Abstract: The present invention is directed to novel system, apparatus and methods for securing the longitudinal position of a diagnostic catheter relative to a patient while maintaining established ventilating parameters within a ventilating circuit or when a patient is intubated and non-mechanically ventilated and it is necessary to deflect exhaled gases from the patient. Disclosed is a tubular elbow having nonlinearly aligned first and second ends connectable to the proximal end of an endotracheal tube adapter and a circuit of a ventilating machine. An access vent is formed through the outer wall of the tubular elbow to enable the diagnostic catheter access to the endotracheal tube adapter. Located at the access vent is a gasket having a centrally located aperture capable of making sealing engagement with the outer surface of the diagnostic catheter when the diagnostic catheter is disposed in the access vent, thereby preventing the loss of established ventilating parameters.