体位変換による左右肺機能の差異に関する筋電図学的研究

Electromyographic Studies on the Genesis of Reciprocal Respiratory Functions due to Postural Changes.

緒言

　側臥位時における左右肺の呼吸機能の相互拮抗性変化については，岸本^1），　Inada^2），　Drew—Miller^3），　Rothstein^4），　Alix^5）等のBroncho—spirometryによる詳細の研究がある。いずれもヒトで側臥位をとつた場合，下側肺の一回換気量，酸素消費量の増加と，上側肺での減少を証している。この原因として，側臥位時の下側肺のうつ血，腹部内臓の移動により下側横隔膜の挙上，その結果の横隔膜運動の増大が考えられている。

　更に生垣^6）はヒトで姿勢変化，片側胸部圧迫時の左右別呼吸機能を精査し，これが単に機械的な原因によるものではなく，高木^7）並びにその協同研究者による皮膚圧・反射がその主因であると主張している。この方向における従来の研究はほとんどヒトに限られているので，私はこれらを更にウサギにおいて追試する一方，ヒト，ウサギにおける呼吸筋の筋電図学的研究によつて，その差異の原因を追求しようとした。

It is well known to clinicians that in the lateral decubitus position the respiratory sound is intensified in the subjacent side and weakened in the suprajacent. The bronchospirometric studies on man have revealed an increase in tidal volume and oxygen uptake in the subjacent lung in the lateral position, and a decrease in them in the suprajacent. These changes have been attributed to an increased pulmonary blood flow, a rise of diaphragm level, an increase of amplitude of diaphragmatic excursion, etc.

Recently Ikegaki made bronchospirometric and roentgenokymograehic studies on man, and concluded that the above-mentioned changes should be chiefly attributed to the skin pressure reflex by Takagi, rather than mechanical factors.

The auther made further experiments on these phenomena on rabbits by means of bronchospi-ometry and electromyography to find the real cause of them.

The results were as follows:

1) Bronchospirometric measurements shows that in the lateral position, tidal volume, oxygen uptake in the subjacent lung tend to increase, while the reverse tends to occure in the suprajacent.

2) If an area of unilateral axillar region is pinched by a paper clip, an increase of tidal volume and oxygen uptake is evidenced on the pressed side, while the reverse on another side.

3) Electromyographic findings show that in the lateral position, the activity of the inspiratory muscles including the diaphragm on the subjacent side increases, while that of the expiratory muscles decreases. In the opposite side the reverse effects are recognized on the muscular tone.

4) Unilateral skin pressure to the axillar region either in rabbit or in man tends to cause an increase of the activity of the inspiratory muscle on that side and the reverse on another side.

In lateral position and/or during the unilateral skin pressure, the respiratory function of the subjacent hemithorax is facilitated and that of the suprajacent is suppressed. It may be reaso-nable to consider that the unilateral pressure on the skin by the body weight plays a significant role in the genesis of the reciprocal changes of the respiratory function due to the postural change.