Background It is important to evaluate the size of respiratory effort to prevent patient self-inflicted lung injury and ventilator-induced diaphragmatic dysfunction. Esophageal pressure (Pes) measurement is the gold standard for estimating respiratory effort, but it is complicated by technical issues. We previously reported that a change in pleural pressure ([DELTA]Ppl) could be estimated without measuring Pes using change in CVP ([DELTA]CVP) that has been adjusted with a simple correction among mechanically ventilated, paralyzed pediatric patients. This study aimed to determine whether our method can be used to estimate [DELTA]Ppl in assisted and unassisted spontaneous breathing patients during mechanical ventilation. Methods The study included hemodynamically stable children (aged Results Of the 14 patients enrolled in the study, 6 were excluded because correct positioning of the esophageal balloon could not be confirmed, leaving eight patients for analysis (mean age, 4.8 months). Three variables that reflected [DELTA]Ppl ([DELTA]Pes, [DELTA]CVP, and c[DELTA]CVP-derived [DELTA]Ppl) were measured and yielded the following results: -6.7 ± 4.8, - -2.6 ± 1.4, and - -7.3 ± 4.5 cmH2O, respectively. The repeated measures correlation between c[DELTA]CVP-derived [DELTA]Ppl and [DELTA]Pes showed that c[DELTA]CVP-derived [DELTA]Ppl had good correlation with [DELTA]Pes (r = 0.84, p Conclusions [DELTA]Ppl can be estimated reasonably accurately by [DELTA]CVP using our method in assisted and unassisted spontaneous breathing children during mechanical ventilation.