Evaluating the ventilatory effect of transnasal humidified rapid insufflation ventilatory exchange in apnoeic small children with two different oxygen flow rates: a randomised controlled trial.

Abstract

Transnasal humidified rapid insufflation ventilatory exchange prolongs safe apnoeic oxygenation time in children. In adults, transnasal humidified rapid insufflation ventilatory exchange is reported to have a ventilatory effect with PaCO2 levels increasing less rapidly than without it. This ventilatory effect has yet to be reproduced in children. In this non-inferiority study, we tested the hypothesis that children weighing 10-15kg exhibit no difference in carbon dioxide clearance when comparing two different high-flow nasal therapy flow rates during a 10-min apnoea period. Following standardised induction of anaesthesia including neuromuscular blockade, patients were randomly allocated to high-flow nasal therapy of 100% oxygen at 2 or 4l.kg-1 .min-1 . Airway patency was ensured by continuous jaw thrust. The study intervention was terminated for safety reasons when SpO2 values dropped <95%, or transcutaneous carbon dioxide levels rose >9.3kPa, or near-infrared spectroscopy values dropped >20% from their baseline values, or after an apnoeic period of 10min. Fifteen patients were included in each group. In the 2l.kg-1 .min-1 group, mean (SD) transcutaneous carbon dioxide increase was 0.46 (0.11)kPa.min-1 , while in the 4l.kg-1 .min-1 group it was 0.46 (0.12)kPa.min-1 . The upper limit of a one-sided 95%CI for the difference between groups was 0.07kPa.min-1 , lower than the predefined non-inferiority margin of 0.147kPa.min-1 (p=0.001). The lower flow rate of 2l.kg-1 .min-1 was non-inferior to 4l.kg-1 .min-1 relative to the transcutaneous carbon dioxide increase. In conclusion, an additional ventilatory effect of either 2 or 4l.kg-1 .min-1 high-flow nasal therapy in apnoeic children weighing 10-15kg appears to be absent.