Christopher Reeve, whose recovery from severe upper spinal cord injury continues to fascinate researchers, became the third patient to try an experimental device that stimulates the diaphragm and permits ventilator-independent breathing. Researchers Anthony F. DiMarco, MD, Raymond Onders, MD, and colleagues at Case Western Reserve University in Cleveland developed the device, which requires only laparoscopic surgery and does not carry the risks associated with traditional phrenic nerve pacing.

Dr. DiMarco told Neurology Reviews, “Our goal is to provide something safer and less expensive than conventional phrenic nerve pacing. Our experience so far suggests that diaphragm pacing provides an overall improved sense of well-being and enables the patient not only to breathe but also to speak more normally. There are also social benefits, since in a casual setting you really can’t tell that a patient is being paced by this device.”

SETTING THE PACE

The procedure for Mr. Reeve was substantially the same as that used in the initial case the investigators reported last year except that they are now using only suction electrodes to identify target areas in the diaphragm rather than the elaborate fine mapping technique described in that report.

Briefly, four trocars are placed into the abdominal wall and a pneumoperitoneum is created. Suction electrodes are used to identify the phrenic nerve motor points, where the phrenic nerves enter the diaphragm. Two stainless steel intramuscular diaphragm electrodes are inserted into the motor points of each hemidiaphragm in the same plane as the diaphragm. Wires from the four electrodes are brought out through the epigastric port, leaving some slack to allow movement, tunneled subcutaneously to the chest, and attached to a connecting circuit. Each wire is then tunneled subcutaneously to the right or left subclavicular region, where the wires exit the chest wall.

Following a 10- to 14-day recovery period, the researchers attach a four-channel electrical stimulator about the size of two decks of playing cards to the four electrodes. This is programmed to produce regular contractions (“pacing”) of the diaphragm. During a period of 14 to 20 weeks, the patient switches from the ventilator to progressively longer periods of pacing.

The first patient to use Dr. DiMarco’s device has been free of mechanical ventilation for two years, continues to do well, and has a maximum inspired volume of more than 1,200 mL. In the second patient, however, the device was not successful. “There was no inspiratory action at all, and we are still trying to figure out why,” Dr. DiMarco said. “We suspect that there were unrecognized problems in phrenic nerve function in this patient.”

BREATHING EASIER?