| ICD-10 | R06.0 |
|---|---|
| ICD-9 | 786.09 |
| DiseasesDB | 15892 |
| MedlinePlus | 003075 |
| MeSH | D004417 |
Dyspnea ( /dɪspˈniːə/ disp-nee-ə; also dyspnoea; Latin: dyspnoea; Greek: δύσπνοια, dýspnoia), shortness of breath (SOB), or air hunger,[1] is the subjective symptom of breathlessness.[2][3]
It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations.[2] In 85% of cases it is due to either asthma, pneumonia, cardiac ischemia, interstitial lung disease, congestive heart failure, chronic obstructive pulmonary disease, or psychogenic causes.[4] Treatment typically depends on the underlying cause.[5]
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Dyspnea does not have a well-defined or universally accepted definition.[4] It is defined by the American Thoracic Society as the "subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity. The experience derives from interactions among multiple physiological, psychological, social, and environmental factors, and may induce secondary physiological and behavioral responses."[6] Other definitions of dyspnea include "difficulty in breathing",[7] "disordered or inadequate breathing",[8] "uncomfortable awareness of breathing",[3] or simple "breathlessness".[2] Acute breathlessness is defined as severe shortness of breath that develops over minutes to hours.[5] Chronic breathlessness on the other hand comes on over weeks or months.[9] Dyspnea is distinct from labored breathing, which is rather a common physical presentation of respiratory distress; however, these two terms are often used interchangeably by health care personnel. The term "dyspnea" is occassionally used to indicate hypoventilation.
While shortness of breath is generally caused by disorders of the cardiac or respiratory system, other systems such as neurological,[10] musculoskeletal, endocrine, hematologic, and psychiatric may be the cause.[4] DiagnosisPro, an online medical expert system, listed 497 distinct causes in October 2010.[11] The most common cardiovascular causes are acute myocardial infarction and congestive heart failure while common pulmonary causes include chronic obstructive pulmonary disease, asthma, pneumothorax, and pneumonia.[2] On a pathophysiological basis the causes can be divided into: (1) an increased awareness of normal breathing such as during an anxiety attack, (2) an increase in the work of breathing and (3) an abnormality in the ventilatory system.[10]
Acute coronary syndrome frequently presents with retrosternal chest discomfort and difficulty catching the breath.[2] It however may atypically present with shortness of breath alone.[12] Risk factors include old age, smoking, hypertension, hyperlipidemia, and diabetes.[12] An electrocardiogram and cardiac enzymes are important both for diagnosis and directing treatment.[12] Treatment involves measures to decrease the oxygen requirement of the heart and efforts to increase blood flow.[2]
Congestive heart failure frequently presents with SOB with exertion, orthopnea, and paroxysmal nocturnal dyspnea.[2] It affects between 1-2% of the general United States population and occurs in 10% of those over 65 years old.[2][12] Risk factors for acute decompensation include high dietary salt intake, medication noncompliance, cardiac ischemia, dysrhythmias, renal failure, pulmonary emboli, hypertension, and infections.[12] Treatment efforts are directed towards decreasing lung congestion.[2]
People with chronic obstructive pulmonary disease (COPD), most commonly emphysema or chronic bronchitis, frequently have chronic shortness of breath and a chronic productive cough.[2] An acute exacerbation presents with increased shortness of breath and sputum production.[2] COPD is a risk factor for pneumothorax; thus this condition should be ruled out.[2] In an acute exacerbation treatment is with a combination of anticholinergics, beta2-adrenoceptor agonists, steroids and possibly positive pressure ventilation.[2]
Asthma is the most common reason for presenting to the emergency with shortness of breath.[2] It is the most common lung disease in both developing and developed countries affecting about 5% of the population.[2] Other symptoms include wheezing, tightness in the chest, and a non productive cough.[2] Inhaled beta2-adrenergic agonist (salbutamol) are first line therapy and usually lead to prompt improvement.[2]
Pneumothorax presents typically with pleuritic chest pain of acute onset and shortness of breath not improved with oxygen.[2] Physical findings may include absent breath sounds on one side of the chest, jugular venous distension, and tracheal deviation.[2]
The symptoms of pneumonia are fever, productive cough, shortness of breath, and pleuritic chest pain.[2] Inspiratory crackles may be heard on exam.[2] A chest x-ray can be useful to differential pneumonia from congestive heart failure.[2] As the cause is usually a bacterial infections antibiotics are typically used for treatment.[2]
Pulmonary embolism classically presents with an acute onset of shortness of breath.[2] Other presenting symptoms include pleuritic chest pain, cough, hemoptysis, and fever.[2] Risk factors include deep vein thrombosis, recent surgery, cancer, and previous thromboembolism.[2] It must always be considered in those with acute onset of shortness of breath owing to its high risk of mortality.[2] Diagnosis however may be difficult.[2] Treatment is typically with anticoagulants.[2]
