筋ジストロフィーの呼吸管理

Respiratory Management in Muscular Dystrophies

はじめに

　進行性筋ジストロフィーは難治性疾患であり，臨床においては対症療法や合併症の対策が診療の主体となる。なかでも呼吸障害は生命予後に直接関係するため，適切な管理を行うことが極めて重要である。しかし，筋ジストロフィーは病型によって発症年齢，障害されやすい筋群，重症度が異なり，呼吸障害の発現の仕方が異なる。また，中枢神経障害，球麻痺，心筋障害，脊柱変形などが合併すると呼吸障害や呼吸管理に大きな影響を及ぼす。本稿では，まず各病型における呼吸障害の特徴について述べ，ついで最近発表されたDuchenne型筋ジストロフィー（Duchenne muscular dystrophy：DMD）呼吸管理ガイドラインに沿った呼吸管理について概説したい。

Abstract

　Respiratory failure is a major contributor to immobility and mortality in progressive muscular dystrophies. The severity of pulmonary impairment and the stage at which it develops differ according to the type of muscular dystrophy. Appropriate respiratory management for each type should be considered. In Duchenne muscular dystrophy (DMD),respiratory impairment manifests in the late teens,and assisted mechanical ventilation is administered. Noninvasive positive-pressure ventilation (NIPPV) has increased the median survival of patients with DMD by 10 year and improved quality of life. In myotonic dystrophy (MyD),the causes of respiratory failure can involve both the central and the peripheral nervous systems in addition to respiratory muscles. Nocturnal desaturation is more severe in MyD than in other muscular dystrophies with similar degrees of respiratory muscle weakness. Cognitive impairment should be taken into account in the management of MyD patients. NIPPV does not appear to improve survival of MyD. Guidelines for DMD have been published. Respiratory function should be assessed serially by measuring forced vital capacity,oxyhemoglobin saturation,peak cough flow,and end-tidal CO₂ level. A respiratory action plan should be enacted with increasing disease severity. Therapeutic measures comprise airway clearance,respiratory muscle training,noninvasive nocturnal ventilation,daytime noninvasive ventilation,and continuous invasive ventilation. At the advanced stage of respiratory failure,attention should be paid to complications related to long-term mechanical ventilation,such as pneumothorax and tracheal hemorrhage. Discussing about end-of-life care among the patient,family,and physician is important before mechanical ventilatory support is required.