Pneumonia

Aka: Pneumonia, Bacterial Pneumonia, Atypical Pneumonia, Community-Acquired Pneumonia, Community Acquired Pneumonia

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II. Definitions

  1. Community Acquired Pneumonia (CAP)
    1. Lower respiratory tract infection
    2. Develops in non-hospitalized patient
    3. May be Bacterial, viral, fungal or parasitic
    4. May be present despite normal Chest XRay

III. Epidemiology: Community Acquired Pneumonia

  1. Incidence: 9.2 to 33 per 1000 person-years in U.S.
    1. All Adults: 248 cases per 100,000/year
    2. Adults 65 to 79 years: 634 cases per 100,000/year
    3. Adults >80 years: 16,430 cases per 100,000/year
  2. Most severe adult cases are in older adults over age 65 years
    1. Hospitalization rate 1,830 per 100,000/year in age over 65 years (contrast with 199 for under age 65 years)
  3. Adult mortality: 60,000 deaths per year from Pneumonia or Influenza (8th leading cause of death)
    1. Overall CAP Mortality 6% at 30 days (even with initial improvement)
    2. CAP Mortality 34% at 30 days for those who fail to initially improve or have unresolved Pneumonia
  4. U.S. cost/year for Community Acquired Pneumonia: $10-17 billion (90% of cost is inpatient care)

IV. Causes: Community Acquired Pneumonia

  1. See Pneumonia Causes
  2. Bacteria: Typical
    1. Streptococcus Pneumoniae (common)
    2. HaemophilusInfluenzae (common)
    3. Staphylococcus aureus
    4. Moraxella catarrhalis
  3. Bacteria: Atypical (named for their failure to be identified on Gram Stain)
    1. Mycoplasma pneumoniae (common, annual Incidence varies in cycles)
    2. Legionella pneumonia (3% of hospitalized CAP)
    3. Chlamydia Pneumonia
    4. Q Fever
    5. Psittacosis
  4. Virus
    1. Covid19 (SARS-CoV-2)
    2. Adenovirus
    3. Influenza A and B
    4. Rhinovirus
    5. Parainfluenza
    6. Respiratory Syncytial Virus
  5. Fungus
    1. Blastomycosis
    2. Coccidioidomycosis
    3. Histoplasmosis

V. Risk Factors

  1. Age over 65 years
  2. Recent Antibiotics
  3. Immune compromised (e.g. HIV Infection)
  4. Respiratory illness (COPD, Asthma)
  5. Vascular disease (CHF, CVA)
  6. Diabetes Mellitus
  7. Chronic Liver Disease
  8. Chronic Kidney Disease
  9. Cancer

VI. Findings: Signs and Symptoms

  1. Bacterial Pneumonia
    1. Cough
      1. Productive of Purulent Sputum with typical Bacteria
      2. Non-productive in atypical cases
    2. Sudden onset
    3. Fever and Chills
    4. Fatigue
    5. Ill appearing patient
    6. Pleuritic Chest Pain
    7. Dyspnea
    8. Tachypnea
    9. Tachycardia
  2. Viral Pneumonia
    1. Non-productive cough
    2. Gradual Onset with prodrome (malaise and Headache)
    3. Chest XRay more impressive than exam
    4. Onset in fall or winter
    5. Wheezing more common in viral causes
    6. Low grade Temperature (<101.3 F)
  3. Mycoplasma pneumonia
    1. Constant, harsh, non-productive cough
    2. Wheezing may occur in Mycoplasma pneumonia
    3. Fever typically lasts longer than 3 days
    4. More common in age over 3 years
  4. Legionella
    1. Onset with myalgias and Headache
    2. Fever to 104 F for first few days
    3. Gastrointestinal symptoms predominate in up to 40%
    4. Cough is late onset, mild, often non-productive

