PNEUMONIADr. Firoz A Hakkim

MBBS MDPULMONARY MEDICINE

• Pneumonia is an infection of the pulmonary parenchyma.

• caused by acute infection, usually bacterial, characterized by clinical and/or radiographic signs of consolidation of a part or parts of one or both lungs.

• ‘Lobar pneumonia’ is a radiological and pathological term referring to homogeneous consolidation of one or more lung lobes, often with associated pleural inflammation.

• Bronchopneumonia’ refers to more patchy alveolar consolidation associated with bronchial and bronchiolar inflammation, often affecting both lower lobes.

PATHOPHYSIOLOGY

• proliferation of microbial pathogens at the alveolar level and the host’s response to those pathogens.

• aspiration from the oropharynx

• Pathogens are inhaled as contaminated droplets.

• hematogenous spread (e.g., from tricuspid endocarditis) or by contiguous extension from an infected pleural or mediastinal space.

• Once engulfed, the pathogens—even if they are not killed by macrophages—are eliminated via either the mucociliary elevator or the lymphatics and no longer represent an infectious challenge.

• Only when the capacity of the alveolar macrophages to ingest or kill the microorganisms is exceeded does clinical pneumonia become manifest.

• Alveolar macrophages initiate the inflammatory response to bolster lower respiratory tract defenses.

• Inflammatory mediators released by macrophages and the newly recruited neutrophils create an alveolar capillary leak.

• The capillary leak results in a radiographic infiltrate and rales detectable on auscultation, and hypoxemia results from alveolar filling.

PATHOLOGY

• Edema• red hepatization• gray hepatization• resolution

• Edema- with the presence of a proteinaceous exudate - and often of bacteria—in the alveoli.

• This phase is rarely evident in clinical or autopsy specimens because it is so rapidly followed by a red hepatization phase.

• red hepatization - presence of erythrocytes in the cellular intraalveolar exudate gives this second stage its name, but neutrophils are also present and are important from the standpoint of host defense.

• Bacteria are occasionally seen in cultures of alveolar specimens collected during this phase.

• gray hepatization - no new erythrocytes are extravasating, and those already present have been lysed and degraded.

• The neutrophil is the predominant cell, fibrin deposition is abundant, and bacteria have disappeared.

• This phase corresponds with successful containment of the infection and improvement in gas exchange.

• Resolution - the macrophage is the dominant cell type in the alveolar space, and the debris of neutrophils, bacteria, and fibrin has been cleared, as has the inflammatory response.

COMMUNITY-ACQUIRED PNEUMONIA

• extensive list of potential etiologic agents in CAP includes bacteria, fungi, viruses, and protozoa.

• Clinical features – patient is frequently febrile, with a tachycardic response, and may have chills and/or sweats and cough that is either nonproductive or productive of mucoid, purulent, or blood-tinged sputum.

• Pleuritic chest pain, gastrointestinal symptoms• increased respiratory rate, use of accessory

muscles of respiration.

• Palpation may reveal increased or decreased tactile fremitus

• percussion note can vary from dull to flat, reflecting underlying consolidated lung and pleural fluid.

• Crackles, bronchial breath sounds, and possibly a pleural friction rub may be heard on auscultation.

Pa view

Lateral view

Management

• Oxygen should be administered to all patients with tachypnoea, hypoxaemia, hypotension or acidosis, with the aim of maintaining the PaO2 at or above 8 kPa (60 mmHg) or the SaO2 at or above 92%.

• Intravenous fluids – severe illness, older patients and those who are vomiting. Inotropic support may be required in patients with shock.

Discharge and follow-up

• depends on their home circumstances and the likelihood of complications.

• Clinical review should be arranged around 6 weeks later and a chest X-ray obtained if there are persistent symptoms, physical signs or reasons to suspect underlying malignancy.

Prevention

• Current smokers should be advised to stop.• Influenza and pneumococcal vaccination.

• Tackling malnourishment and indoor air pollution, and encouraging immunisation against measles, pertussis and Haemophilus influenzae type b are particularly important in children.

THANK YOU