Sighs are thought to have a role in regulating breathing control. They may preceed a central apnea (sigh-CA) or a pause (sigh-P), particularly in quiet sleep. Recent techniques characterizing cardiorespiratory synchronization (CRS) provide sensitive measures of cardiorespiratory coupling, which is an important factor in breathing control. We speculated that the strength of CRS and direction of cardiorespiratory coupling (DC), would differ between sigh-P and sigh-CA; before and after a sigh; and with maturation.
Prospective study. CRS and DC were calculated from the respiratory signal and heart rate before and after sighs recorded during overnight polysomnography.
The data were selected from 15 subjects of a prospective cohort of 34 healthy infants at ages 2 weeks, 3 months and 6 months.
Measurements and results:
Both CRS and respiratory modulation on heart rate (RMH) (negative DC index) were decreased around sigh-CA compared with sigh-P at all ages. Short-term CRS decreased after both sigh-P and sigh-CA in infants aged 2 weeks and 3 months. Long term CRS did not change before and after sigh-P or sigh-CA. CRS and RMH were increased at 3 months and 6 months compared to 2 weeks.
A sigh was not found to be associated with apparent resetting of breathing control in healthy infants less than 6 months of age. Cardiorespiratory coupling appears to be a leading marker of changes in breathing control, preceding central apnea associated with a sigh.
Nguyen CD; Dakin C; Yuill M; Crozier S; Wilson S. The effect of sigh on cardiorespiratory synchronization in healthy sleeping infants. SLEEP 2012;35(12):1643-1650.