人工呼吸器管理患者の横隔膜の厚さ

人工呼吸器管理患者の横隔膜の厚さを調査した論文を紹介します。

Horiana B. Grosu, et al: Diaphragm Muscle Thinning in Mechanically Ventilated Patients. Chest, Published online before print June 21, 2012, doi: 10.1378/chest.11-1638

人工呼吸器管理患者7人の横隔膜の厚さを毎日、超音波で計測したという研究です。結果ですが、1日平均6％、横隔膜の厚さが薄くなっていきました。程度の差はありますが、全ての患者で薄くなりました。ただし、横隔膜の厚さと呼吸機能に関連があるかどうかは不明です。

これは呼吸筋のサルコペニア（廃用、栄養、疾患が重複した二次性）といえます。呼吸筋のサルコペニアをどのように評価すればよいのかと考えていましたが、超音波で横隔膜の厚さを計測する方法もありますね。ラットでの実験は下記のようにいくつかありますが、人での研究は初めて知りました。

人工呼吸器管理と横隔膜機能不全
http://rehabnutrition.blogspot.jp/2012/03/blog-post_20.html

横隔膜は加齢による変化を認めない
http://rehabnutrition.blogspot.jp/2012/03/blog-post_1486.html

呼吸筋のサルコペニアと解釈すれば、治療としてのリハ栄養はとても重要だと考えます。サルコペニアの呼吸障害という概念とエビデンスが、今後広まることを期待しています。

Abstract

Background: Approximately 40% of patients in medical intensive care units require mechanical ventilation (MV). Around 20%-25% of these patients will encounter difficulties in discontinuing MV. Multiple studies have suggested that MV has an unloading effect on the respiratory muscles that leads to diaphragmatic atrophy and dysfunction, a process called ventilator-induced diaphragmatic dysfunction (VIDD). VIDD may be an important factor affecting when and if MV can be discontinued. A sensitive and specific diagnostic test for VIDD could provide the physician valuable information that might influence decisions regarding extubation or tracheostomy. The purpose of this study was to quantify, using daily sonographic assessments, the rate and degree of diaphragm thinning during MV.

                      

Methods: Seven intubated patients receiving MV during acute care were included. Diaphragm muscle thickness was measured daily using sonography from the day of intubation until the patient underwent extubation or tracheostomy or died. We analyzed our data using standard descriptive statistics, linear regression, and mixed model effects.

                      

Results: The overall rate of decrease in the diaphragm thickness of all seven patients over time averaged 6% per day of MV, which differed significantly from zero. Similarly, the diaphragm thickness decreased for each patient over time.

                      

Conclusion: Sonographic assessment of the diaphragm provides noninvasive measurement of diaphragmatic thickness and the degree of diaphragm thinning in patients receiving MV. Our data show that diaphragm muscle thinning starts within 48 hours after initiation of MV. However, it is unclear if diaphragmatic thinning correlates with diaphragmatic atrophy or pulmonary function. The relationship of diaphragm thinning and diaphragm strength remains to be elucidated.