patients who will meet one of the following criteria will be excluded from the study: patients with cardiac problems e.g. atrial fibrillation, left bundle-branch block, heart failure. sever cases of copd (fev1/fvc< 50%) mitral or aortic valvular disease, pericardial effusion. recent myocardial infarction.

patients who will meet one of the following criteria will be excluded from the study: patients with cardiac problems e.g. atrial fibrillation, left bundle-branch block, heart failure. sever cases of copd (fev1/fvc< 50%) mitral or aortic valvular disease, pericardial effusion. recent myocardial infarction.