[Mass flow anesthesia delivery system and its application].

Microcomputer-based anesthesia delivery system using mass flow control devices has been developed. System is superior in computer control to conventional anesthesia machine because there is no mechanical setting. System consists of three thermal mass flow controllers (TMFC), one vapor source controller (VSC), personal computer system, and air circuits. Personal computer system has facilities of digital output, analogue input and analogue output interfaces. TMFCs and VSC are devices which operational principle is based on the thermal conductance and they are controlled by electrical signals from computer in the system. TMFCs control the mass flow of nitrous oxide, oxygen and carbon oxide according to each input voltage signal. VSC regulates mass vapor of halothane in order to keep set value up by means of alteration of oxygen carrier gas flow. Computer always monitors the gas flow of the TMFCs and VSC so that computer compensates the change of the carrier gas flow of VSC by regulating the TMFC for oxygen. Mixed gas from TMFCs and VSC is supplied through the air circuit to subject. Characteristics of the system was measured by mass spectrometer and flowmeter. Stability was 0.05% change after 30 minutes at the initial set of 3%. Experiment on animals using mongrel dogs has been performed to verify the system functions.