VII. Signs

  1. General findings
    1. Measured Fever
      1. Positive Likelihood Ratio: 2.1
      2. Negative Likelihood Ratio: 0.71
    2. Ill appearing patient
    3. Dyspnea
    4. Tachypnea
    5. Tachycardia
    6. Hypoxia (check Oxygen Saturation)
  2. Localized findings at involved lung region
    1. Egophony
      1. Positive Likelihood Ratio: 8.6
      2. Negative Likelihood Ratio: 0.96
    2. Dullness to percussion
      1. Positive Likelihood Ratio: 4.3
      2. Negative Likelihood Ratio: 0.79
    3. Rales
    4. Diminished breath sounds
    5. Bronchial breath sounds
    6. Tactile fremitus
  3. References
    1. Metlay (1997) JAMA 278(17): 1440-5 [PubMed]

VIII. Diagnosis: General

  1. See Diehr Rule to Diagnose Pneumonia
  2. Normal Vital Signs and Lung Exam in primary care reduces likelihood of Pneumonia to <0.4%
    1. Criteria: Normal Body Temperature, Respiratory Rate, Heart Rate and Lung Exam
    2. Community Acquired Pneumonia Likelihood reduced to<0.4% if criteria met
    3. Marchello (2019) J Am Board Fam Med 32(2): 234-47 [PubMed]
  3. Findings with highest Test Sensitivity for Pneumonia
    1. Fever and chills
    2. Pleuritic Chest Pain
    3. Cough productive of mucopurulent Sputum
    4. Dyspnea
    5. Tachypnea (especially in over age 65 years)
  4. Findings with highest Specificity
    1. Asymmetric breath sounds
    2. Pleural rubs
    3. Egophony
    4. Increased tactile fremitus

IX. Diagnosis: IDSA Pneumonia Criteria

  1. Major Criteria
    1. Septic Shock and need for Vasopressors
    2. Respiratory Failure requiring Mechanical Ventilation
    3. Leukopenia (WBC <4000 cells/ul) without other known cause
      1. Fore example, not due to Chemotherapy or underlying condition
  2. Minor Criteria
    1. Respiratory Rate >30 breaths per minute
    2. PaO2/FIO2 Ratio <250
    3. Multilobar infiltrates
    4. Confusion or Disorientation
    5. Blood Urea Nitrogen or BUN > 20 mg/dl (Uremia)
    6. Thrombocytopenia (Platelet Count <1000,000 cells/ul)
    7. Hypothermia (core Temperature <36.8 C)
    8. Hypotension (requiring aggressive fluid Resuscitation)
  3. Interpretation
    1. Pneumonia diagnosis positive if 1 major criteria or 3 minor criteria

