van Lunteren E, Arnold J S, Cherniack N S
Department of Medicine, University Hospitals of Cleveland, OH 44106.
Respir Physiol. 1988 Feb;71(2):201-12. doi: 10.1016/0034-5687(88)90016-3.
To determine whether increases in electromyographic activity (EMG) are necessary for respiratory muscle shortening to occur during airway occlusion, respiratory changes in parasternal intercostal muscle length were measured using sonomicrometry in 11 anesthetized dogs during unoccluded (UB) and occluded (OB) breaths before and after vagotomy. During UB the extent of parasternal intercostal inspiratory shortening was greater after than before vagotomy both during oxygen breathing and during progressive hyperoxic hypercapnia. The relation between parasternal shortening, parasternal EMG, and tidal volume was not substantially affected by vagotomy. During OB parasternal intercostal EMG increased significantly compared to UB when the vagi were intact, but airway occlusion did not significantly change EMG activity post-vagotomy. However, both before and after vagotomy the parasternal intercostal shortened during OB in all animals. Parasternal intercostal inspiratory shortening during OB as a % of that during UB was significantly greater before compared to after vagotomy during oxygen breathing and moderate hypercapnia, but vagal integrity made no significant difference at high CO2. These results suggest that (1) pulmonary stretch receptor afferents inhibit parasternal intercostal inspiratory shortening but in proportion to their inhibitory effects on parasternal intercostal EMG and tidal volume, and (2) even when the EMG stays constant the parasternal intercostal muscle does not contract isometrically during occluded breaths.
为了确定在气道阻塞期间呼吸肌缩短发生时肌电图活动（EMG）的增加是否必要，在11只麻醉犬迷走神经切断前后，于未阻塞（UB）呼吸和阻塞（OB）呼吸期间，使用超声测量法测量胸骨旁肋间肌长度的呼吸变化。在UB期间，无论是在吸氧时还是在进行性高氧高碳酸血症期间，胸骨旁肋间肌吸气缩短程度在迷走神经切断后均大于切断前。胸骨旁缩短、胸骨旁EMG与潮气量之间的关系并未因迷走神经切断而受到实质性影响。在OB期间，当迷走神经完整时，胸骨旁肋间肌EMG与UB相比显著增加，但气道阻塞在迷走神经切断后并未显著改变EMG活动。然而，在迷走神经切断前后，所有动物在OB期间胸骨旁肋间肌均缩短。在吸氧和中度高碳酸血症期间，OB期间胸骨旁肋间肌吸气缩短占UB期间的百分比在迷走神经切断前显著高于切断后，但在高二氧化碳水平时迷走神经完整性并无显著差异。这些结果表明：（1）肺牵张感受器传入神经抑制胸骨旁肋间肌吸气缩短，但与其对胸骨旁肋间肌EMG和潮气量的抑制作用成比例；（2）即使EMG保持恒定，在阻塞呼吸期间胸骨旁肋间肌也不会等长收缩。
