Rest for the weary dialysis patient.

People who suffer total kidney failure can prolong their lives with regular hemodialysis - a mechanical filtering technique that cleanses the blood of waste products and toxins. But this life-saving treatment also produces debilitating side effects. For example, many dialysis patients are constantly jarred from sleep by brief episodes of interrupted breathing, called sleep apnea, and involuntary muscle twitching.

Now, nephrologist Robert L. Benz has shown that a small bedside respirator can offer significant relief to dialysis patients desperately seeking a good night's sleep.

Benz, medical director of the Haverford Dialysis Unit at Lankenau Hospital in Wynnewood, Pa., first tried to treat his patients with sleeping pills. When this proved unsuccessful, he enlisted eight dialysis patients in a sleep study and observed the relentless nocturnal disquiet responsible for their lack of energy and mental alertness during the day.

These patients experienced anywhere from 7.5 to 140 episodes of sleep apnea per hour, Benz explains, and their calf muscles twitched an average of four times per minute. These events momentarily awakened the study participants throughout the night, depriving them of restorative deep sleep.

Even more troubling, especially for patients with heart or lung conditions, is the oxygen starvation caused by sleep apnea. In the worst case, this can cause erratic heart rhythms or even cardiac arrest, Benz notes.

In many of these patients, he explains, sleep apnea traces to the autonomic nervous system in the brain stem. Nitrogen wastes that accumulate in the bodies of dialysis patients may impair this part of the brain, causing interruptions in breathing and involuntary muscle movements, he speculates.

Although the full physiological explanation for sleep disorder in dialysis patients awaits discovery, Benz' therapy has proved effective. Called nasal continuous positive airway pressure (NCPAP), it is essentially a small respirator that assists and stimulates regular breathing throughout the night.

Among his eight study participants, the average incidence of sleep apnea fell from 64.4 episodes per hour to six. Oxygen concentrations in the patients' bloodstreams increased over 10 percent. And most important, says Benz, the patients felt rested the next day.