In a nutshell: breathe in for four, hold for seven, and breathe out for eight. You must inhale through your nose and exhale through your mouth. The four-count inhale allows chronic under-breathers to take in more oxygen. The seven-count hold gives the oxygen more time to thoroughly permeate the bloodstream, and the eight-count exhale slows the heart rate and releases a greater amount of carbon dioxide from the lungs. red or ruby mermaid trumpet garments for prom