Paroxysmal nocturnal dyspnoea
|Paroxysmal nocturnal dyspnoea|
Paroxysmal nocturnal dyspnea or paroxysmal nocturnal dyspnoea (PND) is an attack of severe shortness of breath and coughing that generally occurs at night. It usually awakens the person from sleep, and may be quite frightening. Though simple orthopnea may be relieved by sitting upright at the side of the bed with legs dangling, in those with PND, coughing and wheezing often persist in this position.
PND is caused in part by the depression of the respiratory center during sleep, which may reduce arterial oxygen tension, particularly in patients with interstitial lung disease and reduced pulmonary compliance.
Similar to orthopnea, in the horizontal position there is redistribution of blood volume from the lower extremities to the lungs. In normal individuals this has little effect on lungs, but in patients in whom the additional volume cannot be pumped out by the left ventricle due to left ventricular weakness, there is a significant reduction in lung capacity which results in shortness of breath. Additionally, in patients with congestive heart failure the pulmonary circulation may already be overloaded because of the failing left ventricle. When a person lies down, the left ventricle is unable to match the output of a more normally functioning right ventricle on increased venous return to the lungs; causing pulmonary congestion. Pulmonary congestion decreases when the patient assumes a more erect position, and this is accompanied by an improvement in symptoms.
Evaluation should begin with a detailed cardiac history and physical exam; echocardiography and CXR may be used though the diagnostic workup varies depending on the suspected cause.
Treatment for paroxysmal nocturnal dyspnea depends on the underlying cause. Options often include oxygen, diuretics, heart medications, antihypertensives, and bronchodilators to reverse wheezing.
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