Paroxysmal nocturnal dyspnoea
Paroxysmal nocturnal dyspnoea or paroxysmal nocturnal dyspnea (PND) refers to attacks of severe shortness of breath and coughing that generally occur 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. Also, in the horizontal position there is redistribution of blood volume from the lower extremities and splanchnic beds to the lungs (orthopnea). In normal individuals this has little effect, but in patients in whom the additional volume cannot be pumped out by the left ventricle because of disease, there is a significant reduction in vital capacity and pulmonary compliance with resultant shortness of breath. Additionally, in patients with congestive heart failure the pulmonary circulation may already be overloaded because the failing left ventricle is suddenly unable to match the output of a more normally functioning right ventricle; causing pulmonary congestion. It is also important to note that left-sided heart failure can lead to right-sided heart failure. Pulmonary congestion decreases when the patient assumes a more erect position, and this is accompanied by an improvement in symptoms.
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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