Objectives. To test prospectively the hypothesis that an infant car seat modification to allow the infant’s head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car seats.

Methods. Seventeen preterm infants who were approved for discharge were evaluated in a car seat for newborns, with and without a foam insert that provided a slot for the back of the infants’ head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry.

Results. Placement of the insert in the car seat was associated with a larger upper airway space (mean ± standard deviation, 5.2 ± 1.3 vs 3.6 ± 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to <85% (1.5 ± 2.1 vs 3.5 ± 3.5 episodes/infant), of bradycardia <90 bpm (0.1 ± 0.3 vs 1 ± 1.7), and of arousal (median [25th, 75th], 2.5 [1.3, 4.0] vs 5.0 [4.0, 7.0]).

Conclusions. The cause of oxygen desaturation in preterm infants who are restrained in car seats is multifactorial. The present data strongly support the hypothesis that flexion of the head on the body is a significant contributor to these episodes and that the mechanism is posterocephalic displacement of the mandible, leading to narrowing of the upper airway. Critically, this pilot study demonstrates that the frequency of episodes of desaturation in a standard newborn car seat can be substantially reduced by placement of a simple foam insert that allows the infant to maintain the head in a neutral position on the trunk during sleep.

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