Abstract
Background The carotid bodies primarily serve as oxaemia sensors that affect tidal breathing. Their function has not been studied in infants with nocturnal hypoxaemia yet. This cross-sectional study aimed to characterise the hyperoxic ventilatory response (HVR) in infants and its relationship to nocturnal hypoxaemia.
Methods The HVR was analysed in term infants aged <24 months with childhood interstitial lung disease (chILD), those with severe recurrent wheezing (wheeze), and non-respiratory controls. The HVR timing was characterised using hyperoxia response time (HRT1) and HVR magnitude was characterised by the relative change in minute ventilation between normoxia and 30-s hyperoxia (VE_dH30). Time spent with an arterial haemoglobin oxygen saturation (SpO2) <90% during overnight monitoring (t90) was estimated.
Results HVR data were available for 23 infants with chILD, 24 with wheezing, and 14 control infants. A significant decrease in minute ventilation under 30 s of hyperoxia was observed in all patients. HRT1 was shorter in chILD (5.6+-1.2 s) and wheeze (5.9+-1.5 s) groups than in the controls (12.6+-5.5 s) (ANOVA p-value <0.001). VE_dH30 was increased in the chILD group (24.3+-8.0%) compared with that in the controls (14.7+-9.2%), p=0.003. T90 was abnormal in the wheeze (8.0+-5.0%) and chILD (32.7+-25.8%) groups and higher in the chILD group than in the controls (p<0.001). HRT1 negatively correlated with t90 in all groups.
Conclusion Significant differences in HVR timing and magnitude were noted in the chILD, wheeze, and control groups. A relationship between nocturnal hypoxaemia and HRT1 was proposed. HVR characterisation may help identify patients with abnormal nocturnal SpO2.