A new analysis of 69 studies comprising some 143,000 children has produced new reference ranges that differ widely from existing published guidelines. The findings are in an Article published Online First by The Lancet. Existing guidelines should be updated, say the authors, led by Dr Matthew Thompson, Oxford University, UK, and colleagues.
The researchers identified 69 studies with heart rate data for some 143,000 healthy children and respiratory rate data for almost 4000 children. Their new reference ranges (centile charts) show decline in respiratory rate from birth to early adolescence, with the steepest fall apparent in infants under 2 years of age; decreasing from a median of 44 breaths per min at birth to 26 breaths per min at 2 years.
Heart rate shows a small peak at age 1 month, and median heart rate increases from 127 beats per min at birth to a maximum of 145 beats per min at about 1 month, before decreasing to 113 beats per min by 2 years of age. Comparison of the new centile charts with existing published reference ranges for heart rate and respiratory rate which are used for paediatric assessment and resuscitation show striking disagreements, with limits from published ranges often completely different. For children 10 years of age for example, the existing reference range classifies about half of healthy children as having an abnormal heart rate or respiratory rate.
The authors conclude: "Our centile charts of respiratory rate and heart rate in children provide new evidence-based reference ranges for these vital signs. We have shown that there is substantial disagreement between these reference ranges, and those currently cited in international paediatric guidelines…For clinical assessment of children, our findings suggest that current consensus-based reference ranges for heart rate and respiratory rate should be updated with new thresholds on the basis of our proposed centile charts, especially for those age groups where there are large differences between current ranges and our centile charts, indicating that many children are likely to be misclassified."
In a linked Comment, Dr Rosalind L Smyth, Institute of Translational Medicine, University of Liverpool and Alder Hey Children's Hospital, Liverpool, UK, says it is surprising the study does not include differences between sexes, in light of normal differences between the heart rates of women and men; she also cautions that other factors such as pain or distress (ie, factors not related to infection) can raise heart rate. She concludes: "These centile charts should initiate important new studies to establish where the clinical boundaries should be set for different ages, to assist clinicians to distinguish between normal and abnormal heart and respiratory rates. These studies will lead to revised algorithms, risk scores, and guidelines, which will incorporate these limits. Such instruments will then need to be extensively validated in different settings and populations before they can be incorporated into clinical practice."
Dr Matthew Thompson, Oxford University, UK and Oregon Health & Science University, USA. T) +44 (0) 7787 537450 E) matthew.thompson@dphpc.ox.ac.uk
Dr Rosalind L Smyth, Institute of Translational Medicine, University of Liverpool and Alder Hey Children's Hospital, Liverpool, UK.T) +44 (0) 151 252 5693 E) r.l.smyth@liv.ac.uk
Journal
The Lancet