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Nocturnal dyspnoea, often referred to as nocturnal dyspnea or paroxysmal nocturnal dyspnea, is a feeling of shortness of breath strong enough that it awakens a person from sleep. Dyspnoea, which can occur at any time, cannot be diagnosed by a medical test because it is a subjective experience. The main symptom of dyspnoea is that the patient perceives a shortness of breath. While it is common for people to experience this feeling during physical exertion, dyspnoea that occurs while a person is resting or asleep is a potential sign of disease.
People suffering from nocturnal dyspnoea may be awakened in the middle of the night by a feeling that they are not receiving enough air. The person’s chest may feel tight, they may breathe heavily, or they may feel like they are suffocating. Though these symptoms can be frightening, the symptoms themselves are not usually dangerous.
Though nocturnal dyspnoea is usually benign, it is often indicative of conditions that may be dangerous. Heart failure, especially when it affects the left ventricle, is a common cause of nocturnal dyspnoea because the left side of the heart is responsible for pumping oxygenated blood through the body. In many people, the left ventricle can have trouble keeping up with the right. This may be a normal condition during periods of exertion, but a lag in the left ventricle during rest can be a symptom of a serious heart disorder.
Lung cancer may be another cause for nocturnal dyspnoea. A tumor that blocks off part of the bronchial passageway may make it difficult or impossible for a person to breathe deeply. A build-up of fluid in the lungs may also lead to a feeling of shortness of breath.
Nocturnal dyspnoea is not characterized by a change in breathing pattern, though such a change can occur at the same time. Hyperventilation, for example, occurs when a person takes a series of quick, shallow breaths. The psychological effects of nocturnal dyspnoea can lead to an episode of hyperventilation, but the rapid breathing is not a sign of dyspnoea.
It is not easy to diagnose nocturnal dyspnoea because there is no physiological measure of the disorder. The severity of dyspnoea is rated by the person experiencing the condition, and the experience of the disease may change from person to person or from one episode to another. A questionnaire given by a doctor is the primary method by which nocturnal dyspnoea is diagnosed.