De Troyer André, Gorman Robert B, Gandevia Simon C
Laboratory of Cardiorespiratory Physiology, Brussels School of Medicine and Chest Service, Erasme University Hospital, 1070 Brussels, Belgium.
J Physiol. 2003 Feb 1;546(Pt 3):943-54. doi: 10.1113/jphysiol.2002.028696.
The external intercostal muscles in humans show marked regional differences in respiratory effect, and this implies that their action on the lung during breathing is primarily determined by the spatial distribution of neural drive among them. To assess this distribution, monopolar electrodes were implanted under ultrasound guidance in different muscle areas in six healthy individuals and electromyographic recordings were made during resting breathing. The muscles in the dorsal portion of the third and fifth interspace showed phasic inspiratory activity with each breath in every subject. However, the muscle in the ventral portion of the third interspace showed inspiratory activity in only three subjects, and the muscle in the dorsal portion of the seventh interspace was almost invariably silent. Also, activity in the ventral portion of the third interspace, when present, and activity in the dorsal portion of the fifth interspace were delayed relative to the onset of activity in the dorsal portion of the third interspace. In addition, the discharge frequency of the motor units identified in the dorsal portion of the third interspace averaged (mean +/- S.E.M.) 11.9 +/- 0.3 Hz and was significantly greater than the discharge frequency of the motor units in both the ventral portion of the third interspace (6.0 +/- 0.5 Hz) and the dorsal portion of the fifth interspace (6.7 +/- 0.4 Hz). The muscle in the dorsal portion of the third interspace started firing simultaneously with the parasternal intercostal in the same interspace, and the discharge frequency of its motor units was even significantly greater (11.4 +/- 0.3 vs. 8.9 +/- 0.2 Hz). These observations indicate that the distribution of neural inspiratory drive to the external intercostals in humans takes place along dorsoventral and rostrocaudal gradients and mirrors the spatial distribution of inspiratory mechanical advantage.
人类的肋间外肌在呼吸作用上呈现出显著的区域差异，这意味着它们在呼吸过程中对肺部的作用主要由神经驱动在其中的空间分布所决定。为了评估这种分布情况，在超声引导下，将单极电极植入六名健康个体的不同肌肉区域，并在静息呼吸期间进行肌电图记录。在每个受试者中，第三和第五肋间间隙背侧部分的肌肉在每次呼吸时均表现出阶段性吸气活动。然而，第三肋间间隙腹侧部分的肌肉仅在三名受试者中表现出吸气活动，而第七肋间间隙背侧部分的肌肉几乎始终处于静息状态。此外，第三肋间间隙腹侧部分的活动（若存在）以及第五肋间间隙背侧部分的活动相对于第三肋间间隙背侧部分活动的起始存在延迟。另外，在第三肋间间隙背侧部分识别出的运动单位放电频率平均为（均值±标准误）11.9±0.3Hz，显著高于第三肋间间隙腹侧部分（6.0±0.5Hz）和第五肋间间隙背侧部分（6.7±0.4Hz）的运动单位放电频率。第三肋间间隙背侧部分的肌肉与同一肋间间隙的胸骨旁肋间肌同时开始放电，并且其运动单位的放电频率甚至显著更高（11.4±0.3对8.9±0.2Hz）。这些观察结果表明，人类肋间外肌神经吸气驱动的分布沿背腹和头尾梯度发生，并且反映了吸气机械优势的空间分布。
