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Irregularities and power law distributions in the breathing pattern in preterm and term infants
U Frey1, M Silverman, A L Barabási
1Department of Child Health, Leicester University, Leicester LE2 7LX, United Kingdom. urs.frey@insel.ch
Insights
Infant breathing irregularities, measured by interbreath intervals (IBI), decrease with maturation. A new exponent, alpha, quantifies breathing stability, linking clinical data to respiratory control neurophysiology.
Area of Science:
- Neonatal physiology
- Respiratory control
- Computational neuroscience
Background:
- Young infants exhibit unstable respiratory patterns, unlike older children, indicating developmental differences in breathing control.
- Irregular breathing, including apnea and hypopnea, is common in infants and requires objective measurement for understanding.
- The neurophysiological basis of infant respiratory control and its maturation remains an area of active research.
Purpose of the Study:
- To examine irregular breathing patterns in preterm and term infants using interbreath interval (IBI) analysis.
- To develop a quantitative measure (exponent alpha) of breathing instability and its relationship to maturation.
- To model infant respiratory control to understand the neurophysiological mechanisms underlying breathing stability.
Main Methods:
- Measured interbreath intervals (IBI) from abdominal movements during sleep in preterm and term infants.
- Developed a threshold algorithm to detect breaths, incorporating apneic and hypopneic periods within IBIs.
- Analyzed the probability density distribution of IBIs using a power law, P(IBI) ~ IBI-alpha, to determine the exponent alpha.
Main Results:
- The probability density distribution of IBIs followed a power law, P(IBI) ~ IBI-alpha.
- The exponent alpha increased with postconceptional age, indicating a decrease in prolonged hypopneas (P = 0.002).
- A computational model based on noisy neural inputs to a respiratory oscillator successfully reproduced the observed IBI properties.
Conclusions:
- Breathing irregularities in infants can be quantitatively characterized by the exponent alpha.
- Maturation of infant respiratory control involves tonic inputs moving away from a critical region in the respiratory oscillator model.
- The exponent alpha provides a link between clinically accessible breathing data and the neurophysiology of infant respiratory control.
Abstract:
Unlike older children, young infants are prone to develop unstable respiratory patterns, suggesting important differences in their control of breathing. We examined the irregular breathing pattern in infants by measuring the time interval between breaths ("interbreath interval"; IBI) assessed from abdominal movement during 2 h of sleep in 25 preterm infants at a postconceptional age of 40.5 +/- 5.2 (SD) wk and in 14 term healthy infants at a postnatal age of 8.2 +/- 4 wk. In 10 infants we performed longitudinal measurements on two occasions. We developed a threshold algorithm for the detection of a breath so that an IBI included an apneic period and potentially some periods of insufficient tidal breathing excursions (hypopneas). The probability density distribution (P) of IBIs follows a power law, P(IBI) approximately IBI-alpha, with the exponent alpha providing a statistical measurement of the relative risk of insufficient breathing. With maturation, alpha increased from 2.62 +/- 0.4 at 41. 2 +/- 3.6 wk to 3.22 +/- 0.4 at 47.3 +/- 6.4 wk postconceptional age, indicating a decrease in long hypopneas (for paired data P = 0.002). The statistical properties of IBI were well reproduced in a model of the respiratory oscillator on the basis of two hypotheses: 1) tonic neural inputs to the respiratory oscillator are noisy; and 2) the noise explores a critical region where IBI diverges with decreasing tonic inputs. Accordingly, maturation of infant respiratory control can be explained by the tonic inputs moving away from this critical region. We conclude that breathing irregularities in infants can be characterized by alpha, which provides a link between clinically accessible data and the neurophysiology of the respiratory oscillator.
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