HFNC treatment in the paediatric ward is safe. Non-responders requiring PICU admission can be identified within the first hour of HFNC treatment by monitoring HR and RR. It is feasible to undertake a randomised controlled trial based on this pilot with the aim of decreasing PICU admissions.

The main physiological impact of high flow nasal cannula (HFNC) therapy is presumed to be a decrease in work of breathing (WOB). To assess this, diaphragmatic electrical activity and esophageal pressure changes were measured off then on HFNC delivered at 2 L/kg/min, in 14 infants with bronchiolitis and 14 cardiac infants. Electrical activity of the diaphragm (Edi) was measured using an Edi catheter with calculations of signal peak (EdiMAX ) and amplitude (EdiAMPL ). Pressure-rate and pressure-time products (PRP, PTP) were calculated from analyses of esophageal pressure. Changes in end-expiratory lung volume were measured using respiratory inductance plethysmography (RIPEEL ). The EdiMAX and EdiAMPL were significantly higher in infants with bronchiolitis than in cardiac infants (P < 0.05). Within the bronchiolitis group, both were significantly reduced between HFNC states from 27.9 µV [20.4, 35.4] to 21.0 µV [14.8, 27.2] and from 25.1 µV [18.0, 32.2] to 19.2 µV [13.3, 25.1], respectively (mean, 95% CI, P < 0.05). A less prominent offload of the diaphragm was observed in cardiac infants (P < 0.05). WOB decreased in both groups with a significant reduction of PRP and PTP (P < 0.05). RIPEEL increased significantly in bronchiolitis only (P < 0.05). HFNC offloads the diaphragm and reduces the WOB in bronchiolitis. A similar effect was demonstrated in cardiac infants, a group without signs of airway-obstruction.

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