Paroxysmal Nocturnal Dyspnoea

Paroxysmal nocturnal dyspnoea is a breathing symptom that happens during sleep and can be very distressing. It is mainly related to heart failure, but other causes can also be associated with this symptom. Assuming an upright position helps the symptom to improve, but it can cause a lot of anxiety.  A doctor should be consulted to address the possible causes. We are going to talk more about what it is, the causes, how it happens and how to treat this condition below.

What is Paroxysmal Nocturnal Dyspnoea?

As explained above, paroxysmal nocturnal dyspnoea (PND) is a feeling of sudden shortness of breath while sleeping. This usually happens a couple of hours after falling asleep; as a result, the person generally wakes up gasping for air. The symptom is mostly resolved after the person sits or gets up.^1,2

The name of the symptom already gives us clues about it. Paroxysmal reflects that this is an intermittent condition that comes and goes, generally suddenly. Nocturnal relates to the nighttime when it is common for people to sleep long periods and therefore the symptoms might appear at that time. Dyspnoea refers to distress in breathing.^1,3

PND differs from regular shortness of breath and other symptoms like orthopnea and sleep apnoea. Some breathlessness might be common after exercising for example, and we know that a lot of health problems might cause difficulty in breathing with mild exertion and even at rest.

Orthopnoea might be confused with PND since this also happens when the person is lying down and gets better once they get or sit up, however, they differ because in this case, the person doesn’t need to be sleeping to trigger the symptom. 

Sleep apnoea can also be mistaken for PND. A person with sleep apnoea experiences multiple episodes of breathing interruptions during sleep; it might not wake the person up though, and it is a medical condition of its own. Sleep apnoea can cause PND, but the opposite is not true. ^3,4

Being a symptom, PND has multiple causes, and it is very important to be assessed by a doctor to address the issue properly and treat the condition. We are going to talk about some of the causes below.

Causes of Paroxysmal Nocturnal Dyspnoea

Most causes of dyspnoea are due to cardiac or pulmonary conditions, which is also the case with PND. The main cause of PND is a heart condition known as congestive heart failure.^1,4

Congestive Heart Failure

In this condition, the heart muscle becomes weak and therefore the heart is unable to pump blood properly. When this happens, the fluid can build up mostly in the lungs and legs. This also leads to a high level of renin, which is an enzyme that acts to retain fluids in the body. All this fluid in the lungs, known as pulmonary oedema or pulmonary congestion, is responsible for causing PND.⁴

Lung conditions

Asthma

This lung disease is caused by the narrowing of the airway when exposed to triggering agents. Generally, the symptoms can be worse at night, and if the lungs become congested, PND can happen.

COPD

Chronic Obstructive Lung Disease is another lung condition caused by long-term inflammation and narrowing of the airways due to exposure to toxic agents, with tobacco being the main substance related to it. It also causes difficulty in breathing and mostly, congestion of the lungs, which is also responsible for PND in this case.

Pneumonia

Inflammation of the lungs can be also associated with infection by viruses and bacteria. This can also bring a breathless sensation, especially if the airway is filled with mucus and congestion from the inflammation process.

Pulmonary embolism

In this condition, a blood clot blocks arteries in the lungs, leading to reduced oxygen influx in the area affected. It mostly causes ongoing dyspnoea, but episodes of paroxysmal nocturnal dyspnoea also can happen.^1,3,4

Sleep apnoea

This is a sleep disorder where a person has brief episodes of apnoea (stopping breathing) while asleep. In this case, different from congestion, the main cause is an obstruction in the airway. As said before, sleep apnoea can cause PND, but not vice versa.⁵

Other related conditions

Some other causes that can also be related to PND are

• Psychogenic disorders: mental health conditions can also cause symptoms like PND. Anxiety and panic attacks caused by mental stressors are the main examples.
• Kidney failure: in this case, the kidneys don’t function properly, which can also generate fluid retention, which when built up in the lungs can lead to PND.
• Acid reflux: gastric acid moving back up the food pipe (oesophagus is unknown as gastric or acid reflux.  If this happens during sleep, it can lead to airway obstruction and PND.^1,3,4

The risk factors of PND are directly related to the particular cause.  Therefore we have PND risk factors that can lead to the diseases mentioned above, i.e.: 

Figure: Risk Factors associated with PND

      Created by Aastha Malik

Symptoms

PND is itself a symptom of a lot of different conditions as we can see above. It has the following characteristics:

• Waking up gasping for air in the middle of the night.
• Getting better after sitting or getting up.
• Sleeping anxiety
• Insomnia.¹

These aspects can help to identify the condition but seek for doctor’s advice and further assessment to discover the cause.

