Hemodynamic alarm system for pulmonary artery catheters in an intensive care unit

A pulmonary artery (PA) catheter (PAC) is placed in a large vein and guided through the right side of the heart to the PA. The PAC measures blood pressure in the PA directly and indirectly in the left atrium through a procedure called "wedging". Since the PAC is in a dynamic environment, inaccurate measurements can result for various reasons (events). We constructed an online fuzzy expert system to monitor cardiac data continuously and alarm when an untoward event was detected. Of 13 patients monitored while developing the prototype system, only two failed to exhibit alarm events. A 200-patient clinical trial confirmed that the system substantially reduced the number and duration of alarm events. The original program used our fuzzy expert system shell "FLOPS". The rule syntax is quite different from fuzzy control systems, using approximate numerical comparisons and categorical outputs. Input is from the cardiac monitor units via RS-232 or Ethernet and output is voice alarm messages, such as "Bed 4-extended damp".