RETNLB and hypoxia: Previous studies have confirmed that bronchoalveolar lavage fluid (BALF) can be used as a minimally invasive sample for lung marker detection in acute respiratory distress syndrome (ARDS) subtypes (Sathe et al., 2023), and can also detect pulmonary macrophage derived markers (such as Fizz1) associated with vascular remodeling in hypoxia induced PAH (HPH, PAH subtypes) (Li et al., 2024).