Hemtanon, N.; Kongsayreepong, S.; Kitisin, N. Change in cardiac index during Trendelenburg maneuver as a predictor of fluid responsiveness among patients under mechanical ventilation with spontaneous breathing activity: A protocol for prospective observational study: Trendelenburg maneuver and fluid responsiveness in mechanically ventilated patients with spontaneous breathing activity. Clin Crit Care 2024, 32, e240006.