Normal Respiratory Mechanics

Normal breathing should expand and compress the thorax, abdomen, and pelvis as one integrated pressure system rather than moving only the belly. During exhalation, the thoracic diaphragm and pelvic floor ascend while the glottis opens. During inhalation, the thoracic diaphragm and pelvic floor descend to accommodate pressure and abdominal contents. A key goal of respiratory mechanics is to keep intrathoracic and intra-abdominal pressure as close to a one-to-one relationship as possible.