Acute bronchitis Click on any of the headings or subheadings to rapidly navigate to the relevant section of the guidemap.
What is acute bronchitis and how does it present clinically?
What clinical conditions should a clinician exclude in a patient presenting with acute bronchitis?
What diagnostic tests should be performed in a patient with suspected acute bronchitis?
Commentary, criticism and controvery
Acute bronchitis is a common clinical condition and 5% of the US-population have an acute cough illness every year. Ninenty percent of those acute cough patients consult a physician and most of those patients are diagnosed with acute bronchitis. Viruses account for 90% of acute bronchitis infections, while bacteria only account for 10% of cases. Despite the lack of scientific evidence that antibiotics are of therapeutic value in acute bronchitis, approximately 40-90% of acute bronchitis patients in the USA receive antibiotic treatment.
This guidemap analyses the clinical conundrum of acute bronchitis, and it offers educational guidance on the optimum diagnostic and therapeutic approach to that clinical condition.
What is acute bronchitis and how does it present clinically?
Acute bronchitis is a self-limiting acute inflammatory disease of the bronchial airways that usually lasts 1-3 weeks. The inflammation of the bronchial airways can be caused by chemical agents (eg. chlorine gas released into the air by incorrect mixing of different household cleaners) or other enviromental pollutants (eg. smoke), but it is most commonly caused by a viral infection. The viral infection usually starts in the nose and upper airways of the throat as an upper respiratory infection. Patients may therefore have symptoms of rhinitis (runny nose, nasal discharge and congestion, post-nasal drip and throat irritation), rhinosinusitis (runny nose, nasal discharge and congestion, post-nasal drip and throat irritation + sinus pressure/pain + maxillary teeth pain), or pharyngitis (sore throat and pain on swallowing), in addition to (or preceding) their acute bronchitis symptoms. A mild fever may/may not be present. Constitutional symptoms (body aches, malaise, fatigue, anorexia) may be present during the first 1-5 days of the illness. Constitutional symptoms may be particularly prominent in certain virus infections such as influenza, but minimal, or non-existent, in other virus infections (eg. rhinovirus or corona virus). The characteristic symptoms of acute bronchitis are due to inflammation of the bronchial airways, and the main symptoms include a cough +/- chest discomfort (central chest rawness or soreness or burning), which is worse on breathing or coughing. A persistent cough may occur concurrently with the upper respiratory symptoms, or follow the URI symptoms by 3-4 days. Sometimes, preceding URI symptoms are either absent or minimal in degree. Inflammation of the bronchial airways often induces the glands in the bronchial mucosa to secrete an increased amount of mucus, which results in sputum production and a productive cough. The color and consistency of the sputum can vary considerably, and it may be clear and thin, or yellow and thick (mucopurulent), in appearance. The presence of mucopurulent sputum does not imply a bacterial infection and it is due to the presence of desquamated bronchial epithelial cells and live/dead white blood cells. The thick sputum can plug up the smaller bronchial airways, which can lead to micro-atelectasis (collapse of small sections of the lung alveolar tissue due to a lack of ventilation and secondary air absorption) and/or secondary bronchopneumonia (infection of the lung alveolar tissue adjacent to the smallest bronchial airways). The bronchial airways may also become hyperresponsive during an attack of acute bronchitis, and they may bronchoconstrict (muscle spasm of the smooth muscle in the bronchial airways causing radial narrowing of the bronchial airways) in response to the inflammation, which results in difficulty breathing and wheezing. The difficulty breathing is due to increased airway resistance as the patient attempts to breathe through narrowed bronchial airways. The wheezing noises are heard mainly during expiration, and they are due to musical-whistling sounds produced by expired air as it passes through narrow airways (like the whistling sounds heard when breathing through narrowly pursed lips). The increased bronchial mucus and/or swelling of the bronchial mucosa lining the bronchial airways (that occurs secondary to the bronchial inflammation) also contributes to the airway narrowing, and the resultant difficulty breathing and wheezing.
In summary, acute bronchitis presents with symptoms of a cough (dry or productive), with a variable degree of difficulty breathing and wheezing.
What clinical conditions should a clinician exclude in a patient presenting with acute bronchitis?
