To the Editor,

We have read with great interest the article of Ishikawa et al. [1] who have identified one-lung ventilation and volume of crystalloid to be modifiable risk factors for early postoperative pulmonary complications (PPCs) in patients undergoing minimally invasive esophagectomy (MIE) in prone position. However, we think clarity on the following points might help overall evaluation regarding the outcome of their study.

First, the impaired preoperative pulmonary function is a known risk factor for PPC. It would be interesting to know whether the ‘lung age’ was assessed by derivation from the inverse calculation of the FEV1 standard regression equation [2]. The ‘lung age’ is associated with the occurrence, severity and time of onset of pneumonia after esophagectomy.

Second, extensive lymph node dissection along the pathway of recurrent laryngeal nerves (RLNs) is found to be associated with increased risk of RLN injury which is associated with difficulties with swallowing, pulmonary aspiration, high incidence of pneumonia, and thereby compromised postoperative life quality [3]. The incidences of complications are influenced by the MIE technique adopted and the extent of lymph node dissection [3]. It would be interesting to have a nitty–gritty of the MIE procedure.

Lastly, the mean crystalloid requirement was higher (4200 ml) in those who suffered PPC than who did not (3550 ml). However, the fluid requirement was as such high in both the groups, as some of their patients with poor preoperative conditions (e.g., hypovolemia) received more crystalloid intraoperatively. Positive fluid balance in first postoperative day was found to be an independent risk factor for PPCs in patients after esophagectomy for cancer [4]. Crystalloid infusion of ≥ 1500 mL in the first postoperative 24 h is a major risk factors for PPC [5].