Leevers A M, Road J D
Department of Medicine, University of British Columbia, Vancouver, Canada.
Respir Physiol. 1993 Sep;93(3):289-303. doi: 10.1016/0034-5687(93)90075-l.
Abdominal muscle activation produced by expiratory threshold loading (ETL) helps prevent an increase in FRC thus, optimizing diaphragm length and defending VT. However, anesthesia may affect abdominal muscle activation, and the pattern of recruitment and level of activation of individual abdominal muscles may well be dependent on body position. Therefore, individual abdominal muscle response to ETL was assessed in awake dogs, lying in the lateral decubitus position. Eight, tracheotomized dogs were chronically instrumented with sonomicrometer transducers and bipolar, fine wire EMG electrodes, in each of the four abdominal muscles. ETL produced increases in active, expiratory shortening of the transversus abdominis (TA), internal oblique (IO) and external oblique (EO). In addition, tonic activity, assessed from a decrease in baseline length, increased in the IO. There was a significant increase in FRC during ETL but it was less than would be expected without tonic and phasic abdominal muscle activation. Although FRC increased, VT and breathing frequency were maintained. As was found previously in supine, anesthetized dogs, the internal abdominal muscle layer (TA and IO) was recruited preferentially; substantiating its greater role in the defence of lung volume.
呼气阈值负荷（ETL）引起的腹肌激活有助于防止功能残气量（FRC）增加，从而优化膈肌长度并维持潮气量（VT）。然而，麻醉可能会影响腹肌激活，并且单个腹肌的募集模式和激活水平很可能取决于体位。因此，在清醒的侧卧犬中评估了单个腹肌对ETL的反应。八只气管切开的犬被长期植入了超声换能器和双极细钢丝肌电图电极，分别置于四块腹肌中。ETL使腹横肌（TA）、腹内斜肌（IO）和腹外斜肌（EO）在主动呼气时缩短增加。此外，通过基线长度的减少评估的紧张性活动在IO中增加。ETL期间FRC显著增加，但低于无紧张性和阶段性腹肌激活时的预期值。尽管FRC增加，但VT和呼吸频率保持不变。正如之前在仰卧麻醉犬中发现的那样，腹内肌层（TA和IO）优先被募集；证实了其在维持肺容积方面的更大作用。
