Effect of flow rate on the end‐expiratory lung volume in infants with bronchiolitis using high‐flow nasal cannula evaluated through electrical impedance tomography

Abstract

Objectives: To evaluate the effects of four flow rates on the functional residual capacity (FRC) and pulmonary ventilation distribution while using a high-flow nasal cannula (HFNC).Working Hypothesis: Our hypothesis is that flow rates below 1.5 L•kg −1 •min −1 lead to FRC loss and respiratory distress.

The effects of flow settings during high-flow nasal cannula oxygen therapy for neonates and young children

“…In the two studies involving infants with bronchiolitis, an increase in flow was associated with an improvement in the patient's S pO 2 / F IO 2 ratio ( supplementary table S4 ) [ 7 , 8 ]. When the flow was increased from 0.5 to 2 L·kg −1 ·min −1 [ 44 , 46 ], no significant differences were observed in V T and minute ventilation, as assessed by respiratory inductance plethysmography [ 45 ], pneumotachography [ 44 ] or electric impedance tomography [ 46 ].…”

“…When the flow was increased from 0.5 to 2 L·kg −1 ·min −1 [ 44 , 46 ], no significant differences were observed in V T and minute ventilation, as assessed by respiratory inductance plethysmography [ 45 ], pneumotachography [ 44 ] or electric impedance tomography [ 46 ]. Moreover, when flow was increased from 0.4 to 2 L·kg −1 ·min −1 , a reduction in respiratory rate was observed in six studies ( figure 3a ) [ 6 , 8 , 43 – 46 ], except for the study conducted by N ascimento et al [ 7 ], in which no significant differences in respiratory rate were observed across flows of 0.5–2 L·kg −1 ·min −1 when using the Vapotherm device.…”

“…Three studies [ 43 , 44 , 46 ] reported decreased inspiratory effort, as measured by change in oesophageal pressure swings, with increasing flows. Moreover, the modified Wood's clinical asthma score and respiratory distress score also decreased with increasing flows [ 6 , 7 ].…”

“…The selection of flow settings for HFNC therapy has been evaluated in numerous studies because it can improve upper airway flow dynamics, affect the positive end-expiratory pressure (PEEP) (i.e. increase functional residual capacity (FRC)), improve oxygenation, increase dead space washout, augment minute ventilation and reduce work of breathing (WOB) [6][7][8][9]. However, the optimal flow setting for HFNC in children remains unclear.…”