Huaiwu He, Yun Long
We read the letter from Wataru Matsuda with interest and are delighted to respond to their questions and comments.
First, our study compared different flow rates in an effort to assess an optimal flow rate (induce recruitment with minimal overdistension). Hence, a small step of incremental flow rate (20 L/min) was selected. Moreover, an initial high flow might bring uncomfortable to patients who were at relatively normal respiratory status without obvious hypoxia. Furthermore, the increasing flow rate process had been reported in the previous study of EIT .
Second, we agreed that the investigation of the difference of HFNC and conventional oxygen therapy was meaningful. The baseline could be taken as conventional oxygen therapy in our study. Actually, the recruited pixel assessed by EIT was compared to the baseline. Therefore, the result could effectively reflect the lung response to HENC. Using EIT to guide the mechanical ventilator setting has become popular in clinical practice .
Third, lung overdistension is an interesting topic. A recent clinical case reported HENC could cause pulmonary hyperinflation with mild pneumomediastinum assessed by high-resolution chest computed tomography scan  in a patient with bronchiolitis obliterans syndrome. Moreover, Kotani et al. reported the regional overdistension was detected at a prone position in an ARDS patient with a low tidal volume . We proposed a novel EIT method to assess lung overdistension in the spontaneous breath condition . Further studies are required to using EIT to assess the effect of HENC on lung overdistension at the prone position.