Pneumonia

Pneumonia is a respiratory infection characterized by inflammation of the alveolar space and/or the interstitial tissue of the lungs. In industrialized nations, it is the leading infectious cause of death. Pneumonia is most commonly transmitted via aspiration of airborne pathogens (primarily bacteria, but also viruses and fungi) but may also result from the aspiration of stomach contents. The most likely causal pathogens can be narrowed down based on patient age, immune status, and where the infection was acquired (community-acquired or hospital-acquired). Pneumonia is classified based on clinical features as either typical or atypical; each type has its own spectrum of commonly associated pathogens. Typical pneumonia manifests with sudden onset of malaise, fever, and a productive cough. On auscultation, crackles and bronchial breath sounds are audible. Atypical pneumonia manifests with gradual onset of unproductive cough, dyspnea, and extrapulmonary manifestations. Auscultation is usually unremarkable. Some patients may present with elements of both types. Diagnostics include blood tests for inflammatory parameters and pathogen detection in blood, urine, or sputum samples. Chest x-ray in cases of typical pneumonia shows opacity restricted to one lobe, while x-ray in atypical pneumonia may show diffuse, often subtle infiltrates. Together with the characteristic clinical features, newly developed pulmonary infiltrate on chest x-ray confirms the diagnosis. Management consists of empiric antibiotic treatment and supportive measures (e.g., oxygen administration, antipyretics).

For specific information on the diagnosis and management of pneumonia in pediatric patients, see “Pneumonia in children.”

Pathogens

For atypical pneumonia bacterial causes, remember the mnemonic: Atypically, Legions of Clams Mind their P's and Q's!
• Legionella pneumophila
• Chlamydia pneumoniae
• Mycoplasma pneumoniae
• Psittacosis (Chlamydia psittaci)
• Q fever (Coxiella burnetii)

“Track my respiration: chlassic strep formation”: C. trachomatis, Mycoplasma, Respiratory syncytial virus, Chlamydia pneumoniae, and Streptococcus pneumoniae are the most common causative agents of pneumonia in children.

Risk factors ^[7]

• Old age and immobility of any cause
• Chronic diseases
  • Preexisting cardiopulmonary conditions (e.g., bronchial asthma, COPD, heart failure)
  • Acquired or congenital abnormalities of the airways (e.g., bronchiectasis, space-occupying lesions, cystic fibrosis)
• Immunosuppression
  • HIV infection
  • Diabetes mellitus
  • Cytostatic and immunosuppressive therapy
  • Alcoholism
  • Malnutrition
• Impaired airway protection
  • Alteration in consciousness (e.g., due to stroke, seizure, anesthesia, drugs, alcohol)
  • Dysphagia
  • Smoking
• Environmental factors
  • Crowded living conditions (e.g., prisons, homeless shelters)
  • Toxins (e.g., solvents, gasoline)
  • Endemic exposures (e.g., areas of high Coccidioides and Histoplasma endemicity)
  • Contaminated water systems (e.g., in hotels, on cruise ships)
  • Zoonotic exposures (e.g., birds, farm animals)
• Cryptogenic organizing pneumonia
  • Specific medications; (e.g., amiodarone, bleomycin) ^[8]
  • Chronic inflammatory disorders (e.g., rheumatoid arthritis)
• Surgical procedures
  • Upper abdominal surgery
  • Chest surgery

Bear in mind immune status and potential exposures when considering potential pathogens in patients with suspected pneumonia.

Consider aspiration pneumonia in patients with altered mental status or other risk factors for aspiration.

Pneumonia can be classified according to etiology, location acquired, clinical features, and the area of the lung affected by the pathology.

