transcutaneous

Transcutaneous is an adjective used in medicine and biology to describe processes, measurements, or devices that act on or pass through the skin. The term derives from Latin trans- meaning across and cutis meaning skin. In practice, transcutaneous methods are typically noninvasive or minimally invasive, relying on the skin as the site of measurement or application rather than requiring internal penetration or implants.

In contrast to transdermal delivery, which refers to substances that pass through the skin into systemic circulation (for example, nicotine or hormone patches), transcutaneous approaches may be used for surface measurements, local therapies, or surface stimulation without necessarily delivering the agent systemically.

Examples include transcutaneous bilirubinometry (TcB) to estimate bilirubin levels in newborns; transcutaneous oximetry (TcPO2 or TcO2) to assess tissue oxygenation; transcutaneous electrical nerve stimulation (TENS) and other transcutaneous electrical stimulation methods; and transcutaneous drug delivery via techniques such as iontophoresis or sonophoresis to deliver substances across the skin to local tissues.

Limitations of transcutaneous methods include variability due to skin properties (thickness, hydration, temperature), electrode-skin impedance, and calibration needs. Safety considerations include potential skin irritation or burns with prolonged stimulation or heating, and accuracy depends on proper contact and device-specific protocols. See also transdermal delivery, TcPO2, TcB, and TENS for related concepts.