CONTINUOUS INTRAARTERIAL BLOOD-GAS AND PH MONITORING IN CRITICALLY ILL PATIENTS WITH SEVERE RESPIRATORY-FAILURE - A PROSPECTIVE, CRITERION STANDARD STUDY

Objective: To evaluate the routine clinical performance of a new intra -arterial fiberoptic blood gas sensor that provides continuous Po-2, P co(2), and pH monitoring. Design: Criterion standard study under routi ne clinical conditions. Setting: Intensive care unit (ICU) in a univer sity hospital. Patients: Twenty-two sensors were tested in 13 patients with acute respiratory failure, including two patients receiving veno -venous extracorporeal lung assist.Patient selection was based on the necessity of frequent blood gas monitoring. Measurements: Sensor-deriv ed Po-2, Pco(2), and pH values were compared with values obtained usin g two different conventional laboratory blood gas analyzers located in the ICU. The median study period was 72 hrs per sensor (range 8 to 17 0 hrs). The quality of blood pressure readings with the sensor introdu ced through the arterial catheter was assessed by a grading system. Re sults: Mean differences between sensor-derived values and the average values of the two conventional blood gas analyzers were as follows: Po -2 +/- 2.4 + 6.5 (SD) torr (-0.3 +/- 0.9 kPa), Pco(2) -2.9 +/- 3.9 tor r (-0.4 +/- 0.5 kPa), and pH -0.04 +/- 0.03. Correlation coefficients were 0.99 (Po-2), 0.94 (Pco(2)), and 0.89 (pH), respectively. The agre ement between the two methods for Po-2 measurement was better for the clinically important range of values (Po-2 <150 torr [<20 kPa]) than f or all measured Po-2 values (range 30 to 522 torr [4 to 69.6 bPa]). Bl ood withdrawal and pressure readings were not adversely affected by th e sensor. No side effects due to the insertion of the sensor were obse rved. Conclusions: The degree of agreement of intra-arterial blood gas sensor values with conventional blood gas analysis is within an accep table range for routine clinical purposes. Acute changes in measured v alues are detected reliably. Continuous intra-arterial blood gas analy sis can add substantially to the safety of patients with acute respira tory failure and can reduce blood sampling requirements for blood gas analysis.