Sinusitis and upper respiratory tract infection
Acute sinusitis or rhinosinusitis (common cold) can result in a post-nasal drip, which runs down the back of the throat into the pharynx. The irritation of the pharynx results in a reactive cough. Direct irritation of the upper airways by an acute upper respiratory tract infection can also produce an acute cough. The presence of those diseases is suggested by the particular combination of symptoms. A common cold is diagnosed when patients present with an acute respiratory illness that is characterized by symptoms and signs related primarily to the nasal passages (rhinorrhea, sneezing, nasal obstruction, and postnasal drip), with or without fever, lacrimation, and throat irritation. Bacterial sinusitis is suspected when maxillary pain/toothache and a purulent nasal discharge accompany the rhinitis symptoms and post-nasal drip (see the sinusitis guidemap for further details). A cobblestone appearance of the pharynx may occur secondary to a chronic post-nasal drip, but this is a non-specific sign. If the patient reports having a post-nasal drip, and constantly has to clear his throat, and mucus is visible in the back of the throat, his treating physician may recommend symptomatic treatment (older generation H1 antihistamine +/- oral/nasal decongestant) for a suspected viral rhinosinusitis. If the cough does not resolve in one week, the treating physician may order sinus X-rays. If the X-rays are positive for sinusitis, he may empirically treat the patient with an antibiotic for 2-3 weeks to see if the cough resolves.
Enviromental irritants
Many volatile enviromental irritants can irritate the upper airways and bronchi if inhaled (irritative bronchitis), and produce an acute or persistent cough. Examples include chlorine gas from swimming pool chemicals, ammonia gas from household cleaning agents, and volatile industrial chemicals such as sulphur dioxide, hydrogen sulfide and organic solvent vapors (eg. lacquers, paint thinners). A singular clue that suggests occupational bronchitis is the presence of a cough during the working days of the week, and the absence of a cough during the weekend and vacation periods. Careful history-taking by a knowledgeable physician will usually uncover the causal agent.
Asthma
The breathing difficulty and wheezing found in acute bronchitis can mimic an asthma attack. However, the bronchial hyperresponsiveness of acute bronchitis only lasts a few weeks, while the breathing difficulty and wheezing due to untreated chronic asthma usually persists. The limited duration of bronchial hyperresponsiveness in acute bronchitis allows a physician to clinically differentiate chronic asthma from acute bronchitis, even if the diagnostic distinction between the two clinical entities is initially unclear. Certain asthmatic patients do not present with breathlessness and expiratory wheezing, and they only present with an unexplained persistent cough. This asthma variant is called cough-variant asthma. Cough variant asthma should be suspected if a coughing patient's cough is worse at night, or if the cough is precipitated by cold or exercise. The diagnosis of cough-variant asthma is generally reserved for patients with a persistent cough (>3 weeks duration), a lack of wheezing, and normal results on pulmonary function tests; but whose cough symptoms improve markedly with bronchodilator therapy and worsen in response to a methacholine challenge test (standard provocative test for asthma). Therefore, in the absence of severe airflow obstruction (difficulty breathing and wheezing), it is prudent for a treating physician to limit clinical evaluation for possible chronic asthma, or cough-variant asthma, to patients with a cough illness lasting longer than 3 weeks -- so as not to incorrectly classify acute bronchitis patients with prominent bronchial hyperresponsiveness as being chronic asthmatics. Interestingly, some physicians have speculated that recurrent attacks of acute bronchitis can predispose a patient to developing chronic asthma, but this speculative theory has never been proven. Nevertheless, chronic asthma should be strongly suspected if a patient frequently suffers from repetitive attacks of acute bronchitis.
