Dyspnea, shortness of breath, or air hunger, is the subjective symptom of breathlessness.
The clinical definition of dyspnea is an uncomfortable awareness of one's breathing effort. It is
a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations.
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. Treatment typically depends on the underlying cause.
Definition The American Thoracic Society defines dyspnea
as: "A subjective experience of breathing discomfort that consists of qualitatively
distinct sensations that vary in intensity." Other definitions describe it as "difficulty
in breathing", "disordered or inadequate breathing", "uncomfortable awareness of breathing", and
as the experience of "breathlessness". Dyspnea is distinct from labored breathing,
which is a common physical presentation of respiratory distress.
Differential diagnosis
While shortness of breath is generally caused by disorders of the cardiac or respiratory
system, other systems such as neurological, musculoskeletal, endocrine, hematologic, and
psychiatric may be the cause. DiagnosisPro, an online medical expert system, listed 497
distinct causes in October 2010. The most common cardiovascular causes are acute myocardial
infarction and congestive heart failure while common pulmonary causes include chronic obstructive
pulmonary disease, asthma, pneumothorax, pulmonary edema and pneumonia. On a pathophysiological
basis the causes can be divided into: an increased awareness of normal breathing such as during
an anxiety attack, an increase in the work of breathing and an abnormality in the ventilatory
system. Acute coronary syndrome
Acute coronary syndrome frequently presents with retrosternal chest discomfort and difficulty
catching the breath. It however may atypically present with shortness of breath alone. Risk
factors include old age, smoking, hypertension, hyperlipidemia, and diabetes. An electrocardiogram
and cardiac enzymes are important both for diagnosis and directing treatment. Treatment
involves measures to decrease the oxygen requirement of the heart and efforts to increase blood
flow. Congestive heart failure
Congestive heart failure frequently presents with shortness of breath with exertion, orthopnea,
and paroxysmal nocturnal dyspnea. It affects between 1-2% of the general United States
population and occurs in 10% of those over 65 years old. Risk factors for acute decompensation
include high dietary salt intake, medication noncompliance, cardiac ischemia, dysrhythmias,
renal failure, pulmonary emboli, hypertension, and infections. Treatment efforts are directed
towards decreasing lung congestion. Chronic obstructive pulmonary disease
People with chronic obstructive pulmonary disease, most commonly emphysema or chronic
bronchitis, frequently have chronic shortness of breath and a chronic productive cough.
An acute exacerbation presents with increased shortness of breath and sputum production.
COPD is a risk factor for pneumothorax; thus this condition should be ruled out. In an
acute exacerbation treatment is with a combination of anticholinergics, beta2-adrenoceptor agonists,
steroids and possibly positive pressure ventilation. Asthma
Asthma is the most common reason for presenting to the emergency with shortness of breath.
It is the most common lung disease in both developing and developed countries affecting
about 5% of the population. Other symptoms include wheezing, tightness in the chest,
and a non productive cough. Inhaled corticosteroids are the preferred treatment for children,
however these drugs can reduce the growth rate. 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. Physical findings may include absent breath sounds
on one side of the chest, jugular venous distension, and tracheal deviation.
Pneumonia
The symptoms of pneumonia are fever, productive cough, shortness of breath, and pleuritic
chest pain. Inspiratory crackles may be heard on exam. A chest x-ray can be useful to differential
pneumonia from congestive heart failure. As the cause is usually a bacterial infections
antibiotics are typically used for treatment. Important to remember: Severity and prognosis
of Pneumonia can be estimated from CURB65, where C=Confusion, U= Uremia, R=Respiratory
rate >30, B= BP<90, 65= Age>65. Pulmonary embolism
Pulmonary embolism classically presents with an acute onset of shortness of breath. Other
presenting symptoms include pleuritic chest pain, cough, hemoptysis, and fever. Risk factors
include deep vein thrombosis, recent surgery, cancer, and previous thromboembolism. It must
always be considered in those with acute onset of shortness of breath owing to its high risk
of mortality. Diagnosis however may be difficult. Treatment is typically with anticoagulants.
Anaemia Anaemia caused by low hemoglobin levels is
often a cause of dyspnea. Menstruation, particularly if excessive, can contribute to anaemia and
to consequential dyspnea in women. Headaches are also a symptom of dyspnea in patients
suffering from anaemia, some patients report a numb sensation in their head, and others
have reported blurred vision caused by hypotension behind the eye due to a lack of oxygen and
pressure, these patients have also reported severe head pain many of which lead to permanent
brain damage, symptoms of this can be loss of concentration, focus, fatigue, language
faculty impairment and memory loss. Other
Other important or common causes of shortness of breath include cardiac tamponade, anaphylaxis,
interstitial lung disease, panic attacks, and pulmonary hypertension. Cardiac tamponade
presents with dyspnea, tachycardia, elevated jugular venous pressure, and pulsus paradoxus.
The gold standard for diagnosis is ultrasound. Anemia, that develops gradually, usually presents
with exertional dyspnea, fatigue, weakness, and tachycardia. It may lead to heart failure.
Anaphylaxis typically begins over a few minutes in a person with a previous history of the
same. Other symptoms include urticaria, throat swelling, and gastrointestinal upset. The
primary treatment is epinephrine. Interstitial lung disease presents with gradual onset of
shortness of breath typically with a history of a predisposing environmental exposure.
Shortness of breath is often the only symptom in those with tachydysrhythmias. Panic attacks
typically present with hyperventilation, sweating, and numbness. They are however a diagnosis
of exclusion. Around 2/3 of women experience shortness of breath as a part of a normal
pregnancy. 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. A relatively unknown
condition involving shortness of breath is empty nose syndrome.
Pathophysiology Different physiological pathways may lead
to shortness of breath including via 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 is not being met by physical breathing.
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 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, asthma causing bronchoconstriction and muscle fatigue leading to ineffective
respiratory muscle action could all contribute to a feeling of dyspnea.
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.
There is also a psychological component to dyspnea, as some people may become aware of
their breathing in such circumstances but not experience the distress typical of dyspnea.
Evaluation The initial approach to evaluation begins
by assessment of the airway, breathing, and circulation followed by a medical history
and physical examination. Signs that represent significant severity include hypotension,
hypoxemia, tracheal deviation, altered mental status, unstable dysrhythmia, stridor, intercostal
indrawing, cyanosis, Tripod Positioning, pronounced use of accessory muscles and absent breath
sounds. A number of scales may be used to quantify
the degree of shortness of breath. It may be subjectively rated on a scale from 1 to
10 with descriptors associated with the number. 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. Blood tests
A number of labs may be 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. 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.
Imaging A chest x-ray is useful to confirm or rule
out a pneumothorax, pulmonary edema, or pneumonia. Spiral computed tomography with intravenous
radiocontrast is the imaging study of choice to evaluate for pulmonary embolism.
Treatment In those who are not palliative the primary
treatment of shortness of breath is directed at its underlying cause. 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. 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.
Palliative Along with the measure above, systemic immediate
release opioids are beneficial in emergently reducing the symptom 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. Epidemiology
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. Some studies have suggested that up to 27% of people suffer from 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.
Etymology Dyspnea literally means disordered breathing.
See also List of terms of lung size and activity
Orthopnea References
External links Dyspnea at GPnotebook