X. Labs

  1. General
    1. Consider specific testing based on risks
      1. See Pneumonia Causes (as well as indications below)
    2. Lab Indications
      1. Moderate or severe Community Acquired Pneumonia
      2. Patient with comorbid conditions
    3. Efficacy of Labs
      1. No value in non-severe Community Acquired Pneumonia
      2. Theerthakarai (2001) Chest 119:181-4 [PubMed]
  2. Sputum Gram Stain and Culture
    1. See Sputum Culture
    2. Adequacy
      1. Good quality sample: <25 epithelial cells/LPF and contains Neutrophils
    3. Indications (IDSA/ATA 2019)
      1. Severe Pneumonia including ICU Admission (consider endotracheal aspirate if intubated)
      2. High risk for MRSA or Pseudomonas aeruginosa infection
      3. Hospitalized and received ParenteralAntibiotics in the last 90 days
      4. Older guideline indications in which Gram Stain and culture may still be indicated
        1. Cavitary infiltrates (obtain specific fungal and Tuberculosis cultures)
    4. Efficacy
      1. Sputum has low diagnostic yield in Community Acquired Pneumonia
        1. Not recommended in outpatient Community Acquired Pneumonia
        2. Ewig (2002) Chest 121:1486-92 [PubMed]
  3. Blood Culture
    1. Indications (IDSA/ATA 2019)
      1. Severe Pneumonia including ICU Admission (highest yield in severe Pneumonia)
      2. High risk for MRSA or Pseudomonas aeruginosa infection
    2. Efficacy
      1. Low sensitivity: Positive in only 5-10% of cases
      2. Does not predict severity or outcome
    3. References
      1. Campbell (2003) Chest 123:1142-50 [PubMed]
  4. Specific Testing with reasonable efficacy
    1. Covid19 PCR
      1. From March 2020 to at least June 2022 is typically obtained on most U.S. hospital admissions
    2. Influenza
      1. Rapid Influenza Test (Influenza DFA)
      2. Obtain in all Community Acquired Pneumonia cases during Influenza season
        1. Treat positive Influenza cases regardless of duration (i.e. even if >48-72 hours)
    3. Legionella pneumophila
      1. Rapid PCR of Sputum (80% Test Sensitivity)
      2. Urinary Antigen
        1. Test Sensitivity 70-90% (for serogroup 1, responsible for >80% of cases)
        2. Test Specificity 99%
      3. Indications (Legionella UAT per IDSA/ATS 2019)
        1. Severe Community Acquired Pneumonia including Intensive Care unit admission
        2. High risk for Legionella infection (e.g. Legionella outbreak)
    4. Mycoplasma pneumoniae
      1. Rapid PCR of Sputum (>30% Test Sensitivity)
    5. Chlamydia Pneumonia
      1. Rapid PCR (>30% Test Sensitivity)
    6. Streptococcus Pneumoniae (Pneumococcus)
      1. Pneumococcal Urine Antigen Test (UAT)
        1. Test Sensitivity 60-80%
        2. Test Specificity >90%
      2. Indications (Pneumococcal UAT per IDSA/ATS 2007)
        1. Intensive Care unit admission
        2. Failed outpatient Antibiotic therapy
        3. Active Alcohol Abuse
        4. Chronic severe liver disease
        5. Leukopenia
        6. Asplenia
        7. Pleural Effusion
    7. Methicillin Resistant Staphylococcus Aureus (MRSA) Nasal Swab
      1. Indications include recent hospitalization with use of ParenteralAntibiotics
      2. See Methicillin Resistant Staphylococcus Aureus (MRSA) for risk factors
    8. Pseudomonas microbiologic screening
      1. Indications include recent hospitalization with use of ParenteralAntibiotics
      2. See Ventilator-Associated Pneumonia
  5. Other Testing
    1. Low Procalcitonin does not exclude Pneumonia
      1. Antibiotics should not be witheld based on low Procalcitonin alone
      2. IDSA does not recommend the use of Procalcitonin in Community Acquired Pneumonia
      3. Montassier (2019) Ann Emerg Med 74(4): 580-91 [PubMed]
  6. Thoracentesis with fluid analysis
    1. Indicated for Pleural Effusion >5 cm
    2. Send for Gram Stain, aerobic and anaerobic culture
  7. Fungal and TB Culture
    1. Cavitary lesions
    2. Foreign travel or immigration
  8. References
    1. Mandell (2007) Clin Infect Dis 44:S27–72 [PubMed]