Diagnosis

Because PND is caused by an underlying condition, the diagnosis of the symptom itself is mostly clinical. The symptoms will already give a clue about what might be associated with PND. However, there are different and multiple tests and scans that can help in identifying the cause.

Heart Failure

• ECG – measures heart electrical activity and can help to identify heart conditions.
• Echocardiogram – this  is an ultrasound of the heart that can see if the heart is pumping the blood properly and identify heart failure.
• Exercise tolerance test – helps to see if there is any limitation of the heart to the stress and assess the blood supply to the heart.
• Cardiac MRI – this can get images of the heart that can show signs of failure of the heart muscle.
• Chest X-ray – can identify images of pulmonary congestion and also see the size of the heart, which is enlarged in congestive heart failure.

Respiratory diseases

• Chest X-ray – as said above can see signs of pulmonary edema, but can also show changes of pulmonary diseases.
• Chest MRI and CT – visualise the pulmonary tissue and identify changes related to diseases like bronchiectasis, fibrosis, COPD, etc.
• Pulmonary function tests – also known as spirometry, these tests help to diagnose narrowing in the airways and identify diseases such as COPD and Asthma.
• Sleep study – also known as polysomnography. In this test, multiple sensors help to analyze the sleep pattern, check breathing pauses, oxygen levels, awakenings and other aspects of a person’s sleep.

Treatments

Treatment will be guided by the cause of the paroxysmal nocturnal dyspnoea, being this cardiac or respiratory.

Heart Failure

• Lifestyle changes – stop smoking, have a healthy diet, moderate consumption of alcohol and regular exercise are very important measures when trying to improve the heart condition
• Medications – heart failure patients generally need diuretics (water pills) to help with the retention of fluids, as well as other medications like beta blockers, which control the heartbeat to help the heart pump blood better. Enzyme inhibitors (such as ACE inhibitors) help to control the retention of fluids, and also help the heart to be stronger ^1,3,4

 Lung Conditions

• Asthma treatment – changes in the environment to avoid triggers, and also inhalers if required
• COPD – smoking cessation, use of inhalers when necessary, treating infections when present and oxygen therapy if required. Some severe cases might require breathing devices to help especially with nighttime breathing, such as a continuous positive airway pressure (CPAP) machine
• Pneumonia – this is treated with medications for inflammation and if caused by bacteria, such as antibiotics
• Pulmonary embolism – mostly treated with anticoagulants, that depending on the case will be used for a limited period of time or for the long term.^1,3,4 

Sleep Apnoea

• Lifestyle changes – as for heart failure; stopping smoking, having a healthy diet, moderate consumption of alcohol, regular exercise and losing weight if necessary can help to improve this condition
• Positive airway pressure – Devices with continuous positive airway pressure (CPAP) bi-level positive airway pressure (BiPAP) and auto-titrating positive airway pressure (APAP), can be used overnight to help with the episodes of apnoea in some cases.⁵

Other conditions will be treated accordingly. Acid reflux can be treated with antacids and also lifestyle changes. Kidney failure will require more complex management, especially depending on the severity, and might even require dialysis. Mental stressors and anxiety can be treated with anxiolytics and talking therapies.

Summary

Paroxysmal nocturnal dyspnoea (PND) is a symptom characterised by a sudden episode of breathlessness during sleep that leads the person to wake up gasping for air. It has multiple causes, most of them being cardiac or respiratory.

Heart Failure is the main cause of PND and it happens due to fluids building up in the lungs. Some respiratory conditions like asthma, COPD, pneumonia, pulmonary embolism and sleep apnoea can also be responsible for PND.

The diagnosis is clinical and investigations can be done to find the cause and treat the condition accordingly.  If PND is suspected, a doctor must be seen so an assessment and proper investigation can be done.