Square Breath or Equal Breath/Samavritti: equalizing the four components of the breath. To perform square breathing, inhale for a count of four, hold the breath in for a count of four, exhale for a count of four, hold the breath out for a count of four, and continue repeating in this manner. This practice can be done with a count of any number; it is recommended to begin with four and increase your counts as you are able. (You can also perform this pranayama technique without holding the breath in or out if that is uncomfortable.)
If you have high blood pressure or lung, heart, eye, or ear problems you should not hold the breath after the inhale. If you have low blood pressure, you should not hold the breath after the exhale. If you are pregnant, perform samavritti without holding the breath in or out (just equal inhales and exhales).