XI. Imaging: Chest XRay

  1. Precautions: Underlying malignancy
    1. Confirm infiltrate resolution at 6 weeks after management (especially in smokers, or those over age 50)
  2. Precautions: Low Test Sensitivity in Pneumonia (esp. in early presentation)
    1. Chest XRay Test Sensitivity 43% (Test Specificity 93%) for pulmonary opacities consistent with Pneumonia
      1. Compared with CT Chest as the gold standard
    2. False Negatives are more common in early presentation
      1. However, Pneumonia is a clinical diagnosis, and may be diagnosed despite negative Chest XRay
    3. Serial Chest XRays may be needed, or consider bedside Lung Ultrasound or CT
      1. Repeat XRay during hospital admission is not needed if patient is clinically improving on management
    4. Negative Chest XRay does not exclude Pneumonia in severe illness
      1. Positive in only 40% of acute pneumococcal Community Acquired Pneumonia (CAP)
      2. Treat empirically as Community Acquired Pneumonia if high suspicion despite negative XRay
  3. Indications: All cases of suspected Community Acquired Pneumonia
    1. Any patient with at least 1 of the following
      1. Temperature >100 F (37.8 C)
      2. Heart Rate >100 beats/min
      3. Respiratory Rate >20 breaths/min
    2. Any patient with at least 2 of the following
      1. Decreased breath sounds
      2. Rales or crackles
      3. No Asthma history to explain findings
    3. Other indications (not included in Ebell protocol)
      1. Hypoxemia
      2. Confusion
      3. Known structural lung disease
      4. Age > 60 years old
      5. Systemic illness signs
    4. Ebell (2007) Am Fam Physician 76(4): 560-2 [PubMed]
  4. Causes: False Positives - alternative causes of infiltrates
    1. Atelectasis
    2. Acute Respiratory Distress Syndrome (ARDS)
    3. Lung Neoplasm
    4. Diffuse Alveolar Hemorrhage (e.g. immune disorder)
    5. Pulmonary Embolism with Lung Infarction
    6. Right-sided endocarditis with septic emboli
    7. Tuberculosis
    8. Interstitial Lung Disease (e.g. acute Chlorine gas inhalation, Farmer's Lung)
  5. Causes: Pneumonia with effusion (and other non-infectious effusions)
    1. Pneumococcal Pneumonia (most common)
    2. Staphylococcal Pneumonia
    3. Haemophilus Influenzae Pneumonia
    4. Legionella
    5. Tuberculosis (especially consider in comorbid HIV Infection)
    6. Predominately left-sided effusions (e.g. Aortic Dissection, Esophageal Rupture)
    7. Predominately right-sided effusions (e.g. CHF, Pancreatitis, hepatitis)
  6. Causes: Lung Cavitary Lesions
    1. Lung Abscess caused by Anaerobic Bacteria (most common)
    2. Staphylococcal Pneumonia
    3. Pseudomonas Pneumonia
    4. Tuberculosis
  7. Interpretation
    1. Lobar infiltrate suggests typical Bacterial Community Acquired Pneumonia (CAP)
    2. Diffuse, bilateral infiltrates suggests atypical Community Acquired Pneumonia (CAP)
  8. References
    1. Swadron (2019) Pulmonary 1, CCME Emergency Board Review, accessed 5/29/2019

XII. Imaging: Advanced

  1. CT Chest
    1. CT Chest is considered gold standard and frequently identifies Pneumonia not seen on Chest XRay
    2. CT Chest identifies more than twice as my Pneumonia cases not visualized on Chest XRay
    3. CT Chest excludes Pneumonia in False Positive Pneumonia cases based on Chest XRay
    4. Self (2013) Am J Emerg Med 31(2): 401–405. [PubMed]
  2. Lung Ultrasound
    1. May be more accurate than Chest XRay in the diagnosis of Pneumonia
    2. Findings consistent with Pneumonia
      1. Localized B-Line artifacts (Interstitial Edema)
      2. Localized liver-like appearance of lung (consolidation)
    3. Also defines other respiratory conditions at the bedside (e.g. Pneumothorax, Pleural Effusion)
    4. Test Sensitivity: 94 to 95%
    5. Test Specificity: 90 to 96%
    6. Chavez (2014) Respir Res 15:50 [PubMed]
    7. Ye (2015) PLoS One 10(6): e0130066 [PubMed]

XIII. Differential Diagnosis

  1. See Pneumonia Causes
  2. See Cough Causes
  3. Common and Important Alternative Diagnoses
    1. Asthma Exacerbation
    2. Acute Exacerbation of Chronic Bronchitis or COPD
    3. Congestive Heart Failure
    4. Gastroesophageal Reflux
    5. Pulmonary Embolism
    6. Acute Respiratory Distress Syndrome
    7. Severe Acute Respiratory Syndrome (SARS)
  4. Uncommon Alternative Diagnoses
    1. Churg-Strauss Syndrome
    2. Inflammatory Lung Disease
    3. Idiopathic Pulmonary Fibrosis
    4. Interstitial pneumonitis
    5. Lung Cancer
    6. Sarcoidosis
    7. Granulomatosis with Polyangiitis (previously known as Wegener's Granulomatosis)
    8. Bronchiolitis Obliterans with Organizing Pneumonia
  5. Bioterrorism Agents
    1. Anthrax
    2. Plague
    3. Tularemia
    4. Q Fever
    5. Brucellosis

