Imagine awakening suddenly from sleep, gasping for air, coughing, wheezing and feeling like you're suffocating. Anxious and scared, you might quickly sit up and put your feet on the floor. Sitting or standing up helps you breathe better again. This frightening occurrence is a sign of heart failure -- and it sometimes happens to people who haven't had any previous symptoms of heart trouble.
The scientific term for this occurrence is paroxysmal nocturnal dyspnea. "Paroxysmal" means "sudden attacks that recur," "nocturnal" means "occurring at night" and "dyspnea" means "difficulty breathing" or "shortness of breath."
Paroxysmal nocturnal dyspnea is also sometimes called cardiac asthma because its signs and symptoms mimic those of asthma. This term is actually misleading -- the two conditions are very different. While asthma is a chronic condition caused by inflammation of the airways, which can lead to breathing difficulties, paroxysmal nocturnal dyspnea is a sign of heart failure.
Paroxysmal nocturnal dyspnea can be accompanied by swelling of the feet or ankles. It's caused by congestion (excessive or abnormal accumulation of blood) in the lungs, perhaps along with accumulation of excess fluid in the lungs (pulmonary edema), which occurs as a result of left-sided heart failure.
Some patients who experience paroxysmal nocturnal dyspnea also experience orthopnea: breathlessness when lying down that is relieved when several pillows raise the head and upper body. People with this condition must keep their heads elevated to breathe comfortably. Paroxysmal nocturnal dyspnea is an intense form of orthopnea. It commonly occurs several hours into sleep (as opposed to immediately upon lying down), and it's relieved by sitting upright, but not as quickly as is orthopnea.
Next, we'll learn what causes paroxysmal nocturnal dyspnea and how you can treat it.
Causes of Paroxysmal Nocturnal Dyspnea
Paroxysmal nocturnal dyspnea and orthopnea have similar causes. One of the causes of orthopnea is pulmonary congestion (excessive or abnormal accumulation of blood in the lungs) when a patient lies down and blood moves from the lower part of the body to the lungs. In normal individuals this has little effect, but in heart failure patients, the diseased left side of the heart can't pump out the additional volume. So blood backs up in the vessels of the lungs, causing shortness of breath.
Also, lung circulation in patients with congestive heart failure may already be overloaded. This condition may be worsened by fluid overload, excess fluid that accumulates in the lower part of the body during the day and moves into the lungs when the patient lies down. Lung congestion decreases when the patient raises his upper body.
In paroxysmal nocturnal dyspnea, increasing amounts of fluid enter the lungs during sleep and fill the small, air-filled sacs in the lungs where oxygen is absorbed from the atmosphere. The failing left side of the heart is suddenly unable to match the output of a more normally functioning right side, resulting in congestion in the lungs, coughing and wheezing, and sometimes the production of sputum (mucus and other matter, which may be bloody). We don't know why paroxysmal nocturnal dyspnea occurs so suddenly in patients with left heart failure.
How is paroxysmal nocturnal dyspnea treated?
Treatment depends upon the exact cause of the episodes. Doctors generally recommend weight reduction for obese patients, and supplemental oxygen may ease symptoms. If the episodes are due to heart failure, steps are taken to treat fluid overload.
Because a diet high in salt can contribute to fluid overload, doctors generally recommend that people who experience breathing difficulties such as paroxysmal nocturnal dyspnea limit the amount of salt in their diets. In addition to not adding salt at the table, following a low-sodium diet involves avoiding most processed foods (including frozen and canned foods, as well as the majority of fast food and takeout food items). Eating home-cooked meals prepared with herbs and spices instead of salt is one of the most effective ways of getting rid of excess fluid in the body.
In addition to recommending a low-sodium diet, doctors often prescribe medicines known as diuretics ("water pills") to relieve the symptoms of fluid overload. While these methods work for a while, they often become ineffective over time. When that happens, people with fluid overload are typically admitted to the hospital, where they're treated with intravenous medicines like loop diuretics, vasodilator drugs and inotropic drugs. Another procedure, known as ultrafiltration, is available to relieve fluid overload. In ultrafiltration therapy, the person's blood is passed through a filter that removes excess fluid. Then the filtered blood (minus the excess fluid) is returned to the patient.
To learn more about paroxysmal nocturnal dyspnea and heart failure, look at the links on the next page.
Related HowStuffWorks Articles
- How Your Heart Works
- How Your Lungs Work
- How Your Kidneys Work
- How Blood Works
- How Orthopnea Works
- How Jugular Venous Distension Works
- How does heart failure affect quality of life?
- How Inotropic Drugs Work
- How Vasodilator Drugs Work
- How Diuretics Work
- How Ultrafiltration Works
- What are the symptoms of heart failure?
- Heart Failure Medication
- What is the cost of heart failure?
- How Fluid Overload and Edema Work
- How Fluid Overload Treatment Works
- How Low-Sodium Diets Work
More Great Links
- Ahmed A, Allman RM, Aronow WS, et al. Diagnosis of heart failure in older adults: predictive value of dyspnea at rest. Arch Gerontol Geriatr. 2004;38:297-307.
- Costanzo MR, Guglin ME, Saltzberg MT, et al. Ultrafiltration versus intravenous diuretics for patients hospitalized for acute decompensated heart failure. J Am Coll Cardiol. 2007; 49:675-683.
- Costanzo MR, Saltzberg M, O'Sullivan J, et al. Early ultrafiltration in patients with decompensated heart failure and diuretic resistance. J Am Coll Cardiol. 2005;46:2047-2051.
- Elkayam U, Hatamizadeh P, Janmohamed M. The challenge of correcting volume overload in hospitalized patients with decompensated heart failure. J Am Coll Cardiol. 2007;49:684-686.
- Mueller C, Frana B, Rodriguez D, et al. Emergency diagnosis of congestive heart failure: impact of signs and symptoms. Can J Cardiol. 2005;21:921-924.
- Wang CS, FitzGerald JM, Schulzer M, et al. Does this dyspneic patient in the emergency department have congestive heart failure? JAMA. 2005;294:1944-1956.