We thank Drs Vargas and Esquinas for their interest in our manuscript. We fully agree that a third study arm including heated humidification would have provided a worthy comparison. Indeed, we have previously published that in infants receiving chronic oxygen therapy, heated humidification reduced the work of breathing and improved clinical outcomes when compared with a heat and moisture exchanger. Minimal adequate air humidification during invasive mechanical ventilation is reported to be 30 mg H2O/L. This is 50% greater humidity than that provided by the cold bubble humidifier in our study. However, the 2015 British Thoracic Society guidelines still state that humidification is unnecessary for patients receiving nasal low-flow oxygen therapy. The additional cost of a heated humidifier during nasal low-flow oxygen therapy is not covered by Brazilian Government Health Insurance, making our results most representative of the British Thoracic Society guidelines and of actual practice here. We were, therefore, also unable to obtain heated humidifiers for this study.