XIV. Management

  1. See Pneumonia Management
  2. See Pneumonia in the Elderly
  3. See Pneumonia in Children
  4. See Pneumonia Accelerated Diagnostic Protocol
  5. See Community Acquired Pneumonia Refractory to Standard Management
  6. See Pneumonia Hospitalization Criteria
  7. See Pneumonia Hospitalization Criteria in the Elderly
  8. See Severe Community Acquired Pneumonia Criteria
  9. See Mortality Prediction Tool for Patients with Community Acquired Pneumonia (CURB-65)
  10. See Pneumonia IRVS Prediction Tool (SMART-COP)
  11. See Hospital Acquired Pneumonia
  12. See Ventilator Associated Pneumonia

XV. Complications

  1. Pulmonary
    1. Parapneumonic Effusion or empyema
    2. Pneumothorax
    3. Lung Abscess
    4. Bronchopleural Fistula
    5. Necrotizing Pneumonia
    6. Acute Respiratory Failure
  2. Metastatic spread
    1. Meningitis or CNS Abscess
    2. Pericarditis or endocarditis
    3. Osteomyelitis or Septic Arthritis
  3. Systemic
    1. Sepsis or SIRS
    2. Hemolytic Uremic Syndrome
  4. References
    1. Bradley (2011) Clin Infect Dis 53(7): e1-52 [PubMed]

XVI. Prognosis: Predictors of increased mortality

  1. See Pneumonia Prognostic Factors in Older Patients
  2. See Mortality Prediction Tool for Patients with Community Acquired Pneumonia (CURB-65)
  3. See Pneumonia Severity Index
  4. Comorbid neurologic disease
  5. Renal disease
  6. Congestive Heart Failure
  7. Hypotension
  8. Tachypnea
  9. Hypothermia
  10. Hypoglycemia (Serum Glucose <70mg/dl on presentation)

XVII. Prevention

  1. See Pneumonia Prevention in the Elderly
  2. See Influenza Vaccine
  3. See Pneumococcal Vaccine (Pneumovax 23)
  4. See Pneumococcal Conjugate Vaccine (Prevnar 13)

XVIII. References

  1. Morris adn Eyre (2022) Crit Dec Emerg Med 36(9): 14-5
  2. Bernstein (1999) Chest 115:9S-13S [PubMed]
  3. Cunha (2001) Med Clin North Am 85(1):43-77 [PubMed]
  4. Fine (1997) N Engl J Med 336:243-50 [PubMed]
  5. Fine (1990) Am J Med 89:713-21 [PubMed]
  6. Gleason (1997) JAMA 278:32-9 [PubMed]
  7. Jain (2015) N Engl J Med 373(5): 415-27 [PubMed]
  8. Kaysin (2016) Am Fam Physician 94(9); 698-706 [PubMed]
  9. Lim (2009) Thorax 64(suppl 3):1-55 [PubMed]
  10. Lutfiyya (2006) Am Fam Physician 73:442-50 [PubMed]
  11. Marrie (2000) Clin Infect Dis 31(4):1066-78 [PubMed]
  12. Metlay (2019) Am J Respir Crit Care Med 200(7):e45-67 +PMID:P 31573350 [PubMed]
    1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6812437/
  13. Metlay (2003) Ann Intern Med 138:109-18 [PubMed]
  14. Watkins (2011) Am Fam Physician 83(11): 1299-306 [PubMed]
  15. Womack (2022) Am Fam Physician 105(6): 625-30 [PubMed]

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