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Breath-to-breath variations in rate and depth of ventilation in sleeping infants
Insights
Infant breathing patterns during sleep show significant variations in tidal volume (VT) and respiratory cycle time (Ttot), especially during rapid-eye-movement (REM) sleep. These breathing changes are linked to the timing of inspiratory activity.
Area of Science:
- Pediatric Pulmonology
- Neonatal Physiology
- Sleep Studies
Background:
- Infant respiratory control is crucial for development.
- Understanding ventilatory patterns during sleep is key to identifying potential issues.
- Previous research has explored infant breathing but breath-to-breath variability needs further investigation.
Purpose of the Study:
- To analyze breath-to-breath variations in ventilatory parameters during infant sleep.
- To examine the interrelationships between tidal volume (VT), respiratory cycle time (Ttot), expiratory time (TE), and inspiratory time (TI).
- To compare these ventilatory dynamics between rapid-eye-movement (REM) and quiet sleep states in 1-month-old infants.
Main Methods:
- Noninvasive ventilatory measurements were conducted over 2-3 hour sleep periods in nine normal infants at 1 month of age.
- Analysis focused on variations in VT, Ttot, TE, and TI on a breath-to-breath basis.
- Interrelationships between these parameters were statistically assessed during both REM and quiet sleep.
Main Results:
- Variations in VT, Ttot, and TE were significantly higher in REM sleep compared to quiet sleep; TI variations did not differ significantly.
- A strong positive linear correlation was observed between VT and TI on a breath-to-breath basis.
- VT/Ttot showed a moderate negative correlation with Ttot in both sleep states, indicating a nonlinear relationship between VT and Ttot, influenced by inspiratory timing variability.
Conclusions:
- Infant tidal volume (VT) is nonlinearly related to total respiratory cycle time (Ttot) during sleep.
- Decreased respiratory frequency may lead to a drop in the ratio of tidal volume to total respiratory cycle time (VT/Ttot).
- Variability in the onset of inspiratory activity significantly impacts the constancy of VT/Ttot and the nonlinear VT-Ttot relationship.
Abstract:
Ventilatory measurements were made noninvasively over 2- to 3-h periods during sleep in each of nine normal infants at 1 mo of age. To assess the changes that occur in ventilation on a breath-to-breath basis, we 1) examined the variations of each of tidal volume (VT), respiratory cycle time (Ttot), expiratory time (TE), and inspiratory time (TI) and 2) studied their interrelationships. We found that the variations of VT, Ttot, and TE but not of TI were significantly greater in rapid-eye-movement (REM) than in quiet sleep. In addition, on a breath-to-breath basis, VT had a positive linear relationship and strong correlation with TI; however, the correlation between VT and TE was weak in both sleep states. VT/Ttot was found to be moderately and negatively correlated with Ttot in both REM and quiet sleep. VT was weakly correlated with Ttot in REM sleep and was, on the average, more correlated with Ttot in quiet sleep. We suggest that in infants 1) on a breath-to-breath basis, VT/Ttot is likely to drop if respiratory frequency is decreased and 2) VT is nonlinearly related to Ttot during sleep; this lack of linearity depends on the lack of constancy of VT/Ttot, which is in turn closely related to the variability of the "on-switching" of inspiratory activity.