長期人工呼吸器患者の筋力低下と嚥下障害

長期人工呼吸管理患者の筋力低下は咽頭機能障害と症候性誤嚥を予測するという論文を紹介します。

Mirzakhani Hooman, et al. Muscle Weakness Predicts Pharyngeal Dysfunction and Symptomatic Aspiration in Long-term Ventilated Patients. Anesthesiology, doi: 10.1097/ALN.0b013e31829373fe

対象は長期間の人工呼吸管理を要した患者30人です。嚥下機能は嚥下内視鏡で、喉頭蓋谷と梨状窩の残留や侵入・誤嚥を評価しました。筋力低下はMRCスコア（両側の肩外転、肘屈曲、手伸展、股屈曲、膝伸展、足背屈をMMTで評価して合計60点満点）で評価しました。

MRCスコアが48点以下の場合を臨床的に意味のある筋力低下としました。結果ですが、筋力低下は咽頭機能障害（喉頭蓋谷と梨状窩の残留や侵入・誤嚥）の存在を予測しました。ROC曲線のAUCは咽頭残留0.77、侵入・誤嚥0.79、症候性誤嚥0.74でした。

筋力低下のある患者のうち70％で、症候性誤嚥のイベント（誤嚥性肺炎や窒息ということでしょうかね）を認めました。筋力低下があると症候性誤嚥のオッズ比が9.8と約10倍、症候性誤嚥のイベントが多いという結果でした。以上より、四肢MMT評価で症候性誤嚥を予測できる可能性があるという結論です。

長期間の人工呼吸管理を要した患者ですので、反回神経麻痺や感覚障害などの影響も否定できませんが、四肢の筋力が弱いと嚥下筋の筋力も弱いサルコペニアの嚥下障害による要素もあると思います。嚥下筋の筋力評価ができなくても、四肢筋力の評価で嚥下障害を推測できるかもしれません。

Abstract

Background: Prolonged mechanical ventilation is associated with muscle weakness, pharyngeal dysfunction, and symptomatic aspiration. The authors hypothesized that muscle strength measurements can be used to predict pharyngeal dysfunction (endoscopic evaluation-primary hypothesis), as well as symptomatic aspiration occurring during a 3-month follow-up period.

Methods: Thirty long-term ventilated patients admitted in two intensive care units at Massachusetts General Hospital were included. The authors conducted a fiberoptic endoscopic evaluation of swallowing and measured muscle strength using medical research council score within 24 h of each fiberoptic endoscopic evaluation of swallowing. A medical research council score less than 48 was considered clinically meaningful muscle weakness. A retrospective chart review was conducted to identify symptomatic aspiration events.

Results: Muscle weakness predicted pharyngeal dysfunction, defined as either valleculae and pyriform sinus residue scale of more than 1, or penetration aspiration scale of more than 1. Area under the curve of the receiver-operating curves for muscle strength (medical research council score) to predict pharyngeal, valleculae, and pyriform sinus residue scale of more than 1, penetration aspiration scale of more than 1, and symptomatic aspiration were 0.77 (95% CI, 0.63-0.97; P = 0.012), 0.79 (95% CI, 0.56-1; P = 0.02), and 0.74 (95% CI, 0.56-0.93; P = 0.02), respectively. Seventy percent of patients with muscle weakness showed symptomatic aspiration events. Muscle weakness was associated with an almost 10-fold increase in the symptomatic aspiration risk (odds ratio = 9.8; 95% CI, 1.6-60; P = 0.009).

Conclusion: In critically ill patients, muscle weakness is an independent predictor of pharyngeal dysfunction and symptomatic aspiration. Manual muscle strength testing may help identify patients at risk of symptomatic aspiration.