Elsevier

The Lancet

Volume 377, Issue 9770, 19–25 March 2011, Pages 1011-1018
The Lancet

Articles
Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies

https://doi.org/10.1016/S0140-6736(10)62226-XGet rights and content

Summary

Background

Although heart rate and respiratory rate in children are measured routinely in acute settings, current reference ranges are not based on evidence. We aimed to derive new centile charts for these vital signs and to compare these centiles with existing international ranges.

Methods

We searched Medline, Embase, CINAHL, and reference lists for studies that reported heart rate or respiratory rate of healthy children between birth and 18 years of age. We used non-parametric kernel regression to create centile charts for heart rate and respiratory rate in relation to age. We compared existing reference ranges with those derived from our centile charts.

Findings

We identified 69 studies with heart rate data for 143 346 children and respiratory rate data for 3881 children. Our 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. 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 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.

Interpretation

Our evidence-based centile charts for children from birth to 18 years should help clinicians to update clinical and resuscitation guidelines.

Funding

National Institute for Health Research, Engineering and Physical Sciences Research Council.

Introduction

Heart rate and respiratory rate are key vital signs used to assess the physiological status of children in many clinical settings. They are used as initial measurements in acutely ill children, and in those undergoing intensive monitoring in high-dependency or intensive-care settings. During cardiopulmonary resuscitation, these indices are critical values used to determine responses to life-saving interventions. Heart rate and respiratory rate remain an integral part of standard clinical assessment of children with acute illnesses,1 and are used in paediatric early warning scores2, 3 and triage screening.4, 5 Early warning scores are used widely in routine clinical care, and there is good evidence that they can provide early warning of clinical deterioration of children in hospital and in emergency situations.6, 7, 8, 9

Reference ranges for heart rate and respiratory rate in children are published by various international organisations (webappendix p 1). Of these publications, only two guidelines cite sources for their reference ranges: the pediatric advanced life support guidelines10 cite two textbooks,11, 12 neither of which cite sources for their ranges, and WHO limits for respiratory rate, which are based on measurements made in developing countries.13 Evidence underpinning guidelines is therefore scarce, and many ranges are probably based on clinical consensus.

Scoring systems underpinning triage and resuscitation protocols for children invariably require measurement of heart rate and respiratory rate. Rates are converted to a numerical score by applying age-specific thresholds. Accurate reference ranges are key to assessing whether vital signs are abnormal. Thresholds that are incorrectly set too low risk overdiagnosing tachycardia or tachypnoea, whereas those set too high risk missing children with these signs. Additionally, a reference range that is applied to an age range that is too broad is likely to lead to incorrect assessment of children in some parts of these age groups.

We aimed to develop new age-specific centiles for heart rate and respiratory rate in children, derived from a systematic review of all studies of these vital signs in healthy children. We use these centiles to define new evidence-based reference ranges for healthy children, which we compare with existing reference ranges.

Section snippets

Search strategy and selection criteria

We searched Medline, Embase, CINAHL and reference lists to identify studies that measured heart rate or respiratory rate in healthy children between birth and 18 years of age, from 1950, to April 14, 2009, with MeSH terms and free text. Webappendix p 2 shows the search strategy that was used to identify relevant studies. There were no language restrictions. Panel 1 shows the inclusion and exclusion criteria. SF and MT assessed eligibility of studies for inclusion, and disagreements were

Results

Figure 1 depicts the study selection process. We identified 69 studies from 2028 publications. 59 of 69 reported data for heart rate from 150 080 measurements of 143 346 children, and 20 reported data for respiratory rate from 7565 measurements on 3881 children, with ten studies reporting data for both vital signs (for scatter plots of data see webappendix p 5). 46 studies were cross-sectional, 12 longitudinal, and 11 case-control. They were undertaken in 20 different countries on four

Discussion

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, such as those shown in webappendix p 1, which are used widely as the basis for clinical decisions when interpreting these signs in children (panel 2). For example, the paediatric advanced warning score and Brighton

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