| abstract |
An assembly for insertion into the cardiovascular system of a patient comprising a catheter having first and second lumens and a distal port. The first lumen opens at the distal port. A probe is received in the second lumen. The probe includes a sensor responsive to a constituent of blood for providing a signal which is related to the constituent. The catheter has a window for allowing the constituent of blood to pass from outside the catheter to the sensor while substantially preventing other constituents of blood from passing from the outside of the catheter to the sensor. |