The physiologic basis for and nursing considerations in the use of subatmospheric concentrations of oxygen in HLHS.

Subatmospheric concentrations of oxygen are used in the preoperative and postoperative care of infants with hypoplastic left heart syndrome (HLHS). This technique increases the pulmonary vascular resistance (PVR) and thereby improves systemic blood flow. There have been no controlled studies of this therapy in humans. Changes in aortic blood flow patterns, suggesting improved systemic circulation after administration of nitrogen, have been shown by Doppler ultrasound. Video segments are included in the electronic version of this article to demonstrate the immediate circulatory effects of therapy. No significant long-term effects on PVR have been found. A clear understanding of the anatomy, physiology, and therapeutic maneuvers used to balance pulmonary blood flow and systemic blood flow is essential for caregivers of infants with HLHS. Infants receiving subatmospheric concentrations of oxygen require meticulous nursing care to detect early changes in the relative vascular resistance and to monitor for the hemodynamic effects of medical and nursing interventions.