Of the hemoglobin processing proteins, HO-1 has received the most attention in past research in critical illness and is known to: (1) Be upregulated in inflammatory and pro-oxidant disease states such as sepsis and ARDS, (2) Be expressed by multiple cell types in the lung, and (3) Decrease pulmonary inflammation and vascular remodeling in animal models of lung injury [25]. Here, HMOX1 is linked to acute respiratory distress syndrome.