Acute exacerbations of chronic bronchitis
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In concomitant presence of emphysema, the underlying condition can be classified as chronic obstructive pulmonary disease (COPD), and the exacerbations termed "acute exacerbation of COPD", and shares many characteristics with that of AECB.
The incidence of AECB varies depending on which definition is used, but by AECB definitions by Anthonisen et al. the typical COPD patient averages two to three AECB episodes per year. With a COPD prevalence of more than 12 million (possibly 24 million including undiagnosed ones) in the United States, there are at least 30 million incidences of AECB annually in the US.
During AECB, breathing becomes much more difficult because of further narrowing of the airways, in addition to increased secretion of mucus, which often is thicker than usual.
AECB can be caused by:
- Allergens, e.g., pollens, wood or cigarette smoke, pollution
- Toxins, including a variety of different chemicals
- Acute viral or bacterial infections. The extra mucus in the airways in chronic bronchitis provides a good place for viruses and bacteria to grow. Bacterial infections are suspected when there is a yellow or greenish colour of the mucus, or it is thicker than usual. However, coloured mucus is not specific to bacterial infections. Common bacterial pathogens of acute exacerbations include Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis. Less common bacterial pathogens include Chlamydia pneumoniae and MRSA. Pathogens seen more frequently in patients with impaired lung function (FEV<35% of predicted) include Haemophilus parainfluenzae (after repeated use of antibiotics), Mycoplasma pneumoniae and gram-negative, opportunistic pathogens like Pseudomonas aeruginosa and Klebsiella pneumoniae.
Although the condition of a patient with chronic bronchitis can become exacerbated by many other factors as well, the scope is generally restricted to the ones that cause the symptoms below.
An acute exacerbation of chronic bronchitis is associated with increased frequency and severity of coughing. It is often accompanied by worsened chest congestion and discomfort. Shortness of breath and wheezing are present in many cases.
In infection, there is often weakness, fever and chills. If due to a bacterial infection, the sputum may be slightly streaked with blood and coloured yellow or green.
The diagnostic criteria for acute exacerbation of chronic bronchitis generally include a production of sputum that is purulent and may be thicker than usual, but without evidence of pneumonia (which involves mainly the alveoli rather than the bronchi). Also, diagnostic criteria may include an increased in frequency and severity of cough, as well as increased shortness of breath.
A chest X-ray is usually performed on people with fever and, especially, hemoptysis (blood in the sputum), to rule out pneumonia and get information on the severity of the exacerbation. Hemoptysis may also indicate other, potentially fatal, medical conditions.
A history of exposure to potential causes and evaluation of symptoms may help in revealing the cause of an acute exacerbation of chronic bronchitis, which helps in choosing the best treatment. A sputum culture can specify which strain is causing a bacterial AECB. An early morning sample is preferred.
Prevention of AECB include:
- Smoking cessation and avoiding dust, passive smoking, and other inhaled irritants
- Yearly influenza and pneumococcal vaccine
- Regular exercise, appropriate rest, and healthy nutrition
- Avoiding people currently infected with e.g. cold and influenza
- Maintaining good fluid intake and humidifying the home, in order to help reduce the formation of thick sputum and chest congestion.
Treatment is often started before the test results confirm the condition.
Treatment of AECB may include:
- Mucolytic agents may be used to help liquefy thick mucus, facilitating clearance from the airways. Thinning of mucus may also be done by drinking plenty of fluids.
- Inhaled bronchodilators open up the airways in the lungs. These include salbutamol and terbutaline (both β2-adrenergic agonists), and ipratropium (an anticholinergic).
- Antibiotics are used if a bacterial infection is the suspected cause. However, antibiotics will not treat exacerbations caused by viruses. Viral infections will usually be cured with time with the aid of proper rest and care. Still, other medications may be needed to control symptoms. Lipid-soluble antibiotics such as macrolides, tetracyclines, and quinolones penetrate the lung tissue well. Macrolides are more active against Streptococcus pneumoniae than the tetracyclines and the older quinolones. Within the macrolides, newer ones are more active against Haemophilus influenzae than the older erythromycin. Regimens should generally be given for five days. Choice of antibiotics is also dependent on the severity of chronic bronchitis:
- "Simple" chronic bronchitis is generally where the patient is 65 years or less, has fewer than four exacerbations per year, has minimal or moderate impairment in respiratory function and no comorbid disease. In patients with "simple" chronic bronchitis, therapy should be targeted towards Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and possibly pathogens of atypical pneumonia. The first-line treatment is a beta-lactam antibiotic such as amoxicillin. The choice will depend on resistance patterns. In patients with penicillin allergy, doxycycline or trimethoprim are preferred.
- More complicated bronchitis may be when the patient is more than 65 years old, has four or more exacerbations per year, has an FEV1/FVC ratio of less than 50% on spirometry, has failed to respond to previous antibiotic treatment, and/or has comorbidity. In these cases, treatment should be aimed at Gram-negative bacteria and the possibility of high antibiotic resistance should be considered. Sputum culture results are of great value in determining antibiotic resistance. First-line treatment is cefuroxime or co-amoxiclav. Third-line treatment, as well as treatment in penicillin-allergic patients, is a fluoroquinolone such as ciprofloxacin. An agent active against Streptococcus pneumoniae may have to be added.
- Corticosteroids such as prednisone reduce inflammation in the airways. They are usually used for short periods.
- Theophylline, taken orally, helps to ease the difficulty of breathing. It may be added if the patient is not already taking it for the chronic bronchitis.
- Oxygen therapy should be initiated if there is a substantial risk of hypoxia. If oxygen is required on an ongoing basis, a portable oxygen concentrator can be used.
There should also be a "care plan" in case of future exacerbations. Patients may watch for symptoms, such as shortness of breath, change in character or amount of mucus, and start self-treatment as discussed with a health care provider. This allows for treatment right away until a doctor can be seen.
See also 
- medbroadcast.com > Acute Exacerbations of Chronic Bronchitis Retrieved on Mars 13, 2010
- Anthonisen NR, Manfreda J, Warren CP, Hershfield ES, Harding GK, Nelson NA (February 1987). "Antibiotic therapy in exacerbations of chronic obstructive pulmonary disease". Ann. Intern. Med. 106 (2): 196–204. PMID 3492164.
- Page 249 in: Balter MS, La Forge J, Low DE, Mandell L, Grossman RF (2003). "Canadian guidelines for the management of acute exacerbations of chronic bronchitis". Can. Respir. J. 10 Suppl B: 3B–32B. PMID 12944998. 
- MORBIDITY & MORTALITY: 2009 CHART BOOK ON CARDIOVASCULAR, LUNG, AND BLOOD DISEASES National Heart, Lung, and Blood Institute
- The British Society for Antimicrobial Chemotherapy > Acute exacerbations of chronic bronchitis (AECB) Retrieved on Mars 13, 2010
- Bach PB, Brown C, Gelfand SE, McCrory DC (2001). "Management of acute exacerbations of chronic obstructive pulmonary disease: a summary and appraisal of published evidence". Ann. Intern. Med. 134 (7): 600–20. PMID 11281745.