Pneumonia
Pneumonia | |
---|---|
Other names | Pneumonitis |
Frequency | 450 million (7%) per year[12][13] |
Deaths | Four million per year[12][13] |
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli.[3][14] Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing.[15] The severity of the condition is variable.[15]
Pneumonia is usually caused by infection with viruses or bacteria, and less commonly by other
Risk factors for pneumonia include cystic fibrosis, chronic obstructive pulmonary disease (COPD), sickle cell disease, asthma, diabetes, heart failure, a history of smoking, a poor ability to cough (such as following a stroke), and a weak immune system.[5][7]
Vaccines to prevent certain types of pneumonia (such as those caused by Streptococcus pneumoniae bacteria, linked to influenza, or linked to COVID-19) are available.[10] Other methods of prevention include hand washing to prevent infection, and not smoking.[10]
Treatment depends on the underlying cause.[19] Pneumonia believed to be due to bacteria is treated with antibiotics.[11] If the pneumonia is severe, the affected person is generally hospitalized.[19] Oxygen therapy may be used if oxygen levels are low.[11]
Each year, pneumonia affects about 450 million people globally (7% of the population) and results in about 4 million deaths.
Signs and symptoms
Symptoms frequency[22] | |
---|---|
Symptom | Frequency |
Cough | 79–91% |
Fatigue | 90% |
Fever | 71–75% |
Shortness of breath | 67–75% |
Sputum | 60–65% |
Chest pain | 39–49% |
People with infectious pneumonia often have a
The typical signs and symptoms in children under five are fever, cough, and fast or difficult breathing.
Bacterial and viral cases of pneumonia usually result in similar symptoms.
Cause
Pneumonia is due to infections caused primarily by bacteria or viruses and less commonly by fungi and
The term pneumonia is sometimes more broadly applied to any condition resulting in inflammation of the lungs (caused for example by autoimmune diseases, chemical burns or drug reactions); however, this inflammation is more accurately referred to as pneumonitis.[16][17]
Factors that predispose to pneumonia include smoking,
Bacteria
Bacteria are the most common cause of
The spreading of organisms is facilitated by certain risk factors.
Viruses
In adults, viruses account for about one third of pneumonia cases,
Fungi
Fungal pneumonia is uncommon, but occurs more commonly in individuals with weakened immune systems due to AIDS,
Parasites
A variety of
Noninfectious
Idiopathic interstitial pneumonia or noninfectious pneumonia
Mechanisms
Pneumonia frequently starts as an
Bacterial
Most bacteria enter the lungs via small aspirations of organisms residing in the throat or nose.
Viral
Viruses may reach the lung by a number of different routes. Respiratory syncytial virus is typically contracted when people touch contaminated objects and then touch their eyes or nose.
Diagnosis
Pneumonia is typically diagnosed based on a combination of physical signs and often a
Diagnosis in children
The World Health Organization has defined pneumonia in children clinically based on either a cough or difficulty breathing and a rapid respiratory rate, chest indrawing, or a decreased level of consciousness.[63] A rapid respiratory rate is defined as greater than 60 breaths per minute in children under 2 months old, greater than 50 breaths per minute in children 2 months to 1 year old, or greater than 40 breaths per minute in children 1 to 5 years old.[63]
In children, low oxygen levels and lower chest indrawing are more sensitive than hearing chest crackles with a stethoscope or increased respiratory rate.[64] Grunting and nasal flaring may be other useful signs in children less than five years old.[65]
Lack of wheezing is an indicator of Mycoplasma pneumoniae in children with pneumonia, but as an indicator it is not accurate enough to decide whether or not macrolide treatment should be used.[66] The presence of chest pain in children with pneumonia doubles the probability of Mycoplasma pneumoniae.[66]
Diagnosis in adults
In general, in adults, investigations are not needed in mild cases.
The diagnosis of influenza-like illness can be made based on the signs and symptoms; however, confirmation of an influenza infection requires testing.[71] Thus, treatment is frequently based on the presence of influenza in the community or a rapid influenza test.[71]
Adults 65 years old or older, as well as cigarette smokers and people with ongoing medical conditions are at increased risk for pneumonia.[72]
Physical exam
Imaging
A chest radiograph is frequently used in diagnosis.[23] In people with mild disease, imaging is needed only in those with potential complications, those not having improved with treatment, or those in which the cause is uncertain.[23][67] If a person is sufficiently sick to require hospitalization, a chest radiograph is recommended.[67] Findings do not always match the severity of disease and do not reliably separate between bacterial and viral infection.[23]
X-ray presentations of pneumonia may be classified as
A CT scan can give additional information in indeterminate cases[41] and provide more details in those with an unclear chest radiograph (for example occult pneumonia in chronic obstructive pulmonary disease). They can be used to exclude pulmonary embolism and fungal pneumonia, and detect lung abscesses in those who are not responding to treatments.[40] However, CT scans are more expensive, have a higher dose of radiation, and cannot be done at bedside.[40]
-
Pneumonia seen by ultrasound[76]
-
Pneumonia seen by ultrasound[76]
-
Pneumonia seen by ultrasound[76]
-
Right middle lobe pneumonia in a child as seen on plain X-ray
Microbiology
In people managed in the community, determining the causative agent is not cost-effective and typically does not alter management.
