Dyspnea has been more specifically 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."[1]
Importantly, dyspnea is a symptom A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality. A symptom is subjective, observed by the patient, and not measured experienced by the individual, rather than a noticeable or measurable sign Signs may have no meaning for, or even be noticed by, the patient, but may be full of meaning for the physician, and are often significant in assisting a physician in diagnosis of medical condition responsible for the patient's symptoms. Thus dyspnea is not the same as tachypnea It is not identical with hyperventilation - tachypnea may be necessary for a sufficient gas-exchange of the body, for example after exercise, in which case it is not hyperventilation (rapid breathing),[3] although both may be present at the same time.
Clinical assessment
Dyspnea can be a worrying and disabling symptom for the patient. In order to assess the level of dyspnea, the doctor might ask the patient to rank the severity from 1 to 10. 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.[4]
| Grade | Degree of dyspnea |
|---|---|
| 1 | no dyspnea except with strenuous exercise |
| 2 | dyspnea when walking up an incline or hurrying on the level |
| 3 | walks slower than most on the level, or stops after 15 minutes of walking on the level |
| 4 | stops after a few minutes of walking on the level |
| 5 | dyspnea with minimal activity such as getting dressed, too dyspneic to leave the house |
Some studies have suggested that up to 27% of people suffer dyspnea,[2] while in dying patients 75% will experience it.[5]
Pathophysiology
In general, dyspnea signals that there is inadequate ventilation.[2] This happens when the body is unable to ventilate enough to sufficiently meet the body's needs. This situation may occur when there is increased ventilatory demand (e.g. during exercise) or reduced ability to ventilate enough (e.g. due to respiratory muscle weakness).[3]
Mechanisms
Although the exact mechanisms of dyspnea are not fully understood, some general details have been found. 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).[5]
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 The lung or pulmonary system is the essential respiration organ in air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located in the chest on either side of the heart. Their principal function is to transport oxygen from the atmosphere into the bloodstream,, and chest wall The bony portion is known as the thoracic cage. However, the wall also includes muscle, skin, and fascia. 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 Hypercapnia or hypercapnea , also known as hypercarbia, is a condition where there is too much carbon dioxide (CO2) in the blood. Carbon dioxide is a gaseous product of the body's metabolism and is normally expelled through the lungs, left heart failure Heart failure is a condition in which a problem with the structure or function of the heart impairs its ability to supply sufficient blood flow to meet the body's needs. It should not be confused with cardiac arrest (see Terminology, below) leading to interstitial edema (impairing gas exchange), asthma Asthma is a chronic medical condition. It has been defined by the National Heart, Lung and Blood Institute of the United States of America as a common chronic disorder of the airways that is complex and characterized by variable and recurring symptoms, airflow obstruction, bronchial hyperresponsiveness , and an underlying inflammation. The causing bronchoconstriction (limiting airflow) and muscle fatigue leading to ineffective respiratory muscle action could all contribute to a feeling of dyspnea.[5]
Efferent signals are the motor neuronal signals descending to the respiratory muscles. The most important respiratory muscle is the diaphragm In the anatomy of mammals, the thoracic diaphragm is a sheet of muscle extending across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration. A diaphragm in anatomy can refer to other flat structures such as the urogenital diaphragm or pelvic diaphragm,. Other respiratory muscles include the external and internal intercostal muscles, as well as 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.[5]
Causes
Pulmonary disorders
- Obstructive lung diseases
- Asthma Asthma is a chronic medical condition. It has been defined by the National Heart, Lung and Blood Institute of the United States of America as a common chronic disorder of the airways that is complex and characterized by variable and recurring symptoms, airflow obstruction, bronchial hyperresponsiveness , and an underlying inflammation. The
