This study evaluates incidence of diaphragmatic dysfunction after cardiac surgery and its effect on outcome of surgery.

Diaphragmatic dysfunction will be assessed by ultrasonography the day before operation and first post operative day, by measuring diaphragmatic thickening during inspiration and expiration.incidence of diaphragmatic dysfunction and its effect on outcome of surgery then will be analysed.

Inclusion Criteria:

• 18 years old and older
• Planned cardiac surgery
• Ready for weaning from mechanical ventilation (fraction of inspired oxygen (FIO2) ≤ 50%, positive end-expiratory pressure(PEEP) level≤ 5 centimeter water (cmH2O), respiratory rate ≤30 breaths/min, partial pressure of oxygen in arterial blood(PaO2)/FIO2 ratio >200 , Glasgow coma score ≥14).
• Stable cardiovascular status (i.e., heart rate <120 beats/min; systolic blood pressure, 90-160 mmHg; and no or minimal vasopressor use, i.e., dopamine or dobutamine ≤5 μg/kg/min or noradrenaline ≤0.05 μg/kg/min).
• Stable metabolic status (i.e., electrolytes and glycaemia within normal range, body temperature <38 °C, hemoglobinemia ≥8-10 g/dL).

Exclusion Criteria:

• Patients with a history of diaphragmatic or neuromuscular disease or evidence of pneumothorax or pneumomediastinum.
• Patients with low EF (EF ≤ 30%).
• Patients with post-operative cerebrovascular stroke.
• Reventilation due to cardiac cause ( arrest, arrhythmias, or failure)
• Patient refusal.

100 adult patients who are ready for elective cardiac surgery.