Orthopnea · What Is It, Causes, Diagnosis, Treatment, and More

Orthopnea is a medical term to describe shortness of breath that occurs while lying flat and is relieved by sitting or standing. Orthopnea can occur progressively over time or spontaneously, depending on the underlying cause. Individuals may describe needing to use multiple pillows to sleep due to breathlessness. An increased number of pillows required to sleep may signify a more severe form of orthopnea. For example, three-pillow orthopnea may be more severe than two-pillow orthopnea. 

Orthopnea occurs when pulmonary congestion causes the lungs to become stiff and non-compliant, which is when the lungs are unable to stretch and expand to effectively bring in air. When recumbent (i.e., lying flat), pulmonary compliance decreases due to the lungs assuming a more posterior position. The work of breathing increases as a result of the changes in compliance, which causes a subsequent increase in respiratory rate in order to properly ventilate the lungs. Concurrently, lying down increases the redistribution of blood from the lower extremity and splanchnic blood vessels (i.e., blood flow from abdominal gastrointestinal organs) to the lungs. The increased blood flow to the heart increases the pressure within the pulmonary blood vessels. In individuals with an underlying disease, the increase in blood volume, increased pressure, and decreased compliance when lying down cannot be overcome, resulting in pulmonary edema and orthopnea.

Orthopnea may be caused by several underlying conditions. The most common cause of orthopnea is due to heart disease, such as congestive heart failure, coronary artery disease, or valvular dysfunction. In heart failure or coronary artery disease, the left ventricle may be unable to adequately pump blood into systemic circulation. Blood will then regurgitate into the left atrium and pulmonary circulation, which increases the pressure in the lungs and causes pulmonary edema (i.e., fluid in the lungs). Additionally, valvular disease, such as mitral stenosis, can also cause fluid to back up into the left atrium and lungs. Those with a history of a myocardial infarction are also at an increased risk of developing orthopnea.

Orthopnea is also often caused by chronic obstructive pulmonary disease (COPD), such as emphysema or chronic bronchitis. Other restrictive lung diseases, such as interstitial fibrosis or pneumoconiosis, may also cause orthopnea. 

Additional causes of orthopnea may include acute respiratory distress syndrome (ARDS), abdominal obesity, ascites, pneumonia, or trauma to the nervous system. 

To diagnose orthopnea, a healthcare professional may begin with a full medical history and physical exam. Questions such as how many pillows are used to sleep, the presence of chest pain or coughing, and exercise tolerance may reveal the underlying cause. Additionally, the presence of wheezing, rales, or dullness to percussion on a pulmonary physical exam can indicate pulmonary involvement, while cardiovascular exam may reveal murmurs, abnormal location of maximal impulse, or additional heart sounds.

Because orthopnea is a symptom of another underlying disease, additional medical testing may be required to uncover the underlying cause. Blood tests, such as a complete blood count (CBC), arterial blood gas (ABG), and B-type natriuretic peptide (BNP), may be required to determine whether the individual has anemia, hypoxia (i.e., insufficient blood oxygen), or excess stretch in the ventricles, respectively. Imaging, such as an X-ray, may also be utilized to visualize any fluid build-up in the lungs, while an echocardiogram can be used to visualize abnormalities of the cardiac anatomy. Spirometry may also be a useful tool if an underlying pulmonary disease is suspected. Additional testing may also be necessary to rule out other causes.