Background: Assessing fluid responsiveness in patients in the prone position with low tidal volume ventilation presents challenges when utilizing pulse pressure variation (PPV) and the inferior vena cava (IVC) distensibility index. These challenges stem from the use of low tidal volume and the difficulty of conducting IVC assessment in the prone position. Consequently, an alternative method for predicting fluid responsiveness in these patients is imperative. Method: This study comprises a prospective investigation that was carried out on hypotensive patients positioned in the prone posture and undergoing lung-protective ventilation at Bhumibol Adulyadej Hospital. Prior to the administration of a 500 ml fluid bolus, end-expiratory occlusion (EEO) and tidal volume challenge (TVC) tests were conducted. Initial recordings of cardiac output, cardiac index, and PPV were documented, followed by subsequent recordings after each procedure. Result: Among the 20 participants in the prone position study, 4 patients developed severe acute respiratory distress syndrome (ARDS) while 16 patients were in that position for surgical reasons. Of these, 7 patients exhibited a positive response to fluid administration, while 13 patients did not. An increase in cardiac index (CI) of more than 5% during EEO is indicative of fluid responsiveness with a sensitivity of 100% and specificity of 92.3%. Moreover, a 3.5% absolute increment in PPV during TVC suggests fluid responsiveness with a sensitivity of 57.1% and specificity of 92.3%. We observed an interrater reliability (kappa) of 0.894 for EEO and 0.529 for PPV. Conclusion: In the case of hypotensive patients undergoing prone positioning and receiving low tidal volume ventilation, both EEO for 15 seconds and TVC methodologies can be employed to evaluate fluid responsiveness. It is important to note that EEO demonstrates greater reliability in this context.