Variability of Transcutaneous Oxygen and Carbon Dioxide Pressure Measurements Associated with Sensor Location

Transcutaneous measurement of oxygen and carbon dioxide pressure (PtcO(2) and PtcCO(2)) is useful in gas exchange monitoring. However, the relationship between PtcO(2), pulse oximetry (SaO(2)) and arterial blood gases (ABG) is unclear. The aim of the present study was to compare PtcO(2) and PtcCO(2) with SaO(2) and ABG, to evaluate the effect of sensor location on the results and stability of PtcO(2) and PtcCO(2), and to assess the impact of body composition on PtcO(2) and PtcCO(2). PtcO(2) and PtcCO(2) were measured in 20 healthy volunteers at three locations: right second intercostal space, lateral surface of the abdomen, and the inner surface of the left arm. The results were recorded 10, 15, and 20 min after sensor fixation and compared with SaO(2) and ABG measured 20 min after electrode placement on the chest. Body composition was evaluated by bioimpedance. The findings were that PtcO(2) was stable on the chest; but on the arm and abdomen it increased and reached maximum at 20 min. Transcutaneous PCO2 stabilized at 10 min in all the three locations. No significant correlations between PtcO(2) and SaO(2) or PaO2 were found. Transcutaneous PCO2 correlated with PaCO2. Both PtcO(2) and PtcCO(2) were not influenced by body composition. We conclude that the value of PtcO(2) in monitoring of blood oxygenation was not unequivocally confirmed; PtcCO(2) reliably reflects PaCO2, irrespective of sensor location. Body composition does not affect PtcO(2) and PtcCO(2).