Abstract: A sealed ventilation circuit interface system, which enables simultaneous patient ventilation and safe tracheal suctioning, is structured to accommodate any of a wide variety of commercially available suction catheters. The interface system comprises a manifold assembly, and an adaptor. The manifold assembly may be attached to a patient for an extended period, while the adaptor is advantageously constructed as a single procedural use disposable device. The adaptor couples with the manifold assembly, and may be configured to effect the introduction of a catheter through a normally closed valve structure carried by the manifold assembly. The adaptor may alternatively be configured to interface the manifold with a bronchoscope or other appliance. A vacuum valve assembly biased in an open position is selectively actuated between open and closed positions and can be locked in a closed position. The vacuum valve remains at either position without ongoing manual pressure.