Paroxysmal nocturnal dyspnea

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"PND" redirects here, but this abbreviation can also mean postnasal drip.

Paroxysmal nocturnal dyspnea (PND) is a medical symptom, also known as cardiac asthma. 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. 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 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) 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 in people with underlying left ventricular dysfunction. The pulmonary hypertension leads to the accumulation of fluid in the lungs, or pulmonary edema.

PND is a symptom of heart failure and other associated conditions such as mitral stenosis, aortic insufficiency, and systemic hypertension. 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.^[1]