sentences:  His final improvement was the addition of a transparent positive pressure dome, allowing ventilation when the chamber was opened to care for the patient.In the mid-1940s, following a suggestion of Dr. Alvin Barach, Emerson perfected the Thunberg barospirator, which caused respiration without moving the lungs at all.Emerson was involved with the development of high-altitude flight valves and SCUBA gear for the Navy shortly before World War II.