Shortness of breath (SOB), known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity", and recommends evaluating dyspnea by assessing the intensity of its distinct sensations, the degree of distress and discomfort involved, and its burden or impact on the patient's activities of daily living. Distinct sensations include effort/work to breathe, chest tightness or pain, and "air hunger" (the feeling of not enough oxygen). The tripod position is often assumed to be a sign.
Dyspnea is a normal symptom of heavy physical exertion but becomes pathological if it occurs in unexpected situations, The best treatment to relieve or even remove shortness of breath typically depends on the underlying cause. </blockquote>Other definitions describe it as "difficulty in breathing", "disordered or inadequate breathing", "uncomfortable awareness of breathing",
Causes
While shortness of breath is generally caused by disorders of the cardiac or respiratory system, others such as the neurological, hematologic, and psychiatric systems may be the cause.
DiagnosisPro, an online medical expert system, listed 497 distinct causes in October 2010. The most common cardiovascular causes are myocardial infarction and heart failure, while common pulmonary causes include chronic obstructive pulmonary disease, asthma, pneumothorax, pulmonary edema, and pneumonia. Ischemic strokes, hemorrhages, tumors, infections, seizures, and traumas at the brain stem can also cause shortness of breath, making them the only neurological causes of shortness of breath.
The tempo of onset and the duration of dyspnea are useful in knowing the etiology of dyspnea. Acute shortness of breath is usually connected with sudden physiological changes, such as laryngeal edema, bronchospasm, myocardial infarction, pulmonary embolism, or pneumothorax. Patients with COPD and idiopathic pulmonary fibrosis (IPF) have a mild onset and gradual progression of dyspnea on exertion, punctuated by acute exacerbations of shortness of breath. In contrast, most asthmatics do not have daily symptoms, but have intermittent episodes of dyspnea, cough, and chest tightness that are usually associated with specific triggers, such as an upper respiratory tract infection or exposure to allergens.
Acute coronary syndrome
Acute coronary syndrome frequently presents with retrosternal chest discomfort and difficulty catching the breath. Dyspnea is one of the three major symptoms of Long COVID, but this subjective symptom does not track with the severity of objective markers of inflammation.
Congestive heart failure
Congestive heart failure frequently presents with shortness of breath with exertion, orthopnea, and paroxysmal nocturnal dyspnea. Acute symptoms are treated with short-acting bronchodilators.
Pneumothorax
Pneumothorax presents typically with pleuritic chest pain of acute onset and shortness of breath not improved with oxygen. It may lead to heart failure.
Cancer
Shortness of breath is common in people with cancer and may be caused by numerous different factors. The most commonly reported cancer types that may affect breathing are lung cancer and mesothelioma. In people with advanced cancer, periods with severe shortness of breath may occur, along with a more continuous feeling of breathlessness. In patients with advanced cancer, breathlessness is frequent and can be debilitating.
Treatments for breathlessness include both non-pharmacological and pharmacological approaches. Non-pharmacological interventions that have been shown to improve breathlessness include the use of fans, exercise, and pulmonary rehabilitation.
Pharmacological treatments involve bronchodilators and corticosteroids to address the underlying causes of shortness of breath, as well as opioids or anti-anxiety medications to alleviate symptoms. However, a review of breathlessness and exercise capacity in patients with advanced cancer proved the use of both opioids and anxiolytics were not effective in improving symptoms when compared to placebo.
While these treatments are effective in reducing breathlessness in cancer patients, a systematic view reported various treatment-related side effects including equipment-related distress, fatigue, and constipation.
Psychological
One common symptom of panic disorder is shortness of breath. This is sometimes referred to as "sigh syndrome" or "sighing dyspnea". Sigh syndrome is characterized by recurrent attempts to take a deep breath, prompted by a feeling of inability to do so, followed by a prolonged and often audible exhalation (i.e. a sigh). Around 2/3 of women experience shortness of breath as a part of a normal pregnancy.
Dyspnea can be a symptom of mast cell activation syndrome (MCAS).
Sarcoidosis is an inflammatory disease of unknown etiology that generally presents with dry cough, fatigue, and shortness of breath, although multiple organ systems may be affected, with the involvement of sites such as the eyes, the skin, and the joints.
In January 2025, Metro reported that vaping increases the risk of inflammation of the lungs by exposing users to the vaporized elements of the oil. Popcorn lung is considered to be one such inflammatory response, and it causes respiratory symptoms such as coughing and dyspnea.
Pathophysiology
Different physiological pathways may lead to shortness of breath including via ASIC chemoreceptors, mechanoreceptors, and lung receptors.
It is thought that three main components contribute to dyspnea: afferent signals, efferent signals, and central information processing. It is believed the central processing in the brain compares the afferent and efferent signals; and dyspnea results when a "mismatch" occurs between the two: such as when the need for ventilation (afferent signaling) is not being met by physical breathing (efferent signaling). In the lungs, juxtacapillary (J) receptors are sensitive to pulmonary interstitial edema, while stretch receptors signal bronchoconstriction. Muscle spindles in the chest wall signal the stretch and tension of the respiratory muscles. Thus, poor ventilation leads to hypercapnia, left heart failure leading to interstitial edema (impairing gas exchange), asthma causing bronchoconstriction (limiting airflow) and muscle fatigue leading to ineffective respiratory muscle action could all contribute to a feeling of dyspnea. As the brain receives its plentiful supply of afferent information relating to ventilation, it can compare it to the current level of respiration as determined by the efferent signals. If the level of respiration is inappropriate for the body's status then dyspnea might occur. There is also a psychological component to dyspnea, as some people may become aware of their breathing in such circumstances but not experience the typical distress of dyspnea. It may be subjectively rated on a scale from 1 to 10 with descriptors associated with the number (The Modified Borg Scale).
Blood tests
Several labs may help determine the cause of shortness of breath. D-dimer, while useful to rule out a pulmonary embolism in those who are at low risk, is not of much value if it is positive, as it may be positive in several conditions that lead to shortness of breath.
Physiotherapy
Individuals can benefit from a variety of physical therapy interventions. Persons with neurological/neuromuscular abnormalities may have breathing difficulties due to weak or paralyzed intercostal, abdominal and/or other muscles needed for ventilation. Some physical therapy interventions for this population include active assisted cough techniques, volume augmentation such as breath stacking, education about body position and ventilation patterns and movement strategies to facilitate breathing. Fan therapy to the face has been shown to relieve shortness of breath in patients with a variety of advanced illnesses including cancer. The mechanism of action is thought to be stimulation of the trigeminal nerve.
Palliative medicine
Systemic immediate release opioids are beneficial in emergently reducing the symptom severity of shortness of breath due to both cancer and non-cancer causes; long-acting/sustained-release opioids are also used to prevent/continue treatment of dyspnea in palliative setting. There is a lack of evidence to recommend midazolam, nebulised opioids, the use of gas mixtures, or cognitive-behavioral therapy yet.
Non-pharmacological techniques
Non-pharmacological interventions provide key tools for the management of breathlessness.
Ensuring that the balance between side effects and adverse effects from medications and potential improvements from medications needs to be carefully considered before prescribing medication. Some studies have suggested that up to 27% of hospitalized people develop dyspnea, while in dying patients 75% will experience it. Acute shortness of breath is the most common reason people requiring palliative care visit an emergency department. Up to 70% of adults with advanced cancer also experience dyspnoea. as are those with the stress on the first syllable
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