Diagnostic criteria for bronchopulmonary infection
A set of syndromes helps recognize an active infectious process in the lungs:
- Systemic inflammatory: fever (ranging from subfebrile to high temperatures).
- Bronchial: new or worsening cough, production of purulent sputum.
- Physical: appearance of moist ringing rales. The ringing quality occurs because the infiltrated (consolidated) lung tissue conducts sound from the bronchi better.
- Laboratory: the hemogram shows leukocytosis (above 8.0×10⁹/L), a left shift in the leukocyte formula (increased neutrophil count), and an accelerated ESR.
- Radiological: on the radiograph, a focus of consolidation (infiltrate) is usually visualized on days 2–3 from the onset of the disease.
Classification of pneumonia
According to the extent of the lesion, pneumonias are divided into lobar (croupous), focal (bronchopneumonia involving segments), and interstitial (inflammation of connective tissue).
According to the conditions of occurrence (etiological approach), the following are distinguished:
- Nosocomial (hospital-acquired): symptoms appear 48 hours or more after hospitalization. A key risk factor is mechanical ventilation. Pathogens are gram-negative aerobes (Klebsiella, Pseudomonas aeruginosa). They are characterized by high mortality.
- Aspiration: caused by anaerobic flora, with a high tendency to form abscesses.
- In immunocompromised patients: provoked by opportunistic flora (Pneumocystis, Legionella, Aspergillus fungi).
Lobar (croupous) pneumonia
Lobar pneumonia is based on a hyperergic reaction of the body to the pathogen (most often pneumococcus). An entire lobe of the lung is affected, and the pleura is inevitably involved in the process (dry pleurisy).
Stages of pathogenesis and physical findings:
- Stage of engorgement (3–4 days): alveoli are filled with fibrinous exudate, but retain airiness. Percussion reveals shortened sound with a tympanic tint. Auscultation reveals weakened breathing and a specific phenomenon — initial crepitation (crepitatio indux).
- Red hepatization: erythrocytes predominate in the exudate.
- Gray hepatization: erythrocytes are replaced by neutrophils, which phagocytose bacteria. In the stage of hepatization (peak), percussion determines a dull sound, auscultation reveals bronchial breathing, and enhanced bronchophony.
- Stage of resolution: exudate is resorbed. Crepitation of resolution appears (crepitatio redux).
Clinical presentation: Acute onset, constant-type fever up to 39–40 °C (febris continua), shaking chills. “Rusty” sputum (due to admixture of fibrin and blood) and chest pain during breathing are characteristic. Herpes eruptions often appear on the affected side.
Focal and interstitial forms
Focal pneumonia (bronchopneumonia) mostly develops as a descending infection — a complication of ARVI against the background of chronic bronchitis or congestion in the lesser circulation. Inflammation involves the parenchyma and adjacent bronchi. The onset is gradual, fever is moderate. If the focus is located superficially, enhanced vocal fremitus and moist fine-bubbling ringing rales are detected. With a deep location of the focus, rales may be the only symptom.
Interstitial (atypical) pneumonia is localized in the connective tissue of the lung stroma. Pathogens are intracellular agents (Mycoplasma, Chlamydia, Legionella). It proceeds with mild symptoms: subfebrile temperature, dry cough, harsh breathing. The radiograph shows no typical dense infiltrate; only enhanced pulmonary markings and peribronchial infiltration are characteristic.
Principles of treatment and complications
Basic therapy includes etiotropic drugs (antibiotics), as well as expectorants and mucolytics. Until bacteriological culture results are obtained, empiric therapy is prescribed: penicillins for typical pneumonias (lobar, focal), and macrolides (e.g., azithromycin) for atypical ones.
In severe cases (especially in the elderly or individuals with cardiac pathology), strict hemodynamic monitoring is required. Life-threatening complications are possible: bacterial-toxic shock, acute respiratory failure, ARDS. Local unfavorable outcomes include carnification (replacement of tissue with a connective scar) and abscess formation.
Dynamics of sounds in lobar pneumonia (“C-B-C” rule): Crepitation (engorgement) → Bronchial breathing (hepatization) → Crepitation (resolution).
Class and exam questions
Why does sputum become “rusty” in lobar pneumonia?
In the stage of red hepatization, a large number of erythrocytes enter the lumen of the alveoli. They are destroyed, and hemoglobin breakdown products along with fibrin give the sputum a characteristic rusty tint.
What is the difference between crepitation and moist rales?
Crepitation occurs in the alveoli when they unstick at the height of inspiration (due to the presence of scant exudate). Moist rales form in the bronchi when air passes through liquid sputum.
Is it possible to diagnose atypical pneumonia by percussion alone?
No, because in interstitial lesions, the alveoli remain air-containing. Tissue consolidation, which produces a dull percussion sound, does not occur; the diagnosis relies on the clinical picture and radiography.
What else to study on this topic
- Features of nosocomial pneumonia pathogens (role of Klebsiella and Pseudomonas)
- Pathogenesis of collapse in the resolution stage of lobar pneumonia
- Iatrogenic and allergic lung lesions (“farmer's lung”)
- Development of acute respiratory failure and cor pulmonale
- Differential diagnosis of pneumonic infiltrate
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