PEP stands for “positive expiratory pressure.” PEP is a back pressure when breathing out. You will feel that breathing out through PEP Buddy is slower and may need a little effort – think how you breathe out when making soap bubbles. PEP Buddy prolongs the exhalation phase of the breathing cycle and overall helps reduce the respiratory rate. This back pressure helps keep the small air tubes of the lung open when breathing out; this way, it reduces or prevents air stacking in the lungs of people with COPD. When someone refers to PEP therapy, they are talking about a breathing technique with a slightly active exhalation against an expiratory resistance.