Abstract
Heated, humidified, high-flow nasal cannula (HHHFNC) is increasingly being used, but there is a paucity of evidence as to the optimum flow rates in prematurely born infants. We have determined the impact of three flow rates on the work of breathing (WOB) assessed by transcutaneous diaphragm electromyography (EMG) amplitude in infants with respiratory distress or bronchopulmonary dysplasia (BPD). Flow rates of 4, 6 and 8 L/min were delivered in random order. The mean amplitude of the EMG trace and mean area under the EMG curve (AEMGC) were calculated and the occurrence of bradycardias and desaturations recorded. Eighteen infants were studied with a median gestational age of 27.8 (range 23.9–33.5) weeks and postnatal age of 54 (range 3–122) days. The median flow rate prior to the study was 5 (range 3–8) L/min and the fraction of inspired oxygen (FiO2) was 0.29 (range 0.21–0.50). There were no significant differences between the mean amplitude of the diaphragm EMG and the AEGMC and the number of bradycardias or desaturations between the three flow rates.Conclusions: In infants with respiratory distress or BPD, there was no advantage of using high (8 L/min) compared with lower flow rates (4 or 6 L/min) during support by HHHFNC.What is known:• Humidified high flow nasal cannulae (HHHFNC) is increasingly being used as a non-invasive form of respiratory support for prematurely born infants.• There is a paucity of evidence regarding the optimum flow rate with 1 to 8 L/min being used.What is new:• We have assessed the work of breathing using the amplitude of the electromyogram of the diaphragm at three HHHFNC flow rates in infants with respiratory distress or BPD.• No significant differences were found in the EMG amplitude results or the numbers of bradycardias or desaturations at 4, 6 and 8 L/min.
Highlights
There is increasing use of non-invasive ventilation for prematurely born infants
In another study compared to a baseline of nasal continuous positive airway pressure (nCPAP) of 6 cm H2O, respiratory rates increased when the infants were transferred to HHFNC at 6 L/min and the flow rate was reduced by 1 L/min every 30 min suggesting that work of breathing (WOB) had increased [10]
There were no significant differences between the diaphragm EMG amplitude (Fig. 2) (p = 0.678) or the AEGMC (p = 0.946) between the three flow rates (Table 1)
Summary
There is increasing use of non-invasive ventilation for prematurely born infants This includes nasal continuous positive airway pressure (nCPAP) and heated, humidified, high flow nasal cannula (HHHFNC). An in vivo study highlighted a linear increase in positive pharyngeal pressure as flow rates during HHHFNC increased from 2 to 8 L/min [21]. In one study [15], no significant differences in the work of breathing were demonstrated between flow rates of 3, 4, or 5 L/min during HHHFNC and nCPAP delivered at 6 cm H2O. In another study compared to a baseline of nCPAP of 6 cm H2O, respiratory rates increased when the infants were transferred to HHFNC at 6 L/min and the flow rate was reduced by 1 L/min every 30 min suggesting that WOB had increased [10]. It is important to determine if different flow rates during HHFNC do affect the WOB
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