Normalization of the blunted ventilatory response to acute hypoxia in congenital cyanotic heart disease.

Patients with congenital cyanotic heart disease have a blunted ventilatory response to hypoxia, but the permanence of the blunting is disputed. To determine how early the blunted ventilatory response develops and whether it is reversible, we studied three groups of children and young adults: five (seven to 13 years of age) with acyanotic heart disease, eight (seven to 16) with cyanotic congenital heart disease (arterial oxygen saturation, 55 to 83 per cent), and 13 (seven to 17) whose cardiac defects were repaired (arterial oxygen saturation, 93 to 98 per cent). The ventilatory response to acute hypoxia was subnormal in the hypoxemic children in that their ventilation showed little increase when arterial oxygen saturation fell by 10 to 20 per cent, compared to a 150 to 300 per cent increase in the control subjects. This characteristic even appeared in a seven-year-old patient, indicating that the disorder occurs in early life. The appearance of blunted ventilatory response is delayed when hypoxia from birth is less severe. After operation, with return of the arterial hypoxemia to normal, the response was in the normal range. We conclude that the blunted response is reversible.