An in vivo mass spectrometer system for the continuous monitoring of Po2 and Pco2. 
A mass spectrometer blood gas catheter system for the continuous in vivo analysis of Po2 and Pco2 has been presented.  This system has been experimentally evaluated and demonstrated to be reliable and reproducible over a period of 30 hr following insertion of the catheter in the abdominal aorta.  Although the present catheter design does not allow insertion through an existing umbilical arterial line in neonates, a clinical evaluation will be undertaken when a more flexible catheter becomes available.