The volume of space in the lung varies as we breathe in and out. However, like any space in the body, it is possible for it to become filled with fluids such as mucus, tissue fluid or even blood. When fluid fills in the space around the lung then it is known as a pleural effusion. If fluid accumulates inside the lung then it is known as pulmonary edema. These conditions can be very serious and may even be associated with deadly conditions, although the initial symptoms may not always be severe.
What is pulmonary edema?
Pulmonary edema is a condition where fluid accumulates in the lungs. The word ‘edema’ means fluid accumulation and this is not the same as mucus that increases with infections or other airway disorders. The fluid in the lungs is rather tissue fluid that seeps from tissue spaces and blood vessels. It hampers the normal gas exchange between air and the bloodstream. Oxygen can therefore not enter the bloodstream and a person feels difficulty breathing. Depending on the severity of pulmonary edema, it can be fatal.
There are a number of different causes of pulmonary edema. Apart from infections, inhalation of toxic gases and other factors, pulmonary edema is most commonly due to heart problems. However, pulmonary edema can also contribute to heart failure. In some cases pulmonary edema can arise slowly and may persist for long periods of time, even months. In acute pulmonary edema arises suddenly, it can be very serious and more likely to be life-threatening.
Symptoms of Pulmonary Edema
In pulmonary edema that develops slowly over the long term, a person may not initially detect any problem. It is only once the accumulation of fluid in the lungs becomes significant to the point that oxygen exchange is impeded that symptoms may become apparent. The signs and symptoms of pulmonary edema includes:
- Shortness of breath (severity may vary).
- Sensation of suffocating, especially when physically active or lying down.
- Abnormal breathing sounds like wheezing, bubbling or gasping.
- Cough, dry or wet. Frothy sputum or streaks of blood in the sputum may be seen.
- Chest discomfort and sometimes chest pain.
- Rapid heart rate, sometimes with palpitations.
- Paleness, blue or even gray color of the skin when oxygen exchange is severely affected.
There may also be other symptoms like a fever, swelling of parts of the body, palpitations and headaches but this depends on the individual cause of pulmonary edema. It is important to note that pulmonary edema should be treated as a medical emergency especially in acute cases.
Causes of Pulmonary Edema
Any condition that damages the tiny capillaries around the air sacs of the lungs, causes lung inflammation, increased pressure with the blood vessels to the lungs or causes fluid accumulation in the body can lead to pulmonary edema. Heart problems are by far the most common cause of pulmonary edema and it may occur gradually over time or arise suddenly.
The heart circulates blood throughout the body. Low-oxygen blood enters the heart on the right side, is sent to the lung for oxygenation and received back by the heart on the left side. The oxygen-rich blood is then pumped out to the rest of the body by the left side of the heart. To ensure that blood flows only in one direction during each phase of the cardiac cycle, there are several valves that play a role. Various different types of heart problems may present with pulmonary edema.
- Coronary artery disease (CAD) where the arteries supplying blood to the heart (coronary arteries) become narrowed due to the build up of fatty plaques. It can eventually become blocked and a portion of the heart muscle dies (heart attack). The heart is weakened and becomes less effective at pumping blood. The blood then becomes backed up and some of the fluid from the lung vessels starts to seep into the lung spaces.
- High blood pressure (hypertension) is an elevation of blood pressure about the normal limit. It is a very common condition these days and is linked to lifestyle factors like cigarette smoking, obesity, advancing age as well as family history. Over time high blood pressure can contribute to coronary artery disease and weaken the heart.
- Cardiomyopathy is a condition where the heart muscle is diseased or damaged. Since the heart is a muscular pump, any damage or disease of the heart muscle (myocardium) will lead to weakening of the heart. As a result the heart’s ability to pump blood is impaired and blood may become backed up, leading t0 pulmonary edema.
- Heart valve disease is where the valves that regulate the direction of flow through the heart and the blood vessels connected to it do not function as it should. As a result blood may flow backwards. Depending on the severity, the blood may become backed up in the vessels or heart and fluid may then leak into the lungs.
- Lung injury may occur when toxic gases are inhaled including smoke inhalation or with trauma to the lung such as sharp force chest trauma. Pulmonary edema can also occur with lung surgery.
- Lung infections like viral pneumonia may also lead to pulmonary edema. This should not be confused with excess mucus build up in the airways that is seen with may respiratory tract infections.
- Near drowning can lead to pulmonary edema when water enters the lungs. Depending on the type of water (example electrolyte concentration in sea water), it may also draw out fluid into the lung spaces.
- High altitude pulmonary edema (HAPE) is seen among mountain climbers and hikers who travel up to very high elevations. The exact cause of this type of pulmonary edema is unclear but seems to be due to increased pressure within the tiny capillaries of the lung.
- Acute respiratory distress syndrome (ARDS) is where there is inadequate exchange of gases between the environment and bloodstream due to lung problems. It may be see with infections, extensive blood loss and severe trauma.
- Kidney disease
- Traumatic head injury
- Brain surgery
- Drug reactions