Identifying the febrile kid who’s too tachypnoeic

Body temperature raises heart rate and respiratory rate in kids, potentially affecting our interpretation of these clinical signs.

Dutch investigators developed centile charts of respiratory rates for specific body temperatures (derivation study), so that abnormally high rates could be identified as a means of predicting lower respiratory infection (validation set).

Respiratory rate increased overall by 2.2 breaths/min per 1°C rise (standard error 0.2) after accounting for age and temperature in the model, which is similar to a previous UK study that suggested a rise in respiratory rate of around 0.5-2 breaths per minute and an increase in heart rate of about 10 beats per minute for every 1 degree celcius above normal.

Cut-off values at the 97th centile were more useful in detecting the presence of LRTI than existing (Advanced Paediatric Life Support) respiratory rate thresholds.

The respiratory rate charts are available here.

Derivation and validation of age and temperature specific reference values and centile charts to predict lower respiratory tract infection in children with fever: prospective observational study
BMJ. 2012 Jul 3;345:e4224

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