Classification
Pneumonitis refers to lung inflammation; pneumonia refers to pneumonitis, usually due to infection but sometimes non-infectious, that has the additional feature of
The setting in which pneumonia develops is important to treatment,[82][83] as it correlates to which pathogens are likely suspects,[82] which mechanisms are likely, which antibiotics are likely to work or fail,[82] and which complications can be expected based on the person's health status.
Community
Community-acquired pneumonia (CAP) is acquired in the community,[82][83] outside of health care facilities. Compared with healthcare-associated pneumonia, it is less likely to involve multidrug-resistant bacteria. Although the latter are no longer rare in CAP,[82] they are still less likely. Prior stays in healthcare-related environments such as hospitals, nursing homes, or hemodialysis centers or a history of receiving domiciliary care can increase patients' risk for CAP caused by multidrug-resistant bacteria.[84]
Healthcare
Health care–associated pneumonia (HCAP) is an infection associated with recent exposure to the health care system,[82] including hospitals, outpatient clinics, nursing homes, dialysis centers, chemotherapy treatment, or home care.[83] HCAP is sometimes called MCAP (medical care–associated pneumonia).
People may become infected with pneumonia in a hospital; this is defined as pneumonia not present at the time of admission (symptoms must start at least 48 hours after admission).
Ventilator-associated pneumonia occurs in people breathing with the help of mechanical ventilation.
Differential diagnosis
Several diseases can present with similar signs and symptoms to pneumonia, such as: chronic obstructive pulmonary disease, asthma,
Prevention
Prevention includes vaccination, environmental measures, and appropriate treatment of other health problems.[23] It is believed that, if appropriate preventive measures were instituted globally, mortality among children could be reduced by 400,000; and, if proper treatment were universally available, childhood deaths could be decreased by another 600,000.[25]
Vaccination
Vaccination prevents against certain bacterial and viral pneumonias both in children and adults. Influenza vaccines are modestly effective at preventing symptoms of influenza,[12][85] The Centers for Disease Control and Prevention (CDC) recommends yearly influenza vaccination for every person 6 months and older.[86] Immunizing health care workers decreases the risk of viral pneumonia among their patients.[78]
Vaccinations against Haemophilus influenzae and Streptococcus pneumoniae have good evidence to support their use.
Medications
When influenza outbreaks occur, medications such as amantadine or rimantadine may help prevent the condition, but they are associated with side effects.[93] Zanamivir or oseltamivir decrease the chance that people who are exposed to the virus will develop symptoms; however, it is recommended that potential side effects are taken into account.[94]
Other
Appropriately treating underlying illnesses (such as HIV/AIDS,
Testing pregnant women for
For people with low levels of vitamin C in their diet or blood, taking vitamin C supplements may be suggested to decrease the risk of pneumonia, although there is no strong evidence of benefit.[105] There is insufficient evidence to recommend that the general population take vitamin C to prevent or treat pneumonia.[105]
For adults and children in the hospital who require a respirator, there is no strong evidence indicating a difference between heat and moisture exchangers and heated humidifiers for preventing pneumonia.[106] There is tentative evidence that laying flat on the back compared to semi-raised increases pneumonia risks in people who are intubated.[107]
Management
CURB-65 | |
---|---|
Symptom | Points |
Confusion | 1 |
Urea>7 mmol/L | 1 |
Respiratory rate>30 | 1 |
SBP<90mmHg, DBP<60mmHg | 1 |
Age>=65 | 1 |
Pneumonia can cause severe illness in a number of ways, and pneumonia with evidence of organ dysfunction may require
For adults with moderate or severe acute respiratory distress syndrome (ARDS) undergoing mechanical ventilation, there is a reduction in mortality when people lie on their front for at least 12 hours a day. However, this increases the risk of endotracheal tube obstruction and pressure sores.[117]
Bacterial
Antibiotics improve outcomes in those with bacterial pneumonia.
For those who require hospitalization and caught their pneumonia in the community the use of a β-lactam such as
The duration of treatment has traditionally been seven to ten days, but increasing evidence suggests that shorter courses (3–5 days) may be effective for certain types of pneumonia and may reduce the risk of antibiotic resistance.
