Dyspnea in young subjects with congenital central hypoventilation syndrome

It has been stated that patients with congenital central hypoventilation syndrome (CCHS) do not perceive dyspnea, which could be related to defective CO₂ chemosensitivity.

We retrospectively selected the data of six-minute walk tests (6-MWT, n = 30), cardiopulmonary exercise test (CPET, n = 5) of 30 subjects with CCHS (median age, 9.3 years, 17 females) who had both peripheral (controller loop gain, CG0) and central CO₂ chemosensitivity (hyperoxic, hypercapnic response test [HHRT]) measurement.

Ten subjects had no symptom during the HHRT, as compared to the 20 subjects exhibiting symptoms, their median ages were 14.7 versus 8.8 years (p = 0.006), their maximal PETCO₂ were 71.6 versus 66.7 mmHg (p = 0.007), their median CO₂ response slopes were 0.28 versus 0.30 L/min/mmHg (p = 0.533) and their CG0 values were 0.75 versus 0.50 L/min/mmHg (p = 0.567). Median dyspnea Borg score at the end of the 6-MWT was 1/10 (17/30 subjects >0), while at the end of the CPET it was 3/10 (sensation: effort). This Borg score positively correlated with arterial desaturation at walk (R = 0.43; p = 0.016) and did not independently correlate with CO₂ chemosensitivities.

About half of young subjects with CCHS do exhibit mild dyspnea at walk, which is not related to hypercapnia or residual CO₂ chemosensitivity.

Young subjects with CCHS exhibit some degree of dyspnea under CO₂ exposure and on exercise that is not related to residual CO₂ chemosensitivity. It has been stated that patients with CCHS do not perceive sensations of dyspnea, which must be tempered. The mild degree of exertional dyspnea can serve as an indicator for the necessity of breaks.