Background: Backrest elevation is one of the important performed nursing activities in Intensive Care Unit (ICU) and often providing an essential focus for planning other nursing activities. Hemodynamic changes occur with positioning which is a core component of critical care nursing to optimize ventilation on mechanically ventilated patients. Aim: This study aims to assess the effect of different backrest positions' degrees on hemodynamic stability of mechanically ventilated patients through the following : assess hemodynamic status among mechanically ventilated patients pre implementation of different backrest positions degrees,implement different backrest positions degrees in 0-30-45 for patients on mechanical ventilation , assess hemodynamic status among mechanically ventilated patients post implementation of different backrest positions degrees.Design: A quasi experimental design was conducted to achieve the aim of the present study. Setting: The study was conducted in the general intensive care unit at Blebies Central Hospital Elsharqia. Study subject: A purposive sample of 40 patients on mechanical ventilators who admitted to ICU in the previous mentioned setting. Tools of data collection: were consisted of patient's assessment tool, mechanically ventilated patients' parameters assessment tool. Results: Revealed that 40.0% of studied patients were 60 years old or more with the mean age 54.9 ± 12.86 as well, 70.0% of them were males, there was highly statistically significant difference was found as regard blood pressure diastolic and central venous pressure, there was a highly statistically significant difference between the studied patients' respiratory assessment at post 0ᵒ, 30ᵒ and 45ᵒ degrees of backrest positions. Conclusion: Implementation of 45 degree backrest position is associated with improvement of hemodynamic status of mechanically ventilated patients. Recommendations: Encourage nurses in intensive care units settings to apply 45 degree head of bed elevation to improve oxygenation and hemodynamic status that involved in nursing  guidelines for mechanically ventilated patients.