Control of breathing in children with mild sleep apnoea: A 6-year follow-up study

Abstract

We have previously shown that children (average age 9 yrs) with mildly elevated obstructive apnoea/hypopnoea indices (OAHI) retained CO2 at rest. Here, we report the results of a 6-yr follow-up study on 14 children from that study. Minute ventilation (V'E) and end-tidal CO2 partial pressure (PET,CO2) were measured during hypercapnic challenge. OAHI decreased from 7.5±4.7 events·h-1 at age 9 yrs to 2.5±1.8 events·h-1 at age 15 yrs (p<0.001), despite an increase in body mass index from 20±4.6 kg·m-2 to 26±5.7 kg·m-2 (p<0.0001). Eupneic V'E increased from 4.1±0.31 L·min-1·m-2 to 5.9±0.4 L·min-1·m-2 (p<0.01), while PET,CO2 fell from 44.1±0.8 to 33±1.0 mmHg (p<0.001). The V'E-PET,CO2 obtained during hypercapnia was left shifted, such that V'E at a PET,CO2 of 50 mmHg increased from 24 L·min-1 at age 9 yrs to 36 L·min-1 at age 15 yrs. Central respiratory drive did not change. We hypothesise that somatic growth of the pharynx coupled with a regression of tonsillar tissue mass with age leads to enlargement of the upper airway lumen, a reduction in airway resistance and increased respiratory airflow at a given level of ventilatory drive. Copyright©ERS Journals Ltd 2010.