- Bronchitis Bronchitis is inflammation of the air passages within the lungs. It occurs when the trachea and the large and small bronchi (airways) within the lungs become inflamed because of infection or other causes
- Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease refers to chronic bronchitis and emphysema, a pair of two commonly co-existing diseases of the lungs in which the airways become narrowed. This leads to a limitation of the flow of air to and from the lungs causing shortness of breath. In contrast to asthma, the limitation of airflow is poorly reversible and
- Cystic fibrosis Cystic fibrosis is a genetic disorder known to be an inherited disease of the secretory glands, including the glands that make mucus and sweat
- Emphysema Emphysema is a chronic obstructive pulmonary disease (COPD, as it is otherwise known, formerly termed a chronic obstructive lung disease). It is often caused by exposure to toxic chemicals, including long-term exposure to tobacco smoke
- Laryngeal The larynx , colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. The larynx houses the vocal folds, and is situated just below where the tract of the pharynx splits into the trachea and the esophagus edema Edema or oedema (British English; both words from the Greek οἴδημα), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin, or in one or more cavities of the body. Generally, the amount of interstitial fluid is determined by the balance of fluid homeostasis, and increased secretion of fluid into the due to allergies Allergy is a disorder of the immune system often also referred to as atopy. Allergic reactions occur to normally harmless environmental substances known as allergens; these reactions are acquired, predictable, and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type I hypersensitivity. It is characterized by
- Hookworm disease
- Diseases of lung parenchyma and pleura
- Contagious
- Anthrax Anthrax is an acute disease caused by Bacillus anthracis. It affects both humans and animals and most forms of the disease are highly lethal. There are effective vaccines against anthrax, and some forms of the disease respond well to antibiotic treatment through inhalation of Bacillus anthracis Bacillus anthracis is a Gram-positive spore-forming, rod-shaped bacterium, with a width of 1-1.2µm and a length of 3-5µm. It can be grown in an ordinary nutrient medium under aerobic or anaerobic conditions. It is the only bacterium with a protein capsule , and the only pathogenic bacteria to carry its own adenylyl cyclase virulence factor (
- Pneumonia The alveoli are microscopic air-filled sacs in the lungs responsible for absorbing oxygen. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Its cause may also be officially described as idiopathic—that is, unknown—when infectious causes
- Non-contagious
- Fibrosing alveolitis Alveolitis can refer to two inflammatory conditions. It can refer to inflammation of the alveoli in the lungs, or the dental alveolus in the jaw
- Atelectasis Atelectasis is a medical condition in which the lungs are not fully inflated. It may affect part or all of one lung. It is a condition where the alveoli are deflated, as distinct from pulmonary consolidation
- Hypersensitivity pneumonitis Hypersensitivity pneumonitis is an inflammation of the alveoli within the lung caused by hypersensitivity to inhaled organic dusts. Sufferers are commonly exposed to the dust by their occupation or hobbies
- Interstitial lung disease Interstitial lung disease , also known as diffuse parenchymal lung disease (DPLD), refers to a group of lung diseases affecting the interstitium of the lung: alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues. The term ILD is used to distinguish these diseases from obstructive airways
- Lung cancer Lung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells. Lung cancer, the most common cause of cancer-related death
- Pleural effusion Pleural effusion is excess fluid that accumulates in the pleural cavity, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during inhalation
- Pneumoconiosis Pneumoconiosis in combination with multiple pulmonary rheumatoid nodules in rheumatoid arthritis patients is known as Caplan's syndrome
