If a transcutaneous monitor reads TcPO2 higher than PaO2, what is the most likely cause?

A transcutaneous monitor measures the partial pressure of oxygen (TcPO2) in the skin, while arterial blood gas analysis measures the partial pressure of oxygen (PaO2) in arterial blood. Typically, TcPO2 values are expected to be lower than PaO2 due to the physiological differences in how oxygen is transported and measured in these two settings.

If a TcPO2 reading is higher than the PaO2, one likely cause is the presence of air leaks. Air leaks can occur when there is a breach in the integrity of the seal around the sensor, allowing ambient air to mix with the measurement site. This can artificially inflate the TcPO2 value, making it misleadingly high compared to the actual oxygen levels in the arterial blood.

High oxygen concentration can also affect TcPO2 readings, but typically, it would elevate both TcPO2 and PaO2 rather than causing a discrepancy where TcPO2 exceeds PaO2. Equipment malfunction and blood clots are less likely to directly result in the scenario where TcPO2 exceeds PaO2 compared to the influence of air leaks on the accuracy of transcutaneous monitoring.