The Kolmogorov entropy (KE) algorithm was applied to local gas holdup fluctuations for estimating the degree of turbulence (chaos) in a large-scale bubble column umn (0.289 m ID and clear liquid height: 1.31 m). The latter was operated with nitrogen and polyalphaolefin liquid (PSS8) in the churn-turbulent regime (0.117 <= U-g <= 0.257 m/s) at both high temperature (T = 441-468 K) and pressure (P = 1.8-2.5 MPa). Measurements in four different zones (z = 0.35, 0.67, 1.1 and 1.52 m) were performed. When the bubble coalescence is weak (local gas holdups < transitional gas holdup), the KE exhibits an initial peak (enhanced turbulence) in the first zone, then a sudden drop in the second zone and finally it increases smoothly in the upper zones. In the case of strong bubble coalescence, the KE exhibits alternating maxima and minima, i.e., instable flow patterns. It was found that at z = 1.52 m, the KE values increase with P. At higher values of T the KE values are lower in all zones.