[Functional electric stimulation of the phrenic nerve and its clinical significance]. / Funktionell elstimulering av nervus phrenicus och dess kliniska betydelse.

The peripheral parts of the phrenic nerve are healthy in some of the patients who require permanent or intermittent care in a respirator owing to reduced respiratory function of central aetiology. In such cases, continual care in a mechanical respirator can be avoided, and diaphragm function maintained by means of functional electrical stimulation (FES) of the phrenic nerve with carefully controlled electrical impulses. The method is suitable for use in certain cases of quadriplegia, or in patients with sleep apnoea. Experience with the method has shown that health care costs can be reduced and the patients' quality of life improved. In some cases, the patient may even regain partial work capacity.

Neurophysiological and technical considerations for the design of an implantable phrenic nerve stimulator.

Sequential stimulation during one muscle contraction of several compartments of a motor nerve, using multiple-electrodes, allows individual nerve-muscle compartments to be stimulated at fairly low frequencies. This provides time for recovery even during muscle contraction. However, the whole muscle is stimulated at near to its optimum fusion frequency, which provides smooth muscle contraction. This stimulation system imitates the natural activation of skeletal muscle. The new phrenic nerve stimulator described utilises the principle of sequential motor nerve stimulation. It also incorporates a sigh function. The sigh current recruits additional axons at certain intervals and thus creates and keeps available a reserve of conditioned muscle. Clinical advantages result: the conditioning phase after the beginning of long-term phrenic nerve stimulation for electroventilation is shortened and muscle fatigue is delayed. A need of increase of gas exchange can be answered by increasing tidal volume instead of respiration rate alone.