Svana Pranayama 
Dog Breathing
The Fire breath open the top part of the inhalation when performed. It makes the inhalation easier and holding the breath easier. The Dog Breathing causes the exhalations to improve and also makes it easier to retain the breath after exhalation.
This breathing exercise is done by first exhaling most of the air in the lungs. A little is left in the lungs so that they are no more than a quarter full. They can be much less also. The mouth is open and the tongue sticks out.
Once this is done fast vigorous breathing is performed that sounds like a dog catching it's breath. This helps to bring eliminate toxins and is a common techniques used to help remove mucus from the lungs.
Stage 1 Svana Pranayama
Breathe out all of the air then open the mouth and stick the tongue out.
Begin to take fast rapid breaths trying to exhale all of the air each time and only breathing in slightly. Do this about 8 times before doing one last long one.
Then breathe normally or begin with Ujjayi
After your lungs have recovered repeat the exercise increasing the duration.
Each time try to force all of the trapped mucus out of the bottom of the lungs.
Stage 2 Svana Pranayama
Breathe out all of the air then open the mouth and stick the tongue out.
Begin to take fast rapid breaths trying to exhale all of the air out each time and only breathing in slightly. Do this at least 8 times before doing one long one.
Repeat this technique 3 times in a row.
