Cyclically operated medical respirators

Claim 1

A multi-mode respirator having a pneumatically operated inspiration control valve, a pneumatically operated expiration control valve, bellow means in a patient gas path for measuring the volume of gas flowing to the patient and the volume of gas flowing from the patient, at least two of the following inspiratory and expiratory mode switches comprising: (a) inspiratory and expiratory volume mode pneumatic switches operatively connected to said bellow means to be operated by said bellow means respectively when the volume of gas flowing to the patient and the volume of gas flowing from the patient reaches predetermined magnitudes; (b) inspiratory and expiratory pressure mode pneumatic switches with pressure sensing means responsive to the pressure of inhaled and exhaled gas and operatively connected to said inspiratory and expiratory pressure mode switches to switch the inspiratory pressure mode switch when the pressure exceeds a predetermined value and to switch the expiratory pressure mode switch when the pressure falls below a predetermined value; and (c) inspiratory and expiratory time mode pneumatic switches each having a control input for pneumatic operation of the switch and each being connected to a separate pneumatic delay including a piston operated through a restricted orifice whereby each time switch operates it a time instant delayed after the application of pneumatic pressure to its control input, each of the mode switches controlling gas flow through a separate gas path, separate selector switches pneumatically in series each with one of the mode switches in said separate gas paths, selector switch operating means operatively connected to said selector switches to effect opening of any one or more of the selector switches in series with inspiratory mode switches and of any one or more of the selector switches in series with expiratory mode switches, a pneumatic change-over valve having an input and two alternative outputs and two control inputs, one control input being effective when pneumatic pressure is applied thereto to change-over the valve in one direction and the other control input being effective when pneumatic pressure is applied thereto to change-over the valve in the other direction, a pneumatic pressure source connected to the input of said first change-over valve, a first pneumatic control circuit for said change-over valve, said first pneumatic control circuit includIng a pneumatic patient gas path having the inspiratory mode switches each with its series selector switch in the respective gas flow paths connected in parallel to one control input of the change-over valve, pneumatic pressure supply means for said first pneumatic control circuit comprising a supply connection from one outlet of said change-over valve or from a source controlled by that outlet, a second pneumatic control circuit for said change-over valve, said second control circuit including the expiratory mode switches, each with its series selector switch, connected in parallel to the second control input of said change-over valve, pneumatic pressure means for said second pneumatic control circuit comprising a supply connection from the second outlet of the change-over valve or from a source controlled by that outlet, means applying pressure from said first and said second outlets of said change-over valve to the inspiratory and expiratory time mode pneumatic delays respectively to initiate operation of the respective time delays when the change-over valve changes over to provide pressure at its first and second outlets, respectively, and means applying pressure from said first and said second change-over valve outlets to said expiratory and said inspiratory control valves respectively or to switch means controlling the application of pressure to said inspiratory control valves.