PaCO2ta

PaCO2ta is a term used to describe a hypothetical or proposed variant of arterial carbon dioxide tension that incorporates time-averaging to reflect sustained rather than momentary levels of CO2 in the blood. The ta in PaCO2ta is intended to signify time-averaged, indicating that the value represents a running average of arterial CO2 over a defined recent time window. The concept is discussed in the context of respiratory physiology as a potential improvement over single-point PaCO2 measurements in settings where ventilation and perfusion can change rapidly, such as critical illness or anesthesia.

Measurement and calculation of PaCO2ta would rely on data from arterial CO2 measurements, obtained via arterial blood gas analysis or continuous monitoring when available, combined with a computational method to compute a rolling or time-weighted average over a specified period. The exact time window and calculation method are not standardized and remain a topic of discussion in theoretical discussions or early research.

Clinical interpretation of PaCO2ta is intended to provide insight into the patient’s sustained ventilatory status. A higher PaCO2ta would indicate persistent hypercapnia over the averaging interval, whereas a lower value would indicate persistent hypocapnia. Because it relies on averaging, PaCO2ta may lag behind rapid shifts in ventilation compared with instantaneous PaCO2 readings and is sensitive to the chosen time window and measurement cadence. At present, PaCO2ta is not widely adopted in clinical practice and requires further validation.

See also: PaCO2, end-tidal CO2, arterial blood gas analysis.