Pulmonary edema is accumulation of fluids within lung causing disturbance of gas exchange. As the condition progresses, diffusion of gasses worsens leading to dyspnea. when a patient with pulmonary edema lies down, it leads to increased venous return to the already congested and compromised heart and lung. This presents as orthopnea and paroxysmal nocturnal dyspnea. Patients have difficulty to breathing on sitting down which aggravates on lying down and patient tend to wake up from sleeping due to this difficulty.