High Fowler’s position is the best option to aid breathing for a patient with acute pulmonary edema.
In fowler's position the upper half of the patient's body is between 60 degrees and 90 degrees in relation to the lower half of their body.
This help to decrease the rate of venous return to the heart which eventually decreases the rate at which fluid get to the lungs. This also help to increase chest expansion which improves breathing.
Lying flat in bed and left side lying position will increase venous return to the heart and this will eventually increase fluid in the lungs.
Semi Fowler's position is not as effective as high fowler's position. The upper half of the body is only raised to between 15 to 45 degrees.
High Fowlers position facilitates breathing by reducing venous return. Lying flat and side-lying positions worsen breathing and increase the hearts workload.