It’s important to note that Kundalini Yoga, as taught by Yogi Bhajan is not at all like other yogas or even Kundalini Yoga involving the transmission of energy of a yogi. When one begins the Kundalini Yoga Sadhana as taught by Yogi Bhajan, a relentless process begin that takes you inexorably through all the stages to abide in your True Identity (Sat Nam).Bastrika in hatha yoga and raja yoga practice is primarily meant to establish a rhythm to the breath with the purpose to make the mind subtle and steady. The diaphragm moves evenly, smoothly, lightly, and in rapid rhythm in and out. In the process, the tendency towards erratic moods and changing thought patterns is subdued.There are a number of ways to come into Breath of Fire. If one has practiced Bastrika correctly then it should not be difficult to shift from Bastrika to Breath of Fire: If you’re doing Bastrika the right way, as described here above, then it is easy to shift gears, so to speak and come into Breath of Fire simply by taking a slightly deeper breath and pumping with that, evenly, but with slightly more force from the Navel and solar plexus. As you ratchet up the power of the breath from Bastrika to Breath of Fire, at each stage, watch through the body that the muscles of the shoulders and neck are relaxed, that the chest and rib cage muscles are relaxed, that the sides, lower back and abdominals are relaxed. Feel the flow and come mentally in connection with the expanding electricity/voltage. Once you feel at ease in the motion and power level of the rhythmic movement of the diaphragm and the expansion / contraction of the navel and solar plexus, then take the volume of the breath to be pumped up another notch by taking a slightly deeper breath and pumping the navel and solar plexus with that.In Bastrika, like Breath of Fire, you should have the feeling of the air or prana down to the navel, through the solar plexus and all the way up behind the sternum and chest cavity without using the muscles of the ribcage or shoulders at all.Many people think that by contracting and expanding the navel that no air should come into the chest cavity, while practicing Breath of Fire, but this is a mistake.When one comes into the Breath of Fire with full power, after a while it will seem that the whole room, not just the body, is filling with lightning bolts, and yet within yourself you will feel at ease. Within 5 minutes the entire blood stream will be purified and alkali. You will feel a sense of alertness and electric clarity spreading through the body evenly and smoothly. And in the process tensions that bind and grip the mind will simply dissolve. The neck and throat areas will open. The center of the head will open and you will have the feeling that you’re on the top of a mountain viewing the panorama with a crystal blue sky above you. (A clear day inEspanola)Then you inhale and hold the breath. With this flow of energy swirling through the body, it’s important that you know how to hold the breath at the end of a session of Breath of Fire, whether sitting in easy pose or from a posture or movement. In easy pose, you expand the lungs from the very bottom, feeling the downward pressure through the navel to the solar plexus, then continuing to breathe downward, with your hands on your knees, you pull and expand the ribcage forward and press down with the hands against the knees to cause the upper part of the ribs to lift. This will enable you to fill the lungs entirely from the bottom, to the top and every area between.

Source: Breath of Fire (Bastrika and Kapalabati) | Luthar.com