A multiparameter sensor for continuous intra-arterial blood gas monitoring: a prospective evaluation

OBJECTIVE: To compare measurements of arterial blood gases made by a new continuous intra-arterial blood gas monitor with measurements in a standard blood gas analyzer in patients in the general and cardiac intensive care units.

DESIGN: Criterion standard study.

SETTING: The cardiac surgical and the general medical intensive care units of a tertiary referral center.

PATIENTS: Thirteen consecutive patients requiring mechanical ventilation and blood gas monitoring.

INTERVENTIONS: All patients had a blood gas sensor placed through a 20-gauge cannula inserted into the radial artery. The duration of monitoring ranged from 9.42 to 117.45 hrs.

MEASUREMENTS AND MAIN RESULTS: A total of 158 simultaneous measurements of pH, PCO2, and PO2 were made from the sensor and the blood gas analyzer, and the bias and precision were calculated on all measured parameters. The overall bias +/- precision values were 0.01 +/- 0.06 for pH, 1.4 +/- 4.8 torr (0.2 +/- 0.7 kPa) for PCO2, and 2.8 +/- 25.6 torr (0.4 +/- 3.4 kPa) for PO2. The bias and precision for PO2 measurements that were < 150 torr (< 20 kPa) were 0.45 +/- 20.7 torr (0.1 +/- 2.8 kPa). The bias and precision for values of PO2 that were > 150 torr (> 20 kPa) were -8.1 +/- 28 torr (-1.1 +/- 3.8 kPa). The mean in vitro 90% response times of pH, PCO2, and PO2 sensors were found to be 78, 143, and 70 secs, respectively. There were no instances of any complications attributable to the sensor.

CONCLUSIONS: The continuous intra-arterial blood gas monitor tested in this study measures and trends arterial blood gases with an acceptable level of clinical accuracy. Longevity and safety of sensor function have also been demonstrated.