Rebreather system that supplies fresh make-up gas according to a user's respiratory minute volume

摘要

A semi-closed circuit rebreather system that adapts to a user's activity level is provided. A vacuum pressure develops in a chamber coupled to a mouthbit as a breathing gas is drawn by the user from the chamber. A positive pressure develops in the chamber as an exhalation gas is expelled by the user into the chamber. An open circuit is coupled to the chamber to supply an increasing mass of fresh make-up gas to the chamber as vacuum pressure in the chamber develops and increases. A closed circuit coupled to the chamber receives and processes the exhalation gas to produce a recycled gas suitable for breathing. No recycled gas is supplied to the chamber until a threshold vacuum pressure is reached therein. The threshold vacuum pressure is indicative of a higher level of respiratory minute volume (RMV). At that point, a volume of recycled gas is supplied to the chamber proportionally with respect to increases in the mass of fresh make-up gas as vacuum pressure increases beyond the threshold vacuum pressure. Thus, during higher levels of RMV, the recycled gas and fresh make-up gas mix in the chamber prior to inhalation therefrom.