7-intruduction to respiratory pathology and pneumonia Flashcards
what is the major function of lungs?
• Major function of the lungs is to excrete carbon dioxide from blood and replenish oxygen
what are the conducting and respiratory zones of the respiratory system?
- -conducting zone (anatomic dead space; i.e., the airways of the mouth, nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles)
- -respiratory zone (lung parenchyma; i.e., respiratory bronchioles, alveolar ducts, alveolar sacs).
what are the functions of the respiratory system?
- -Ventilation (distribution of air in the airway)
- -Respiration: gas exchange (absorption of O2 into the blood and release of CO2 into the air)
- -Immune defense (ciliary clearance, alveolar macrophages, goblet cells)
what is the function of the conducting zone?
- -Conduction of air in and out of the respiratory tree
- -Anatomic dead space (no gas exchange)
- -Warms and humidifies air
- -Mucociliary clearance: ciliated epithelium transports mucus, bacteria, and dust towards the throat, where it is either swallowed or expelled through the mouth
lung parenchyma consists of…
- -Respiratory bronchioles
- -Alveolar ducts
- -Alveolar sacs, which contain several pulmonary alveoli surrounded by capillaries
what is the function of lung parenchyma?
- -Oxygen and carbon dioxide exchange across the blood-air barrier
- -Alveolar macrophages phagocytose fine dust particles (< 2 μm)
what is pneumonia?
- -Inflammatory consolidation of the lung parenchyma caused by the formation of intra-alveolar inflammatory exudate resulting from infection
- -A respiratory infection characterized by inflammation of the alveolar space and/or the interstitial tissue of the lungs.
what are the pulmonary reflexes?
- Cough reflex
- Mucociliary apparatus
- Alveolar macrophages
- Mucus secretion
- IgA antibodies
- Microflora of upper respiratory tract
- Nasal hairs
how breakdown of pulmonary defenses occurs?
1)Loss of cough reflex Eg Coma; Anaesthesia 2)Injured mucociliary apparatus Eg Smoking 3)A decrease in alveolar macrophages Eg Alcohol, smoking 4)Pulmonary congestion/edema 5)Accumulation of secretions 6)Obstruction
what is the pulmonary edema?
the accumulation of fluid in the alveoli. The cause can be cardiogenic (e.g., cardiac failure with increased pulmonary capillary pressure) or noncardiogenic (e.g., ARDS, pulmonary embolism, transfusion-related acute lung injury, high altitude, preeclampsia, and opioid overdose). Causes reduced diffusion capacity, hypoxemia, and dyspnea.
what are the causes of secondary pneumonia?
- -Bronchial asthma, COPD, heart failure, cystic fibrosis
- -Viral upper respiratory tract infections with bacterial superinfection
- -Anatomical abnormalities such as tubercular caverns, bronchial tumors, or stenosis (post-obstructive pneumonia)
- -Aspiration (aspiration pneumonia)
CAP vs HAP?
- -pneumonia that is acquired outside of a health care establishment
- -nosocomial pneumonia, with onset > 48 hours after admission
typical vs atypical pneumonia
1) Pneumonia featuring classic symptoms typical findings on auscultation and percussion. Manifests as lobar pneumonia or bronchopneumonia
2) Pneumonia with less distinct classical symptoms and often unremarkable findings on auscultation and percussion. Manifests as interstitial pneumonia
what are the risk factors of pneumonia?
1)Personal risk factors – Elderly >65 years – Smokers – Malnourished – Immunocompromised – Recurrent RTI’s – Medications 2)Environmental risk factors – Seasonal; more common in Winter 3)Organism virulence
why immobility leads to increase risk of pneumonia?
Immobility leads to poor ventilation of the lungs, which increases the risk of bacterial colonization and infection.
what is the pathophysiology of pneumonia?
- -Pulmonary protective mechanisms (cough reflex, mucociliary clearance , alveolar macrophages ) fail → microbial infiltration of the pulmonary parenchyma cannot be prevented
- -Pathogen infiltrates pulmonary parenchyma → interstitial and alveolar inflammation → impaired alveolar ventilation → Ventilation/perfusion (V/Q) mismatch with intrapulmonary shunting (right to left) → hypoxia due to increased alveolar-arterial oxygen gradient (This effect is worsened if the affected lung is in the dependent position since perfusion is better to the dependent lung than the non-dependent lung)
why there is a right to the left shunt of blood in pneumonia?
Caused by continued blood flow to consolidated, poorly ventilated areas, resulting in the passage of blood from the right heart to the left heart without getting oxygenated (i.e. a right to left shunt).
what are the common organisms responsible for pneumonia?
1)Bacteria – Streptococcus pneumoniae (60% of CAP) – Haemophilus influenzae – Staphylococcus aureus – Mycoplasma pneumoniae (atypical) – Legionella pneumophilia (atypical) 2)Viral – Influenza pneumoniae – Respiratory syncytial virus 3)Fungal – Rare; immunocompromised – PCP
what are the common causes of typical pneumonia?
