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54 Cards in this Set
- Front
- Back
Lower Respiratory Tract Infections
Overview |
Inflammatory processes involving airways, lung parenchyma, &/or pleural space
Etiologic causes extremely numerous & varied Wide host spectrum (young → elderly; healthy → immunocompromised) Inhalation or aspiration of microbes into endobronchial tree major route of infection |
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Types of Lower Respiratory Tract Infections
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1. Bronchiolitis
2. Bronchitis 3. Pneumonia 4. Lung abscess 5. Pleural empyema |
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Bronchitis
(definition and classification) |
Inflammation of the bronchial mucosa, resulting in a productive cough, with minimal or no fever & no evidence of pneumonia by PE or CXR
Classification: - Acute bronchitis (Normal hosts) - Acute exacerbations of chronic bronchitis (Pts with underlying lung disease) |
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Acute Bronchitis
Etiology |
Mostly viral (Rhino, flu, paraflu, adeno, RSV)
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Acute Bronchitis
Epidemiology |
Fall, Winter, Spring
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Acute Bronchitis
Clinical features |
Productive cough
low grade fever Normal lung exam |
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Acute Bronchitis
Lab features |
WBC usually normal
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Acute Bronchitis
Diagnosis |
Based on clinical setting & features
occasionally CXR |
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Acute Bronchitis
Therapy |
Antibiotics RARELY indicated
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Pneumonia
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Microbial infection of lung parenchyma characterized by:
- Fever - Dyspnea - Cough with production of purulent sputum - Infiltrates on CXR |
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Pneumonia Classification
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Community-acquired pneumonia (CAP)
Healthcare-associated pneumonia (HCAP) - Hospital-acquired pneumonia (HAP) - Ventilator-associated pneumonia (VAP) = 80-85% of HAP Pneumonia in the compromised host |
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Community Acquired Pneumonia
Epidemiology |
4 million cases/yr in US; annual attack rate 12-15/1000 adults.
15-20% of pts require hospitalization (600,000 pts). Of those pts hospitalized with CAP, ~10% will die. Aggregate cost > $4 billion. |
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Hospital Acquired Pneumonia
Epidemiology |
Develops in 0.5% to 1.0% of all hospital admissions.
Rates in ICU are 15% to 20% and, for mechanically ventilated pts, 18% to 60%. For pts with VAP, crude mortality may be 50% to 90%. |
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Stepwise approach to diagnosis in the patient with possible pneumonia
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1. Presumptive clinical diagnosis
2. Confirmed clinical diagnosis 3. Presumptive etiologic diagnosis 4. Definitive etiologic diagnosis |
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Presumptive clinical diagnosis
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Applicable Sources of Data:
- History (symptoms) - Findings on lung exam Important Diagnostic Clues: - Fever/chills, cough, purulent sputum - Dullness, rales, bronchial breath sounds |
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Confirmed clinical diagnosis
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Applicable Sources of Data:
- Sputum examination - CXR Important Diagnostic Clues: - Gross purulence - Infiltrate(s) |
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Presumptive etiologic diagnosis
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Applicable Sources of Data:
- Epidemiology - Clinical Settings - Clinical features - Sputum stains/smears Important Diagnostic Clues: - Nosocomial vs. community - Normal vs. Abnormal Host - Typical vs. atypical - Organism types/morphologies |
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Definitive etiologic diagnosis
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Applicable Sources of Data:
- Cultures - Serologies - Immunodiagnostics Important Diagnostic Clues: - Specific organism(s) implicated |
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Approach to dx of Pneumonia
Epidemiologic Background of Disease |
1. Exposure history
2. Travel history 3. Unusual contacts 4. Recent hospitalization or ATB Rx |
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Brucella
Pneumonia Epidemiologic Assocations |
Exposure to cattle, goats, pigs
Abattoir worker or veterinarian |
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Melioidosis
Pneumonia Epidemiologic Assocations |
SE Asia
Australia Central/S. America |
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Plague
Pneumonia Epidemiologic Assocations |
Exposure to ground squirrels, prairie dogs, rats
Typically in SW |
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Psittacosis
Pneumonia Epidemiologic Assocations |
Exposure to birds (parakeets, parrots, turkeys)
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Coccidioidomycosis
Pneumonia Epidemiologic Assocations |
Travel to San Joaquin Valley or arid SW
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Histoplasmosis
Pneumonia Epidemiologic Assocations |
Exposure to bat droppings or bird droppings
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Approach to dx of Pneumonia
Clinical Setting of Disease |
1. Community vs hospital-acquired
2. Age of host 3. Predisposing conditions 4. Host immune deficits |
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Common causes of community-acquired pneumonia
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S. pneumoniae
Anaerobes Legionella Mycoplasma Chlamydophilia Viruses |
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Infrequent causes of community-acquired pneumonia
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H. influenzae
K. pneumoniae Staph. aureus Enterobacter E. Coli Pseudomonas Nocardia M. tuberculosis |
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Rare causes of community-acquired pneumonia
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Proteus
Salmonella Yersinia pestis Strep. pyogenes |
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healthcare-associated or hospital-acquired pneumonia is typically caused by ...
