Lower Respiratory Tract Infections

Study Notes

Acute bronchitis, bronchiolitis, chronic bronchitis, and pneumonia are types of lower respiratory tract infections.

A self-limited inflammation of the bronchi due to upper airway infection, most often viral.
Patients present with a cough lasting more than five days, typically one to three weeks.
Diagnosis is based on history and physical examination.
Empiric antibiotic therapy is not recommended, and 60-80% of patients are still given antibiotics unnecessarily.

Most often associated with respiratory viruses, including:
- Rhinovirus
- Coronavirus
- Parainfluenza
- Respiratory syncytial virus
- Influenza A and B
- Human metapneumovirus
Nonviral causes include:
- Bordetella pertussis
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae

Some viruses, like influenza, can invade the lower airway, while others, like rhinovirus, may trigger inflammatory mediators.
Exposure to cigarette smoke and air pollutants can increase attacks of acute bronchitis.

Caused by Bordetella pertussis and B. parapertussis
Incidence has increased worldwide over the past 15-20 years
Patients with partial immunity may have atypical cases resembling viral bronchitis
Patients with paroxysms of coughing and a cough of at least two weeks duration without an apparent cause may be tested for pertussis

Symptomatic and directed primarily at controlling cough
Medications include:
- Codeine and dextromethorphan
- Nonsteroidal anti-inflammatory drugs
- β2-adrenergic bronchodilators (for apparent bronchospastic component)
Antibiotics are not recommended, except for M. pneumoniae and C. pneumoniae, which may be treated with macrolide, tetracycline, or FQ
Influenza may be treated with neuraminidase inhibitors (oseltamivir or zanamivir) within 48 hours of symptom onset

Acute viral lower respiratory tract illness occurring during the first 2 years of life
Characterized by acute onset of wheezing and hyperinflation, commonly associated with cough, rhinorrhea, tachypnea, and respiratory distress
Respiratory syncytial virus (RSV) is the major pathogen, along with parainfluenza viruses, adenoviruses, rhinoviruses, and M. pneumoniae