Pneumonia is an acute infection of the lung parenchyma. Microorganisms reach the alveoli (usually by aspiration of oropharyngeal secretions or inhalation), overcome host defenses, and trigger inflammation. Alveoli fill with exudate, white cells, and fibrin (consolidation). Consolidated alveoli are perfused but not ventilated, creating an intrapulmonary shunt — hypoxemia may improve only partly with oxygen.

Classification by setting (guides likely organisms and antibiotics)

The older "healthcare-associated pneumonia" category is no longer used to choose antibiotics; individual risk factors for MRSA and Pseudomonas are assessed instead.

Risk factors: age 65 years or older, smoking, COPD and other chronic diseases, diabetes, alcohol use, immunosuppression, dysphagia and impaired consciousness (stroke, sedation, dementia), recent viral infection, immobility, and — in hospital — intubation, surgery, and poor oral hygiene.

Subjective

• Cough (productive in bacterial pneumonia; sputum may be rust-colored with pneumococcus), fever, chills
• Pleuritic chest pain (sharp, worse on inspiration)
• Dyspnea, fatigue, myalgia, anorexia

Objective

• Tachypnea, tachycardia, fever, low SpO₂
• Crackles, bronchial breath sounds over consolidation, diminished breath sounds
• Dullness to percussion, increased tactile fremitus, egophony
• Use of accessory muscles, splinting of the chest

Older adults may have few classic signs: new confusion or delirium, falls, loss of appetite, tachypnea, and normal or low temperature. A new change in mental status in an older adult should prompt assessment for pneumonia.

Severity tools

• CURB-65: Confusion; Urea > 7 mmol/L (BUN > 19 mg/dL); Respiratory rate ≥ 30/min; Blood pressure systolic < 90 or diastolic ≤ 60 mmHg; age ≥ 65 — 1 point each. Higher scores support hospital or ICU care
• The Pneumonia Severity Index (PSI) is also used to decide on site of care
• Severe CAP = 1 major criterion (septic shock requiring vasopressors, or respiratory failure requiring mechanical ventilation) or 3 or more minor criteria (e.g., respiratory rate ≥ 30, confusion, BUN ≥ 20 mg/dL (7.1 mmol/L urea), systolic BP < 90 needing aggressive fluids, multilobar infiltrates, PaO₂/FiO₂ ≤ 250)

Sepsis screening: the current definition (Sepsis-3, 2016) defines sepsis by infection-related organ dysfunction, measured as an acute rise in the SOFA score of 2 points or more; bedside qSOFA flags risk (respiratory rate ≥ 22, altered mentation, systolic BP ≤ 100 mmHg), but the Surviving Sepsis Campaign advises against qSOFA alone as a screening tool (prefer SIRS, NEWS, or MEWS). The historical 1992 SIRS definition required 2 or more of: temperature > 38 °C (100.4 °F) or < 36 °C (96.8 °F), heart rate > 90, respiratory rate > 20 or PaCO₂ < 32 mmHg, WBC > 12,000 or < 4,000/µL or > 10% bands. SIRS no longer defines sepsis but still appears in many screening tools; hypotension is not a SIRS criterion — it indicates shock.

Antibiotics — start promptly after cultures are obtained: within 1 hour for septic shock or probable sepsis; within 3 hours for possible sepsis without shock (Surviving Sepsis Campaign).

• Duration: the 2025 American Thoracic Society CAP guideline suggests fewer than 5 days (minimum 3 days) for non-severe CAP once the client is clinically stable, and 5 days or more for severe CAP
• Evaluate response at 48–72 hours — improving temperature, WBC, respiratory rate, oxygenation, and sputum. A chest X-ray may take weeks to clear and is not expected to normalize early
• Switch from IV to oral when clinically stable and able to swallow
• Systemic corticosteroids are suggested for hospitalized adults with severe CAP (not for influenza pneumonia) and are not recommended for non-severe CAP (2025 ATS)
• Healthy outpatients with non-severe CAP who test positive for a respiratory virus usually do not need empiric antibiotics (2025 ATS)
• Aspiration pneumonia: routine anaerobic coverage is not needed unless lung abscess or empyema is present
• Supportive: oxygen, fluids, antipyretics, nutrition; noninvasive or invasive ventilation for respiratory failure

Drug safety

Listed in priority order.

