  We observed the high velocity outflow originating from NGC6334I in several CO
transitions with the APEX telescope, with the goal of deriving the physical
parameters of the gas. Using an LVG analysis, we studied line ratios between
the CO(3-2), CO(4-3), and CO(7-6) data as a function of the density and of the
kinetic temperature of the gas. An upper limit on the CO column density is
derived by comparison with 13CO data. We constrained the temperature to be
higher than 50 K and the H_2 density to values higher than n~10^4 cm^{-3}
towards the peak position in the red lobe, while T>15 K and n>10^3 cm^{-3} are
derived towards the peak position in the blue lobe. The physical parameters of
the outflow, its mass and its energetics, have been computed using the
temperatures derived from this analysis. We conclude that high kinetic
temperatures are present in the outflow and traced by high excitation CO lines.
Observations of high-J CO lines are thus needed to infer reliable values of the
kinetic temperatures and of the other physical parameters in outflows.
