How does alveolar surface tension affect pulmonary ventilation?
Alveolar surface tension is regulated by the spread of pulmonary surfactants, a lipid and protein mix that keeps the surface tension of the alveoli consistent across the lungs. Because oxygen transference is harder with high surface tension (oxygen molecules cannot easily pass through a membrane with high surface tension), the surfactants allow lower the surface tension to facilitate transfer. Breathing expands the alveoli, spreading the surfactants across the membrane and increasing surface tension; as the alveoli become larger, their ability to transfer oxygen decreases. When the alveoli are contracted, the surfactants are concentrated and so it is easier to transfer oxygen. In this manner, the alveolar surface tension is directly related to pulmonary ventilation (respiration) because it regulates the speed and consistency of alveolar oxygen transference.