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Preterm infants with apnea show immature respiratory reflexes, leading to poor inspiratory effort and load compensation. This immaturity may contribute to the development of apnea of prematurity.
Area of Science:
- Neonatal Physiology
- Respiratory Medicine
- Developmental Pediatrics
Background:
- Apnea of prematurity is a common condition in preterm infants.
- Airway obstruction can trigger apneic events.
- The role of respiratory reflexes in apnea of prematurity requires further elucidation.
Purpose of the Study:
- To determine the activity of protective respiratory reflexes in preterm infants experiencing apnea.
- To compare reflex activity between infants with and without apnea.
- To investigate the contribution of respiratory reflex immaturity to the etiology of apnea of prematurity.
Main Methods:
- Airway occlusion technique used in 18 preterm infants with apnea and 18 matched controls.
- Measurement of inspiratory prolongation and effective elastance of the respiratory system.
- Infants were matched for birth weight, gestational age, and postnatal age.
Main Results:
- Infants with apnea exhibited significantly reduced inspiratory prolongation (7.3% vs. 30.6%, P < .025).
- Effective elastance was lower in the apneic group (1.1 vs. 1.5 cm H2O/mL, P < .025), indicating impaired load compensation.
- Respiratory reflexes were found to be significantly more immature in infants with apnea.
Conclusions:
- Preterm infants with apnea demonstrate poor maintenance of inspiratory effort when exposed to respiratory loads.
- A decreased ability for load compensation is observed in infants with apnea.
- Functional immaturity of respiratory reflexes is a potential contributing factor to apnea of prematurity.
Abstract:
Airway obstruction is a cause of apnea in preterm infants. The activity of protective respiratory reflexes was determined in 18 preterm infants with apnea (mean of 32 episodes of more than 20 seconds duration per day) and in 18 neonates without apnea used as control subjects. This was done in order to elucidate the role of respiratory reflexes in apnea of prematurity. The infants were matched for birth weight (1,068 g v 1,065 g), gestational age (30.2 weeks v 30.2 weeks), and postnatal age (8.6 days v 8.3 days). The airway occlusion technique was used to determine the inspiratory prolongation of the occluded breath and the effective elastance of the respiratory system. Inspiratory prolongation is a measure for the reflex influence on inspiratory duration, and effective elastance reflects load compensating ability. Inspiratory prolongation was 7.3% +/- 33.5% in infants with apnea and 30.6% +/- 22.7% in the control group (P less than .025). Effective elastance was 1.1 +/- 0.5 cm H2O/mL in the apneic group and 1.5 +/- 0.5 cm H2O/mL in the infants without apnea (P less than .025). The results indicate that during exposure to respiratory loads, the infants with apnea maintained inspiratory effort poorly and had a decreased ability for load compensation. Their respiratory reflexes were significantly more immature than the reflex activity of the infants without apnea. This functional immaturity of respiratory reflexes may be a contributing factor in the etiology of apnea of prematurity.