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Episodic bradycardia in preterm infants
C J Upton1, A D Milner, G M Stokes
1Department of Neonatal Medicine and Surgery, City Hospital, Nottingham.
Insights
Bradycardia in preterm infants is often triggered when breathing resumes against a closed airway after apnea. Hypoxemia can intensify this reflex, impacting infant cardiorespiratory events.
Area of Science:
- Neonatal Physiology
- Cardiorespiratory Regulation
- Pediatric Pulmonology
Background:
- Preterm infants, particularly those born at 32 weeks' gestation or less, are susceptible to cardiorespiratory events like bradycardia.
- Apnea of prematurity is a common concern, often preceding or coinciding with other physiological disturbances.
Purpose of the Study:
- To investigate the specific factors that precipitate bradycardia in preterm infants.
- To elucidate the relationship between apnea, upper airway function, and the occurrence of bradycardia.
Main Methods:
- Studied 27 preterm infants (≤32 weeks gestation) across 89 occasions.
- Utilized polygraphic recordings for electrocardiography, oxygen saturation, and respiratory effort.
- Measured upper airway flow using a mask and pressure transducer during apneic episodes.
Main Results:
- Bradycardia onset positively correlated with apnea duration.
- Airway closure was observed in 88% of apneas associated with bradycardia, significantly higher than in apneas without bradycardia (64%).
- Bradycardia frequently occurred as respiratory effort resumed post-apnea.
Conclusions:
- Bradycardia in preterm infants is suggested to be a reflex response to resuming respiration against a closed upper airway.
- This reflex appears to be potentiated by hypoxemia, highlighting the interplay between airway obstruction and oxygen levels.
Abstract:
To analyse factors likely to precipitate bradycardia, 27 preterm infants born at 32 weeks' gestation or less were studied on 89 occasions. Polygraphic recordings of electrocardiography, oxygen saturation, and respiratory effort were made. Subsequently, upper airway flow was measured by a mask and pressure transducer. In 605 episodes detected during initial recordings, time of onset of bradycardia correlated positively with apnoea duration, with bradycardia often occurring as respiratory effort resumed. Airway closure occurred in 88% of apnoeas associated with bradycardia during flow measurements, and was significantly more common than in apnoea without bradycardia (64%). We suggest that bradycardia is most commonly a reflex response to the resumption of respiratory effort against a closed upper airway as apnoea is terminated, and that this reflex is potentiated by hypoxaemia.