NEW YORK—(AP)—The most complete rest ever known, inside a new kind of iron lung, is a recent treatment for tuberculosis shown at the National Tuberculosis Assn. annual meeting here yesterday.

In this [iron] lung a person’s lungs neither expand nor contract. In fact, they do not move a bit. Lung rest, as complete as possible, always has been one of the important steps in recovering from TB.

The [iron] lung is a long, rounded tube, big enough for a man to lie at ease inside, made of shining steel and with plastic windows. A person can enter and leave at will. Inside, he can talk, read and breathe normally, if he wishes.

But by pressing a button, he can stop all movement of lungs and breathing muscles. The secret is slightly compressed air. The iron lung does the compression, rhythmically, taking air from the room outside the tube.

The compressed air flows by its own force into the lung tissues. But it does not expand them, because simultaneously with this inflow, the occupant’s chest is pressed from the outside by air at exactly the same pressure. The occupant doesn’t even feel the compressed air, any more than people feel the changes in air pressure that the weatherman calls highs and lows. But it takes the patient a few days to learn not to try to breathe.

He gets enough oxygen, because the compressed air contains as much as would be present in a normal lungful.

Twenty of these new lungs are now in use in nine American cities. The exhibit is by Drs. Alvin L. Barach, George Foster Herben, Jones H. Cullen and Chismore Eastlake of New York. Dr. Barach started this treatment 10 years ago and the war interfered with development. These New York doctors have treated 22 patients, all bad cases with cavities in the lungs, after other treatments failed to close the cavities.