An iron lung—or negative pressure ventilator—is an airtight metal tank that encloses all of the body except the head and forces the lungs to inhale and exhale through regulated changes in air pressure. It was invented in 1928 by American industrial hygienist Philip Drinker. Though Drinker devised the iron lung to help victims of coal gas poisoning, it became a preferred treatment for polio, which tends to paralyze the respiratory muscles. What methods have largely replaced the iron lung? Discuss