Letting breath out is an entropic activity in sequence after inhaling breath or inhalation, a syntropic activity. The two combined together is breathing (one dual motion) as in the Universal Heart Beat.
"Exhalation is for the purpose of discontinuing the apparent existence of form in matter.
"Exhalation is dissolution. It is disintegration. It de-vitalizes, exhausts, fatigues. It discontinues that which is known as life and leads ever toward that which is known as death." Russell, The Universal One, Book 02 - Chapter 01 - Dynamics of Mind - Concerning Light Units of Matter
"All motion is oscillatory, swinging in sequence between two apparently opposing forces, gravitation and repulsion, which are respectively electric and magnetic.
"This oscillatory motion is a pulsating in-breathing and out-breathing, an inhalation and an exhalation, which is a characteristic of all matter, whether it be in units, or systems of units, or mass.
"These two apparently opposite forces are the father-mother forces of Mind, which, added together, make but the One force." Russell, The Universal One, Book 01 - Chapter 02 - The Life Principle
Rhythmic Balanced Interchange
Universal Heart Beat