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What is CAP?

community-acquired pneumonia: acute infection of the pulmonary parenchyma acquired outside of the hospital


What are the two categories of nosocomial pneumonia?

hospital-acquired pneumonia (HAP)
ventilator-associated pneumonia (VAP)


What is HAP?

hospital-acquired pneumonia: pneumonia acquired ≥48 hours after hospital admission, and did not appear to be incubating at the time of admission.


What is VAP?

ventilator-associated pneumonia: pneumonia acquired ≥48 hours after endotracheal intubation.


What was HCAP, and how is it treated now?

Health care-associated pneumonia; currently treated as CAP

Referred to pneumonia acquired in health care facilities (eg, nursing homes, hemodialysis centers) or after recent hospitalization


What are the non-modifiable (/less modifiable) risk factors for pneumonia?

- Older age (≥65)
- Chronic comorbidities
- Viral respiratory tract infection
- Impaired airway protection (LOC, dysphagia)


What chronic comorbidities are risk factors for CAP?

COPD (comorbidity with highest risk for hospitalization)

- other chronic lung disease (bronchiectasis, asthma)
- CHF and other chronic heart disease
- stroke
- DM
- malnutrition
- immunocompromise


Once you have one risk factor for CAP, does having more increase your risk?

Yes: risk factors are additive
eg CHF, smoking, COPD


What are the three categories of most common causes of CAP?

Typical bacteria
Atypical bacteria
Respiratory viruses


What is the single most common bacterial cause of pneumonia?

Streptococcus pneumoniae (pneumococcus)


What pathogens are "typical bacterial" causes of CAP? (7 listed)

•S. pneumoniae (most common bacterial cause)

•Haemophilus influenzae

•Moraxella catarrhalis

•Staphylococcus aureus

•Group A streptococci

•Aerobic gram-negative bacteria (eg, Enterobacteriaceae such as Klebsiella spp or Escherichia coli)

•Microaerophilic bacteria and anaerobes (associated with aspiration)


What pathogens are "atypical bacterial" causes of CAP? (5 listed)

•Legionella spp

•Mycoplasma pneumoniae

•Chlamydia pneumoniae

•Chlamydia psittaci

•Coxiella burnetii


What defines "atypical" bacterial causes of CAP?

- resistant to beta-lactams

- can't be visualized on Gram stain or cultured using traditional techniques


What respiratory viruses cause CAP? (8 listed)

•Influenza A and B viruses


•Parainfluenza viruses


•Respiratory syncytial virus

•Human metapneumovirus

•Coronaviruses (eg, Middle East respiratory syndrome coronavirus)

•Human bocaviruses


What features are associated with CAP due to community acquired MRSA?

Necrotizing or cavitary pneumonia
Gross hemoptysis
Septic shock
Respiratory failure


What recent discovery has changed our understanding of pneumonia?

Lung microbiome: lung parenchyma was previously thought to be sterile

e.g. change from pathogen colonization of sterile lung to pathogen competition with microbiome -- and dysbiosis as a risk factor for pneumonia


What are the most common symptoms associated with CAP?

- Cough (with or without sputum production)
- dyspnea
- pleuritic chest pain


What are the most common physical exam findings associated with CAP?

- tachypnea (RR > 24: 45-70%; most sensitive sign in older pt)
- increased WOB
- adventitious breath sounds, including rales/crackles (about 1/3 of pt) and rhonchi
- fever (80%, though freq absent in older pt)

Tactile fremitus, egophony, and dullness to percussion also suggest pneumonia.


What is the gold standard for diagnosis of pneumonia?

Infiltrate on CXR, in context of supportive clinical syndrome (eg, fever, dyspnea, cough, and sputum production)


What are the most common lab findings associated with CAP?

- CBC: Leukocytosis (15-30), leftward shift
- leukopenia can occur; generally poor prognosis
- inflammatory markers (CRP< ESR, procalcitonin)


What other features might CAP present with (not most common, but not rare)?

- GI (N/V/D)
- MS changes


What features on CXR are consistent with CAP?

- lobar consolidations
- interstitial infiltrates
- cavitations


What if the CXR is negative, but you still really suspect pneumonia based on clinical picture?


Esp if immunocompromised (less infl response so less infiltrate) or known exposure to pathogen that causes pneumonia (eg legionella)


Name 2 score tools used to calculate mortality and determine site of treatment for CAP

PSI (Pneumonia Severity Index), aka PORT score


When do you treat a pt with CAP as ambulatory?

Otherwise healthy
Normal vital signs aside from fever
No concern for complication


When do you admit a pt with CAP?

SpO2 <92% on RA (sig change from baseline)

Also consider for practical concerns like inability to take oral meds, functional impairment, social issues affecting adherence or followup


What groups are not well represented in CAP scoring, and should be considered for admission even with mild scores?

patients with early signs of sepsis, rapidly progressive illness, or suspected infections with aggressive pathogens


When do you admit a pt to ICU for CAP?

- respiratory failure requiring mechanical ventilation
- sepsis requiring vasopressor support


What criteria support early ICU admission, due to anticipated progression to sepsis? (name 5; 9 listed)

Three of:
- Hypotension requiring fluids
- T < 36
- RR ≥ 30
- PaO2/FiO2 ratio ≤250
- BUN ≥ 7 mmol/L
- Leukocyte count <4
- Platelet count <100
- Multilobar infiltrates


What microbiologic testing of CAP should be performed in outpatients?

Outpt: none -- empiric Abx good