Other important or common causes of shortness of breath include cardiac tamponade, anemia, anaphylaxis, interstitial lung disease, panic attacks,[4][5][13] and pulmonary hypertension. Cardiac tamponade presents with dyspnea, tachycardia, elevated jugular venous pressure, and pulsus paradoxus.[13] The gold standard for diagnosis is ultrasound.[13] Anemia, that develops gradually, usually presents with exertional dyspnea, fatigue, weakness, and tachycardia.[13] It may lead to heart failure.[13] Anaphylaxis typically begins over a few minutes in a person with a previous history of the same.[5] Other symptoms include urticaria, throat swelling, and gastrointestinal upset.[5] The primary treatment is epinephrine.[5] Interstitial lung disease presents with gradual onset of shortness of breath typically with a history of a predisposing environmental exposure.[4] Shortness of breath is often the only symptom in those with tachydysrhythmias.[12] Panic attacks typically present with hyperventilation, sweating, and numbness.[5] They are however a diagnosis of exclusion.[4] Around 2/3 of women experience shortness of breath as a part of a normal pregnancy.[8] Neurological conditions such as spinal cord injury, phrenic nerve injuries, Guillain-Barre syndrome, amyotrophic lateral sclerosis, multiple sclerosis and muscular dystrophy can all cause an individual to experience shortness of breath.[10]
A number of different physiological pathways may lead to shortness of breath including via chemoreceptors, mechanoreceptors, and lung receptors.[12]
It is currently thought that there are three main components that contribute to dyspnea: afferent signals, efferent signals, and central information processing. It is believed that the central processing in the brain compares the afferent and efferent signals, and that a "mismatch" results in the sensation of dyspnea. In other words, dyspnea may result when the need for ventilation (afferent signaling) is not being met by the physical breathing that is occurring (efferent signaling).[14] Afferent signals are sensory neuronal signals that ascend to the brain. Afferent neurons significant in dyspnea arise from a large number of sources including the carotid bodies, medulla, lungs, and chest wall. Chemoreceptors in the carotid bodies and medulla supply information regarding the blood gas levels of O2, CO2 and H+. 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 leading 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.[14]
Efferent signals are the motor neuronal signals descending to the respiratory muscles. The most important respiratory muscle is the diaphragm. Other respiratory muscles include the external and internal intercostal muscles, the abdominal muscles and the accessory breathing muscles.
As the brain receives its plentiful supply of afferent information relating to ventilation, it is able to 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. It is worth noting that there is a psychological component of dyspnea as well, as some people may become aware of their breathing in such circumstances but not experience the distress typical of dyspnea.[14]
| Grade | Degree of dyspnea |
|---|---|
| 0 | no dyspnea except with strenuous exercise |
| 1 | dyspnea when walking up an incline or hurrying on the level |
| 2 | walks slower than most on the level, or stops after 15 minutes of walking on the level |
| 3 | stops after a few minutes of walking on the level |
| 4 | with minimal activity such as getting dressed, too dyspneic to leave the house |
The initial approach to evaluation begins by assessment of the airway, breathing, and circulation followed by a medical history and physical examination.[2] Signs that represent significant severity include hypotension, hypoxemia, tracheal deviation, altered mental status, unstable dysrhythmia, stridor, intercostal indrawing, cyanosis, and absent breath sounds.[4]
A number of scales may be used to quantify the degree of shortness of breath.[15] It may be subjectively rated on a scale from 1 to 10 with descriptors associated with the number (The Modified Borg Scale).[15] Alternatively a scale such as the MRC Breathlessness Scale might be used - it suggests five different grades of dyspnea based on the circumstances in which it arises.[16]
A number of labs maybe helpful in determining 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 a number of conditions that lead to shortness of breath.[12] A low level of brain natriuretic peptide is useful in ruling out congestive heart failure; however, a high level while supportive of the diagnosis could also be due to advanced age, renal failure, acute coronary syndrome, or a large pulmonary embolism.[12]
A chest x-ray is useful to confirm or rule out a pneumothorax, pulmonary edema, or pneumonia.[12] Spiral computed tomography with intravenous radiocontrast is the imaging study of choice to evaluate for pulmonary embolism.[12]
In those who are not palliative the primary treatment of shortness of breath is directed at its underlying cause.[5] Extra oxygen is effective in those with hypoxia; however, this has no effect in those with normal blood oxygen saturations, even in those who are palliative.[3][17]
Individuals can benefit from a variety of physical therapy interventions.[18] Persons with neurological/neuromuscular abnormalities may have breathing difficulties due to weak or paralyzed intercostal, abdominal and/or other muscles needed for ventilation.[19] Some physical therapy interventions for this population include active assisted cough techniques,[20] volume augmentation such as breath stacking,[21] education about body position and ventilation patterns[22] and movement strategies to facilitate breathing.[21]
Along with the measure above, systemic immediate release opioids are beneficial in reducing the symptom of shortness of breath due to both cancer and non cancer causes.[3][23] There is a lack of evidence to recommend midazolam, nebulised opioids, the use of gas mixtures, or cognitive-behavioral therapy.[24]
Shortness of breath is the primary reason 3.5% of people present to the emergency department in the United States. Of these approximately 51% are admitted to hospital and 13% are dead within a year.[25] Some studies have suggested that up to 27% of people suffer from dyspnea,[26] while in dying patients 75% will experience it.[14] Acute shortness of breath is the most common reason people who are palliative visit an emergency department.[3]
Dyspnea ( /dɪspˈniːə/ disp-nee-ə; from Latin dyspnoea, from Greek dyspnoia from dyspnoos) literally means disordered breathing.[4]
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