Background and objectiveThe American Academy of Pediatrics recommends that preterm infants complete a predischarge ‘car seat challenge’ observation for cardiorespiratory compromise while in a car seat. This static challenge does not consider the more upright position in a car or the vibration of the seat when the car is moving. This pilot study was designed to assess the cardiorespiratory effects of vibration, mimicking the effect of being in a moving car, on preterm and term infants.MethodsA simulator was designed to reproduce vertical vibration similar to that in a rear-facing car seat at 30 mph. 19 healthy newborn term and 21 preterm infants, ready for hospital discharge, underwent cardiorespiratory measurements while lying flat in a cot (baseline), static in the seat (30°), simulator (40°) and during motion (vibration 40°).ResultsMedian test age was 13 days (range 1–65 days) and median weight was 2.5 kg (IQR: 2.1–3.1 kg).Compared with baseline observations, only the total number of desaturations was significantly increased when infants were placed at 30° (p=0.03). At 40°, or with vibration, respiratory and heart rates increased and oxygen saturation decreased significantly. Profound desaturations <85% significantly increased during motion, regardless of gestational age.ConclusionsThis is the first study to assess the effect of motion on infants seated in a car safety seat. Term and preterm infants showed significant signs of potentially adverse cardiorespiratory effects in the upright position at 40°, particularly with simulated motion, not identified in the standard challenge. A larger study is required to investigate the significance of these results.

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Introduction The AAP recommends preterm infants undergo a “car seat challenge” before discharge, to observe for any differences in cardiorespiratory function whilst seated in a car seat compared to lying flat in a cot. The infant can be discharged if there is no compromise. This static (30°) challenge does not take into account the more vertical positioning of the seat or effects of vibration when it is secured in a moving vehicle. Aim To investigate the effect of vibration, mimicking that experienced in a moving car, on cardio-respiratory function, compared to the standard challenge. Methods A novel simulator was designed to represent the vibrations felt in a rear facing car seat during a normal urban cycle. 40 term & preterm babies, ready for discharge after birth, were recruited. The babies were their own control. Observations of heart & respiratory rates, saturation & end tidal CO2 levels were recorded flat in a cot, static in the seat (30°) & simulator (40°) & during vibration (motion). Results 19 term & 21 preterm infants were tested; 22 were male (55%). Gestation range was 25+2 weeks to 41+5 weeks (median 35+5). Median birthweight was 2.5 kg (range 0.8 kg to 4.8 kg). Age at testing was 1 to 65 days (median 13 days). There were no significant differences in outcome variables for infants in the cot & 30° position. However, compared to rest, in the static 40° position infants had significantly faster heartbeats, lower oxygen saturation & higher respiratory rates. When in motion these differences persisted & the number of desaturations below 85% were significantly higher. Conclusions Testing all infants at 30° would suggest they could travel. However both term & preterm babies showed signs of cardio-respiratory distress in the 40° position with a significant increase in profound desaturations during motion, which were underestimated by the standard challenge. A larger study is required to confirm these results. This may lead to revision of the current car seat challenge or the design of infant car seats.