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Surgical implantation of an electric stimulator freed spinal cord injury patient J.T. Townsend Jr. (center)from his respirator.

December 2005 – Ventilators May Be Replaced by Device

By: Betsy Bates

SAN FRANCISCO – A novel electrical stimulation system that acts on the diaphragm has freed some patients with spinal cord injuries from ventilators and significantly improved breathing capacity in patients with Lou Gehrig’s disease, Raymond P. Onders, M.D., said at the annual clinical congress of the American College of Surgeons.

He presented results in 22 patients as a preliminary report of ongoing trials in spinal cord injury and amyotrophic lateral sclerosis (ALS). Studies of primary alveolar hypoventilation (Ondine’s curse) are also underway.

Laparoscopic motor point diaphragm pacing stimulates contractions of the muscles that control breathing by use of electrodes attached to an external battery pack about the size of a television remote control. The system conditions the diaphragm muscles, enhancing their effectiveness, while producing negative pressure within the chest and oxygenating the posterior lobes of the lung that are vulnerable to pneumonia in ventilator-dependent patients.

During surgery, a laparoscope is introduced through the umbilicus to permit viewing of the diaphragm from below. Suction cup electrodes are used to stimulate every section of the diaphragm, guided by a grid algorithm.

Once identified, the electrodes are placed and wires threaded to the external battery pack, which lasts several weeks.

“We are really excited about this. We have been working on this for a decade, and now we have clinical results,” he said.

The system developed by Dr. Onders has enabled 17 of 18 patients with spinal cord injuries to wean themselves off ventilators, including a 19-year-old who had no recollection of breathing, having been on a ventilator since he broke his neck at age 2.

The only failure was in a patient who turned out to have a nonfunctioning phrenic nerve as a result of his injury.

The phrenic nerve enervates the diaphragm and is therefore required for independent breathing. Theoretically, the technology could enhance breathing capacity of virtually any patient requiring a ventilator whose phrenic nerves are intact, said Dr. Onders, director of minimally invasive surgery at University Hospitals of Cleveland.

Moreover, the simple system frees many patients and their families from the expense, inconvenience, noise, and lifestyle restrictions associated with ventilator dependence, Dr. Onders said.

Four patients with ALS, also known as Lou Gehrig’s disease, have received diaphragm pacing devices as well, and Dr. Onders characterized their progress as “very impressive.”

The first three patients have doubled their life expectancy as calculated by the arc of decline in forced vital capacity, with their mean life expectancy rising from 6.2 months to 11.7 months and counting – none have died since receiving their pacers.

Their diaphragms are thicker, they are breathing more easily, and they report an improvement in their ability to talk. (The fourth patient with ALS has not had the pacing system long enough to quantify results.) One patient with ALS is currently using the diaphragm pacer 24 hours a day to breathe, although the device – deemed “investigational” by the FDA – is not intended as a life support system.

With ALS, the goal is to prevent the need for a ventilator by compensating for the death of motor neurons that inexorably deprive ALS patients of the ability to breathe.

Conditioning the diaphragm enhances its performance, just as muscles around the knee are strengthened following surgery by use of a TENS unit, Dr. Onders explained. A hoped for secondary goal in ALS would be to foster “collateral sprouting,” the transference of tasks to adjacent motor neurons as the disease progresses.

“As one axon dies, the one next to it will take over for it,” he said, describing a theory that has proved true in the extremities and may apply to motor neurons enervating diaphragmatic muscles as well.

During surgery to implant the pacer wires, the diaphragm of one ALS patient in Dr. Onders’ study appeared striped, which also lends credence to the idea that stimulation could be used to tap into undamaged muscle and nerves.

“It was one of those ‘Eureka!’ moments during surgery,” he said. “Parts of the muscle were denervated and parts were normal.”

During fluoroscopy following surgery, ALS patients took “sniff ” tests to determine how much of their diaphragms they could control during breathing, versus the degree of control the pacer signals had over their diaphragm muscles. Surprisingly, in one patient, the pacer could produce 2 cm of diaphragm movement Trauma 13 to the 1 cm she could control by sniffing.

The laparoscopic procedure costs approximately $12,000 and is reimbursed by Medicare. The device currently made by Synapse Biomedical, a university-owned company, would cost approximately $10,000.

Ventilators cost $120,000 a year and reduce the average life expectancy of spinal cord injury patients by 13 years.

One of Dr. Onders’ patients was Christopher Reeves. Two are former high school football players who suffered spinal cord injuries on the field.

Another lost her home in Hurricane Rita but did not panic in the power outage since she no longer needs her ventilator to breathe, and the pacer that conditions her diaphragm operates on a battery that lasts 2 weeks.

Dr. Onders said he has noted no decrease in potency of the device over time in patients with either spinal cord injuries or ALS; in fact, one spinal cord patient has used the device for more than 62 straight months.

“Our goal is to get people out into society more. We designed the whole thing to make it simple,” Dr. Onders said.