The disintegration process of an annular liquid sheet assisted by inner and outer swirling gas jet(s) under different ambient pressures is studied for the design of new injectors in cryogenic propulsion. In such a geometry, the effect of ambient pressure has never been reported before. The liquid used is water and the gas used is air. Determination of the gas swirl intensity at the injector exit commands an intensive study, taking into account experimental results obtained in a similar configuration. The motion is captured using a very high speed camera at a rate of 12,500 and 14,000 fps. Four break-up mechanisms, namely, "bubble train," "bubble breakup," "pure-pulsating," and "Christmas tree," have been identified. The flow map of these regimes, governed by the momenta of the liquid and the gas, has been carried out and the results have been found to be in good agreement with the literature. At the end of this article, the oscillation frequency of the liquid sheet is related to the injector exit conditions, gas and liquid velocities, gas densities, and gas swirl intensities.