A suction catheter adaptor assembly comprising: an airway adaptor comprising: an inner surface defining a passageway between a proximal end and a distal end of the airway adaptor, the distal end configured to couple with an artificial airway; and a valve configured to occlude the passageway, the valve comprising: a resiliently flexible annular member; and a plurality of valve segments separated by a slit; and an adaptor body having a seal, the adaptor body comprising an inner surface defining a passageway between a proximal end and a distal end of the adaptor body, the distal end of the adaptor body configured to couple with the proximal end of the airway adaptor, the seal configured to extend across the adaptor body passageway, the seal comprising: a radial flange having an access aperture; and a plunger comprising a cylindrical shaft extending distally from the radial flange toward the distal end of the adaptor body and terminating in an annular edge, wherein the adaptor body is structured such that deflection of the radial flange toward the distal end of the adaptor body moves the plunger away from the proximal end of the adaptor body; wherein the adaptor assembly is structured such that, when the distal end of the adaptor body is coupled with the proximal end of the airway adaptor, deflection of the radial flange toward the distal end of the adaptor body engages the annular edge of the plunger against the annular member of the airway adaptor valve, such that the plurality of valve segments are deflected toward the distal end of the airway adaptor to open the slit and fluidly couple the airway adaptor passageway and adaptor body passageway. an airway adaptor comprising: an inner surface defining a passageway between a proximal end and a distal end of the airway adaptor, the distal end configured to couple with an artificial airway; and a valve configured to occlude the passageway, the valve comprising: a resiliently flexible annular member; and a plurality of valve segments separated by a slit; and an adaptor body having a seal, the adaptor body comprising an inner surface defining a passageway between a proximal end and a distal end of the adaptor body, the distal end of the adaptor body configured to couple with the proximal end of the airway adaptor, the seal configured to extend across the adaptor body passageway, the seal comprising: a radial flange having an access aperture; and a plunger comprising a cylindrical shaft extending distally from the radial flange toward the distal end of the adaptor body and terminating in an annular edge, wherein the adaptor body is structured such that deflection of the radial flange toward the distal end of the adaptor body moves the plunger away from the proximal end of the adaptor body; wherein the adaptor assembly is structured such that, when the distal end of the adaptor body is coupled with the proximal end of the airway adaptor, deflection of the radial flange toward the distal end of the adaptor body engages the annular edge of the plunger against the annular member of the airway adaptor valve, such that the plurality of valve segments are deflected toward the distal end of the airway adaptor to open the slit and fluidly couple the airway adaptor passageway and adaptor body passageway.