Invited speakers

Introduction: Sighs (deep inspirations) are thought to have an importantrole in restoring lung volume, resetting the mechanical propertiesof lung tissue and in changing neurorespiratory control. Especially, inquiet or non-rapid eye movement sleep, sighs may be followed bycentral apnea. Sighs reduce in frequency with maturation over the fi rstyear of life. We speculated that strength of cardiorespiratory synchronization(CS) and direction of cardiorespiratory coupling (DC), as ameasure of neurorespiratory control, would differ before and after sigh,and between sighs with and without central apnea, and that there wouldbe a maturational effect.Methodology: CS and DC were assessed by a phase dynamics methodpreceding and following sigh (with and without central apnea) in 15healthy infants at 2 weeks, 3 months and 6 months of age. The CSindex varied from 0 (unsynchronized) to 1 (perfectly synchronized).The DC index varies from −1 (if the direction of coupling is from respirationto heart rate) to 1 (in the opposite directional coupling fromheart rate to respiration), and −1 < DC index < 1 indicates bidirectionalcoupling.Results and discussion: Our results show a signifi cant decrease in CSand respiratory modulation on heart rate (RMH) (interpreted by “negative”DC index) prior to sighs with central apnea compared to sighsalone. Prior to a sigh, CS index was lower with sigh followed by centralapnea (0.58, 0.66, 0.64 at 2 weeks, 3 months and 6 months of age,respectively) than with sigh alone (0.63, 0.71, 0.76, respectively). Onthe other hand, prior to a sigh, DC index was higher with sigh followedby central apnea (−0.45, −0.67, −0.77 at 2 weeks, 3 months and6 months of age, respectively) than with sigh alone from (−0.50, −0.79,−0.80, respectively). We found that RMH increased after a sigh (withor without central apnea), suggesting the involvement of sighs in regulationand resetting of the neurorespiratory controller. Using neonataldata as a reference, CS and RMH increased at 3 months and furtherincreased at 6 months of age. The greatest change was observed between2 weeks and 3 months of age.Conclusion: CS in infants changes with maturation and is differentbefore a sigh with and without central apnea as well as changes beforeand after a sigh, suggesting a neuroregulatory role of sigh.