Transpulmonary pressure

Transpulmonary pressure is a term used to describe the difference between the alveolar pressure and the intrapleural pressure in the lungs. During human ventilation, air flows because of pressure gradients. Pressure in the respiratory system can be measured either in the air spaces of the lungs (alveolar pressure) or in the pleural fluid (intrapleural pressure). Since atmospheric pressure is relatively constant, pressure in the lungs must be higher or lower than atmospheric pressure for air to flow between the atmosphere and the alveoli.