1. Airway and oxygenation
   • Monitor respiratory rate, work of breathing, SpO₂, mental status
   • Give oxygen as prescribed to the ordered target (commonly SpO₂ 92–96%; 88–92% for clients at risk of hypercapnia such as COPD). If a client with COPD has SpO₂ 88% with distress, continue the prescribed oxygen and notify the provider promptly — do not stop oxygen
   • Elevate the head of bed (semi- to high-Fowler's). With one-sided pneumonia, positioning with the good lung down improves ventilation–perfusion matching
2. Circulation and sepsis — monitor BP, heart rate, urine output, lactate; report hypotension, rising lactate, or confusion; give fluids as ordered
3. Obtain cultures, then give antibiotics without delay
4. Airway clearance
   • Coughing and deep breathing, incentive spirometry (10–15 breaths every 1–2 hours while awake, or as ordered), early mobilization
   • Fluids 2–3 L/day unless restricted (heart failure, kidney disease) to thin secretions
   • Chest physiotherapy if ordered: percuss with a cupped hand, avoid painful or pleuritic areas, do not perform right after meals, and have the client cough or be suctioned after drainage to remove the loosened secretions
   • Suction if unable to clear secretions
5. Comfort — antipyretics, analgesia for pleuritic pain (splint the chest with a pillow when coughing), oral care
6. Aspiration prevention — swallow screen before oral intake in at-risk clients; upright 90° for meals and for 30–60 minutes after; supervise eating; thickened liquids or modified diet as ordered
7. Nutrition — small frequent high-calorie, high-protein meals
8. Rest and activity — cluster care; progress activity as tolerated

Preventing hospital-acquired and ventilator-associated pneumonia

• Hand hygiene; head of bed 30–45 degrees for ventilated and tube-fed clients
• Regular oral care including toothbrushing
• Daily sedation interruption and spontaneous breathing trials; early mobility
• Subglottic secretion drainage endotracheal tubes where available; drain ventilator circuit condensate away from the client
• Incentive spirometry and early ambulation after surgery
• Prophylactic antibiotics are not used — they promote resistance

• Take all antibiotic doses for the full prescribed course, even when feeling better
• Rest, drink fluids, and increase activity gradually; fatigue may last several weeks
• Continue deep breathing and incentive spirometry at home as instructed
• Do not use over-the-counter cough suppressants for a productive cough without advice — coughing clears secretions
• Stop smoking; avoid secondhand smoke
• Vaccination: pneumococcal (in the US, recommended for all adults 50 years and older and for younger adults at risk), annual influenza, COVID-19, and RSV as recommended
• Hand hygiene and cough etiquette
• On fluoroquinolones: avoid sun exposure, report tendon pain or swelling immediately
• Return for worsening breathlessness, chest pain, confusion, fever persisting beyond 2–3 days of treatment, or inability to keep fluids or medicines down

• S. pneumoniae is the most common bacterial cause of CAP
• HAP = ≥ 48 hours after admission; VAP = ≥ 48 hours after intubation
• Classic findings: fever, productive cough, pleuritic pain, crackles, dullness, increased fremitus
• Older adults: confusion may be the first sign
• Cultures before antibiotics — but never delay antibiotics
• Evaluate treatment response at 48–72 hours; the X-ray lags behind clinical improvement
• Short antibiotic courses are now standard for non-severe CAP once stable
• Fluoroquinolones: tendon rupture and photosensitivity
• Unilateral pneumonia: good lung down
• VAP prevention: HOB 30–45°, oral care, sedation interruption, no prophylactic antibiotics
• Aspiration pneumonia classically affects the right lower lobe
• Rising PaCO₂ with falling pH = respiratory acidosis → ventilatory failure