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Increased respiratory frequency and variability in high risk babies who die of sudden infant death syndrome
D C Shannon1, D H Kelly, S Akselrod
1Pediatric Pulmonary Unit, Massachusetts General Hospital 02114.
Insights
Sudden infant death syndrome (SIDS) is linked to autonomic instability in high-risk infants. Increased respiratory variability and frequency were key indicators, aiding in identifying infants at risk.
Area of Science:
- Physiology
- Pediatrics
- Autonomic Nervous System
Background:
- Sudden infant death syndrome (SIDS) poses a significant risk to infants.
- Autonomic instability has been hypothesized as a characteristic of SIDS.
- Variability in heart rate and respiratory frequency are indicators of autonomic function.
Purpose of the Study:
- To test the hypothesis that autonomic instability characterizes high-risk infants who died of SIDS.
- To identify physiological markers associated with SIDS risk.
Main Methods:
- Computer-based analysis of heart rate and respiration power spectra.
- Comparison of SIDS infants, asymptomatic siblings, and controls.
- Analysis of respiratory bandwidth and mean respiratory frequency.
Main Results:
- Confirmed increased respiratory bandwidth (p = 0.009) in SIDS infants.
- Found increased mean respiratory frequency during quiet breathing (p = 0.001).
- Established a significant relationship between respiratory bandwidth and mean respiratory frequency (r = 0.604, p = 0.0002).
Conclusions:
- High-risk infants who died of SIDS exhibit autonomic instability.
- Respiratory variability and frequency are significant indicators.
- A discriminant function achieved 82% sensitivity and 100% specificity for risk identification.
Abstract:
We have tested the hypothesis that autonomic instability, reflected in increased variability of heart rate and respiratory frequency, characterized high risk babies who died of sudden infant death syndrome. Using computer-based methods, we compared the power spectra of instantaneous heart rate and respiration on coded tape recordings from seven asymptomatic siblings and 10 babies with symptomatic apnea who died of sudden infant death syndrome to 34 age- and sex-matched controls. We confirmed our previous observation of increased respiratory bandwidth, an index of variability in respiratory frequency (p = 0.009) but failed to confirm our finding of increased low frequency fluctuations in heart rate (p = 0.18). In addition, we found an increase in mean respiratory frequency during quiet breathing (p = 0.001) and a significant relationship between respiratory bandwidth and mean respiratory frequency (r = 0.604, p = 0.0002). These variables along with those from a previous analysis of the same data base yield a discriminant function with 82% sensitivity and 100% specificity. These results confirm previous suggestions that high risk babies who die of sudden infant death syndrome exhibit autonomic instability.