ELECTRONIC APPARATUS AND INSTRUMENTS FOR USE IN SURGERY AND MONITORING PATIENTS, NAMELY, MONITORS AND VISUAL DISPLAY UNITS FOR USE IN CARDIAC OUTPUT MONITORING AND FOR THE MONITORING OF OXYGEN LEVELS; ELECTRONIC PATIENT MONITORS; SURGICAL, MEDICAL AND CARDIOVASCULAR APPARATUS AND INSTRUMENTS, NAMELY, CATHETERS AND THE INSTRUMENTATION FOR USE IN CARDIAC OUTPUT MONITORING AND FOR THE MONITORING OF OXYGEN LEVELS AND SEALS AND FITTINGS THEREOF; SYNTHETIC AND NON-SYNTHETIC HEART VALVE PROSTHESIS C...