Dependent Lung Pulmonary Artery Hypoplasia as a Cause of Hypoxia during One-lung Ventilation

Hypoxemia remains a well-described occurrence during one-lung ventilation.¹  We recently observed unexpected refractory hypoxemia during one-lung ventilation in a previously healthy nonsmoking 30-yr-old female undergoing left thoracotomy in the right lateral decubitus position to facilitate complex descending aorta to left subclavian/carotid artery bypass grafting to treat upper limb and cerebral ischemia resulting from Takayasu’s arteritis. Despite endotracheal suctioning, reconfirmation of optimal bronchial blocker positioning, optimizing the fraction of inspired oxygen, and using both dependent lung positive end-expiratory pressure and nondependent lung continuous positive airway pressure,²  the Pao₂ remained ~50 mmHg. No intracardiac shunt was seen on transesophageal echocardiography. Only intermittent two-lung ventilation temporarily corrected the hypoxemia. A postoperative computed tomography angiogram three-dimensional reconstruction (panel A) was performed to evaluate the vascular reconstruction and showed a hypoplastic right pulmonary artery (10 mm diameter;...