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Response to external obstruction in preterm infants with apnea
C J Upton1, A D Milner, G M Stokes
1Department of Neonatal Medicine, City Hospital, Nottingham, United Kingdom.
Insights
External airway obstruction triggers apnea in preterm infants. This response, particularly post-obstruction apnea, correlates with spontaneous apnea frequency and changes over time in the neonatal period.
Area of Science:
- Neonatal Physiology
- Respiratory Control
Background:
- Preterm infants are susceptible to apnea.
- External airway obstruction can elicit apneic responses in neonates.
Purpose of the Study:
- To investigate the time course of apneic responses to airway obstruction in preterm infants.
- To determine the relationship between obstruction-induced apnea and spontaneous apnea occurrence.
Main Methods:
- Studied 23 preterm infants (median birthweight 1.14 kg, gestation 29 weeks).
- Measured upper airway flow using a face mask and pneumotachograph.
- Intermittently applied external airway obstruction and analyzed 380 occlusions for apneic events.
Main Results:
- Apnea occurred during obstruction in 19% and after obstruction in 32% of occasions.
- Obstruction-induced apnea was significantly more frequent than pre-obstruction apnea (8%).
- An obstruction score, reflecting apnea frequency, positively correlated with spontaneous apnea and peaked between days 15-28 of postnatal life.
Conclusions:
- External airway obstruction is a significant trigger for apnea in a proportion of preterm infants.
- The temporal pattern of obstruction-induced apnea may reflect the natural course of apnea in susceptible neonates.
Abstract:
A proportion of preterm infants respond to an external airway obstruction by becoming apneic. We have studied 23 infants (median birthweight, 1.14 kg; gestation, 29 weeks) on 80 occasions, to determine the time course of the response and its relationship with spontaneous apnea occurrence. Upper airway flow was measured with a face mask and pneumotachograph, and a tap was turned intermittently to produce an occlusion. A total of 380 occlusions were analyzed. The infants became apneic during the obstruction on 72 occasions (19%), and after the obstruction on 122 occasions (32%). Both of these events were significantly more common than immediately prior to the obstruction, when apnea occurred on 29 occasions (8%). Of the apneas following occlusion 57% were central in type. The point in the respiratory cycle at which obstruction occurred had no effect on the production of apnea. An obstruction score was calculated for each study. This was the mean of the number of apneas during and after each obstruction, expressed as a percentage of the number of obstructions per study. This score was positively correlated with the number of spontaneous apneas recorded. Obstruction score rose from a mean of 20% during days 0-14, to 34% during days 15-28, and thereafter it declined. This pattern may be relevant to the time course of apnea in susceptible infants.