It has already enabled the actor to regain his sense of smell.
The 50-year-old actor was paralyzed from the neck down in a horseback riding accident in 1995. Since then, he has lived with the constant hum of a respirator pumping air into his lungs.
After the electrodes were implanted in his diaphragm and the respirator was turned off, "All you could hear was me breathing through my nose - regular rhythmic breathing from my nose for the first time in nearly eight years," Reeve said Thursday.
So far he has been able to breathe for about 15 minutes without a respirator. Before the surgery, Reeve was able to use his neck muscles to breathe without a respirator for only a few minutes. With the stimulator in place, he can breathe more easily and more deeply, said Dr. Anthony DiMarco of University Hospitals of Cleveland.
Use of the electrodes eventually might strengthen Reeve's diaphragm muscles enough to allow him to do without a respirator altogether, said Dr. John McDonald, director of the spinal cord injury program at Washington University in St. Louis. He has helped design the actor's treatment program.
However, DiMarco said does not expect Reeve to ever be able to breathe without some stimulation because the damage to the actor's spinal cord cut off the brain's commands to the diaphragm.
The actor also has his sense of smell when the respirator is off. During one of those sessions, his medical team brought coffee, oranges and other test objects into his room.
"I actually woke up and smelled the coffee," he said.
Over time, the implant should also allow Reeve to speak more normally. His voice is weak now. The implant also could greatly reduce other medical complications caused by the respirator, including infections, doctors said.
Reeve was the third person to undergo the procedure. It was performed at the Cleveland hospital Feb. 28.
The operation, called diaphragm pacing via laparoscopy, involves threading tiny wires through small incisions in the diaphragm. The wires connect the electrodes to a control box worn outside the body.
The control box sends a signal to the electrodes 12 times a minute, causing the diaphragm to contract and air to be sucked into the lungs. When the nerve is unstimulated, the diaphragm relaxes and the air is expelled.
"Our initial test in the operating room to activate Reeve's diaphragm yielded impressive results," Dr. Raymond Onders, who performed the operation, said in a statement.
The first person to receive the implant, 38-year-old Tom Conlan of Medina, was paralyzed in a 1998 swimming accident. He has been breathing with the help of the implants for two years, he said, but keeps a respirator in his closet since the implants are experimental.
In the second patient, the implant system failed to properly stimulate the diaphragm, doctors said.
According to University Hospitals, the alternative treatment for someone with Reeve's paralysis is a thoracotomy, in which doctors open the patient's chest to attach electrodes directly to the nerves that control breathing. But the surgery is riskier than the one Reeve underwent and costs twice as much, at $100,000.
The researchers estimated that out of 10,000 spinal cord injuries in the United States each year, about 1,000 patients require mechanical breathing assistance for some time after the injury. About 300 may require mechanical assistance for the rest of their lives.
Reeve's surgery was funded by a joint research project of the federal Food and Drug Administration and U.S. Surgical Corp., which makes surgical devices, with the assistance of the Veterans Administration and the National Institutes of Health.
"My recovery doesn't mean anything if it doesn't translate into better care for other patients," Reeve said.