–Streptococcus pneumoniae (most common)
Most common also in nursing home patients
–Haemophilus influenzae
what are the common causes of atypical pneumonia?
- -Mycoplasma pneumoniae (most common in the ambulatory setting)
- -Chlamydophila pneumoniae
- -Legionella pneumophila → legionellosis
- -Coxiella burnetii
Mycoplasma and Chlamydophila pneumoniae are common in the elderly. True/False
False
Mycoplasma and Chlamydophila pneumoniae are common in children and adolescents.
what are the common causes of HAP?
- -Gram-negative pathogens
1) Pseudomonas aeruginosa
2) Enterobacteriaceae - -Staphylococci (Staphylococcus aureus)
- -Streptococcus pneumoniae
what is the HAP?
Pneumonia that occurs > 48 hours after admission to hospital and did not appear to be developing at that time. A subtype of HAP is ventilator-associated pneumonia that occurs 48–72 hours following endotracheal intubation.
influenza is often complicated by pneumonia caused by?
Staphylococcus aureus is often a serious complication of influenza pneumonia in both children and adults.
common causes of pneumonia in immunocompromised patients
- -Encapsulated bacteria
- -Pneumocystis jirovecii → Pneumocystis jirovecii pneumonia
- -Aspergillus fumigatus → aspergillosis
- -Candida species → candidiasis
- -Cytomegalovirus
Pneumonia in newborn infants is commonly caused by what organisms?
- -Escherichia coli
- -Group B streptococcus (Streptococcus agalactiae)
- -Streptococcus pneumoniae
- -Haemophilus influenzae
what are the routes of infection in pneumonia?
- -Most common: microaspiration (droplet infection) of airborne pathogens or oropharyngeal secretions
- -Aspiration of gastric acid (Mendelson’s syndrome) , or of food or liquids
- -Hematogenous dissemination in rare cases (Most likely in the context of staphylococcal infection at a different site, e.g., as a complication of endocarditis)
type 1 vs 2 pneumocytes?
1) Type I pneumocytes: thin squamous cells that line the alveoli
- -Comprise 95% of the total alveolar area
- -Connected to each other by tight junctions
- -Form the blood-air barrier, together with the endothelial cells of the capillaries and the basement membrane between the two cells.
2) Type II pneumocytes: cuboidal alveolar cells
- -Comprise 5% of the total alveolar area, but 60% of total number of cells
- -Contain lamellar bodies, which secrete surfactant (surface-activating lipoprotein complex)
- -Mainly composed of the phospholipids dipalmitoylphosphatidylcholine (DPPC or lecithin) and phosphatidylglycerol.
- -Reduces alveolar surface tension and thereby prevents the alveoli from collapsing.
- -Can also proliferate to replace Type I or Type II pneumocytes following lung damage
what are the steps of evolution of signs and symptoms of Pneumonia
- Organisms in alveoli multiply
- Immune cells attack
- Influx of white blood cells, protein, fluid, red cells
- Release of cytokines
- Release of vasodilators increase vascular permeability causing congestion
- Alveoli filled with fluid = CONSOLIDATION
- Hampers O2 flow –>Shortness of breath
- Bronchoconstriction and increase in mucus secretion stimulates Cough reflex
- Pain receptor on alveoli –>Chest pain
- Cytokine release ->Pyrexia
what are the classic lobar pneumonia progression in stages?
- -Congestion (day 1): serous exudate in blood-rich lungs, numerous bacteria evident
- -Red hepatization (days 2–3): exudate rich in fibrin and inflammatory cells with many bacteria still visible; lungs take on a liver-like texture. Lung loses some spongy quality
- -Gray hepatization (days 4–7): erythrocytes are degraded but inflammatory cells persist; most bacteria have been destroyed by this stage. The lung is now firm
- -Resolution (day 8 to week 4): fibrinolysis by enzymatic means and removal of the purulent exudate via productive cough
what is the lobar penumonia?
An infection localized to one pulmonary lobe, most commonly caused by Streptococcus pneumoniae, Haemophilus influenzae, gram-negative bacilli, and Staphylococcus aureus.
Affects sections of a lobe
Starts distally and spreads to involve an entire lobe
what are the signs and symptoms of lobar pneumonia?
- -Decrease in chest expansion
- -Shortness of breath (SOB)
- -Cough
- -Chest pain
- -Pyrexia
- -Dull to percussion
- -Tactile fremitus
- -Bronchial breathing, crackles
- -Vocal resonance
in red hepatization stage pneumococci are dead. True/False
False
• Red Hepatization (2-3 days)
- Exudate of RBCs, neutrophils, and fibrin
- Pneumococci alive
- Lobes are distinctly red, firm and airless, with liver-like consistency
• GrayHepatization (4-6 days)
- Grey, firm lobe with exudate of neutrophils and fibrin
- RBCs disintegrate
- Dying pneumococci
what cells play a major role in regeneration?
- Type II pneumocytes key for regeneration
