LONG-TERM EVALUATION OF A CONTINUOUS INTRAARTERIAL BLOOD-GAS MONITORING-SYSTEM IN PATIENTS WITH SEVERE RESPIRATORY-FAILURE

Objective: The purpose of this study was to evaluate the reliability a nd accuracy of a new continuous intra-arterial blood gas monitoring sy stem (IABG; PB3300. Puritan Bennett) over a prolonged period of time ( >7 days). Design: Prospective criterion standard study. Setting: Anest hesiological intensive care unit in a university hospital. Patients: 1 1 sensors were tested in 10 mechanically ventilated patients with seve re respiratory failure. Interventions: PO2, PCO2, and pH measured usin g IABG were compared to values obtained from 2 conventional blood gas analyzers. The quality of blood pressure tracings was assessed using a scoring system consisting of 5 grades. Results: The median study peri od was 205h/sensor (range: 169-506h). 320 blood samples were obtained. The ranges of measured parameters were: PO2=46-433 mmHg, PCO2=25-79 m mHg, pH=7.25-7.55. The mean (SD) differences for the whole study perio d were: -4.3 (11.9) mmHg for PO2, for the clinically important range ( PO2<150 mmHg) -1.9 (5.4) mmHg, -2.8 (4.5) mmHg for PCO2, and -0.03 (0. 04) for the pH value. The MD (SD) in relation to the sensor lifetime w ere for days 1-3: -1.1 (5.1) mmHg for PO2, -0.4 (3.9) mmHg for PCO2, a nd -0.01 (0.03) for the pH value; for days 4-6: -1.5 (6.0) mmHg for PO 2, -3.3 (4.0) mmHg for PCO:, and -0.03 (0.03) for the pH value; for da ys 7-9: -2.5 (4.7) mmHg for PO2, -5.1 (4.6) mmHg for PCO, and -0.04 (0 .04) for the pH value; for days >9: -4.9 (4.4) mmHg for PO2, -5.3 (4.1 ) mmHg for PCO2, and -0.05 (0.03) for the pH value. Conclusions: The I ABG reliably measured blood gases and pH values with acceptable clinic al performance based on the overall results, There was, however, a dec line in the agreement of the sensors and conventional values with incr easing sensor lifetime. The mean differences (bias) and the standard d eviation of differences (precision) of PO2, PCO2 and the pH values wer e acceptable for clinical purposes up to day 6, The arterial blood pre ssure tracings and blood withdrawal were not adversely affected. No si de effects due to the sensors occurred, In summary, a prolonged sensor use for a period of up to 6 days appears to be reasonable. This syste m offers on-line information on oxygenation, ventilation, and acid-bas e status and allows immediate detection of acute and potentially life- threatening events.