Reference heart and lung rates for children range widely from published guidelines

Fleming S. Lancet. 2011;doi:10.1016/S0140-6736(10)62226-X.

Reference ranges for children’s heart and lung rates vary widely from published guidelines, according to analysts in Britain.

Using data from 69 studies compiled from Medline, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and reference lists, analysts at Oxford University in England reviewed heart rates for 143,346 healthy children and respiratory rates for 3,881 children; all children were aged birth to 18 years. The analysts developed centile charts for age-to-heart and age-to-breathing rate ratios using non-parametric kernel regression, then compared their charts to existing reference ranges. Children with illnesses that may affect heart or respiratory rate, or whose heart rate was known to have been measured during exertion, were excluded from the study.

The centile charts demonstrated a decline in respiratory rates from birth to early adolescence; infants aged younger than 2 years showed a decrease from a median of 44 breaths/minute at birth to 26 breaths/minute at 2 years. Analysts found that median heart rate increased from 127 beats/minute at birth to a maximum 145 beats/minute at about 1 month of age; heart rate decreased to 113 beats/minute by age 2 years.

“Comparison of our centile charts with existing published reference ranges for heart rate and respiratory rate show striking disagreement, with limits from published ranges frequently exceeding the 99th and 1st centiles, or crossing the median,” analysts wrote.

In children aged 2 to 5 years, the advanced pediatric life support lower limit for heart rate is 95 beats/minute; in the analysis, this limit correlated with the 25th centile, reaching the median heart rate at the upper end of the age range. In children aged 2 to 10 years, the advanced pediatric life support upper limit is 140 beats/minute, which is more than the 99th centile of the analysts’ chart for most of the age range.

“On the basis of age distribution of children typically seen in a primary care setting, we estimate that the specificity of advanced pediatric life support could be improved by as much as 20% for heart rate and 51% for respiratory rate if revised centile charts are used. The validity of our centiles and any cutoffs derived from them should be assessed both in healthy children and in those presenting with a range of diseases,” analysts wrote.

Subgroup analysis indicated that setting, method of measurement and economic development had a significant effect on heart rate, but not on respiratory rate.

“The investigators identified significant heterogeneity with study setting (community vs. clinical or laboratory), measurement technique (manual vs. automated), developing vs. developed country location, and when the study was published,” Rosalind L Smyth, MD, of the Institute of Translational Medicine, University of Liverpool and Alder Hey Children’s Hospital, United Kingdom, wrote in an accompanying editorial. “However, other potentially important sources of heterogeneity, such as ethnic origin and sex, have not been explored. The omission of sex is surprising, in view of the consistent and well-recognized differences between normal heart rates of men and women.”

Disclosure: The researchers reported no relevant financial disclosures.