This document discusses respiration and factors that affect it. Respiration is the process of breathing that involves inhaling air into the lungs and exhaling air out. The diaphragm and ribs work together to expand and contract the lungs and chest. Respiration is controlled by centers in the brainstem and chemoreceptors that respond to oxygen, carbon dioxide, and hydrogen ion levels. The rate, depth, rhythm, effort, and sounds of breathing can provide clinical information. Damage to the phrenic nerve that controls the diaphragm can cause breathing difficulties but may be treated with a pacemaker.