Which of the following is a disadvantage of transcutaneous blood gas monitoring?

• A. It requires arterial puncture
• B. The heated probe may burn the skin and placement must be moved every 3-4 hours
• C. It cannot monitor PaO2
• D. It does not require calibration

Answer: (B)

Transcutaneous blood gas monitoring relies on a heated probe placed on the skin to estimate arterial PO2 and PCO2. The main drawback is the risk of skin burns from the heated element, so the probe must be moved to a new site every few hours (often 3–4 hours) to prevent injury and to maintain accuracy as skin perfusion and tissue properties change. This method is noninvasive and does not require arterial puncture, and it does monitor PaO2, but it does require periodic calibration against arterial values for reliable readings, so those points are not disadvantages in the same way.