Abdominal breathing refers to the form of respiratory movements, which in humans can be divided into two main categories: thoracic breathing and abdominal breathing. Abdominal breathing, specifically, refers to the abdominal bulge during the patient’s inhalation. At this time, the diaphragm descends and squeezes the abdominal organs downward, thus increasing the pressure inside the abdominal cavity and then causing the abdomen to bulge. During exhalation, the diaphragm muscle contracts, causing the roof of the diaphragm to rise upward, at which point the pressure inside the abdominal cavity decreases, resulting in a depressed abdomen. In some patients, such as adult males and pediatric patients, this form of respiratory movement is very pronounced. In women, thoracic respiration is the main form of breathing, although abdominal respiration may be used in some special cases. For example, if a woman suffers severe trauma to the thorax, or if she is immobilized by an external fixation device, she may breathe abdominally to compensate for some of the thoracic breathing.