• Paul A Leonard, J Graham Douglas, Neil R Grubb, David Clifton, Paul S Addison, and James N Watson.
• Department of Accident and Emergency Medicine, The Royal Hospital for Sick Children, Sciennes Rd, Edinburgh EH9 1LF, UK. paul_leonard@blueyonder.co.uk
• J Clin Monit Comput. 2006 Feb 1;20(1):33-6.

ObjectiveTo determine if an automatic algorithm using wavelet analysis techniques can be used to reliably determine respiratory rate from the photoplethysmogram (PPG).MethodsPhotoplethysmograms were obtained from 12 spontaneously breathing healthy adult volunteers. Three related wavelet transforms were automatically polled to obtain a measure of respiratory rate. This was compared with a secondary timing signal obtained by asking the volunteers to actuate a small push button switch, held in their right hand, in synchronisation with their respiration. In addition, individual breaths were resolved using the wavelet-method to identify the source of any discrepancies.ResultsVolunteer respiratory rates varied from 6.56 to 18.89 breaths per minute. Through training of the algorithm it was possible to determine a respiratory rate for all 12 traces acquired during the study. The maximum error between the PPG derived rates and the manually determined rate was found to be 7.9%.ConclusionOur technique allows the accurate measurement of respiratory rate from the photoplethysmogram, and leads the way for developing a simple non-invasive combined respiration and saturation monitor.

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