Purpose: In this study, we aimed to compare cardiac output, echocardiographic pulmonary velocity-time integral, and end-tidal carbon dioxide values before and after the passive leg raising maneuver in healthy volunteers. Methods: The Ethical Commission approved the study. A total of 36 volunteers were included after signed informed consent in our study. After 12 h of fasting, vital signs, cardiac output, pulmonary velocity-time integral, and end-tidal carbon dioxide were measured when the participants were lying supine. Then, participants' legs were elevated to 45 degrees passively, and all measurements were repeated. Pulmonary velocity-time integral was obtained in parasternal short-axis view with the aid of pulse Doppler. Pulmonary root measurements were recorded. Echocardiographic stroke volume and cardiac output were calculated. The differences between values of cardiac output, pulmonary velocity-time integral, and end-tidal carbon dioxide before and after passive leg raising were statistically compared. The level of significance was accepted as p < 0.05. Results: Significant differences were found between pre- and post-passive leg raising values of these three measurements. The effect of passive leg raising on pulmonary velocity-time integral measurements was greater. The change in end-tidal carbon dioxide was not correlated with either cardiac output or pulmonary velocity-time integral alteration. Conclusion: Our results showed that measurement of pulmonary velocity-time integral changes after passive leg raising is a more useful bedside method to predict fluid responsiveness than measurement of end-tidal carbon dioxide and cardiac output alteration.