ST. LOUIS—On May 27, 1995, actor Christopher Reeve suffered a spinal cord injury that left him with no motor or sensory function below his shoulders. Today, he has regained sensory function in more than 70% of his body and has 20% of normal motor function. His goal for this year? To get off his ventilator entirely.[1] According to the physicians caring for him, this goal may well be achievable.

A NOVEL THERAPY PROGRAM

Two researchers from the University of Florida at Gainesville—A. Daniel Martin, PhD, PT, Associate Professor in the Department of Physical Therapy, and Paul Davenport, PhD, from the Department of Physiological Sciences—developed Mr. Reeve’s breathing exercise program. The two doctors theorized that the increase in carbon dioxide caused by reducing the amount of air from the ventilator during exercise would trigger autonomic breathing.

“We suspect that many patients with spinal cord injuries and other medical problems remain ventilator dependent because of a muscle rehabilitation problem that nobody is addressing systematically,” said Dr. Martin. “Little attention has been given to increasing the capacity to do [the work of breathing] by increasing the strength and endurance of respiratory muscles.”

In animal models, said Dr. Martin, the respiratory muscles undergo severe deconditioning that is observable after as little as six hours of mechanical ventilation. To stop this decline in muscle strength, Dr. Martin and his colleagues developed a regimen called inspiratory muscle strength training (IMST). The regimen uses a conventional positive expiratory pressure threshold device in the range of 4 to 20 cm H2O. When training pressure exceeds 20 cm H2O, a threshold inspiratory muscle device is used.

The usual direction of the positive expiratory pressure is reversed by having the patient inhale through the opening normally used for exhalation. “This has sometimes been done with emphysema patients to increase respiratory muscle strength, but at a low pressure setting … that builds endurance but not strength,” Dr. Martin observed. “IMST [sessions] include three to five sets of six repetitions, for a total of 18 to 30 training breaths per day.” The pressure against which the patient inhales is adjusted to an exertion rating of 6 to 8 on a patient-rated scale of 0 to 10.

Drs. Martin and Davenport recently described how they used IMST to wean nine out of 10 consecutive patients from mechanical ventilation.[2] They now routinely use IMST for patients at high risk of ventilator dependence.

Dr. Martin explained that although the strength of respiratory muscles increases rapidly during the first two or three weeks of IMST, this is not due to muscle growth. Rather, he said, “strength increases rapidly because the nervous system becomes better at [activating the muscle and] because the muscle becomes more efficient at transducing the electrical signal into contractile activity.”

For Mr. Reeve, the IMST program worked. He is still ventilator dependent but can breathe correctly without the ventilator for up to 90 minutes.

Regaining the ability to breathe independently is a great achievement. “With exercise and training I am able to move my diaphragm and breathe quite well off the vent, which is one of the most comforting aspects of my recovery,” Mr. Reeve said. He added that “getting off the ventilator would mean I no longer need care from others 24/7.”

RETRAINING THE SPINAL CORD

Mr. Reeve’s improvement from an American Spinal Injury Association (ASIA) grade A function level to grade C is unprecedented; it is the first documented occurrence of a patient improving two ASIA grades of function more than two years after a spinal cord injury when no initial recovery had occurred. His achievement raises new questions about how much recovery is possible for adults with these types of injuries.

John W. McDonald III, MD, PhD, Medical Director of the Spinal Cord Injury Program at Washington University School of Medicine in St. Louis, credits Mr. Reeve’s long-term dedication to his rehabilitation program for much of his recovery. “We hypothesize that patterned neuronal activity is one factor that is important after injury in order to optimize spontaneous regeneration,” Dr. McDonald said. He added that patients with less severe injuries (ASIA grades B or C) might have even better outcomes.

Mr. Reeve’s therapy includes stationary cycling with functional electrical stimulation (FES) of the hamstring, quadriceps, and gluteal muscles. He also performs daily range-of-motion physical therapy, surface electrical stimulation of muscles, and breathing exercises. He takes pamidronate to maintain bone mass.

In 1998, he added treadmill walking in a weight-supported harness to his exercise regimen. V. Reggie Edgerton, MD, and colleagues at the University of California in Los Angeles developed the walking component of Mr. Reeve’s rehabilitation program. They based the treadmill program on the theory that paraplegics who still had upper body control could regain their ability to walk by “retraining” the spinal cord through repetitive exposure to patterns associated with walking and stepping.

THE “N OF ONE” STUDY

In 2000, Dr. McDonald and Mr. Reeve began collaborating on a two-year “N of One” study to see what further improvements are possible. Mr. Reeve called this his “project for 2001 and 2002.”

By July of 2001, Dr. McDonald had documented an improvement in light touch sensation to 52% of normal, and Mr. Reeve’s motor function had improved sufficiently to have his ASIA grade changed to C. He can move most of the muscles in his upper arms and has some movement in his legs but cannot yet stand unsupported.

Mr. Reeve also has 50% of normal pinprick sensation and 66% of normal light touch sensation. He can differentiate between hot and cold, knows when he has to change position, can sit for up to 16 hours and—most importantly—is able to resume work. Having achieved this much, his goal for 2003 is to be able to get off mechanical ventilation entirely.

PATIENTS NEED ACCESS TO THERAPY

Whether other patients will be able to duplicate Mr. Reeve’s achievements may depend on available resources. Unfortunately, most people with spinal cord injuries lose access to rehabilitation equipment and support staff once they go home, and the duration of inpatient rehabilitation has decreased progressively during the past decade.

Limitations to the widespread use of patterned neural activity are the prohibitive cost and restricted availability of FES bikes: One bike can cost up to $16,000. Insurance usually does not pay for the bikes, and they are not practical for typical home use because of their size. Dr. McDonald also noted that people with spinal cord injury who have resumed their lifestyles and work do not have time to get to a rehabilitation center three times a week. These people are in need of a therapy program they can do at home in a reasonable amount of time.

—Reported by Janis Kelly
Written by Gale Jurasek and Janis Kelly