Chronic bronchitis and other chronic cough illnesses
Most patients with acute bronchitis improve spontaneously in 7-21 days, and the definition of acute bronchitis generally implies an acute cough illness that lasts less than 21 days. The official definition of "chronic bronchitis" is a chronic cough illness that results in sputum production on most days for at least 3 months per year, for at least two consecutive years. Therefore, according to the official definition of chronic bronchitis, patients who have a prolonged acute bronchitis illness lasting longer than 21 days cannot accurately be described as having chronic bronchitis. They should be described as having a subacute cough illness (and not chronic bronchitis). A subacute cough illness lasts 3-8 weeks, while persistent coughing for longer than 8 weeks defines a chronic cough illness. Chronic bronchitis is usually caused by cigarette smoking and other air pollutants, and it is a chronic cough illness that occurs mainly in genetically susceptible people. Chronic cough illness can be due to a multitude of causes, and a physician should consider investigating a chronic cough illness lasting longer than 3-4 weeks. Multiple studies have shown that in approximately 95 percent of cases in immunocompetent patients, chronic cough illness results from a postnasal-drip syndrome related to conditions of the nose and sinuses, asthma, gastroesophageal reflux disease, chronic bronchitis due to cigarette smoking or other irritants, bronchiectasis, or the use of an angiotensin-converting-enzyme inhibitor drug. In the remaining 5 percent of cases, chronic cough illness is due to a variety of diseases, such as lung cancer, heart failure, and respiratory aspiration secondary to pharyngeal swallowing disorders.
For more detailed information on many common diseases that can present as a cough, read the excellent guideline "Managing Cough as a Defense Mechanism and as a Symptom", which can be freely accessed online by clicking here.
Pneumonia
Pneumonia is an infection of the alveolar tissue of the lung, usually due to a virus or bacterial infection. Like acute bronchitis, pneumonia can also present with difficulty breathing and a productive cough. The sputum may be mucopurulent or blood-tinged. Blood-tinged sputum can also occur in acute bronchitis if the bronchial inflammation is severe, and it is not possible to clearly differentiate acute bronchitis from pneumonia based on the color and nature of the sputum.
Although acute bronchitis can occasionally present with a moderate fever, it more commonly presents with no/mild fever. Also, although patients with acute bronchitis complain of difficulty breathing, they often do not appear overtly breathless at rest. The presence of a high fever and/or overt breathlessness at rest strongly suggests the possibility of pneumonia.
Pneumonia should be clinically suspected if:-
If pneumonia is clinically suspected, a chest X-ray should be performed. The clinical presence of pneumonia is suggested by specific abnormal chest X-ray findings. The presence of pneumonia usually warrants antibiotic therapy, because many cases of pneumonia are due to a primary bacterial or a secondary bacterial infection (secondary to an antecedent viral pneumonia). Because elderly patients may not manifest a high fever when developing pneumonia, a physician should have a much lower threshold for ordering a chest x-ray in elderly patients with an acute cough illness that is suggestive of a lower respiratory tract infection.
- abnormal vital signs (fever >38°C, or heart rate >100 beats/minute, or respiratory rate >24 breaths/minute, or low oxygen reading on pulse oximetry testing) are present
- focal clinical signs of pneumonia are detected by ausculating the lungs with a stethoscope
Pertussis (whooping cough)
Surprisingly, 10-20% of adult patients presenting with acute bronchitis have serological evidence of a recent pertussis infection. Pertussis is due to the Bordetella pertussis bacteria, and the layperson name for pertussis is "whooping cough". In non-vaccinated people, whooping cough presents with a triphasic illness. The first stage is the catarrhal stage. It resembles an acute uncomplicated viral upper respiratory infection and symptoms include nasal congestion, mucoid rhinorrhea, sneezing and a dry cough. Fever is absent or minimal. The second stage is the paroxysmal stage. It presents with intense, protracted bouts of coughing in severe paroxyms lasting up to several minutes. Patients often manifest gasping inspiration between coughing paroxyms, thus producing the characteristic whooping sound of whooping cough. Whooping is most frequently seen in older infants and young children. The coughing paroxyms are often provoked by feeding in young infants. Infants younger than 6 months of age may have episodic apneic spells (spells of not breathing), but they do not usually whoop because they apparently lack the strength to inspire so loudly. Post-tussive vomiting is common in young children. The third stage is called the convalescent stage. It manifests with a chronic cough that usually lasts for several additional weeks, so that the total duration of illness is typically 6 to 10 weeks in uncomplicated cases.