Etiology

• Primary pneumonia: no apparent preexisting conditions that may predispose to pneumonia
• Secondary pneumonia
  • Bronchial asthma, COPD, heart failure, cystic fibrosis
  • Viral upper respiratory tract infections with bacterial superinfection
  • Anatomical abnormalities such as tubercular caverns, bronchial tumors, or stenosis (postobstructive pneumonia) ^[9]
  • Aspiration pneumonia

Location acquired

• Community-acquired pneumonia (CAP): pneumonia that is acquired outside of a healthcare establishment
• Hospital-acquired pneumonia (HAP): pneumonia onset > 48 hours after a patient is admitted to a hospital without evidence of disease at the time of admission ^[10]
  • Ventilator-associated pneumonia (VAP): pneumonia occurring in patients who are on mechanical ventilation breathing machines in hospitals (typically in the intensive care unit)
• Healthcare-associated pneumonia (HCAP): A historical term for pneumonia acquired in healthcare facilities; this terminology is no longer in use.

Clinical features

• Typical pneumonia
  • Pneumonia featuring classic symptoms (typical findings on auscultation and percussion)
  • Manifests as lobar pneumonia or bronchopneumonia
• Atypical pneumonia
  • Pneumonia with less distinct classical symptoms and often unremarkable findings on auscultation and percussion
  • Manifests as interstitial pneumonia

Area of lung affected by the pathology

• Lobar pneumonia: pneumonia affecting one lobe of a lung
  • Multilobar pneumonia refers to the involvement of multiple lobes in a single lung or both lungs.
  • Panlobar pneumonia involves all the lobes of a single lung.
• Bronchial pneumonia: pneumonia affecting the tissue around the bronchi and/or bronchioles
• Interstitial pneumonia: pneumonia affecting the tissue between the alveoli
• Cryptogenic organizing pneumonia (formerly known as bronchiolitis obliterans organizing pneumonia): a noninfectious pneumonia of unknown etiology characterized by the involvement of the bronchioles, alveoli, and surrounding tissue

Routes of infection

• Most common: microaspiration (droplet infection) of airborne pathogens or oropharyngeal secretions
• Aspiration of gastric acid (aspiration pneumonitis) , food, or liquids
• Hematogenous dissemination (rare)

Pathogenesis

1. Failure of protective pulmonary mechanisms; (e.g., cough reflex, mucociliary clearance , alveolar macrophages )
2. Infiltration of the pulmonary parenchyma by the pathogen → interstitial and alveolar inflammation
3. Impaired alveolar ventilation → ventilation/perfusion (V/Q) mismatch with intrapulmonary shunting (right to left)
4. Hypoxia due to increased alveolar-arterial oxygen gradient
   • Hypoxia is worsened when the affected lung is in the dependent position, as perfusion to the dependent lung is better compared to the nondependent lung.
   • In the case of a large unilateral pulmonary abscess, it may be helpful to position the patient so that the affected lung is in the dependent position in order to prevent the pus from filling the unaffected lung.

Pattern of involvement

• Lobar pneumonia
  • Classic (typical) pneumonia of an entire lobe; primarily caused by pneumococci
  • Characterized by inflammatory intra-alveolar exudate, resulting in consolidation
  • Can involve the entire lobe or the whole lung

• Bronchopneumonia: mostly commonly a descending infection that affects the bronchioles and adjacent alveoli
  • Primarily caused by pneumococci and/or other streptococci
  • Characterized by acute inflammatory infiltrates that fill the bronchioles and the adjacent alveoli (patchy distribution)
  • Usually involves the lower lobes or right middle lobe and affects ≥ 1 lobe
  • Manifests as typical pneumonia
  • Necrotizing bronchopneumonia and pneumatocele are caused by Staphylococcus aureus and are often preceded by an influenza infection. ^[11]
• Interstitial pneumonia: interstitial inflammation, typically caused by Mycoplasma and viral infections
  • Characterized by a diffuse patchy inflammation that mainly involves the alveolar interstitial cells
  • Bilateral multifocal opacities are classically found on chest x-ray.
  • Manifests as atypical pneumonia
  • Often has an indolent course (walking pneumonia)
• Miliary pneumonia: multiple small infiltrations caused by hematogenous dissemination (e.g., of tuberculosis)
• Cryptogenic organizing pneumonia: characterized by inflammation of the bronchioles and surrounding structures

Typical pneumonia

Typical pneumonia is characterized by a sudden onset of symptoms caused by lobar infiltration.

