Transcutaneous PCO2 and PO2: a multicenter study of accuracy

Area of Science:

• Medical Devices
• Respiratory Physiology
• Clinical Monitoring

Background:

• Arterial blood gas analysis is the gold standard for measuring blood gas tensions.
• Transcutaneous monitoring offers a non-invasive alternative for continuous assessment.
• Accurate transcutaneous measurement requires understanding factors like temperature and metabolic offset.

Purpose of the Study:

• To compare arterial (PaCO2) and transcutaneous (PsCO2) carbon dioxide tension measurements.
• To evaluate the accuracy of transcutaneous PCO2 monitoring across various patient populations and CO2 levels.
• To determine optimal settings for transcutaneous PCO2 monitors, including temperature correction and skin metabolic offset.

Main Methods:

• A multicenter study involving 756 samples from 251 patients.
• Comparison of simultaneous arterial and transcutaneous measurements of oxygen and carbon dioxide tensions.
• Analysis of data stratified by patient age (neonates, children, adults) and PaCO2 ranges.
• Evaluation of transcutaneous PCO2 monitors with inbuilt temperature correction (4.5%/°C).

Main Results:

• High correlation (R=0.929) between PsCO2 and PaCO2 across all patients.
• The ratio of PsCO2/PaCO2 was approximately 1.04 at higher PaCO2 levels (>40 mm Hg).
• Mean bias (PsCO2 - PaCO2) was +1.3 ± 3.9 mm Hg overall, with variations across different PaCO2 ranges.
• Bias was lower at lower PaCO2 (<30 mm Hg) and increased significantly at higher PaCO2 levels.

Conclusions:

• Transcutaneous PCO2 monitoring provides a reliable, non-invasive alternative to arterial PCO2 measurement.
• Adjusting the skin metabolic offset to 6 mm Hg is recommended for transcutaneous PCO2 monitors with 4.5%/°C temperature correction.
• These findings support the use of optimized transcutaneous monitoring in diverse clinical settings, including neonates and patients under anesthesia.