For the 200 infants included in the study, the average oxygen saturation level was 97.9 percent in the crib, 96.3 percent in the car bed and 95.7 percent in the car seat.
Greater differences were seen in average minimal oxygen levels: 87.4 percent for the hospital crib, 83.7 percent for the car bed and 83.6 percent for the car seat.
Children in car seats and car beds spent more time with oxygen levels below 95 percent than did children in cribs, according to the study. And the longer the child was in the car seat, the worse the respiratory problem became.
Car beds may be safer in this respect than car seats, but even that is not ideal, the study noted.
In addition to keeping children out of car seats for long and unnecessary periods of time, the authors suggested that manufacturers consider modifications to the design of the seats.
"It's important for people to realize that doing some of these things is not benign and has potential risks involved," said Browning, who is also a pediatric pulmonologist at Driscoll Children's Hospital in Corpus Christi, Texas. "Use the car seats when you need to, but otherwise children need to be in a different setting."
The study still leaves many questions unanswered, such as whether the oxygen effect is long-term, said Dr. Judy Schaechter, associate professor of pediatrics at the University of Miami Miller School of Medicine and director of the Injury Free Coalition for Kids of Miami.
"Does this go away after a few days or does it last three months," she said. "Clearly, if it turns out to be real, we have to look at manufacturing of car seats."
The study was funded by the Japanese company Aprica, whic
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