Causes of orthopnoea

Orthopnoea is dyspnoea that occurs when lying flat and eases when sitting or standing upright. It is usually graded by the number of pillows needed to sleep comfortably.

Mechanism

Lying down increases venous return from the legs and splanchnic circulation to the central circulation. This raises ventricular preload, and so pulmonary venous and capillary hydrostatic pressures. Orthopnoea is a specific symptom of heart failure and correlates well with the severity of pulmonary congestion (Goldman-Cecil Medicine, heart failure section on clinical manifestations). In respiratory causes, the supine position also pushes the abdominal contents up against the diaphragm, which reduces lung volumes and diaphragmatic efficiency.

Cardiac (most common)

Left heart failure, with either reduced or preserved ejection fraction. This is the classic cause, from ischaemic heart disease, hypertension, or cardiomyopathy.
Mitral valve disease, especially mitral stenosis, and aortic valve disease (aortic stenosis or regurgitation).
Acute pulmonary oedema, for example after myocardial infarction, from arrhythmia, or from acute mitral regurgitation.
High-output states such as severe anaemia, thyrotoxicosis, and arteriovenous shunts.
Large pericardial effusion or constrictive pericarditis. Malignant effusions can present with orthopnoea, cough, and venous distension (Pye's Surgical Handicraft, malignant pericardial effusions).
Congenital heart disease with left-to-right shunt.

Orthopnoea is usually minimal in mitral stenosis in some patients, but it becomes prominent once pulmonary pressures rise (Braunwald's Heart Disease).

Respiratory

Severe COPD or asthma, especially nocturnal asthma.
Large pleural effusion.
Bilateral diaphragmatic paralysis. This is a characteristic cause of marked orthopnoea with a paradoxical inward abdominal movement on lying flat.
Neuromuscular disease such as motor neurone disease, myasthenia gravis, Guillain-Barré syndrome, and high spinal cord injury.
Interstitial lung disease and pulmonary fibrosis (usually mild).
Bronchiectasis with secretion pooling.
Obstructive sleep apnoea or obesity hypoventilation syndrome can cause nocturnal breathlessness.
Upper airway obstruction, including goitre, mediastinal mass, and laryngeal or tracheal tumour.
Pulmonary embolism and pulmonary hypertension (uncommon).

Abdominal and other

Massive ascites from cirrhosis, malignancy, or nephrotic syndrome.
Gross obesity.
Late pregnancy.
Large abdominal masses or hepatomegaly.
Gastro-oesophageal reflux or aspiration. This causes cough and breathlessness when supine and can mimic orthopnoea.
Anxiety and panic. Chronic fluid overload from renal failure can also contribute.

Special variants

Platypnoea is the opposite: dyspnoea worse on sitting or standing. It is seen with hepatopulmonary syndrome, a patent foramen ovale with right-to-left shunt, and arteriovenous malformations.
Trepopnoea is dyspnoea in one lateral decubitus position. It occurs with unilateral lung disease, a large effusion, or heart failure.
Bendopnoea is dyspnoea on bending forward, seen in heart failure with raised wedge pressure.
Paroxysmal nocturnal dyspnoea is severe breathlessness that wakes the patient from sleep, typically about 1 hour after lying down. It is usually cardiac.

Clinical approach

Ask how many pillows are needed, whether the patient sleeps in a chair, and whether there is PND, oedema, cough, wheeze, or weight gain.
Examine for raised JVP, a third heart sound, crackles, murmurs, effusion, ascites, and paradoxical abdominal breathing.
Investigate with BNP or NT-proBNP, ECG, chest X-ray, and echocardiography. Add spirometry, and consider supine versus upright spirometry if diaphragmatic weakness is suspected.

A search for recent systematic reviews on this topic (last 2 years) found nothing that updates or contradicts the above.

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