Respiratory Tract Flashcards
What is the leading cause of infectious death and the fifth leading cause overall?
Pneumonia
What the three ways infectious agents gain entry to the lower respiratory tract?
Aspiration of upper airway resident flora, inhalation of aerosolized material, and, less frequently, metastatic seeding of the lung from blood
What size of particle is ideal for evading anatomic barriers, yet having an impact on alveoli? What size are most bacteria?
2 to 5 microns, 0.5 to 2 microns
What host defenses are present at terminal airways and alveoli?
Humoral and cell mediated defenses but not mucociliary apparatus
Examples of mucociliary apparatus inhibitors
Smoking impairs ciliary and macrophage activity, congenital defects impair secretion clearance and promote mucus compaction (Kartagener`s syndrome and Cystic Fibrosis)
What increases one`s risk for aspiration?
Nasogastric and endotracheal tubes
What is the most useful classification of pulmonary pathogens?
Community acquired vs nosocomial
Most pulmonary infection patients with complain of some difficulty breathing, associated with cough and fever. When present with a physical exam suggesting consolidation should prompt what?
More detailed evaluation, including chest x-ray
Community acquired pnemonia (CAP) is divided into typical and atypical groups. What does typical CAP present with?
acute illness with fever, chaking chills, purulent sputum, and dense lobar infiltrate on x ray
Typical CAP is most commonly caused by:
Streptococcus pneumonia
What is Faget`s sign?
Patients with atypical CAP are more likely to have relative bradycardia or pulse/temperature deficit on physical exam
What months are most viral infections, including influenza, usually seen?
December to March
What are important nosocomial respiratory pathogens? What pathogen targets cystic fibrosis patients?
Gram negative enteric flora, S. aureus; Pseudomonas
Why is specimen collection key to recovery of Strep pneumoniae?
Streptococci have an autolytic mechanism activated when adverse conditions are encountered, older cells die to give younger cells the best chance of survival, this can greatly reduce number of streptococci in 30 mins
What are the four criteria that suggest an infectious source in hospital acquired pneumonia?
1) New or changing infiltrate on chest x-ray 2) Change in respiratory secretions 3) Change in ventilatory requirements 4) Positive culture from sterile site with same organism found in respiratory culture
Definition of sputum
bolus of respiratory secretions coughed from deep in the lung and expectorated by the patient
What is considered an adequate specimen based on PMN leukocytes and epithelial cells?
> 25 PMN leukocytes and
Rapid antigen tests have clinical utility for which organisms?
influenza A, S. Pneumoniae, Legionella
Which imaging study is an integral part of pneumonia diagnosis? Why is the test not definitive? What test has both high sensitivity and specificity?
X-ray; non-specific; CT scan
Blood cultures are prognostic of an increasing risk of what, especially in pneumococcal disease?
Morbidity
If pleural fluid is visible on chest x-ray, what should be obtained next and why?
Lateral decubitus film to see if the fluid can be drained
How is an exudative effusion classified? Transudative?
pleural fluid /serum protein ratio > 0.5, pleural fluid/serum LDH ratio > 0.6, or pleural fluid LDH >200; protein and LDH ratios less than 0.5 and 0.6 respectively
How is empyema classified?
purulent pleural fluid pH1000mg/dl)
True False: For most commonly acquired pneumonia, measurement of oxygenation is unnecessary.
True
