Reference ranges for heart, respiratory rates in children are skewed

New evidence-based reference ranges for heart and respiratory rates in children show substantial disagreement with existing consensus-based international guidelines, according to a meta-analysis published online in the Lancet.

Researchers came to their conclusion on the basis of a review of 69 studies in which heart-rate data were assessed in 143,346 children, and respiratory rate data were assessed in 3,881 children. They developed centile charts for heart and respiratory rates, some that were vastly different from current ranges. When using existing guidelines, many children are likely to be misclassified.

For example, the existing reference range most in agreement with the researchers' centiles-the advanced pediatric life-support reference ranges-classifies 40% and 63% of healthy 10-year-olds as having an abnormal heart and respiratory rate, respectively.

None of the current guidelines showed good agreement with the researchers' centile charts from birth to age 18 years. Published ranges in existing guidelines often exceeded the 1st and 99th centiles using the data from the meta-analysis, they found.

The centile charts show declines in respiratory rate from birth to early adolescence, with the steepest decrease in infants younger than 2 years, falling from a median of 44 breaths per minute at birth to 26 breaths per minute at 2 years.

The meta-analysis also demonstrated that median heart rate increases from 127 beats per minute at birth to a maximum of 145 beats per minute at about 1 month and then declines to 113 beats per minute by age 2 years.

Fleming S, Thompson M, Stevens R, et al. Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age; a systematic review of observational studies. Lancet. 2011. Epub ahead of print.