• Severe malaise
• High fever and chills
• Productive cough with purulent sputum (yellow-greenish)
  • Crackles and bronchial breath sounds on auscultation
  • Decreased breath sounds
  • Enhanced bronchophony, egophony, and tactile fremitus
  • Dullness on percussion
• Tachypnea and dyspnea (nasal flaring, thoracic retractions)
• Pleuritic chest pain when breathing, often accompanying pleural effusion
• Pain that radiates to the abdomen and epigastric region (particularly in children; see also “Pneumonia in children”)

Suspect bacterial pneumonia in immunocompromised patients with acute high fever and pleural effusion.

Atypical pneumonia

Atypical pneumonia typically has an indolent course (slow onset) and commonly manifests with extrapulmonary symptoms.

• Nonproductive, dry cough
• Dyspnea
• Auscultation often unremarkable
• Common extrapulmonary features include fatigue, headaches, sore throat, myalgias, and malaise.

This classification does not have a major impact on patient management because it is not always possible to clearly distinguish between typical and atypical pneumonia.

General principles ^[12][13]

• Pneumonia diagnosis is based on new pulmonary infiltrates on chest imaging in patients with respiratory symptoms and systemic inflammatory response.
• The choice of microbiological studies is guided by a severity assessment for CAP or the presence of HAP or VAP.
• In ambulatory settings, normal vital signs and an unremarkable lung examination indicate a very low likelihood of CAP. ^[14][15]

Diagnosis of pneumonia can be challenging due to the lack of a gold-standard test and numerous mimics (e.g., COPD exacerbation, heart failure), especially when diagnostic testing is ambiguous. ^[13]

Diagnosis of CAP ^[12][13]

• New pulmonary infiltrate on chest imaging (e.g., CXR)
• AND ≥ 1 new or increased respiratory symptom: e.g., cough, sputum, dyspnea, or pleuritic pain
• AND ≥ 1 of the following:
  • Fever or hypothermia
  • Leukocytosis, bandemia, or leukopenia
  • Hypoxemia

Consider chest CT or empiric treatment when clinical suspicion for CAP remains high despite a negative CXR, as false negatives are possible. ^[16][17]

Laboratory studies

Routine studies

• CBC: leukocytosis
• ↑ CRP, ↑ ESR
• ↑ Serum procalcitonin (PCT): an acute phase reactant that can help diagnose bacterial lower respiratory tract infections ; ^[12][18]
  • Obtain for patients with IDSA/ATS criteria for severe CAP. ^[12][18]
  • Consider for patients with nonsevere CAP alongside viral diagnostics. ^[12][18]
  • PCT levels ≥ 0.25 mcg/L correlate with an increased probability of a bacterial infection.
  • Low PCT level after 2–3 days of antibiotic therapy can help facilitate the decision to discontinue antibiotics. ^[19][20]
    • Decrease of PCT to ≤ 80% of peak level
    • Decrease of PCT to < 0.25 mcg/L
• ABG: ↓ PaO₂ ^[21]
• BMP, LFTs

Do not rely solely on inflammatory markers (e.g., CRP, procalcitonin) to guide decisions on antibiotic therapy. ^[18][22]

