FUNCTIONAL NEURAL COUPLING BETWEEN DIAPHRAGM AND PARASTERNAL INTERCOSTAL MUSCLES IN HUMANS

Abstract

This chapter explores functional neural coupling between diaphragm and parasternal intercostal muscles in humans. In a study described in the chapter, electrical activity of intercostal muscles was measured from pairs of fine silver wires, uninsulated over four to eight mm at each end, inserted directly into the muscle by means of a 26 gauge needle. The wires were bent back over the tip of the needle. After insertion into the appropriate muscle, the needle was withdrawn leaving the wires, with hooks at their ends, remaining in the muscle. In this way, the wire electrodes were in a stable position, and records could be obtained for a period of one to two hours without apparent charge because of electrode movement. Nine observations in six adult male subjects yielded acceptable records, apparently uncontaminated by adjacent musculature. It was found that in all subjects, the parasternal intercostal muscles were active during quiet inspiration and quiet during expiration. This activity was invariably seen clearly on the tracings from the wire electrodes inserted into the muscle, but only infrequently discernable from the parasternal surface EMG records. In contrast, no phasic activity was seen during quiet breathing from the wire electrodes in the seventh interspaces laterally or posteriorly.