Paroxysmal Nocturnal Dyspnea (PND)

PhotoAlto/James Hardy/Getty Images

Paroxysmal nocturnal dyspnea, often called "PND" by doctors, is a particularly distressing symptom usually caused by heart failure. With PND, a person who is asleep suddenly wakes up with severe dyspnea, gasping for air, often coughing, and feeling a compelling need to get out of bed and assume an upright posture - at the very least sitting up at the edge of the bed, and often needing to go to an open window for air.

The breathlessness generally improves over several minutes, and the patient may be able to return to sleep - unless the residual anxiety from this very dramatic event prevents it.

Sometimes, however, the PND does not resolve but persists as an episode of acute heart failure, requiring a trip to the emergency room. Whether or not the PND resolves on its own, it is always a dangerous sign, and anyone who experiences this symptom needs to contact their doctor right away.

What Causes Paroxysmal Nocturnal Dyspnea?

Paroxysmal nocturnal dyspnea is usually caused by congestive heart failure, usually (but not always) in people who also have had episodes of dyspnea with exertion, or orthopnea. Patients who have PND also usually have at least some edema (swelling) in their feet and legs.

Lying down to go to sleep can cause significant fluid shifts in a person with heart failure. Fluid tends to shift from the tissues to the plasma, increasing plasma volume.

Also, fluid that has “pooled” in the legs or the abdomen during the day is freed from gravity, and is able to redistribute to the lungs. Sometimes these fluid shifts cause shortness of breath as soon as a patient lies down - that is, orthopnea. But with PND the fluid shifts do not cause symptoms right away.

Rather, they lead to a chain of events that eventually (after the patient has had a chance to fall asleep) produces a delayed - and much more severe - onset of dyspnea.

Can PND Be Caused By Conditions Other Than Heart Failure?

The usage of the term “PND” is not completely agreed upon by doctors. Cardiologists generally consider PND to be a term of art, and they tend to use it exclusively in patients with congestive heart failure. This usage imparts a particular significance to “PND.” Patients with heart failure who develop PND are very likely to have a severe episode of acute heart failure very soon - and so they ought to have aggressive therapy right away to prevent that severe, possibly life-threatening episode from occurring. So when cardiologists say “PND” they are making a diagnostic and prognostic statement.

However, strictly speaking “paroxysmal nocturnal dyspnea” really just means “sudden-onset shortness of breath at night,” and as such it can be applied to any medical condition that may produce dyspnea during sleep.

So among the medical community at large, “PND” is just a description of a symptom. Thus, you will hear “PND” applied to several different medical conditions that can cause sudden dyspnea at night. These conditions are quite numerous, and include sleep apnea, asthma, and pulmonary embolus. They also include cardiac conditions other than congestive heart failure, such as diastolic heart failure and acute cardiac ischemia (as with acute coronary syndrome).

The Bottom Line

It’s not up to you to figure out whether your acute dyspnea at night is due to heart failure or to some other cause. It’s up to your doctor. What you need to know is that PND always indicates a serious medical problem, and whatever the cause turns out to be, you need to get medical help right away if you experience this symptom.


Yancy CW, Jessup M, Bozkurt B, et al. 2013 ACCF/AHA guideline for the management of heart failure: executive summary: a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. Circulation 2013; 128:1810.

Continue Reading