Background: One technique to keep the airway open and eliminate secretions from ventilated patients is to suction the endotracheal tube. There are a number of dangers involved in this process. Variations in blood pressure, heart rate, respiratory rate, and oxygen saturation are among the initial issues with suctioning. It is recommended to utilize closed-circuit endotracheal suctioning (CES) to avoid hypoxemia, which is brought on by the loss of lung volume via open endotracheal suctioning (OES). This study was aimed to compare the effects of open versus closed suctioning in mechanically ventilated patients on suctioning time, gas exchange, and cardiorespiratory parameters. Design: A quasi- experimental research design (two groups) was carried out to achieve the aim of this study. Setting: The study was conducted at general intensive care at Sohag University Hospital. Subjects: A convenient sample included 100 critically ill patients undergoing mechanical ventilation were recruited from the previously selected setting within six months and was randomly assigned to the closed suction group (n = 50) and the open suction group (n = 50). Tools: One tool was used for data collection: I: Patient assessment sheet which included three parts: Part (I): bio-demographic data Part (II): Cardiorespiratory parameters assessment sheet, and Part (III): Gas exchange assessment sheet. Results: The mean duration of suction for patients in open and closed suctioning was 15.41 ± 2.37 and 7.50 ± 2.50 seconds, respectively.  An improvement in patients' suctioning time, gas exchange, and cardiorespiratory parameters was noticed after closed suctioning .The closed suction system group have a higher mean Oxygen saturation than those in the open group during suction and after suction measurements. Closed suction has a considerable positive impact on suctioning time, gas exchange, and cardiopulmonary parameters. Conclusion: The implementation of the closed suction system leads to decrease instabilities in the cardiorespiratory parameters compared to open suction system in mechanically ventilated patients. Recommendation: This study emphasizes on the need for further research with a large sample in different clinical settings to contribute to the body of knowledge and evidence related to endotracheal suction.