Bronchitis, Asthma, EIB, and Influenza: Diagnosis & Treatment

Introduction to Respiratory Tract Infections

Respiratory tract infections are highly infectious diseases that involve the respiratory tract. They are divided into upper (URTI or URI) and lower respiratory tract infections (LRTI or LRI). LRIs include pneumonia, bronchitis, and influenza, and they tend to affect patients more seriously than URIs, which include the common cold, tonsillitis, sinusitis, and laryngitis. This paper examines four respiratory conditions — bronchitis, bronchial asthma, exercise-induced bronchospasm, and influenza — and explores their risk factors, etiology, pathology, differential diagnosis, and treatment. Most of these respiratory infections present with similar symptoms and can therefore be easily mistaken for one another, making it important to carefully examine the available evidence regarding each condition.

Bronchitis: Etiology, Pathology, and Treatment

Bronchitis is an inflammation of the bronchi, which are the main passages of air to the lungs. It may present as either an acute or a chronic inflammation and has a potential for recurring. Acute bronchitis usually follows a viral infection of the respiratory system. The first signs are that it affects the nose, throat, and sinuses before spreading to the lungs. Bronchitis may also lead to a secondary bacterial infection in the airways. The at-risk groups for bronchitis include smokers, people with lung and heart disease, the elderly, and young children. Chronic bronchitis, on the other hand, usually begins with a cough lasting several months accompanied by excessive production of mucus. Chronic bronchitis is one type of COPD (chronic obstructive pulmonary disease) (Salameh, Waked, Baldi, Brochard, & Saleh, 2006). It is worsened by allergies, air pollution, and occupational hazards such as coal mining, grain handling, textile manufacturing, and other respiratory infections.

Etiology

Acute bronchitis usually presents as a single isolated case or as a series of recurring illnesses. There is typically hypertrophy and hyperplasia of mucus-secreting cells in the bronchus, which characterizes chronic bronchitis as observed in rats exposed to a gaseous chemical irritant for 4–6 weeks (Melbostad, Wijnand, & Magnus, 1997). When bacteria colonize the bronchi, the bacteria implicated are normally normal flora of the nasopharynx region. Therefore, the use of antibiotics to treat bronchitis should be done carefully to avoid harming the normal flora bacteria (Gelb, Nix, & Gellman, 1998).

Pathology

The first changes to occur in patients with bronchitis include congestion and edema of the bronchial mucosa. At this stage, secretions are few and scanty, but they increase over time as mucus-producing cells and goblet cells become more active. These secretions become progressively more purulent depending on the degree and type of infection. Epithelial desquamation also takes place, and in more severe cases, necrotic changes are observed that extend down to the bronchioles, causing obstruction of the terminal air passages and resulting in patchy atelectasis due to associated inflammation of the alveoli (alveolitis). In many cases, there is complete recovery of the mucous membrane, but some episodes of acute bronchitis may heal by scarring, causing permanent damage to the mucosa and the related alveoli. This damage predisposes the patient to further attacks of acute bronchitis that may eventually become chronic (Toro et al., 1997).

Most cases of bronchitis result from an infection in the upper respiratory tract that then descends to the bronchi. Chemical or traumatic bronchitis arises from exposure to certain gases or vapors that irritate the bronchi, or from atmospheric pollutants that produce minor transient damage to the bronchial epithelium. This is accompanied by paralysis of ciliary action, which in turn permits bacterial infection from the upper respiratory tract (Toro et al., 1997).

Symptoms

Some symptoms of both acute and chronic bronchitis include discomfort in the chest, a cough that produces mucus, fatigue, fever, and shortness of breath that is worsened by exertion or mild activity, as well as wheezing. Additional symptoms of chronic bronchitis include ankle, foot, and leg swelling; frequent respiratory system infections; and blue-tinged lips due to low oxygen levels in the body. With acute bronchitis, even after the infection has cleared, patients often experience a dry, lingering cough that persists for several weeks (Toro et al., 1997).

Differential Diagnosis

The healthcare provider first listens to the patient's lungs using a stethoscope, checking for abnormal sounds called rales and any other signs of abnormal breathing, including wheezing. Other diagnostic tests include a chest X-ray, lung function tests, and sputum samples to check for bacterial infection or inflammation. Yellow-green mucus typically indicates a bacterial infection. A pulse oximetry test is conducted to determine blood oxygen levels — this test is quick, painless, and performed using a device placed on the patient's fingertip. An arterial blood gas test provides a more accurate measurement of both oxygen and carbon dioxide levels but requires a needle to be inserted into the patient's artery and is more painful (Toro et al., 1997).

It is important to exclude any primary precipitating disorder from the diagnosis of bronchitis. The buccal mucosa should be examined for the presence of Koplik's spots. In patients with mitral stenosis, acute bronchitis may be confused with the onset of left ventricular failure. In patients with chronic renal disease, bronchitis may be difficult to distinguish from early uraemia, but rapid response to antibiotics can help establish the difference. Failure to respond to antibiotics suggests a drug-resistant organism or a viral cause. Many asthmatic children may experience recurrent episodes of coughing and wheezing — even those without allergic tendencies — so bronchopulmonary changes due to mucoviscidosis must also be excluded (Toro et al., 1997).

Treatment

Since acute bronchitis is typically caused by a viral infection, antibiotics cannot be used to treat it. The infection usually resolves on its own within about one week. During recovery, patients should avoid smoking and exposure to secondhand smoke, drink plenty of fluids, and rest adequately. In the case of fever, aspirin or acetaminophen (Tylenol) may be taken. The patient should also be advised to use a humidifier to maintain room humidity (Toro et al., 1997).

For chronic bronchitis, antibiotic treatment should be started promptly, with the choice of antibiotic guided by the results of bacteriological examination of the patient's sputum. Options include penicillin, chloramphenicol, streptomycin, erythromycin, and tetracycline. Streptomycin should not be used unless tuberculosis has been excluded. Ampicillin and tetracycline are typically given in 500 mg doses three times daily for 5–6 days, followed by a maintenance dose of 500 mg twice daily for a further 7–10 days (Toro et al., 1997).