Microbiological studies ^{[10][12][13][18]}

• Severe CAP ^[12][13]
  • Obtain the following in all patients:
    • Blood cultures (2 sets)
    • Sputum culture and Gram stain
    • Influenza and COVID-19 testing
    • Pneumococcal urinary antigen
    • Legionella pneumophila urinary antigen
  • Obtain a MRSA nasal swab for patients with:
    • Current empiric coverage for MRSA
    • History of parenteral antibiotics in a hospital setting within the past 90 days
    • History of MRSA colonization or infection in the past year
  • If available:
    • Obtain a bacterial molecular panel.
    • Consider obtaining an expanded viral molecular panel (e.g., RSV, rhinovirus, enterovirus) when it would alter management.
• Nonsevere CAP
  • Obtain the following during periods of community transmission or recent potential exposure (e.g., recent travel to areas with high transmission):
    • Influenza and COVID-19 testing
    • Legionella pneumophila urinary antigen
  • Obtain sputum culture and Gram stain for patients with:
    • History of parenteral antibiotics in a hospital setting within the past 90 days
    • Current empiric coverage for MRSA or P. aeruginosa
    • Structural lung disease
  • Obtain a MRSA nasal swab for patients with:
    • Current empirical coverage for MRSA
    • History of parenteral antibiotics in a hospital setting within the past 90 days
  • If available, consider the following when it would alter management:
    • Expanded viral molecular panel (e.g., RSV, rhinovirus, enterovirus)
    • Bacterial molecular panel
• HAP or VAP ^[10]
  • Obtain respiratory culture and Gram stain (noninvasive methods are preferred). ^[10]
  • Consider additional testing based on individual patient factors and severity.

Test for COVID-19 and influenza in all patients with possible CAP during periods of community transmission or if they are at high risk of exposure (e.g., recent travel to areas with high transmission). ^[12]

Avoid routine blood cultures and sputum Gram stain in patients with CAP, except when severe or there is concern for MRSA or Pseudomonas infection. ^[18]

Imaging

Chest x-ray (posteroanterior and lateral)

• Indications: all patients suspected of having pneumonia
• X-ray findings in pneumonia
  • Lobar pneumonia
    • Opacity of one or more pulmonary lobes
    • Presence of air bronchograms: appearance of translucent bronchi inside opaque areas of alveolar consolidation
  • Bronchopneumonia
    • Poorly defined patchy infiltrates scattered throughout the lungs
    • Presence of air bronchograms
  • Atypical or interstitial pneumonia
    • Diffuse reticular opacity
    • Absent (or minimal) consolidation
  • Parapneumonic effusion

A new pulmonary infiltrate on chest x-ray in a patient with classic signs and symptoms of pneumonia confirms the diagnosis.

Typical pneumonia usually appears as lobar pneumonia on x-ray, while atypical pneumonia tends to appear as interstitial pneumonia. However, the underlying pathogen cannot be conclusively identified based on imaging results alone.

Chest CT (usually without contrast)

• Indications
  • Inconclusive chest x-ray
  • Recurrent pneumonia
  • Poor response to treatment
• Advantages: more reliable evaluation of circumscribed opacities, pleural empyema, or sites of consolidation
• Findings: ^[23]
  • Localized areas of consolidation (hyperdense)
  • Air bronchograms
  • Ground-glass opacities
  • Pleural effusion/empyema
    • Hyperdense fluid collection
    • Split pleura sign
  • Nodules
    • Large (e.g., in tuberculosis or fungal pneumonia)
    • Peribronchial (e.g., bronchopneumonia)
    • Disseminated (e.g., septic emboli or varicella-zoster pneumonia)

CT is more sensitive and specific than CXR for the diagnosis of pneumonia.

Lung ultrasound in pneumonia

Point-of-care ultrasound of the lungs (lung POCUS) has high sensitivity and specificity for the diagnosis of pneumonia. ^[24][25]

• Indications
  • Evaluation of suspected pneumonia
  • Assessment of undifferentiated dyspnea ^[26]
• Characteristic findings ^[27][28]
  • Consolidation
  • Irregular and serrated lung margins
  • Air bronchograms
  • Unilateral B-lines
  • Pleural effusion

In the emergency department, consider POCUS to quickly confirm pneumonia and assess for other causes of dyspnea.