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S. aureus and GNRs such as Pseudomonas
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Community-acquired pneumonia is most often due to ...
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selected typical and atypical bacteria (eg, S. pneumoniae, M. pneumoniae, Chlamydophila pneumoniae) or viruses
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Post-influenza
puts patient at risk for this pathogen: |
S. pneumoniae
S. aureus H. influenzae |
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Altered consciousness/ esophageal dysmotility
puts patient at risk for this pathogen: |
Oral flora
(anaerobes/aerobes) |
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Alcoholism
puts patient at risk for this pathogen: |
Oral flora
S. pneumoniae S. aureus Klebsiella |
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Chronic Lung Disease
puts patient at risk for this pathogen: |
S. pneumoniae
H. influenenzae (nontypeable) |
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Cystic Fibrosis
puts patient at risk for this pathogen: |
P. aeruginosa
S. aureus Stenotrophomonas |
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Hypogammaglobulinemia
puts patient at risk for this pathogen: |
S. pneumoniae
H. influenzae type B ENCAPSULATED BACTERIA |
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Depressed cell-mediated immunity
puts patient at risk for this pathogen: |
Typical and atypical mycobacteria
Fungi (crypto, endemic mycoses) Viruses (CNV, VZV, HSV, measles) Pneumocystis jirovecii Toxoplasma gondii INTRACELLULAR PATHOGENS |
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Decrease in the number of fulling functional granulocytes
puts patient at risk for this pathogen: |
(Neutrophil deficiencies)
Oral bacterial flora Enterobacteriaceae Pseudomonas aeruginosa Aspergillus - Pyogenic extracellular bacteria (early) - Filamentous fungi (late) |
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Complement defects
puts patient at risk for this pathogen: |
Streptococcus pneumoniae
H. influenzae type B ENCAPSULATED BACTERIA |
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Approach to dx of pneumonias
Clinical features of disease |
1. Tempo of onset
2. Typical vs atypical sxs/signs 3. Extrapulmonic signs 4. Radiographic pattern 5. Special considerations |
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Etiologic Agents of TYPICAL Pneumonias
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Streptococcus pneumoniae
Klebsiella pneumoniae Haemophilus influenzae Moraxella catarrahalis [Legionella pneumophila] |
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Etiologic Agents of ATYPICAL Pneumonias
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Mycoplasma pneumoniae
Chlamydophila pneumoniae Chlamydophila psittaci Coxiella burnetii Legionella pneumophila Non-pneumophila Legionella species Viruses |
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What are the characteristics of TYPICAL Pneumonias
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sudden in onset and are characterized by high spiking fevers, severe rigors, cough productive of purulent sputum, leukocytosis (WBC count >15,000), and lobar infiltrates on CXR.
The prototypical causative pathogen would be S. pneumoniae. |
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What organism is suspected with:
Lobar consolidation? |
Pyogenic extracellular bacteria (S. pneumo, GNRs)
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What organism is suspected with:
Interstitial infiltrates? |
Viruses
Mycoplasma |
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What organism is suspected with:
Cavitation without air-fluid level? |
TBC
fungi |
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What organism is suspected with:
Consolidation + pleural effusion? |
S. pneumo
Staph GNRs anaerobes |
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What organisms are foung in oropharyngeal colonization (incidence)?
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S. aureus 35-40%
S. pyogenes (GABHS) 0-9% S. pneumoniae 0-50% N. meningitidis 0-15% H. influenzae 5-20% Gram-negative bacteria 2% |
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Sputum
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Potential for Oropharyngeal contamination --> Deeply expectorated specimen not spit!!
Prompt transport to lab Good Gram stain Assessment of adequacy of specimen (WBCs vs squames) Interpretation by experienced observer |
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How often is there a confirmation of the cause of pneumonia?
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< 50% of patients
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What are the most useful diagnostic tests for pneumonia?
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the most useful diagnostic tests are sputum & blood cultures and selected antigen screens on urine
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What is the gold standard for clinical diagnosis of pneumonia?
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abnormal CXR
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Laboratory Aspects of Pneumonias
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WBC count: increase WBC with bands (bacterial).
Serologies: 4 x increase. Retrospective. “Difficult to culture” pathogens. Antigen detection: Encapsulated pathogens. Sputum (false +’s), blood, urine. DNA probes: Culture identification; limited role for direct probe of clinical specimens. PCR: Wave of future; evolving. Skin testing: Tuberculosis. |