Background: Endotracheal Tube Suctioning (ETS) is one of the most common invasive procedures carried out in the critical care units, many life-threatening complications can occur when the ETS procedure is not performed correctly; Nurses' play a crucial role in preventing these complications. Aim of the study: Is to assess the correlation between current nurse's practice regarding endotracheal suctioning and patient's cardiorespiratory parameters at critical care units. Research design: Descriptive correlative research design was utilized for conduction of this study. Sample: Subjects included in the study were two groups; (50) nurses and (50) patients according to the inclusion criteria. Setting: The study was conducted in the critical care units of Qena University Hospital and international Hospital in Luxor. Data collection tools: First Tool:  Structured questionnaire sheet, it includes (three parts): First part: Personal data sheet of the nurses. Second part: Selected Personal and medical data sheet of the patients. Third part: Structured knowledge questionnaire sheet about endotracheal suctioning. Second Tool: Observational checklist regards endotracheal suctioning. Third Tool: Cardiorespiratory parameters. Study duration: Data collection of this study was carried out within ten months from 1st January to the end of October. Results: the study revealed that the mean ages among the studied nurses group ranged between (28.60 ± 4.65 years) and the mean ages between studied patients group was between (48.39 ± 12.75). Majority of nurses had unsatisfactory knowledge and unsatisfactory practice 70%, 75%, respectively, regarding endotracheal suctioning. There was significant relation between nurses ‘knowledge and practices and patients' cardiorespiratory parameters (heart rate, tidal volume, arterial oxygen saturation and partial pressure of oxygen and partial pressure of carbon dioxide). Conclusion: Based on the results of the current study, it can be concluded that, there was significant relation between nurses'performane and patients ‘cardiorespiratory parameters. Recommendation: Updating knowledge and practice for ICU staff nurses and newly employed nurses through carrying out periodic training educational programs about endotracheal suctioning through in-service training hospital office. Instruct the critical care units' manager and head nurse in study setting to use evidence based practice guidelines regarding endotracheal suctioning.