The addition of corticosteroids to standard antibiotic treatment appears to improve outcomes, reducing death and morbidity for adults with severe community acquired pneumonia, and reducing death for adults and children with non-severe community acquired pneumonia.[131][132] A 2017 review therefore recommended them in adults with severe community acquired pneumonia.[131] A 2019 guideline however recommended against their general use, unless refractory shock was present.[77] Side effects associated with the use of corticosteroids include high blood sugar.[131] There is some evidence that adding corticosteroids to the standard PCP pneumonia treatment may be beneficial for people who are infected with HIV.[48]
The use of granulocyte colony stimulating factor (G-CSF) along with antibiotics does not appear to reduce mortality and routine use for treating pneumonia is not supported by evidence.[133]
Viral
Aspiration
In general,
Follow-up
The British Thoracic Society recommends that a follow-up chest radiograph be taken in people with persistent symptoms, smokers, and people older than 50.[67] American guidelines vary, from generally recommending a follow-up chest radiograph[136] to not mentioning any follow-up.[78]
Prognosis
With treatment, most types of bacterial pneumonia will stabilize in 3–6 days.
Complications may occur in particular in the elderly and those with underlying health problems.[137] This may include, among others: empyema, lung abscess, bronchiolitis obliterans, acute respiratory distress syndrome, sepsis, and worsening of underlying health problems.[137]
Clinical prediction rules
Clinical prediction rules have been developed to more objectively predict outcomes of pneumonia.[28] These rules are often used to decide whether to hospitalize the person.[28]
- CURB-65 score, which takes into account the severity of symptoms, any underlying diseases, and age[138]
- Pneumonia severity index (or PSI Score)[28]
Pleural effusion, empyema, and abscess
In pneumonia, a collection of fluid may form in the space that surrounds the lung.[139] Occasionally, microorganisms will infect this fluid, causing an empyema.[139] To distinguish an empyema from the more common simple parapneumonic effusion, the fluid may be collected with a needle (thoracentesis), and examined.[139] If this shows evidence of empyema, complete drainage of the fluid is necessary, often requiring a drainage catheter.[139] In severe cases of empyema, surgery may be needed.[139] If the infected fluid is not drained, the infection may persist, because antibiotics do not penetrate well into the pleural cavity. If the fluid is sterile, it must be drained only if it is causing symptoms or remains unresolved.[139]
In rare circumstances, bacteria in the lung will form a pocket of infected fluid called a lung abscess.[139] Lung abscesses can usually be seen with a chest X-ray but frequently require a chest CT scan to confirm the diagnosis.[139] Abscesses typically occur in aspiration pneumonia, and often contain several types of bacteria. Long-term antibiotics are usually adequate to treat a lung abscess, but sometimes the abscess must be drained by a surgeon or radiologist.[139]
Respiratory and circulatory failure
Pneumonia can cause respiratory failure by triggering acute respiratory distress syndrome (ARDS), which results from a combination of infection and inflammatory response. The lungs quickly fill with fluid and become stiff. This stiffness, combined with severe difficulties extracting oxygen due to the alveolar fluid, may require long periods of mechanical ventilation for survival.[43] Other causes of circulatory failure are hypoxemia, inflammation, and increased coagulability.[40]
Sepsis is a potential complication of pneumonia but usually occurs in people with poor immunity or
Epidemiology
Pneumonia is a common illness affecting approximately 450 million people a year and occurring in all parts of the world.
Children
In 2008, pneumonia occurred in approximately 156 million children (151 million in the developing world and 5 million in the developed world).
History
Pneumonia has been a common disease throughout human history.
Sir William Osler, known as "the father of modern medicine", appreciated the death and disability caused by pneumonia, describing it as the "captain of the men of death" in 1918, as it had overtaken tuberculosis as one of the leading causes of death at the time. This phrase was originally coined by John Bunyan in reference to "consumption" (tuberculosis).[157][158] Osler also described pneumonia as "the old man's friend" as death was often quick and painless when there were much slower and more painful ways to die.[21]
Viral pneumonia was first described by Hobart Reimann in 1938. Reimann, Chairman of the Department of Medicine at Jefferson Medical College, had established the practice of routinely typing the pneumococcal organism in cases where pneumonia presented. Out of this work, the distinction between viral and bacterial strains was noticed.[159]
Several developments in the 1900s improved the outcome for those with pneumonia. With the advent of penicillin and other antibiotics, modern surgical techniques, and intensive care in the 20th century, mortality from pneumonia, which had approached 30%, dropped precipitously in the developed world. Vaccination of infants against Haemophilus influenzae type B began in 1988 and led to a dramatic decline in cases shortly thereafter.[160] Vaccination against Streptococcus pneumoniae in adults began in 1977, and in children in 2000, resulting in a similar decline.[161]
Society and culture
Awareness
Due to the relatively low awareness of the disease, 12 November was declared in 2009 as the annual World Pneumonia Day, a day for concerned citizens and policy makers to take action against the disease.[162][163]
Costs
The global economic cost of community-acquired pneumonia has been estimated at $17 billion annually.
References
Footnotes
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