Alveolar surface

The alveolar surface is the physiological interface within the lung where gas exchange between inspired air and the blood occurs [9]. It is anatomically composed of the alveolar-capillary barrier, which includes the alveolar epithelium (Type I and Type II pneumocytes), a shared basement membrane, and the capillary endothelium [9, 10]. A critical component of this surface is the pulmonary surfactant layer, a complex mixture of lipids and proteins that reduces surface tension to prevent alveolar collapse (atelectasis) during the respiratory cycle [6, 19]. In clinical pharmacology, the alveolar surface is the primary site of action for exogenous surfactant replacement therapies, such as poractant alfa, which are used to treat Neonatal Respiratory Distress Syndrome [4, 16]. The integrity of this surface is often compromised in conditions like Acute Respiratory Distress Syndrome (ARDS) or pulmonary fibrosis, leading to impaired oxygenation [7, 11]. Additionally, the expansive surface area of the alveoli serves as a critical portal for the delivery of various inhaled medications [15].

Other names

Alveolar-capillary barrierAlveolar-capillary interfaceAlveolar liningPulmonary alveolar surfaceAlveolar air-liquid interface

Exogenous surfactant drugs spread across the alveolar surface to lower surface tension at the air-liquid interface, preventing atelectasis and improving lung compliance [4, 6].