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अपाने जुह्वति प्राणं प्राणेऽपानं तथापरे ।
प्राणापानगती रुद्ध्वा प्राणायामपरायणाः ॥४-२९॥

apaane juhwati praaNaM praaNe'paanaM tathaapare ।

praaNaapaanagatii ruddhwaa praaNaayaamaparaayaNaaH ॥४-२९॥

Source: Automatic ITRANS Transliteration

Others sacrifice exhalation in inhalation, inhalation in exhalation.
Suppressing the flow of inhalation and exhalation, practitioners of "breath extension"

Others, practitioners of "breath extension" suppress the flow of inhalation and exhalation, thereby sacrificing exhalation in inhalation and inhalation in exhalation.

Source: Milind S. Pandit

Those who are engaged in yogic practice, reach the breathless state by offering inhalation into exhalation and exhalation into inhalation as sacrifice (by using short breathing Kriya techniques).

Source: The Bhagavad-Gita: The Sacred Song

And there are even others who are inclined to the process of breath restraint to remain in trance, and they practice stopping the movement of the outgoing breath into the incoming, and incoming breath into the outgoing, and thus at last remain in trance, stopping all breathing. Some of them, curtailing the eating process, offer the outgoing breath into itself, as a sacrifice.

Source: Bhagavad Gita As It Is