Lower Respiratory Tract Infections

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Lower Respiratory Tract Infections

• Charles S. Bryan, M.D.
• November 20, 2007

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Lower respiratory infections anatomic
classification

• Tracheitis bronchitis tracheobronchitis
• Bronchiolitis
• Bronchopneumonia
• Segmental pneumonia
• Lobar pneumonia
• Interstitial pneumonia

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Acute bronchitis (chest cold)

• Usually of viral etiology
• A common cause for overuse of antibiotics
• Bordetella pertussis (whooping cough) sometimes
  causes acute bronchitis in adults
• Mycoplasma pneumoniae and Chlamydia pneumoniae
  may play a role in stubborn cases

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Acute exacerbations of chronic bronchitis

• Chronic bronchitis is usually due to cigarette
  smoking and often associated with COPD
• Extent to which specific bacterial pathogens
  explain exacerbations is controversial.
• However, repeated bacterial infections
  (especially H. influenzae) contribute to
  deterioration of lung function.

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Bronchiectasis

• Abnormal dilatation of bronchi with chronic
  productive cough.
• Can be clue to cystic fibrosis (associated with
  S. aureus and Pseudomonas species)
• Uncommon associations immunodeficiency
  disorders, dyskinetic cilia syndrome

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Bronchiectasis

• 42 year old W.F. with chronic productive cough
• Sputum smear positive for AFB

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Pneumonia

• 6th leading cause of death in U.S.A.
• About 3 million cases per year 500,000
  hospital admissions
• About 50 of cases and the majority of deaths are
  due to bacteria
• Precise diagnosis is usually desirable but
  difficult to obtain

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Pneumonia (2)

• Streptococcus pneumoniae the most common cause of
  community-acquired pneumonia requiring
  hospitalization
• Haemophilus influenzae and Moraxella catarrhalis
  are increasing in frequency
• Legionella species and Chlamydia pneumoniae have
  emerged
• Pneumocystis carinii (HIV disease)

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Pneumonia pathogenesis

• Endogenous vs. exogenous (inhalation)
• Bronchogenous vs. lymphohematogenous
• Pulmonary clearance mucociliary blanket,
  alveolar macrophages
• Factors that impair pulmonary clearance viral
  URI smoking alcohol uremia bronchial
  obstruction 100 oxygen others

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Pneumonia pathophysiology

• Hypoxemia due to ventilation/perfusion
  mismatching
• Hyperdynamic circulation with increased cardiac
  output
• Toxic cardiomyopathy
• Increased oxygen demands
• Decreased lung compliance increased work of
  breathing

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Typical versus atypical pneumonia

• Typical (virulent bacteria) abrupt onset
  productive cough with purulent sputum pleuritic
  chest pain impressive physical findings
  leukocytosis or leukopenia
• Atypical (viral, Mycoplasma pneumoniae,
  others) gradual onset, nonproductive cough
  substernal chest pain unimpressive physical
  exam white blood count normal

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Typical versus atypical pneumonia
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Which is typical, which atypical?
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Pneumonia some clues

• Chills single chill suggests S. pneumoniae,
  multiple chills suggests S. aureus or Klebsiella
  pneumoniae
• Relative bradycardia viral infection Mycoplasma
  pneumoniae Psittacosis Tularemia Legionella
  species

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Pneumonia some clues (2)

• Tularemia rabbits and hares ticks and fleas
  inhalation (e.g., after mowing over carcasses)
• Psittacosis birds
• Plague ground squirrels, chipmunks, rabbits,
  prairie dogs, rats
• Legionnaires disease contaminated aerosols (air
  coolers hospital water supplies)

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Pneumonia some clues (3)

• Histoplasmosis dust from soil enriched with bird
  or bat droppings Mississippi and Ohio River
  valleys
• Coccidiodomycosis southern California (esp.. San
  Joachin Valley) southwestern Texas, Arizona, New
  Mexico
• Pneumocystis carinii HIV risk factors

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Pneumonia some clues (4)

• Q fever (Coxiella burnetii) goats, cattle, sheep
• Meliodosis travel to S.E. Asia, East Indies,
  Australia, Guam, South or Central America
• Brucellosis cattle goats pigs abattoir works
  and veterinarians
• Anthrax cattle, swine, horses goat hair, wool,
  or hides

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Pneumococcal pneumonia Predisposing factors

• Sickle cell disease
• Asplenia
• IgG disorders agammaglobulinemia, myeloma,
  chronic lymphocytic leukemia
• Nephrotic syndrome
• Cirrhosis
• Alcoholism

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Classic pneumococcal pneumonia

