Physiologic Studies of Paroxysmal Hyperpnea in Cyanotic Congenital Heart Disease

PAROXYSMAL hyperpnea occurs in younger children with cyanotic congenital heart disease with decreased pulmonary blood flow.These episodes, also called hypoxic spells or blue spells, are characterized by increasing cyanosis in spite of an increased rate and depth of respiration.Gradual dulling of the sensorium may progress to unconsciousness.'The patients subject to paroxysmal hyperp- nea have in common an inadequate pulmonary blood flow and a right-to-left shunt.Any increase in systemic venous return, in the face of a fixed or even diminished pulmonary blood flow, would result in an in- crease in right-to-left shunting and a further lowering of arterial saturation.Hyperpnea in normal subjects results in increased cardiac output,2 3 and in dogs there is evidence that hyperpnea causes an increase in pulmonary vascular resistance.4We have studied four children with tetral- ogy of Fallot subject to paroxysmal hyperp- nea utilizing an isothermal catheter flow- meter to study the effects of normal inspira- tory effort on flow in the venae cavae.In one of these patients, arterial blood gases and pH were obtained in the waking and sleeping states. MethodsMellander and Rushmer's 5 device for heating a coil of wire in proximity to a thermistor mounted on a catheter was modified by Katsura et al.,6