Paroxysmal nocturnal dyspnea

Cardiac asthma is a medical symptom, also known as paroxysmal dyspnea or paroxysmal nocturnal dyspnea ("PND").

It is defined as sudden, severe shortness of breath at night that awakens a person from sleep, often with coughing and wheezing. It is most closely associated with congestive heart failure

Congestive heart failure

Heart failure is a condition in which a problem with the structure or function of the heart impairs its ability to supply sufficient blood flow to meet the body's needs...

. PND commonly occurs several hours after a person with heart failure has fallen asleep. PND is often relieved by sitting upright, but not as quickly as simple orthopnea.

Cardiac asthma is a medical symptom, also known as paroxysmal dyspnea or paroxysmal nocturnal dyspnea ("PND").

It is defined as sudden, severe shortness of breath at night that awakens a person from sleep, often with coughing and wheezing. It is most closely associated with congestive heart failure

Congestive heart failure

Heart failure is a condition in which a problem with the structure or function of the heart impairs its ability to supply sufficient blood flow to meet the body's needs...

. PND commonly occurs several hours after a person with heart failure has fallen asleep. PND is often relieved by sitting upright, but not as quickly as simple orthopnea. Also unlike orthopnea, it does not develop immediately upon lying down.

PND is caused by increasing amounts of fluid entering the lung

Lung

The lung or pulmonary system is the essential respiration organ in air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located in the chest on either side of the heart...

 during sleep and filling the small, air-filled sacs (alveoli) in the lung responsible for absorbing oxygen from the atmosphere. This fluid typically rests in the legs (peripheral edema

Peripheral edema

Peripheral edema is the swelling of tissues, usually in the lower limbs, due to the accumulation of fluids.The condition is commonly associated with aging, but can be caused by many other conditions, including congestive heart failure, trauma, alcoholism, altitude sickness, pregnancy, hypertension...

) during the day when the individual is upright. At night, when recumbent for an extended period, this fluid is reabsorbed, increasing total blood volume and blood pressure, leading to pulmonary hypertension

Pulmonary hypertension

In medicine, pulmonary hypertension is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion...

 in people with underlying left ventricular dysfunction. The pulmonary hypertension leads to the accumulation of fluid in the lungs, or pulmonary edema

Pulmonary edema

Pulmonary edema , or oedema , is fluid accumulation in the lungs. It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the heart to remove fluid from the lung circulation or a direct injury to the lung parenchyma...

.

PND is a symptom of heart failure and other associated conditions such as mitral stenosis

Mitral stenosis

Mitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.-Overview:In normal cardiac physiology, the mitral valve opens during left ventricular diastole, to allow blood to flow from the left atrium to the left ventricle...

, aortic insufficiency

Aortic insufficiency

Aortic insufficiency , also known as aortic regurgitation , is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle....

, and systemic hypertension

Hypertension

Hypertension is a chronic medical condition in which the blood pressure is elevated. It is also referred to as high blood pressure or shortened to HT, HTN or HPN. The word "hypertension", by itself, normally refers to systemic, arterial hypertension.Hypertension can be classified as either...

. It was first described by Charles Lepois in the 1500s.

The experience of PND is often described as awakening suddenly to a feeling that one is suffocating, with wheezing respirations and coughing. It can be quite frightening.