COMMUNITY ACQUIRED PNEUMONIA…..AN OVERVIEW DR E. A. ODEGHE

OUTLINE Introduction Aetiology Viral pneumonias Pathology Clinical features Examination findings Investigations Treatment Complications Poor prognostic factors Prevention

INTRODUCTION Definition: inflammation of the lung parenchyma, which is characterized by consolidation of the affected part and a filling of the alveolar air spaces with exudate, inflammatory cells, and fibrin Community acquired or Health care associated. Lobar /Focal/ nonsegmental pneumonia Multifocal/lobular (bronchopneumonia) Interstitial (focal diffuse) Important cause of morbidity and mortality worldwide. Usually acquired through inhalation or aspiration of pulmonary pathogenic organisms into a lung segment or lobe; less common is the haematogenous route

AETIOLOGY Typical or atypical organisms Typical organisms- commonest organisms are Strep. pneumoniae, H. influenzae, M. catarrhalis…account for approximately 85% of CAP cases. Less common… S. aureus, E.coli, K. pneumoniae, S. faecalis

AETIOLOGY… ATYPICAL ORGANISMS Most common…Legionella species, Mycoplasma pneumoniae, Chlamydophila spp. Less common… viruses (influenza virus, adenovirus, respiratory syncytial virus, human parainfluenza virus, measles, varicella zoster) mycobacteria, parasites

VIRAL PNEUMONIAS Can vary from a mild, self-limited illness to a life-threatening disease. The commonest causes are influenza virus, respiratory syncytial virus, adenovirus, and parainfluenza virus. Less common are varicella- zoster virus and measles virus. Routes include large-droplet spread over short distances, hand contact with contaminated skin and fomites with subsequent inoculation onto the nasal mucosa or conjunctiva, and small- particle aerosol spread

PATHOLOGY Pathogenesis of most viral pneumonias is not well known. After contamination, viruses multiply in the epithelium of the upper airway, destroy respiratory cilia, cause disruption of the respiratory epithelium, clearing the way for bacterial infection Severe pneumonias may result in extensive consolidation of the lungs They also generally cause impairment of T cells, macrophages, and neutrophil function and thus increase risk of bacterial super-infection

CLINICAL SYMPTOMS Incubation period depends on the specific virus. Symptoms: fever, chills, dry cough, rhinitis/rhinorrhoea, myalgias, headache, fatigue Travel history is important. With bacterial superinfection, symptoms last longer, cough becomes productive of sputum and the patients becomes more ill.

EXAMINATION FINDINGS Fever and/or chills Cough Tachypnoea and/or dyspnoea Tachycardia or bradycardia Wheezing/ Rhonchi Crepitations Dullness to percussion Decreased breath sounds Hypoxia

INVESTIGATIONS Full blood count: anaemia, leucocytosis (lymphocytosis or neutrophilia) Sputum for microscopy, culture, sensitivity Chest x-ray Rapid antigen detection on nasal swabs by ELISA and immunofluorescence Serologic tests Gene amplification by RT-PCR Blood culture Examination of bronchoalveolar lavage samples Viral culture of tissue from the respiratory tract, sputum, and samples obtained by nasopharyngeal washing, bronchoalveolar lavage Lung biopsy for histopathologic studies and viral culture

TREATMENT General measures – Oxygen, bed rest, antipyretics, analgesics, fluids, respiratory isolation Specific measures – mechanical ventilation if respiratory failure is present or impending, antibiotics (if infiltrate is seen on the chest radiograph )

ANTIVIRAL AGENTS Acyclovir for varicella or herpes pneumonia Respiratory syncythial virus – ribavirin, immunoglobulin only for severe disease Adenovirus – cidofovir Parainfluenza virus – ribavirin Influenza virus – Acyclovir, Oseltamivir, Zanamir

COMPLICATIONS Complications of CAP include empyema, cavitation, precipitation of myocardial infarction or heart failure and overwhelming pneumococcal sepsis in asplenic/hyposplenic patients. Viral pneumonias…Secondary bacterial infections, encephalitis, hepatitis

POOR PROGNOSTIC FACTORS Significant co-morbidity eg cardioresp disease Increased respiratory rate Hypotension Fever Anaemia Hypoxia Multilobar involvement Immunosuppression eg asplenia/hyposlenia Elderly patients Virulent organisms.

PREVENTION INF…vaccination; zanamivir, oseltamivir, amantadine RSV…RSV immunoglobulin, Palivizumab Measles…intravenous Ig VZV… VZV Ig