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Car seat test for preterm infants: comparison with polysomnography
  1. Dawn E Elder1,
  2. Letitia Russell4,
  3. Deidre Sheppard1,
  4. Gordon L Purdie2,
  5. Angela J Campbell3
  1. 1
    Department of Paediatrics, Wellington School of Medicine and Health Sciences, University of Otago, New Zealand
  2. 2
    Department of Public Health, Wellington School of Medicine and Health Sciences, University of Otago, New Zealand
  3. 3
    Department of Medicine, Wellington School of Medicine and Health Sciences, University of Otago, New Zealand
  4. 4
    Department of Child Health Services, Capital and Coast District Health Board, Wellington, New Zealand
  1. Dr Dawn Elder, Department of Paediatrics, WSMHS, PO Box 7343, Wellington, New Zealand; dawn.elder{at}


Objectives: To monitor preterm infants in a cot and a car seat and compare an observed car seat trial with polysomnography (PSG).

Design: Non-randomised controlled trial.

Setting: Regional neonatal unit.

Patients: Preterm infants before discharge.

Interventions: Nap PSG respiratory and sleep variables were measured including gastro-oesophageal pH. Nurse observations included respiratory distress, apnoea measured by apnoea alarm, oxygen saturation and heart rate. Infants were studied supine in a cot and then in a car seat. Nursing observations were compared with PSG during the car seat trial only. Criteria for failure of the PSG and observed tests were predefined.

Main outcome measures: Difference in respiratory instability between cot and car seat. Concurrence regarding failure of the car seat trial between nurse-observed data and PSG.

Results: 20 infants (median gestation 33 weeks (range 28–35 weeks; median postmenstrual age (PMA) at study 36.5 weeks (range 35–38 weeks)) were studied. There were sufficient car seat data on 18 infants for comparison. There were fewer central apnoeas and arousals in the cot than the car seat (p = 0.047 and p = 0.024, respectively). Airway obstruction was not more common in the car seat. Younger PMA at time of study predicted failure in both car seat (p = 0.022) and cot (p = 0.022). The nurse-observed test had low sensitivity for predicting PSG failure but more accurately predicted airway obstruction on PSG.

Conclusions: Immature infants exhibit respiratory instability in cots and car seats. A car seat test does not accurately detect all adverse events during sleep in the seat.

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  • Funding: This study was funded by the New Zealand Cot Death Association. The PSG equipment was funded by the New Zealand Lotteries Board.

  • Competing interests: None.

  • Abbreviations:
    postmenstrual age