Most adults in the USA were vaccinated against pertussis during childhood and are variably protected against a pertussis infection. However, the protection wears off after 5-10 years, and a person may therefore get a pertussis infection if he is in close contact with a person with an active pertussis infection. Because he is partially protected as a result of previous pertussis vaccinations, the patient does not manifest the typical whooping cough syndrome. He usually presents with a non-specific cough illness, resembling acute bronchitis, that lasts longer than 3 weeks (usually 4-6 weeks). The only clue to the presence of a pertussis infection may be the fact that he was in recent contact with a person with a known pertussis infection (eg. during a local outbreak of the disease). It is difficult to definitively diagnosis a pertussis infection, because the special nasopharyngeal culture test that needs to be performed is often negative later in the illness (after the first week of coughing), and serological tests may be insensitive and not readily available. Virtually all diagnostic tests for pertussis do not provide an immediate answer, and empiric antibiotic treatment is usually based on the level of the treating physician's clinical suspicion of pertussis. A standard blood count may show an absolute lymphocytosis (proportionately increased number of lymphocyte blood cells), but that finding is non-specific and it is also seen in other conditions. Lymphocytosis is also rare in adults who were previously vaccinated against pertussis. Although it is often difficult to definitively diagnose a pertussis infection, it is very important to diagnose, and treat, pertussis to prevent spread of the infection from person-to-person. Secondary attack rates of pertussis among unvaccinated household contacts of an infected patient are often higher than 90%. An erythromicin-type antibiotic is usually prescribed for 14 days when pertussis is suspected. Although it may have no effect on the clinical course of the patient's cough illness if it is not precribed early (in the first week of the illness), it does make the patient non-contagious, so that he does not spread the infection to other people. That is critically important, because if a non-vaccinated person contracts pertussis from the infected patient, it can result in a serious life-threatening illness or death. Close household contacts of a suspected pertussis patient should also be treated with a 14-day course of erythromicin. Because a history of previous pertussis immunization does not guarantee current protection against infection and clinical illness, this antibiotic chemoprophylactic regimen is suggested for all close contacts of patients with pertussis, regardless of age or immunization status. In addition to antibiotic chemoprophylaxis, it is also recommended that close contacts, who are un-immunized or incompletely immunized against pertussis, should be re-vaccinated against pertussis.
Detailed information on pertussis can be found in this emedicine.com chapter
What diagnostic tests should be performed in a patient with suspected acute bronchitis?
Acute bronchitis is a clinical diagnosis, and there is no diagnostic test that can verify the diagnosis. Diagnostic testing is mainly useful in excluding other diseases, which can be confused with acute bronchitis.
Sputum gram stain for bacteria
Staining a sputum sample with special gram stain dyes allows for the detection of bacteria in the sputum sample. This diagnostic test has no value in acute bronchitis, because the only bacteria (mycoplasma, chlamydia) that infrequently cause acute bronchitis cannot be identified in a gram stain. Any bacteria present in the gram stain are likely to be resident bacteria commensals, which have no causal connection with the acute respiratory illness. A sputum gram stain may occasionally be useful in patients with pneumonia if it shows a "dominant" bacterial organism.
Diagnostic test for influenza virus
Although many viruses (influenzae A and B, parainfluenzae, respiratory syncitial, corona, adenovirus, rhinovirus) can cause acute bronchitis, the influenzae virus accounts for a high percentage of viral bronchitis cases during the local influenza outbreak season (early-mid winter). The importance of this etiological distinction is that while there is no effective therapy for most viruses causing acute bronchitis, specific antiviral therapy (a neuraminidase inhibitor) can shorten the duration of an influenza illness by 1-2 days if the antiviral treatment is administered in the early stages of the illness. However, the antiviral drug must be administered within 48 hours (preferably 30 hours) of the onset of the illness to be effective. Diagnostic testing for influenza is therefore warranted if clinical symptoms suggestive of influenza have not been present for longer than 48 hours. During a local outbreak of influenza, a strong clinical suspicion of influenza is accurate enough (>70% accurate) to warrant empiric treatment, and influenza diagnostic testing is not necessary -- neuraminidase inhibitor therapy can be empirically prescribed if the illness is < 48 hours old. The clinical diagnosis of influenza is strongly suggested by the clinical combination of a sudden high fever, prominent constitutional symptoms and a variable combination of upper respiratory tract or bronchitis symptoms -- when influenza is endemic in the local community.
