On-line arterial blood gas analysis with optodes: current status

Area of Science:

• Biomedical Engineering
• Medical Technology
• Critical Care Medicine

Background:

• Blood gas and pH monitoring are crucial in intensive care.
• Photochemical sensors (optodes) offer an alternative to traditional methods.
• Both intravascular (in vivo) and extravascular (ex vivo) optode placements are explored.

Purpose of the Study:

• To review the principles of optode technology for blood gas analysis.
• To identify challenges with in vivo intravascular optode measurements.
• To assess the clinical utility of continuous in vivo and on-demand ex vivo systems in the ICU.

Main Methods:

• Description of absorbance and fluorescent optical sensor principles.
• Analysis of factors affecting intravascular optode accuracy (thrombosis, wall effect, flow).
• Comparison of on-demand extravascular systems with conventional laboratory blood gas analyzers.

Main Results:

• Intravascular optode accuracy is compromised by thrombosis, wall effects, and reduced blood flow.
• Extravascular on-demand systems overcome intravascular limitations and achieve comparable accuracy to lab analyzers.
• Large-scale patient studies and cost-benefit analyses are lacking for both approaches.

Conclusions:

• Intravascular optode monitors require demonstrated reliability and accuracy in diverse patient groups for routine clinical use.
• Extravascular on-demand blood gas analysis is accurate, aids trend monitoring, and reduces infection risk, decision time, and blood loss.
• The precise clinical role of on-line blood gas analysis remains to be clearly defined due to a lack of extensive patient studies.