Advanced diagnostics for pneumonia

Bronchoscopy

• Indications
  • Suspected mass (e.g., recurrent pneumonia)
  • Need for pathohistological diagnosis (e.g., biopsy of a central mass discovered on CT)
  • Inconclusive results on CT
  • Poor response to treatment

Diagnostic thoracentesis

• Indications: consider if pleural effusion > 10 mm is present to evaluate for pleural empyema ^[21][29]
• Findings: See “Diagnostics” and “Parapneumonic effusion” in “Pleural effusion”.
• Consider therapeutic thoracentesis in large effusions (≥ half of the hemithorax) or if the effusion is suspected of causing dyspnea ^[29]
• Consider tube thoracostomy if pleural empyema (e.g., echogenic debris on lung ultrasound) or complicated effusion (e.g.,pH < 7.20, glucose < 60 mg/dL, LDH above three times the upper limit of serum LDH, positive culture) is suspected ^[29]

Criteria for hospitalization ^[18][22]

Every patient should be assessed individually; clinical judgment is the most important factor. The pneumonia severity index (PSI) and the CURB-65 score are tools that can help to determine whether to admit a patient.

• Pneumonia severity index (PSI/PORT score) ^[18][30]
  • Patients are assigned to one of five risk classes based on a more complex point system than in CURB-65.
  • Points are distributed based on patient age, comorbidities, and lab results.
• CURB-65 score ^[31]
  • Confusion (disorientation, impaired consciousness)
  • Serum Urea > 7 mmol/L or BUN > 20 mg/dL
  • Respiratory rate ≥ 30/min
  • Blood pressure: systolic BP ≤ 90 mm Hg or diastolic BP ≤ 60 mm Hg
  • Age ≥ 65 years
  • Interpretation
    • Each finding is assigned 1 point.
    • CURB-65 score 0 or 1: The patient may be treated as an outpatient.
    • CURB-65 score ≥ 2: Hospitalization is indicated.
    • CURB-65 score ≥ 3: Consider ICU level of care.
  • CRB-65 score (if serum urea is not known or unavailable)
    • CRB-65 score of 0: The patient may be treated as an outpatient.
    • CRB-65 score of ≥ 1: Hospitalization is recommended.

The CURB-65 score and PSI are tools for evaluating the risk of mortality. They have not been validated for determining the necessity for ICU admission.

Criteria for ICU admission (severe CAP) ^[18][22]

• The IDSA/ATS criteria for severe CAP can be used to triage patients with CAP and guide diagnostic testing and empiric antibiotic therapy decisions. ^[18]
• The decision of whether to admit a patient to the ICU should be based on clinical judgment.

Approach

• Evaluate all patients for hypoxemia and sepsis and manage as indicated.
• Determine the appropriate level of care using clinical judgment and prediction tools (e.g., PSI score and IDSA/ATS criteria for severe CAP).
• Begin empiric antibiotic therapy based on severity and patient risk factors (e.g., VAP vs. CAP).
• Consider antiviral therapy for influenza and COVID-19 as indicated.
• Glucocorticoids
  • Not routinely recommended as adjunct therapy for CAP ^[18][20]
  • Consider initiating hydrocortisone within 24 hours of diagnosis in patients being treated for severe CAP in the ICU. ^[32]
• Reevaluate therapy within 48 hours.

Consider deferral of antibiotic therapy in patients with a viral diagnosis and low probability of bacterial co-infection, e.g., PCT levels < 0.25 mcg/L ^[12][13]

Initial stabilization ^[20][33][34]

• Identification and management of sepsis
• Fluid resuscitation and management of septic shock as needed
• Respiratory support as needed
  • Supplemental oxygen for hypoxia
  • HFNC oxygen therapy_, NIPPV, or intubation for respiratory failure

Empiric antibiotic therapy for community-acquired pneumonia ^[12][13][18]

Outpatient

• Duration of treatment
  • 3 to 5 days of therapy is usually sufficient for CAP that is treated in the outpatient setting. ^[13][35]
  • Any patient being treated in a primary care setting should be re-examined after 48–72 hours to evaluate the efficacy of the prescribed antibiotic.
• Additional considerations: Knowing local resistance patterns of S. pneumoniae to macrolides is critical when deciding on an empiric antibiotic regimen.

