Clinical trial of an ex vivo arterial blood gas monitor

Purpose: The purpose of this study was to test the performance of a patient attached, on demand ex vivo arterial blood gas (ABG) monitor, and to compa re the frequency of ABG analysis using the monitor, where the monitor was o perated by intensive care unit (ICU) staff on shock trauma and neurosurgica l intensive care patients for less than or equal to 6 days, with standard c linical laboratory analysis. Materials and Methods: The ABG monitor (SensiCath; Optical Sensors Inc., Mi nneapolis, MRI) incorporates fiber optic pH, PCO2, PO2, and thermistor temp erature sensors in a 0.3-mL sensor chamber that attaches in line with the p atient's arterial pressure tubing and connects via a fiberoptic cable to a bedside instrument. The monitor and standard clinical laboratory performanc e were compared following an institutionally approved protocol. Adult ICU p atients (n = 30) were studied for whom an arterial cannula was required, th e expected ICU stay was >72 hours, greater than or equal to 2 ABG analyses/ day were anticipated, and informed consent had been obtained. Paired compar ison ABG analyses and quality assurance checks were performed daily. The fr equency of ABG analyses in this study, for which monitor values were used f or clinical decision making, was compared with the frequency previously rep orted for the same ICUs, for which the monitor and laboratory results were compared but only the latter were used for clinical decision making. Results: Five hundred ABG analyses, 436 over the first 72 hours, were obtai ned using the monitor for patient management over 3,248 patient hours (85 /- 47 hours/ patient). Monitor-laboratory comparison ABG analyses (n = 258) indicated stable performance over 6 days: For pH, the range of laboratory measurements was 7.200 to 7.540, accuracy (mean difference between monitor and laboratory measurement) was +0.013, and precision (standard deviation o f difference between monitor and laboratory measurements) was +/-0.031. For PCO2, range: 18 to 78.5, accuracy: -0.8, precision: +/-3.4 mm Hg. For PO2, range: 41.0 to 344.0, accuracy: +2,3, precision: +/-12.8 mm Hg. The freque ncy of ABG analyses obtained using the monitor (ie, 15.0 +/- 11.6 ABGs/pati ent/72 hours) was significantly greater than that using the clinical labora tory lie, 8.8 +/- 4.2 ABGs/patient/72 hours) (P =.01). Conclusion: The ABG monitor provides performance comparable to standard cli nical laboratory analysis for less than or equal to 6 days (less than or eq ual to 144 hours), consistent with ICU arterial cannula changeout schedules . More frequent ABG analyses are obtained by critical care practitioners us ing the monitor compared with the clinical laboratory system, suggesting th at clinical decision making based on ABG data may be limited by the frequen cy of ABG analysis. Copyright (C) 1998 by W.B, Saunders Company.