Chest X-ray
A chest X-ray is usually normal in acute bronchitis and routine chest radiography is therefore not indicated. However, a chest X-ray is warranted if pneumonia is clinically suspected (see above), or if the patient has a history of underlying chronic lung disease, or if the cough lasts longer than 3-4 weeks (subacute cough illness). Although a post-nasal drip, asthma, and gastro-esophageal reflux account for >75% of chronic cough illness in adults, and although those three clinical conditions are usually associated with a negative chest X-ray, a chest X-ray may be abnormal in other clinical conditions (eg. bronchial foreign body, bronchiectasis, tuberculosis, lung cancer) that can produce a persistent cough.
Antibiotic therapy
Routine antibiotic treatment of acute bronchitis does not have a significant beneficial impact on the duration or severity of the illness, or on potential complications, such as the development of pneumonia. In fact, the duration of the cough symptom may only be decreased by one day, and patients do not get back to work sooner. Patients should therefore think of acute bronchitis as being a "chest cold", and they should expect to have a cough illness that lasts 7-14 days. The Centers for Disease Control and Prevention have undertaken the monumental task of educating physicians in the specialties of Pediatrics, Emergency Medicine, Family Practice, and Internal Medicine to not treat acute uncomplicated bronchitis with antibiotics, and their official guideline on the "Principles of Appropriate Antibiotic Use for Treatment of Acute Respiratory Tract Infections in Adults" can be freely accessed online by clicking here and their guideline "Principles of Appropriate Antibiotic Use for Treatment of Uncomplicated Acute Bronchitis: Background" can be freely accessed online by clicking here. I would recommend that all intelligent laypeople read those official guidelines if they seek detailed background information relating to this important issue.
Antibiotics are not routinely indicated in the treatment of acute bronchitis because 90% of cases are due to viral infections, which do not respond to antibiotic therapy. Bacteria (mycoplasma, chlamydia and pertussis) account for <10% of cases in healthy patients who have no history of underlying lung disease, and there is no definite evidence that antibiotic treatment significantly shortens the duration of the illness in those healthy patients. However, remember that antibiotic therapy is indicated for a pertussis infection if there is strong clinical suspicion of that disease (eg. acute bronchitis developing during a local outbreak of whooping cough, or if the patient presents with the characteristic, but infrequently heard whoop, or if post-tussive vomiting is a prominent symptom) -- to decrease shedding of the pathogen and subsequent spread of the disease. The situation of acute bronchitis due to mycoplasma and chlamydia organisms is extraordinarily complex. There are no readily available rapid diagnostic tests that can be used to diagnose the presence of those bacteria. Also, experts disagree on whether antibiotic therapy is clinically beneficial. Some experts think that acute bronchitis due to mycoplasma/chlamydia is a self-limiting illness and that antibiotic therapy is not warranted. Other experts think that untreated acute bronchitis due to mycoplasma results in recurrent wheezing episodes, and they recommend a 14 day course of erythromicin antibiotic if a mycoplasma infection is diagnosed. There is no evidence that bacteria -- Streptococcus pneumonia, Hemophilus influenzae, Moraxella catarrhalis -- that commonly cause bacterial sinusitis or otitis media, produce acute bronchitis in healthy patients who have no underlying lung disease. By contrast, those SP/HI/MC bacterial organisms do produce acute bronchitis flare-ups in patients with chronic obstructive lung disease (which includes the diagnostic entities of chronic bronchitis and emphysema), and appropriate antibiotic therapy is routinely indicated if chronic obstructive lung disease patients develop acute bronchitis. Antibiotic therapy may also be appropriate if the patient has underlying heart failure or other co-morbid immunodeficiency diseases (eg. diabetes mellitus, HIV infection). Some physicians empirically prescribe antibiotics if a patient's cough is persistent and lasts longer than 2 weeks. However, a persistent cough in a patient with acute bronchitis could merely be due to persistent bronchial hyperresponsiveness and it doesn't imply a bacterial infection.
Antibiotic therapy is indicated if a bacterial superinfection develops in a patient with acute bronchitis, and patients should therefore seek medical attention if they develop clinical symptoms suggestive of a bacterial superinfection -- high fever, and/or increasing shortness of breath, and/or blood-tinged sputum -- at any time during the course of their acute bronchitis illness.