Inpatient

• Duration of treatment
  • 5–7 days is usually sufficient.^[35]
  • Consider longer courses in patients with one of the following:
    • Not responding to treatment
    • Concern for MRSA or P. aeruginosa infection
    • Concurrent meningitis
    • Unusual pathogens (e.g., Burkholderia pseudomallei, fungal infection)
• Additional considerations
  • If aztreonam is used instead of a β-lactam antibiotic (e.g., for penicillin allergy), the addition of MSSA coverage (e.g., a fluoroquinolone) is necessary.
  • Anaerobic coverage is not routinely recommended for suspected aspiration pneumonia (unless lung abscess or empyema is suspected). ^[18]

If aztreonam is used as an alternative to other β-lactam antibiotics, additional coverage for MSSA must be included (e.g., a fluoroquinolone).

Empiric antibiotic therapy for hospital-acquired pneumonia ^[10]

• Duration of treatment
  • Empiric antibiotic therapy should be narrowed and/or de-escalated as soon as feasible.
  • Seven days of therapy are usually sufficient. ^[10]
• Additional considerations: Resistance patterns can vary widely; local antibiograms should be considered when starting empiric treatment.

Patients with structural lung disease and/or at high risk for mortality should receive double antipseudomonal coverage!

Empiric antibiotic therapy for ventilator-associated pneumonia ^[10]

• Recommended combination therapy
  • An antipneumococcal, antipseudomonal β-lactam
    • Aztreonam
    • Imipenem
    • Meropenem
    • Ceftazidime
    • Cefepime
    • Piperacillin-tazobactam
  • PLUS one of the following antibiotics with MRSA activity:
    • Vancomycin
    • Linezolid
  • PLUS one of the following:
    • A fluoroquinolone
      • Levofloxacin
      • Ciprofloxacin
    • An aminoglycoside
      • Amikacin
      • Gentamicin
      • Tobramycin
    • A polymyxin
      • Colistin
      • Polymyxin B
• Duration of treatment: Seven days of therapy are usually sufficient. ^[10]
• Additional considerations:
  • Risk factors for multi-drug resistant organisms (e.g., presence of structural lung disease, recent IV antibiotic therapy, local resistance patterns) should be considered when deciding on an empiric regimen
  • Empiric antibiotic therapy for ventilator-associated tracheobronchitis is not routinely recommended. ^[10]

Supportive therapy for pneumonia

• Sufficient rest (not absolute bed rest) and physical therapy
• Hydration with PO or IV fluids, supplemental oxygen as needed
• Incentive spirometer
• Antipyretics, analgesics as needed (e.g., acetaminophen )
• Expectorants and mucolytics ^[36]
• Antitussives (e.g., codeine )

• Calculate the PSI score to identify patients who would benefit from admission.
• Assess severity of CAP with the IDSA/ATS criteria for severe CAP.
• Order microbiological workup as indicated by patient severity and risk factors.
• Community-acquired pneumonia: Start empiric antibiotics for CAP.
• Consider hydrocortisone for patients being treated for severe CAP in the ICU.
• Hospital-acquired pneumonia: Start empiric antibiotics for HAP.
• Ventilator-associated pneumonia: Start empiric antibiotics for VAP.
• Evaluate and treat sepsis if present.
• Administer supplemental O₂ if patient is hypoxemic.
• Consider advanced diagnostic evaluation.
• Provide supportive care for pneumonia (e.g., antipyretics, IV fluids).
• Continuous pulse oximetry
• Trend inflammatory markers, procalcitonin.
• Narrow antibiotic therapy as soon as feasible.

