Introduction:
Dyspnea is a subjective experience perceived by a patient as a sensation of difficult and uncomfortable breathing. As the name suggests, paroxysmal nocturnal dyspnea is difficulty in breathing when a patient lies down and is most commonly seen at night, causing sleep disturbances. They often get only one or two hours of sleep. The patient is forced to stand or sit upright for relief, breaking their sleep cycle. The main cause of paroxysmal nocturnal dyspnea is left ventricular failure. The failing ventricle will lose its ability to pump enough blood resulting in pulmonary congestion. This article will discuss the causes, clinical significance, and management of paroxysmal nocturnal dyspnea.
What Causes Paroxysmal Nocturnal Dyspnea?
Paroxysmal nocturnal dyspnea can be attributed to some underlying medical condition. Most clinicians use it exclusively as a symptom of heart failure, whereas some consider it may be due to other medical conditions.
Heart Failure:
Paroxysmal nocturnal dyspnea occurs in left ventricular failure. Its mechanism is similar to orthopnea (sensation of breathlessness in the lying down position). In left ventricular failure, the left side of the heart cannot pump enough blood due to cardiac overload and increased pulmonary congestion. The mechanism of paroxysmal nocturnal dyspnea is similar to that of orthopnea (difficulty in breathing on lying down and relief in sitting in an upright position or standing up). When a patient lies down to sleep, the blood from the lower extremities and other body parts gets redistributed in the lungs. The left ventricle cannot pump the additional blood volume in individuals with left ventricular failure. As a result, there will be pulmonary congestion (fluid build-up in the layer surrounding the lungs), vital capacity (maximum amount of air that is expired after a maximal inspiration), and pulmonary compliance (a measure of the lung’s ability to stretch or expand) reduces significantly, resulting in shortness of breath and the patient suddenly wakes up from their sleep.
Other factors responsible for paroxysmal nocturnal dyspnea include a decrease in responsiveness of the respiratory center in the brain and reduced adrenergic (responses stimulated by hormones like epinephrine or norepinephrine) activity of the myocardium (muscles of the heart) during sleep.
Respiratory Conditions:
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Asthma: The airway becomes inflamed and narrow, making breathing difficult.
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Chronic Obstructive Pulmonary Disease: Group of lung diseases that obstruct the airway and make breathing difficult.
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Post Nasal Drip: Secretions from the nose draining into the throat, causing cold and congestion.
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Pulmonary Edema: Caused by excess fluid in the lungs.
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A Pulmonary Artery Embolism: Occurs when a blood clot in the lung artery blocks blood flow to some parts of the lungs.
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Restrictive Lung Disease: The total volume of air the lungs can hold is reduced.
Other Medical Conditions:
Paroxysmal nocturnal dyspnea can be related to several other medical conditions:
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Stomach Acid Reflux: Entry of the acids produced in the stomach into the esophagus.
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Kidney Failure: The kidney loses its ability to remove wastes and balance body fluids.
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Anxiety or Panic Attacks: A feeling of uneasiness and fear causing a person to feel tense and have a rapid heartbeat.
What are the Symptoms of Paroxysmal Nocturnal Dyspnea?
Attacks of paroxysmal nocturnal dyspnea usually occur within a few hours after the patient has fallen asleep. The person wakes up from sleep suddenly in an attempt to gasp for air, accompanied by a cough. They sit upright or stand up, trying to open their airways. After a while, the breathing will return to normal. However, it might take half an hour or even more for the patient to recover and go back to sleep.
For many people, episodes of paroxysmal nocturnal dyspnea attacks are distressing, and most of them find it difficult to fall back to sleep once an episode is resolved. One or more episodes may lead to sleep anxiety or insomnia in some. If the symptoms of an episode are not resolved after a change in posture, like sitting upright or standing, immediate medical emergency assistance is required.
How is Paroxysmal Nocturnal Dyspnea Diagnosed?
The underlying medical condition is determined first and foremost for a patient with paroxysmal nocturnal dyspnea. The physician will take a thorough medical history, clinical examination, and tests to assess the symptoms and the state of the patient’s heart and lungs.
Tests are performed to confirm the diagnosis of the medical condition responsible for paroxysmal nocturnal dyspnea. Diagnostic tests performed are as follows:
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Biopsy - A piece of tissue removed from the body to test in the laboratory.
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Blood Tests - A laboratory analysis of the things found in the blood.
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Bronchoscopy - A procedure to examine the lungs and air passage.
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Chest CT Scan - An imaging procedure that uses a combination of x-ray and computer technology to obtain images of the inside of the body.
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Chest X-ray - Used for imaging of the tissues and organs in the chest region.
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Coronary Artery Angiogram - A procedure to view the heart’s blood vessels.
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Echocardiogram or Cardiac Ultrasound - Type of scan used to look at the heart and nearby blood vessels.
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12-Lead Electrocardiogram - A medical test to record the medical activity of the heart.
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Chest MRI - Magnetic resonance imaging (MRI) of the chest to give a detailed view of the structures in the chest cavity.
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Pulmonary Function Tests - Non-invasive tests to study the functioning of lungs.
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Cardiac Stress Test - Measures the heart’s ability to respond to external stress.
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Thoracoscopy - An minimally invasive procedure to diagnose and treat lung diseases.
How is Paroxysmal Nocturnal Dyspnea Managed?
The treatment of paroxysmal nocturnal dyspnea may vary depending on the underlying medical condition. The clinician can formulate the best treatment plan depending on the symptoms presented by the patient.
1) Heart Failure: Left ventricular failure needs to be treated to reduce the episodes of paroxysmal nocturnal dyspnea. The treatment strategy comprises medications to improve the heart’s functioning.
- ACE (angiotensin-converting enzyme) inhibitors help relax the blood vessels and remodel the heart.
- Diuretics get rid of the excess fluid in the body.
- Beta-blockers help in decreasing the heart rate.
- Digoxin helps control the heart rate.
- Aldosterone antagonists control stress hormones and prevent the worsening of symptoms.
2) Respiratory Disorders: Treating the disorders will help ease the symptoms of paroxysmal nocturnal dyspnea caused by the respiratory system. For instance, long-term medications for asthma control can reduce the episodes of shortness of breath at night.
3) Other Medical Conditions: Antacids and changes in lifestyle will help in the treatment of stomach acid reflux. Other treatment modalities aim to reduce stress and improve the patient’s sleep quality.
Conclusion:
Left ventricular heart failure is one of the most serious causes of paroxysmal nocturnal dyspnea. The course of the disease differs from person to person and is typically a long-term disease that worsens over time. However, with advances in medical technology, several treatment options are now available that slow down the progression of the disease and prevent repeated episodes of paroxysmal nocturnal dyspnea.
