Published in:
01-12-2003 | Original
Experiences with continuous intra-arterial blood gas monitoring: precision and drift of a pure optode-system
Published in: Intensive Care Medicine | Issue 12/2003
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Objective
The utility of continuous intra-arterial blood gas analysis (CBGA) with combined electrochemical and optode sensors has been demonstrated. More recently, a pure optode sensor with a changed sensing element architecture has become available. The aim was to determine the measurement accuracy and long-term stability of the new sensor.
Design
A prospective explorative study was performed. Simultaneous measurements of intermittent blood gas analyses (IBGA) (ABL 610, Radiometer, Copenhagen) and CBGA (Diametrics Medical, High Wycombe, Bucks., UK) were compared using Bland-Altman analysis.
Patients
Twenty-five patients admitted to the ICU and requiring mechanical ventilation for an expected minimum of about 96 h were included.
Results
Mean monitoring time was 106.1 (range 15–231) hours. Bias and precision for PO2 were −0.2 kPa (1%)±1.8 kPa (9.5%); PCO2: 0.03 kPa (0.6%)±0.44 kPa (9.3%); pH: −0.001 (0.01%)±0.04 (0.45%). The sensor showed no change of measurement characteristics during 4 days of measurement. However, in 69 cases continuous monitoring was interrupted (reversible sudden drops of PO2 measurement) possibly caused by thrombotic deposition and/or sensor bending and accidental sensor retraction.
Conclusions
The precision and bias of the PCO2- and pH-sensing elements were in line with the findings of the older sensor technology. The possibility that the PO2 optode could offer greater accuracy than the older technology is suggested by comparisons with results reported in previous studies. No sensor drift occurred during long-term measurement over more than 4 days.