的性状の変化および脳波よりみた眠りの深さとの関連について検索し，2〜3の知見をえたので報告し，いびきの成因，治療について考察する。

　Aerodynamics, cineradiographic and EEG studies were performed in patients with micrognathia complaining of marked snoring. The snoring was caused by periodic upper airway obstruction followed by hyperventilation.

　During sleep a decreased muscular tonus causes intermittent drooping of the tongue down to the posterior wall of the pharynx with resulting obstruction of the upper airway. The airflow was markedly decreased, particularly in the inspiratory phase, although thoracoabdominal respiratory efforts were continued.

　However, after the lapse of 25-40 seconds of this obstructed respiratory movements, the tongue is suddenly elevated by resumption of the musculartonus, aud the inspiration is marked by a peak airflow of more than 1000cc/sec. The hyperventilation of this nature continues for 10-20seconds.

　The airflow with hightened velocity through the narrow nasopharynx caused fluttering of the soft palate resulting in a marked snoring. The contrast media placed on the posterior wall of the pharynx also showed a marked vibration revealing evidence of apparent local turbulance. The blood gas and pH analysis during the airway obstruction revealed an increase of P^CO2 and decrease of pH. Changes of EEG pattern correlated well with changes in the respiratory pattern.

　During hypoventilation phase the EEG showed a sleeping pattern with predominence of humps and spindel waves. But as ventilatory difficulty progressed the sleeping pattern in EEG changed suddenly into an awake pattern with predominence of α-wave which was frequently preceded by K-complex characteristic of awakening response. With EEG changes turning into an awakening pattern, the hypoventilation suddenly alterneted into hyperventilation with a marked snoring.