Fig. 1.

The methods for calculation of TWA-PaCO₂. If the patient had 4 ABG measurements within 10 days after ICU admission, and the period between each two PaCO₂ measurements varied. The calculation formula was as follows: $\left(\left(\frac{P1+P2}{2}\right)\times T1+\left(\frac{P2+P3}{2}\right)\times T2+\left(\frac{P3+P4}{2}\right)\times T3)÷(T1+T2+T3\right)$.