Fixed Wing Flight Physiology Considerations in Transport of Infants with Shunt-dependent Single Ventricle Heart Disease

Introduction: We present a case of an infant with cyanotic, single-ventricle congenital heart disease who was transported by fixed wing flight. Our pediatric tertiary care center has done 49 of these flights over the past 3.5 years. With this case, we illustrate how the variables of flight affect the complex cardio-pulmonary physiology of such patients. Knowledge of these relationships can help transport teams anticipate how to best prepare patients for transport, as well as mitigate stressors, to optimize care during transport.

Case Description: The patient is a 6-month-old male with hypoplastic left heart syndrome, status post Stage 1 Norwood operation, with right-ventricle-to-pulmonary-artery (Sano) shunt. He was transported to his local institution for heart transplantation after advanced management of ongoing chylous effusions at our center. During transport, he was on infusions of milrinone to support cardiac output, bumetanide for diuresis, and dexmedetomidine for sedation. His oxygen saturation goal of 75-85% was achieved via titration of nasal canula oxygen. Blood pressures were supported with small fluid boluses. He had a right pleural chest tube. In collaboration with our pilot, we adjusted cruising altitude to maintain sea level cabin pressure.

Discussion: Air transport of shunt-dependent single ventricle patients requires meticulous attention to multiple factors due to the delicate balance of systemic to pulmonary vascular resistance. Altitude changes can precipitate respiratory and cardiovascular changes. As altitude increases, the partial pressure of oxygen decreases, leading to increased work of breathing, increased metabolic demand, and additional cardiac stress. To reduce this, we utilized sedation and increased oxygen support. Maintaining oxygen saturation below 85% prevented pulmonary overcirculation, avoiding further compromise to cardiac output.

Altitude increases result in barometric pressure decreases. Gas volumes expand with decreased barometric pressure, so the chest tube was unclamped to prevent pneumothorax, and the nasogastric tube was vented to minimize abdominal distention. Altitude increases may lead to edema, tachycardia, and hypotension. To mitigate the effects of the drop in barometric pressure due to the altitude rise, we maintained sea-level cabin pressure. Our balanced pressurization required a lower cruising altitude, thus accepting more turbulence, longer flight time, and increased fuel requirement.

Gravitational forces in the supine, rear-facing patient, push blood toward the feet during acceleration and takeoff, resulting in decreased preload, left ventricular stroke volume, and cardiac output. The opposite is true during deceleration and landing. We supported preload with isotonic fluid boluses. The patient’s lower extremities were elevated through takeoff to limit venous pooling. The plane’s ascent was gradual.

Conclusion: We describe the successful fixed wing transport of an infant with shunt-dependent single ventricle heart disease. Careful attention to the physical and environmental nuances of air transport allows clinicians to optimize the complex physiologies of these fragile patients.