The 9 round breathing meditation is an exercise often done to clear the energy channels or winds before one engages in meditations. This has a calming effect on the mind, making it serviceable. As an additional benefit, it has been said to promote health. His Holiness the Dalai Lama explains how to do the 9 round breathing meditation.
His Holiness particularly recommends to do this meditation when the mind is disturbed because the meditation has a neutralizing effect.