Mycoplasma pneumonia ^[37]

• Epidemiology
  • One of the most common causes of atypical pneumonia
  • More common in school-aged children and adolescents
  • Outbreaks most commonly occur in schools, colleges, prisons, and military facilities.
• Clinical features
  • Generalized papular rash
  • Erythema multiforme
  • See “Atypical pneumonia”.
• Diagnostics
  • Subclinical hemolytic anemia: associated with elevated cold agglutinin titers (IgM)
  • Interstitial pneumonia; , often with a reticulonodular pattern on chest x-ray
  • Chest x-ray can show extensive pulmonary involvement in patients with mild pneumonia.
• Treatment
  • A macrolide, doxycycline, or fluoroquinolones
  • Beta-lactam antibiotics are not effective
  • See “Empiric antibiotics for CAP” for dosages and duration of treatment.

Other types of pathogen-specific pneumonia

• Legionnaire disease
• Pneumocystis pneumonia
• Pseudomonas aeruginosa: causes VAP
• Tuberculosis
• Primary influenza pneumonia
• Various viral infections (e.g., respiratory syncytial virus, hantavirus, adenovirus, CMV, SARS-CoV, SARS-CoV-2)
• Ornithosis

Definitions

• Aspiration
  • The inhalation of foreign material into the respiratory tract
  • Most commonly occurs after instrumentation of the upper airways or esophagus (e.g., upper GI endoscopy) or secondary to vomiting and regurgitation of gastric contents
• Aspiration pneumonia: a type of pneumonia that occurs as a result of oropharyngeal secretions and/or gastric contents aspiration
• Aspiration pneumonitis
  • Aspiration of gastric acid that initially causes tracheobronchitis, with rapid progression to chemical pneumonitis
  • May cause ARDS in extreme cases

Patients may develop aspiration pneumonitis without pneumonia, aspiration pneumonia without pneumonitis, or aspiration pneumonitis complicated by pneumonia. ^[38]

The risk of developing aspiration pneumonia and the severity of lung injury are directly related to the volume of aspirated material. ^[39][40]

Etiology

• Pathogens ^[18][38]
  • Gram-positive and gram-negative aerobic bacteria predominate in community-acquired infections (e.g., S. pneumonia, S. aureus, H. influenza, Enterobacteriaceae).
  • Gram-negative bacilli predominate in hospital-acquired infections (e.g., P. aeruginosa, Klebsiella spp.).
  • Mixed infections with anaerobic organisms; may occur (e.g., Fusobacterium, Peptostreptococcus, Bacteroides).
• Risk factors for aspiration (predispose individuals to reduced epiglottic gag reflex and dysphagia)
  • Altered consciousness: alcohol, sedation, general anesthesia, stroke
  • Apoplexy and neurodegenerative conditions
  • Gastroesophageal reflux disease, esophageal motility disorders
  • Congenital defects (e.g., tracheoesophageal fistula)
  • Use of a nasogastric feeding tube

Aspiration pneumonitis and pneumonia are unusual following aspiration of tube feeds or blood, which are typically high-pH and sterile. ^[38]

Clinical features ^[38][41]

• Aspiration pneumonitis
  • Immediate symptoms: bronchospasms , dyspnea, wheezing and/or crackles, hypoxemia
  • Late symptoms: fever, shortness of breath, cough
• Aspiration pneumonia
  • Immediate symptoms: often none
  • Late symptoms: fever, shortness of breath, cough with foul-smelling sputum

Diagnostics of pulmonary aspiration

Clinical diagnosis supported by characteristic laboratory and imaging findings

• Laboratory and microbiological studies: same as for the diagnosis of pneumonia.
• ABG: e.g., ↓ PaO₂
• Imaging: The lung region in which the infiltrates are seen depends on the patient's position on aspiration. ^[42][43]
  • Supine position: superior segment of the right lower lobe and posterior segment of the right upper lobe (most common sites of aspiration)
  • Standing/sitting: posterior basal segment of the right lower lobe
  • Right lateral decubitus position: posterior segment of the right upper lobe and right middle lobe
  • Left lateral decubitus: posterior segment of the left upper lobe and lingula

