Objective To find out whether a correlation of heart rate (HR) and respiratory frequency (RF) defined as HR-RF ratio (HRR) may be helpful to identify arousals in term and preterm infants.
Methods Polygraphic recordings were performed in 25 term infants (gestational age 40.1±1.1 weeks) and 25 preterm infants (gestational age 31.1±1.3 weeks) during undisturbed daytime sleep. Arousals were scored as suggested by the “International Paediatric Work Group on Arousals” and divided into cortical (CA) and subcortical arousals (SCA). HRR was defined as HR over RF. Arousals were compared to a 30 s period preceding an arousals.
Results Two-hundred arousals were scored (100 CA and 100 SCA). HRR increased during arousals in term infants (p<0.001). This was true for CA (p<0.001) and SCA (p<0.05) of term infants. By contrast, in preterm infants HRR remained unchanged during CA and SCA.
Conclusions An increase of HRR during arousals is a simple parameter to identify arousals in term infants, but not in preterm infants suggesting that an unchanged HRR might be an indicator of an immature arousal response.