A suction catheter assembly for use in removing undesirable fluid from a patient includes an aspirating catheter having a proximal end and a distal end, the distal end being suitable for insertion into a patient; a vacuum connecting member located in the vicinity of the proximal end of the catheter; a patient connecting member mounted to surround the aspirating catheter in the vicinity of the distal end of the catheter, the patient connecting member housing a wiper/seal member sealingly engaging with the outside surface of the catheter; a protective sleeve surrounding at least the majority of the length of the catheter and extending between the vacuum connecting member and the patient connecting member, the protective sleeve being adapted to permit the distal end of the catheter to be extended from the protective sleeve into the patient and to be withdrawn from the patient; and a separate one-way valve member within the patient connecting member so that the one-way valve permits gas flow therethrough from inside the sleeve and into the patient connecting member but prevents any substantial gas flow through the one-way valve into the sleeve so that any gas trapped in the sleeve can escape into the patient connecting member through the one-way valve.