The initial CXR may be negative in early aspiration pneumonia. ^[38]

Treatment of pulmonary aspiration ^[38]

• Acute aspiration: airway management and respiratory support
  • Immediate oropharyngeal suctioning
  • Intubation if there is ongoing risk of aspiration (e.g., post-extubation, ↓ LOC)
  • O₂ therapy and inhaled bronchodilators as needed
• Aspiration pneumonitis: typically requires supportive care only
  • Antibiotics are usually not required ^[18]
  • Consider empiric antibiotics for patients with any of the following :
    • Respiratory failure or suspected septic shock
    • Acid suppression medications
    • Small bowel obstruction
• Aspiration pneumonia: antibiotic therapy following standard pneumonia treatment regimens
  • Choose agents based on site of acquisition, illness severity, and risk factors for resistant organisms (see “Empiric antibiotics for CAP“ and “Empiric antibiotics for HAP”).
  • Consider coverage for anaerobic bacteria (e.g., with ampicillin-sulbactam, moxifloxacin) in patients with severe periodontal disease, lung abscess, or empyema. ^[18][38][44]
• All patients: supportive care for pneumonia, monitoring, consider serial imaging.

Aspiration pneumonia requires antibiotic therapy while aspiration pneumonitis typically self-resolves within 24–48 hours with supportive care alone. ^[18][45]

Avoid routine anaerobic coverage for aspiration pneumonia without lung abscess, empyema, or severe periodontal disease. ^[44]

Complications

• Acute respiratory failure, acute respiratory distress syndrome (ARDS)
• Abscess

Prevention ^[38]

• Treatment of underlying causes to reduce the risk of aspiration
• NPO status prior to elective procedures with general anesthesia
• Formal swallowing evaluation when clinically appropriate
• Aspiration precautions for patients with risk factors for aspiration
  • Regular oral care
  • Elevation of the head of the bed
  • Dysphagia-modified diet
  • One-on-one observation with meals
  • Suctioning equipment at bedside

• Overview
  • CAP is responsible for approx. 5% of antepartum admissions for nonobstetric complications. ^[46]
  • Physiological changes during pregnancy (e.g., decreased functional residual capacity) may increase the risk for a severe disease course.
• Diagnostics: Pregnancy should not rule out chest x-ray, if indicated.
• Management
  • Outpatient management: only in patients with mild disease and no comorbidities, if optimal follow-up is feasible
  • Low threshold for hospital admission: The presence of comorbidities (e.g., asthma, immunologic disorders, renal disease) warrants inpatient management.
  • The approach to antibiotic therapy during pregnancy is the same as that for the general adult population, excluding potentially teratogenic medications, e.g.,:
    • Clarithromycin
    • Fluoroquinolones
    • Tetracyclines

• Parapneumonic pleuritis
  • Fibrinous pleuritis: inflammation → increased vessel permeability → fibrin-rich exudate deposited on the serosal surface of the pleura → pleuritic chest pain and friction rub
  • Analgesics can be used for the relief of symptoms.
• Parapneumonic pleural effusion (common)
• Pleural empyema
• Lung abscess
• ARDS
• Respiratory failure
• Sepsis

We list the most important complications. The selection is not exhaustive.

• Mortality increases with age.
• The mortality risk can be evaluated with the CURB-65 score. ^[47]
  • Score 0: ∼ 1%
  • Score 1–2: ∼ 10%
  • Score 3: ∼ 14%
  • Score 4: ∼ 40%
• HAP is associated with a mortality rate of > 20%.

• Immunization (see “ACIP immunization schedule” for information on doses and intervals)
  • Pneumococcal vaccination
  • Influenza vaccination
  • COVID-19 vaccination
• Smoking cessation
• Prevention of ventilator-associated infections

• One-Minute Telegram 108-2024-3/3: Confronting diagnostic discordance in pneumonia
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