- Pneumothorax In medicine , a pneumothorax is a potential medical emergency wherein air or gas is present in the pleural cavity. A pneumothorax can occur spontaneously. It can also occur as the result of disease or injury to the lung, or due to a puncture to the chest wall. A pneumothorax can result in a collapsed lung, or can be created therapeutically to
- Non-cardiogenic pulmonary edema Pulmonary edema , or oedema (British English, Greek οίδημα), is fluid accumulation in the lungs. It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the heart to remove fluid from the lung circulation ("cardiogenic pulmonary edema") or a direct injury to the lung parenchyma (" or acute respiratory distress syndrome Acute respiratory distress syndrome , also known as respiratory distress syndrome (RDS) or adult respiratory distress syndrome (in contrast with IRDS) is a serious reaction to various forms of injuries to the lung
- Sarcoidosis Sarcoidosis , also called sarcoid or Besnier-Boeck disease, is a multisystem disorder characterized by non-caseating granulomas (small inflammatory nodules). The cause of the disease is still unknown. Virtually any organ can be affected; however, granulomas most often appear in the lungs or the lymph nodes. Symptoms usually appear gradually but
- Contagious
- Pulmonary vascular diseases
- Acute or recurrent pulmonary emboli Pulmonary embolism is a blockage of the pulmonary artery or one of its branches, usually occurring when a deep vein thrombus (blood clot from a vein) becomes dislodged from its site of formation and travels, or embolizes, to the arterial blood supply of one of the lungs. This process is termed thromboembolism
- Pulmonary hypertension In medicine, pulmonary hypertension is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion. Pulmonary hypertension can be a severe disease with a, primary or secondary
- Pulmonary veno-occlusive disease Hepatic veno-occlusive disease or veno-occlusive disease is a condition in which some of the small veins in the liver are blocked. It is a complication of high-dose chemotherapy given before a bone marrow transplant and is marked by weight gain due to fluid retention, increased liver size, and raised levels of bilirubin in the blood. The name
- Superior vena cava syndrome Superior vena cava syndrome , or superior vena cava obstruction (SVCO), is usually the result of the direct obstruction of the superior vena cava by malignancies- such as compression of the vessel wall by right upper lobe tumors, such as thymoma and/or mediastinal lymphadenopathy. The most common malignancies that cause SVCS is bronchogenic
Other causes of diminished breathing
- Obstruction of the airway
- Cancer Cancer is a class of diseases in which a group of cells display uncontrolled growth (division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood). These three malignant properties of cancers differentiate them from benign tumors, of the larynx The larynx , colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. The larynx houses the vocal folds, and is situated just below where the tract of the pharynx splits into the trachea and the esophagus or pharynx The pharynx is the part of the neck and throat situated immediately posterior to (behind) the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea
- Empty nose syndrome
- Pulmonary aspiration The patient may either inhale the material, or it may be blown into the lungs during positive pressure ventilation or CPR. As the right main bronchus is more vertical and of slightly wider lumen than the left, aspirated material is more likely to end up in this branch or one of its subsequent bifurcations
- Epiglottitis Epiglottitis is inflammation of the epiglottis - the flap that sits at the base of the tongue, which keeps food from going into the trachea . Due to its place in the airway, swelling of this structure can interfere with breathing and constitutes a medical emergency. The infection can cause the epiglottis to either obstruct or completely close off
- Vocal cord dysfunction Vocal cord dysfunction is a condition that affects the vocal cords which is characterized by vocal cord closure usually during inspiration. This closure may cause airflow obstruction and wheezing. This syndrome can mimic asthma, anaphylaxis, collapsed lungs, pulmonary embolism, or fat embolism, and can lead to an inaccurate diagnosis and
- Immobilization of the diaphragm
- Lesion of the phrenic nerve The phrenic nerve is made up mostly of motor nerve fibres for producing contractions of the diaphragm. In addition, it provides sensory innervation for many components of the mediastinum and pleura, as well as the upper abdomen, especially the liver, and the gall bladder
