Lung ventilator including volume meter for measuring total volume

Claim 1

A lung ventilator comprising a gas dosing unit for delivering periodically predetermined volumes of breathing gas, a patient conduit means an inspiratory gas conduit connecting said dosing unit with said patient conduit means for conveying breathing gas from said dosing unit to a patient during the inspiratory phase of each respiratory cycle, an expiratory gas conduit connected to said patient conduit means for conveying expirated gas from the patient during the expiratory phase of each respiratory cycle, an inspiratory valve means in said inspiratory gas conduit providing a one-way gas flow from said dosing unit to said patient conduit means an expiration valve means in said expiratory gas conduit operated in synchronism with said dosing unit to Be open during the expiratory phase and closed during the inspiratory phase of each respiratory cycle, gas volume measuring means connected to said expiratory gas conduit downstream of said expiration valve means for measuring the gas volume being conveyed through said expiratory gas conduit, additional valve means connected to the portion of said expiratory gas conduit extending between said expiration valve means and said gas volume measuring means for putting said portion of the expiratory gas conduit in communication with the ambient atmosphere when said additional valve means is in its open state, and control means operating in synchronism with said dosing unit for keeping said additional valve means in its open state during the inspiratory phase and in its closed state during the expiratory phase of each respiratory cycle.