• Antecedent upper respiratory infection
• Sudden onset with single violent chill, then
  fever
• Pleuritic chest pain
• Signs of lobar consolidation on exam
• If untreated, terminates gradually by lysis or
  suddenly by crisis

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Atypical pneumococcal pneumonia

• Caught early signs of consolidation may be
  absent
• Elderly fever, classic history may be absent
• COPD CXR and physical findings are distorted
• Ethanolism blunted history prostration,
  leukopenia
• Epilepsy lack of history fever and tachycardia
  may be attributed to seizures anaerobes may
  co-exist
• Recurrent pneumonia In same area, suggests
  obstruction or bronchiectasis

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Some current problems with pneumococcal disease

• Failure of antibiotic therapy to improve survival
  during first 3 days
• Vaccine efficacy and distribution
• Resistance to penicillin G
• Overwhelming sepsis in asplenic persons
• Need for developing better diagnostic techniques

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Group A streptococcal pneumonia

• Rare, except during influenza epidemics
• Large empyema (pus in the chest) is
  characteristic

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Hemophilus influenzae pneumonia

• 2 to 18 of community-acquired pneumonias
  increasing in adults
• Predispose underlying lung disease, alcoholism,
  recent URI, advanced age
• Often a patchy segmental pneumonia or
  bronchopneumonia
• Virtually-diagnostic Grams stain small,
  pleomorphic gram-negative coccobacilli

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Moraxella catarrhalis pneumonia

• AKA Neisseria catarrhalis Branhamella
  catarrhalis
• A large gram-negative diplococcus
• Causes pneumonia and bronchitis especially in
  persons with chronic lung disease
• Often a patchy bronchopneumonia

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Mycoplasma pneumoniae pneumonia

• The classic primary atypical pneumonia
• Typically occurs in younger adults, often the
  parents of young children
• Subtle presentation
• Favors lower lobes
• Pleural effusion may occur (up to 20)

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Some nonrespiratory manifestations of Mycoplasma
pneumoniae pneumonia

• Myringitis (sometimes bullous)
• Hemolytic anemia
• Arthritis, arthralgias, myalgias
• Pericarditis, myocarditis
• Hepatitis (mild)
• Erythema multiforme, other rashes
• Meningitis, meningoencephalitis, neuropathy

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Chlamydia pneumoniae pneumonia

• Accounts for perhaps 6 to 10 of
  community-acquired pneumonias
• C. pneumoniae more commonly causes pharyngitis
  and hoarseness
• Bronchitis is often insidious
• Pneumonia usually mild and localized but
  difficult to eradicate

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Legionella pneumophila pneumonia

• Up to 23 of community-acquired pneumonias but
  with wide geographic distribution
• L. pneumophila is not part of the normal flora a
  true inhalation disorder
• CXR patchy or nodular infiltrates that may
  progress rapidly up to 50 are bilateral

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Legionella pneumophila pneumonia (2)

• Relative bradycardia in 65
• Neurologic findings in 26
• Grams stain may show purulence without a
  predominant microorganism
• Laboratory may have hyponatremia elevations of
  AST (SGOT), alkaline phosphatase, and bilirubin
  proteinuria, hematuria, and renal failure

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Aspiration (mouth flora) pneumonia

• usually presents as a subacute illness in
  patients with some combination of alcoholism,
  malnutrition, homelessness, and poor dentition
• sputum often has foul odor
• Necrotizing pneumonia lung abscess(es) with
  air-fluid levels empyema

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Nosocomial pneumonia

• Role of oropharyngeal colonization, especially of
  gram-negative rods by end of one week, 45 of
  ICU patients are colonized pneumonia develops in
  23 of colonized patients versus 3.3 of
  non-colonized patients
• Risk factors to colonization more advanced
  illness, longer duration in the hospital,
  antibiotics, intubation, azotemia, underlying
  pulmonary disease

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A pulmonary infiltrate

• 26 year old WM presenting with shortness of
  breath, low-grade fever, nonproductive cough
• PE Loud murmur of mitral regurgitation

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Complications of pneumonia

• Pleuropulmonary lung abscess adult respiratory
  distress syndrome (ADS) pleural effusion
  empyema bronchopleural fistula bronchiectasis
  fibrosis slow resolution
• Extrapulmonary meningitis brain abscess
  endocarditis pericarditis arthritis
  osteomyelitis

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Pneumonia Summary

• 6th leading cause of death and most common
  nosocomial infection causing death
• Precise diagnosis desirable but all-too-often not
  obtained
• Better diagnostic methods are needed
• Meanwhile, use Grams stain!