LUNG DEFENSE MECHANISM Flashcards
Most common entry of microorganism into the lower RT?
Aspiration
Increase in aspirated volume
loss of control of the upper airway which should be patent in order to protect us from aspiration
2nd most common mode of infection
Inhalation
Infection that has spread to the lungs
Hematogenous spread
Non-pulmonary infection that spreads to the lungs
contiguous Extension
Mechanical components in lung defense
- Turbinates and nares -
- Branching architecture of tracheobronchial tree
- particle deposition in the RT
- Expulsive mechanism
Most important mechanism involved in protection of the respiratory tract
Mucociliary escalatory
Transport rate of Mucociliary escalator
3mm/min, becoming more rapid proximally
Conditions that can cause clearance impairment
- Advanced age
- Smoking
- Viral infections
- Pulmonary dysfunctions
Double layer of Mucus
External Gel Layer
Internal Sol layer
External Gel Layer
Viscous, elastic
traps and transport deposited particles
Loss of elasticity can impair clearance
Internal sol layer
Thin liquid where cilia can move easily
Mucus is more abundant where? proximally or distally?
proximally
Cilia
biphasic, periodic motion and strikes the gel with their tips
Presence of Normal Bacterial flora
adhere to the mucosal oropharynx and serve as protective organisms
Prevent the binding of pathogenic bacteria to mucosal areas
Most important defense mechanism in the alveolar level
Alveolar macrophages
Defenses at the alveolar level
- Alveolar macrophages
- lymphoid nodule
- lymphokines
- surfactants
- Immunoglobulins
- COmplement
- Chemotactic factors
Surfactant proteins
SP A and D
antiviral and antibacterial
capable of opsonization
Functions of alveolar macrophages
- phagocytosis
- possess immunologic form (T-lymphocytes)
- release cytokines to trigger inflammatory response
Enables macrophages to recruit and activate other inflammatory cells
Cytokines (LT B4 and IL 8)
Events that follow capillary leak
Hemoptysis
Radiographic infiltrates
Rales on physical examination
Factors Affecting Host Defense
- Medical Illness
- Immunosupression
- Cortocosteroids
Drugs that cause immunosupression
ATG/ALG OKT3 Corticosteroids Cyclosporine Azathioprine Tacrolimus, Sirolimus Mycophenolate Mofetil
Side effects of immunosuppression
Granulocytopenia
Bone marrow depression
Subtle changes on macrophages
Infections caused by chronic steroid intake
TB Legionella Nocardia Streptococci Aspergillus, Candida CMV, HSV, RSV Pneumocystis
First line of defese against infection
innate immunity
Does not confer long lasting immunity
innate immunity
Initial response of innate immunity
limit infection, initiate specific or adaptive immune response
Found on the surface and within endosome of host cells
TLR
LPS in g(-) are detected by
TLR4
types of adaptive immune response
Cellular and humoral
consists of T lymphocytes, macrophages, NK cells
Cellular immunity
Recognizes and combats pathogens that proliferate intracellularly
Cellular immunity
Components of the adaptive immune response
dendritic cells, macrophages, B lymphocytes
CD8 (+)
cytotoxic T cells
CD4 (+)
Helper T cells
Stimulate inflammatory response
Cytokines
RES
Monocyte-derived phagocytic cells
Produced by B lymphocytes
Antibodies
Immunoglobulin that predominates in the circulation
IgG
Earliest specific antibody to appear in infetion
IgM
Important in allergic and Parasitic disease
IgE
monomeric IgA
Serum
Have receptors for both antibody and C3b which aid in the clearance of infectious agents
PMN
group of serum proteins that adhere to and in some cases disruot the surface of the invading organisms
Complement system
Complement that acts as opsonin
C3b
Complements that directly kill some bacterial invaders thru bacteriolysis
C7.8,9
complement that acts as chemoattractants
C5a
Pathways for complement activation
Classical, Alternative, Mannose binding
IV drug USe
S aureus
Risk of aspiration
Anaerobes
HIV
Pneumocystis, CMV
Alcoholic
Lung abscess
HIV
Interstitial pneumonia
Respiratory symptoms
cough 90% Expectoration 66% Dyspnea 66% Pleuritic Pain 50% Hemoptysis 15%
Community acquired pneumonia is present in 20 to 50% of those who have
cough fever tachypnea tachycardia pulmonary crackles
Typical CAP
Acute, chills, productive cough, purulent or bloody expectoration, pleuritic pain, consolidation by X-ray, crackles by PE, ELevated WBCs (neutrophils)
Atypical CAP
Legionella, mycoplasma, chlamydia Gradual onset Fever Nonproductive cough Systemic complaints more prominent than respiratory ones Normal white count
Elderly and immunocompromised
changes in sensorium, loss of appetite, electrolyte imbalance, history of falls, sleepiness, increased sleeping time, incontinence
Specificity of Gram stain for pneumococcal pneumonia
> 80%
Good sputum mechanism
EC <10/LPfF
PMN >25/LPF
Blood cultures
at least 2
Overall yield : 20%
Endotracheal aspirate
quantitative cultures
>105 CFU/ml = pneumonia
CXR : whole Lobe
LOBAR
CXR: bulging fissure sign
CUrrant jelly sputum
Lobar: Klebsiella
CXR: Diffuse pattern
Bronchopneumonia
S. aureus, P aeruginosa, E. colu
CXR: Blateral or symmetrical, lung abscess, and pneumatocoeles
Bronchial: Staphylococcal
CXR: Reticular pattern
Interstitial
Mycoplasma and Viruses
CXR: lung fluid level
Lung abscess
CXR:apical
TB