Bronchodilators
Cough is the main symptom for which acute bronchitis patients seek relief, and bronchodilator therapy has been shown to reduce the severity and duration of the cough. Bronchodilator therapy is especially useful if a patient manifests bronchial hyperresponsiveness and presents clinically with wheezing and difficulty breathing, in addition to a cough. In adults, two puffs of an albuterol bronchodilator inhaler can be self-administered (preferably through an aerochamber device) every 4-6 hours for 1-2 weeks. Use of a metered-dose inhaler alone can sometimes provoke coughing, and a spacer or aerochamber is recommended. Children should use an age-appropriate dose of an oral, or inhalant bronchodilator.
Antitussive cough medication
Antitussive therapy is indicated when the cough serves no useful function such as clearing the airways of sputum. Specific antitussive therapy is directed at the cause of the cough, or the mechanism causing the cough eg. bronchodilators for the bronchial hyperresponsiveness of acute bronchitis, or decongestants and antihistamines if allergic rhinosinusitis results in a post-nasal drip. Non-specific antitussive therapy is directed at the symptom and not the cause or mechanism. The two non-specific antitussive medications used to suppress a cough include codeine and dextromethorphan. However, an acute cough due to colds or an upper respiratory tract infection does not necessarily respond well to codeine or dextromethorphan therapy. Those antitussive drugs appear to have a greater beneficial effect in patients with a chronic cough (> 3 weeks), or a cough associated with chronic lung disease. Even if those drugs only have a modest antitussive effect in acute bronchitis, they may be useful for a patient with a constant hacking cough that prevents sleep or precipitates recurrent vomiting. It is very important to appreciate the major disadvantage of attempting to suppress a productive cough -- if sputum is retained in the bronchial airways, it can cause mucus plugging of the smaller airways, and increase the likelihood of a secondary bronchopneumonia. Therefore, unnecessary use of antitussives should be actively discouraged if a patient has a cough that is productive of thick sputum. The patient should instead be advised to expectorate sputum as much as possible in order to keep the airways cleared of sputum. It is also questionable whether codeine and/or dextromethorphan antitussives are effective in children and the American Academy of Pediatrics does not recommend their use in pediatric acute bronchitis. Click here for free online access to the American Academy of Pediatrics' guideline on the "Use of Codeine- and Dextromethorphan-Containing Cough Remedies in Children".
Protussives
These drugs are used to enhance expectoration of sputum. Guaifenesin is the protussive drug that is most frequently used in an outpatient setting, and it is a mucolytic agent that reputedly decreases the viscosity of sputum. It is frequently prescribed for the treatment of acute bronchitis and it is a key component of many "over-the-counter" cough preparations. Although there is widespread disagreement on the true effectiveness of the drug in clinical practice, a patient can safely use the agent if it turns out to be clinically efffective. Unfortunately, guaifenesin is frequently combined with multiple other agents in "over-the-counter" cough medications, and those additional components may produce harmful side-effects that outweigh the limited benefit of guaifenesin. This piece of advice especially applies to children. Read this article "Toxicity of Over-the-Counter Cough and Cold Medications" if you want to appreciate the dangers associated with the use of over-the-counter cold and cough medications in children -- it is freely available online by clicking here. Therefore, if a patient decides to use guaifenesin, it should be used alone, and multiple-drug cough preparations containing guaifenesin should not be used..
Humidity and hydration
As a general principle, it is advantageous to ensure that the patient's room humidity is reasonably high, because inhalation of dry air can thicken bronchial secretions. A cool mist vaporiser may be particularly useful in dry climates. Adequate hydration is also recommended.
Commentary, criticism and controvery
Insightful questions and comments from readers will be included in this section.
Disclaimer: My medical guidemaps reflect my personal approach to clinical problems, and although my personal approach is primarily based on a thorough evaluation of the evidence-based medical literature, my personal approach should not be regarded as the "standard of care". My medical guidemaps should only be used if the reader-user has substantial reason to believe that the clinical advice contained in the guidemaps is valid and accurate. My medical guidemaps do not represent a personal medical service and they should not be used as a substitute for consulting a physician or other health-care provider. My medical guidemaps should be perceived as being an altruistic educational resource that is only applicable to medical practice in the USA and certain other countries.