Diaphragmatic pacemaker

A diaphragmatic pacemaker, in medicine, is a surgically-implanted device used to help patients breathe following complications from spinal cord injuries. The device works through pacing of the diaphragm.

Mechanism
In patients with a diaphragmatic pacemaker, their breathing is helped by setting the respiratory rate by electrical stimulation (pacing) of the phrenic nerve. The pacing is accomplished via electrodes surgically implanted into the diaphragm, which is controlled by the phrenic nerve.

Diaphragm pacing stimulates a normal breath response as follows: when an electrical current is passed through the electrodes, the diaphragm contracts, expanding the chest cavity, causing air to be sucked into the lungs (inspiration). When the nerve is not stimulated, the diaphragm relaxes and air moves out of the lungs (expiration).

Procedure
This procedure is currently experimental. It is being tested in patients with injuries that cut across (transect) the cervical spinal cord high in the neck and result in paralysis of all four limbs (tetraplegia) and respiratory failure which require constant mechanical ventilatory support. For the procedure to work, the function of the phrenic nerve must be normal.

Diaphragm pacing originally required a surgical opening of the chest cavity (thoracotomy) to implant the electrodes. It is now done by laparoscopy through small openings in the chest. Patients undergo laparoscopic implantation of electrodes in the muscle of the diaphragm and initial electrical stimulation. Following a recovery period of a week or so, diaphragm pacing is initiated. Wires from the electrodes in the diaphragm run to and from a control box worn outside the body. The pacing is performed according to a reconditioning program in which the duration and frequency of electrode stimulation is gradually increased until full-time diaphragm pacing is achieved.

The actor Christopher Reeve, who was paralyzed and on a respirator after fracturing his neck in a horseback riding accident, underwent the procedure in 2003.