Pulmonary edema is a condition where fluid builds up in the lung's small air sacs, making it hard to breathe. It usually happens when the heart's ability to pump blood is compromised, a situation known as congestive heart failure, which affects 3 million Americans. When this happens, pressure builds up in the blood vessels leading to the lungs, forcing fluid out of the small capillaries and into the air sacs they surround. The normally air-filled lungs become filled with fluid, and the exchange of oxygen and carbon dioxide can no longer happen properly. Pulmonary edema can happen suddenly and quickly (called flash pulmonary edema) or more slowly and chronically.
Pulmonary edema can happen for several reasons, but the most common is heart failure. Typically, the heart's left ventricle becomes weaker and weaker until it can no longer pump blood properly. Coronary artery disease is the main culprit of heart failure, but problems with the heart's valves, high blood pressure or damage to the heart muscle for reasons other than blood flow problems, can also impair the heart's pumping ability. Other causes of pulmonary edema unrelated to the heart include lung infections like pneumonia, inhaling certain toxins like ammonia, chlorine or even material from your own stomach (aspirating vomit), kidney disease and smoke inhalation. A condition called acute respiratory distress syndrome causes the lungs to fill with fluid quickly, usually because of trauma, major systemic infection or shock. People who travel to or exercise at high altitudes are also at risk for pulmonary edema.
Many symptoms of pulmonary edema are related to the fact that lungs are filled with fluid instead of air: shortness of breath, wheezing or gasping, feeling like you're suffocating or drowning, coughing up frothy sputum, which can be blood-tinged, and heart palpitations. If the pulmonary edema is more chronic, you might feel tired and short of breath when you exercise, and you might wake up at night feeling like you can't catch your breath until you sit up (this is called paroxysmal nocturnal dyspnea). Pulmonary edema is usually treated with oxygen by mask and certain medications like diuretics, which dilate the veins and the pressure going to your heart and lungs.