Ever since his lung surgery, President Reagan has been getting physical therapy treatments every four hours to prevent infection by keeping his damaged lung inflated and helping him cough up old blood and mucus. k

The treatments are the most uncomfortable part of Reagan's day, according to Mary Tiemann, chief chest physical therapist at George Washington University Hospital. Until last weekend, docters were requiring that Reagan receive treatments even in the middle of the night.

A typical session usually lasts 10 to 15 minutes. The therapist first asks Reagan to lie on his right side, and then claps on the left side of his back with cupped hands. This loosens secretions in the underlying lung, and because of gravity they move from the lung toward the windpipe.

Next, the therapist asks Reagan to take deep breaths, and as he exhales, slowly vibrates the area over his ribs, below and behind his surgical incision. Tiemann said this is also designed to move mucus out of the damaged area of lung.

Next, the president does deep-breathing exercises and is urged to cough up as much material as he can. "He never really coughed up a lot," she said.

Finally, he performs shoulder exercises to keep the joint from stiffening up from disuse.