School of Yoga bhastrikā (bellows) prāṇāyāma.

In bhastrikā-prāṇāyāma, the practitioner rapidly inhales and exhales using the diaphragm only.

School of Yoga explains – bhastrikā technique –

• Sit in padmāsana, siddhāsana or vajrāsana.
• Keep mouth closed. Also, let the tongue touch the top of the palate to close the circuit of prāṇa flow.
• Place hands in chin or chinmaya-mudra.
• Breathing in through the nostril, draw the diaphragm down rapidly. 
• At the end of inhalation, exhale rapidly, pushing the air our vigorously.
• Repeat 20 to 50 times to a maximum of 2 sittings.

School of Yoga explains – bhastrikā benefits: 

• This prāṇāyāma strengthens the upper respiratory tract. The mucosa along the track is cleaned out. Therefore, when the waste is discharged, there is maintenance of body temperature, hence homeostasis.
• The rapid movement of air also strengthens the trachea and lungs. Consequently, there is activation of stagnant alveoli, resulting in improved lung function.
• Bhastrikā helps in preventing cold.
• Also, the rapid movement of air increases volumetric efficiency of the lungs and heart function.
• This breathing strengthens the functioning of the thoracic nerves whch control the functioning of the heart and lungs.

Hatha Yoga Pradeepika on bhastrikā (Chapter 2, verse 59 to 67)

• Bhastrikā– When the feet are placed on the opposite thighs, it is called padmāsana, the destroyer of all sins.
• Assuming balanced padmāsana and an erect body, the intelligent practitioner should exhale through the nostrils.
• It should then be inhaled rapidly with force until there is an experience of resound in the heart, throat upto the skull.
• It should be expelled repeatedly and filled again and again like a blacksmith using his bellows.
• In the same manner, he should move the prana within the body and when experiencing fatigue, inhale using the right (piṅgalā-nāḍī) nostril.
• As soon as the lungs are filled quickly with air, the right nostril should be closed with the ring finger and kept confined.
• Having performed kumbhaka properly, it should be expelled through the left nostril. This destroys vata (air), pitta (bile) and kapha (phlegm) and increases gastric fires.
• The kundalini is quickly aroused; pleasant, purifying and beneficial. Any phlegm and other impurities which may be accumulated at the entrance to the brahma-nāḍī are destroyed.
• Bhastrikā should be performed plentifully for it breaks the 3 knots that are firmly placed on the suṣumṇā-nāḍi. (brahma-granthi in the anāhata, vishnu-granthi in the viśuddhi and rudra-granthi in the ājñā )

Internal Links: Dharma (conditioning), Stress and Situational Awareness, Prana, Asana overview 1, Asana Overview 2, Asana Focus or gazing, Hatha Yoga Pradeepika, 

External Links: Prana, Chakra, Pancha Tattva, Pancha Prana, Pancha Kosha, Nadi, Breathing

Prāṇāyāma Techniques – bhastrikā