Identifying the Relative Change in Ventilation With Changes in Infant Sleeping Position

BACKGROUND AND RATIONALE

The safe transportation of infants has formed a critical part of public health policy for many years. Clearly crash tolerance of the seat, the ease of installation, the position of the seat and the relative position to airbags has been the focus of intensive research. However as with all safety devices, there are some limitations. Respiratory instability is a potential concern due to the upright position in the car seat. This is particularly true in the premature newborn and has resulted in the recommendation to perform car safety seat testing before discharge from hospital for these infants.

Recently there have also been concerns raised about term infants. Merchant et al showed that mean oxygen saturations declined in both term and premature infants reaching a nadir of 95% after about 70 minutes of placement in a car safety seat with 8% noted to have an SaO2 of less than 90% for more than 20 minutes. Also, in an earlier study by Bass and Mehta, selected high risk full term infants were found to have increased risk of developing hypoxia.

It has been generally accepted that the potential for adverse effects from these hypoxic events are substantially offset by the crash protection afforded by these devices. Unfortunately, the portability of car seats and contemporary busy lifestyles are resulting in infants spending extended periods of time in the car seat for reasons other than transport. Callahan et al found in 187 infants that 94% spent greater than 30 minutes in seating devices including car seats each day. The mean time spent in seating devices was 5.7+/- 3.5 hours and ranged from 0 to 16 hours. Prolonged use of car seats in infants too young to sit unsupported may also potentially result in prolonged periods of oxygen desaturation.

A recent comprehensive review of peer reviewed published evidence noted that hypoxia has frequently been associated with significant defects in cognition. In some studies changes in cognitive function were seen with even mild levels of oxygen desaturation. Such changes were observed in all groups except premature babies. The young child may be relative resistant, as their physiology is adapted for the relatively hypoxic intrauterine environment. However a recent study also suggests that premature infants may also have problems. Thus a cautious approach has been adopted where children who fail to maintain adequate oxygen saturation while placed in the car seat are discharged in a car bed.