LAUSR

Objective There is a lack of objective measures to assess children with acute wheezing episodes. Increased respiratory rate (RR) and pulsus paradoxus (PP) are recognised markers, but poorly recorded in practice. We examined whether they can be reliably assessed from a pulse oximeter plethysmogram (‘pleth’) trace and predict clinical outcome. Patients and methods We studied 44 children aged 1–7 years attending hospital with acute wheeze, following initial ‘burst’ bronchodilator therapy (BT), and used custom software to measure RR and assess PP from oximeter pleth traces. Traces were examined for quality, and the accuracy of the RR measurement was validated against simultaneous respiratory inductive plethysmography (RIP). RR and PP at 1 hour after BT were compared with clinical outcomes. Results RR from pleth and RIP showed excellent agreement, with a mean difference (RIP minus pleth) of −0.5 breaths per minute (limits of agreement −3.4 to +2.3). 52% of 1 min epochs contained 10 s or more of pleth artefact. At 1 hour after BT, children who subsequently required intravenous bronchodilators had significantly higher RR (median (IQR) 63 (62–66) vs 43 (37–51) breaths per minute) than those who did not, but their heart rate and oxygen saturation were similar. Children with RR ≥55 per minute spent longer in hospital: median (IQR) 30 (22–45) vs 10 (7–21) hours. All children who subsequently required hospital admission had PP-analogous pleth waveforms 1 hour after BT. Conclusion RR can be reliably measured and PP detected from the pulse oximeter pleth trace in children with acute wheeze and both markers predict clinical outcome. Trial registration number UKCRN15742. This study utilises pulse oximetry wave forms to measure respiratory rate and plusus paradoxus, providing real time objective measurements of these parameters.