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The development of stability of respiration in human infants: changes in ventilatory responses to spontaneous sighs
Insights
Infant respiratory control matures significantly in the first months of life. A spontaneous sigh response evolves from stable but sluggish in newborns to potentially unstable, then stable and rapid in older infants.
Area of Science:
- Neonatal physiology
- Respiratory control
- Infant development
Background:
- Respiratory control mechanisms undergo significant adaptation in early infancy.
- Understanding infant respiratory dynamics is crucial for identifying potential difficulties.
- Previous studies have not fully characterized the maturational changes in sigh-induced respiratory responses.
Purpose of the Study:
- To analyze the maturational changes in the respiratory response to spontaneous sighs in infants from birth to 7 months.
- To characterize the stability and oscillatory properties of infant breathing patterns.
- To investigate the relationship between these changes and respiratory adaptation post-birth.
Main Methods:
- Serial respiratory recordings using impedance pneumography and barometric plethysmography in 15 normal full-term infants.
- Sleep state estimation using electroencephalogram and electro-oculogram.
- Computer-assisted analysis of respiratory minute volume (VE) following sighs, fitted with second-order equations to determine damping ratio (xi) and natural frequency (omega n).
Main Results:
- Three-quarters of sigh responses were accurately modeled, with residual responses mainly from the youngest infants.
- In neonates (≤4 days), the response was stable but sluggish.
- Between 4 days and 3-4 months, oscillatory period decreased (25-12s), indicating potential instability; thereafter, a stable, rapid recovery response emerged.
Conclusions:
- Infant respiratory control demonstrates a clear maturational trend from birth to 7 months.
- The observed changes in respiratory response dynamics may relate to adaptation at birth and susceptibility to respiratory issues.
- Further research into adult respiratory stability factors may illuminate infant respiratory control mechanisms.
Abstract:
Serial respiratory recordings using impedance pneumography and barometric plethysmography were made from shortly after birth to 7 months in fifteen normal full-term infants. Each recording was made with the infant asleep and sleep state was estimated from records of electroencephalogram and electro-oculogram made in parallel. The respiratory records obtained during non-rapid eye movement (r.e.m.) sleep were analysed with computer assistance and stretches of the record, approximately 1 min before and up to 2 min after a spontaneous sigh and ensuing apnoeic pause, were processed and presented as sequential values of the fractional deviation of VE, the breath by breath minute volume, from the mean. That part of the sequence which represented the respiratory response to the sigh was then fitted with second order equations representing the critically or underdamped response. The results were presented for each curve in terms of xi, the damping ratio and omega n, the frequency of the undamped respiratory oscillation. Three-quarters of the responses could be so fitted with an error of 20% or less. The residual responses were mainly from infants within a few days of birth. In the youngest infants (4 days or less), the respiratory response to a sigh was highly stable but sluggish: during the period 4-8 days to 3-4 months, the oscillatory period diminished from ca. 25-12 s and respiration was potentially unstable since a small reduction in the damping factor would cause prolonged oscillation while, from 3-4 months, the more mature type of response which was stable with a rapid recovery supervened. The possible mechanisms responsible for this trend are discussed in terms of the factors thought to determine respiratory stability in the adult together with the possible relevance of the results to the normal process of respiratory adaptation at birth and to the respiratory difficulties encountered by some infants in the new-born period and early infancy.