- Polycystic liver disease Polycystic liver disease usually describes the presence of multiple cysts scattered throughout the normal liver tissue, in association with Polycystic kidney disease
- Tumor A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells . Tumor is not synonymous with cancer. A tumor can be benign, pre-malignant or malignant, whereas cancer is by definition malignant in the diaphragm
- Restriction of the chest volume
- Ankylosing spondylitis Ankylosing spondylitis , previously known as Bechterew's disease, Bechterew syndrome, and Marie Strümpell disease , a form of Spondyloarthritis, is a chronic, inflammatory arthritis. It affects joints in the spine and the sacroilium in the pelvis, causing eventual fusion of the spine
- Broken A bone fracture is a medical condition in which there is a break in the continuity of the bone. While many fractures are the result of high force impact or stress, bone fracture can also occur as a result of certain medical conditions that weaken the bones, such as osteoporosis, certain types of cancer, or osteogenesis imperfecta, where the ribs
- Kyphosis Kyphosis also called "hunch back" or "hunchbackism" or "hunchbackedness", in general terms, is a common condition of a curvature of the upper (thoracic) spine. It can be either the result of degenerative diseases (such as arthritis), developmental problems, osteoporosis with compression fractures of the vertebrae, and of the spine
- Obesity Obesity is associated with many diseases, particularly heart disease, type 2 diabetes, breathing difficulties during sleep, certain types of cancer, and osteoarthritis. Obesity is most commonly caused by a combination of excessive dietary calories, lack of physical activity, and genetic susceptibility, though a limited number of cases are due
- Pregnancy Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Human pregnancy is the most studied of all mammalian pregnancies. Obstetrics is the surgical field that studies and cares for high risk pregnancy
- Pectus excavatum
- Scoliosis Scoliosis is a medical condition in which a person's spine is curved from side to side, shaped like an "s", and may also be rotated. To adults it can be very painful. It is an abnormal lateral curvature of the spine. On an x-ray, the spine of an individual with a typical scoliosis may look more like an "S" or a "C"
- Disorders of the cardiovascular system
- Disorders of the blood and metabolism
- Disorders affecting breathing nerves and muscles
- Psychological conditions
- Medications
- Other
See also
- Air hunger
- Apnea, absence of respiration
- Tachypnea, fast respiration
- Bradypnea, slow respiration
- Eupnea, normal respiration
- Orthopnea
- Trepopnea
- Paroxysmal nocturnal dyspnea
Footnotes
- ^ a b American Heart Society (1999). "Dyspnea mechanisms, assessment, and management: a consensus statement". Am Rev Resp Crit Care Med 159: 321–340.
- ^ a b c Murray and Nadel's Textbook of Respiratory Medicine, 4th Ed. Robert J. Mason, John F. Murray, Jay A. Nadel, 2005, Elsevier
- ^ a b West JB (2008). Pulmonary pathophysiology: the essentials (7 ed.). Baltimore: Lippincott Williams & Wilkins. pp. 45.
- ^ Stenton C (2008). "The MRC breathless scale.". Occup Med 58: 226–7. doi:10.1093/occmed/kqm162. PMID 18441368.
- ^ a b c d Harrison's Principles of Internal Medicine (Kasper DL, Fauci AS, Longo DL, et al (eds)) (16th ed.). New York: McGraw-Hill.
References
Lippincott Williams & Wilkins (2006). Stedman's Medical Dictionary, 28th Edition. Baltimore, Maryland: Julie K. Stegman. pp. 601. ISBN 0-7817-3390-1.
External links
- Dyspnea at GPnotebook
- How Heart Failure causes shortness of breath – An animated journey through Heart Failure
Categories: Abnormal respiration | Pulmonology | Symptoms
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borzack
Mon, 29 Jun 2009 14:15:55 GM
Itchy skin; Hives or rash; Swollen airways; Chest pain; . Shortness of breath. ; Nausea; Diarrhea; Stomach pain; Anaphylaxis. What Are the Symptoms of Food Intolerance? Typical symptoms of food intolerance are: ...
Q. Hello, I have been having shortness of breath for the past month now. I do have asthma but I do not get attacks I just have a shortness of breath each time I breath out. I am 19 years old I do not smoke? could I have lung cancer?
Asked by Bryce S - Thu Apr 23 13:53:44 2009 - - 5 Answers - 0 Comments
A. Please go to the doctor and describe all your symptoms. There could be other difficulties.
Answered by Lifelong Student - Thu Apr 23 15:36:21 2009
