Liquid breathing trials and animal studies with a demand regulated liquid breathing system

Experimental results of in vivo animal tests conducted on a demand regulated liquid breathing system are presented. When a liquid replaces gas as the medium in which oxygen and carbon dioxide are transported, several problems not typical in gas respiration occur. The increased mass and viscosity of a liquid as compared with a gas necessitate some means of mechanical assistance. The lower diffusion rates of gases in liquids as compared with gas rates place several constraints on the design of a mechanically assisted liquid breathing system. The liquid breathing system reported in this study was designed to be demand regulated, i.e. the animal has control over cycling the pumps which mechanically assist the circulation of an oxygenated liquid to and from the lungs. This system consists of a gas operated diaphragm punp, demand controller, liquid regenerator with heater and gas scrubber, and ancillary equipment. A demand controller is described which obtains a control signal from an esophageal balloon catheter in the animal, and govern operations of the pneumatically driven diaphragm pump.