Pathology of Pulmonary Infection Flashcards
What types of Microorganism Pathogenicity exist? How invasive it is, infectivity etc
Primary - very invasive and infectious to healthy people Facultative (most common)- A bit of illness needed for invasion to occur Opportunistic -cause infections in immuno compromised host
What does the capacity to resist infection depend on?
State of Host Defence Mechanisms Age of Patient
Give examples of upper respiratory tract infections. Pathology all involves inflammation.
Coryza - common cold Sore throat syndrome Acute Laryngotracheobronchitis (Croup) Laryngitis Sinusitis Acute Epiglottitis
What causes acute epiglottitis?
Group A beta-haemolytic Streptococci Haemophilus influenzae (type b - Hib) Rarely caused by Parainfluenza virus type 4 but other viruses may also be reponsible
Describe the effects of acute epiglottitis
Potentially life threatening, affects children. Swells up and obstructs airway. Causes extreme respiratory difficulty.
Give examples of Lower Respiratory Tract Infections
Bronchitis Bronchiolitis Pneumonia Consequences Possible Complications
How do lower respiratory tract infections compare to upper?
More morbidity and mortality rate with lower respiratory tract infections
What are the respiratory tract defence mechanisms?
Macrophage-mucociliary escalator system General immune system -Humoral and cellular immunity Respiratory tract secretions Upper respiratory tract as a ‘filter’ Cough reflex
Which part of the respiratory tract is sterile?
Lower
Which part of the upper respiratory tract acts as a filter?
Nose
What components of the the upper respiratory tract as a filter?
Hair, moist, mucous and cilia in epithelium.
What is the effect of alveolar macrophages?
Phagocytose, (if they cannot digest) travel towards the ciliary escalator for digestion
Why might the macrophage pass through the alveolar membrane?
To reach Interstitial pathway via lymph to the lymph nodes
Where does particle deposition occur?
Deposition on the conducting airways Deposition on the terminal bronchioles/ proximal alveoli
How can the ciliary escalator fail?
Viral infections (influenza) – damage to normal respiratory epithelium – no longer functional or cilia, severe when there is no mucociliary membrane. Common cause of bacterial chest infections.
What are the three ways you can classify pneumonia?
Anatomical, aetiological and microbiological.
What are the Aetiological Classifications of Pneumonia?
Community Acquired Pneumonia (usually treated by GP’s) Hospital Acquired (Nosocomial) Pneumonia (more likely to be severe, bacteria more likely to be resistant) Pneumonia in the Immunocompromised (AIDS patients) Atypical Pneumonia (unusual infectious agents) Aspiration Pneumonia (result in the inhalation of gastric content) Recurrent Pneumonia – signal that there is something particularly odd going on)
Which type of pneumonia is usually treated by GP’s?
Community acquired pneumonia
What are the different patterns of pneumonia?
Bronchopneumonia
Segmental
Lobar
Hypostatic
Aspiration
Obstructive, Retention, Endogenous Lipid
What does
- A) Bronchopneumonia
- B) Lobar pneumonia
Affect?
A) Both lungs and the bronchi
B) One or more sections or lobes of the lungs
What causes most cases of bacterial pneumonia?
Streptococcus pneumonia
Other culprits:
Staphylococcus aureus
Haemophilus influenzae
Klebsiella pneumoniae
What is the classic type of pneumonia that is community acquired?
Shows lung consolidation of one lung segmental lobe
What is hypostatic pneumonia?
Infection in the dependent portions of the lungs due to decreased ventilation of those areas
Failure to drain bronchial secretions
Occurs primarily in old people or those debilitated by disease who remain recumbent in the same position for long periods
What is aspiration pneumonia?
Aspiration pneumonia is a lung infection that develops after you aspirate (inhale) food, liquid, or vomit into your lungs.
What is the effect of acute inflammation in bronchopneumonia?
Lung filled with pus, neutrophils and inflammatory exudate
It is the most common hypostatic pneumonia story
How does the action of bacteria differ in lobar pneumonia?
Organisms are more aggressive, greater tissue reaction, greater spread of organism. Infection stops at the pleura
What are the outcomes of pneumonia?
Most Resolve
Pleurisy, Pleural Effusion and Empyema
•Organisation – formation of fibrous tissue, inflammatory area becomes scar tissue
–mass lesion
–COP(cryptogenic organising pneumonia (BOOP))
–Constrictive bronchiolitis
Lung Abscess - necrosis, hole in lung
Bronchiectasis
Pneumonia is still a potentially fatal disease
What happens during the organisation in pneumonia?
Formation of fibrous tissue, inflammatory area becomes scar tissue
What is a lung abscess?
Pus forms in the space where there was tissue destruction.
What organisms are more likely to cause abscess?
Staph aureus, some pneumococci, Klebsiella
When is lung abscess metastatic?
Pyaemia
What is Bronchiectasis?
Abnormal dilation of the bronchi in the periphery of the lung.
Symptoms: SOB, coughing up blood, chest pain, clubbing.
The mechanism of disease is breakdown of the airways due to an excessive inflammatory response.
Involved airways (bronchi) become enlarged and thus less able to clear secretions. These secretions increase the amount of bacteria in the lungs, result in airway blockage and further breakdown of the airways.
It is classified as an obstructive lung disease, along with chronic obstructive pulmonary disease and asthma.
What causes Bronchiectasis?
Severe Infective Episode
Recurrent Infections - many causes
Proximal Bronchial Obstruction (occurs in the trachea or main bronchi) (tumour)
Lung Parenchymal Destruction
What are the symptoms of Bronchiectasis?
75% start in childhood
COUGH, ABUNDANT PURULENT FOUL SPUTUM
Haemoptysis, signs of chronic infection
Coarse crackles
Clubbing
Thin section CT, (previously bronchography)
Postural Drainage
Antibiotics
Surgery
How might you get a recurrent lung infection?
Local Bronchial Obstruction - Tumour, Foreign body?
Local Pulmonary Damage - Bronchiectasis?
Generalised Lung Disease - Cystic Fibrosis?, COPD?
Non-Respiratory Disease - Immunocompromised (HIV, other)?, Aspiration?
What causes aspiration pneumonia?
Vomiting
Oesophageal Lesion
Obstetric Anaesthesia (any anaesthetic used in childbirth)
Neuromuscular Disorders Sedation
Where is the most common location for aspiration pneumonia?
Apical segment of right lower lobe
What are oppurtunistic pathogens and can you give an example of one?
Infection by organisms not normally capable of producing disease in patients with intact lung defences
–Pneumocystis jirovecii
What is the difference between laminar flow versus turbulent flow?
Laminar - Smooth, streamlined, highly ordered, much less resistance
Turbulent - Velocity fluctuations, highly disordered, increased pressure difference is needed to maintain flow, this response itself increases resistance
Larger airways are more prone to turbulent flow than smaller airways
In cases of upper airway obstruction the development of turbulent flow is a very important mechanism of increased airway resistance
What are the definitions of respiratory failure?
Type I PaO2 <8 kPa (PaCO2 normal or low) Type II PaCO2 >6.5 kPa (PaO2 usually low)
What are values for normal Pa O2 and Pa CO2?
Normal PaO2 10.5 – 13.5 kPa Normal PaCO2 4.8 – 6.0 kPa
What are the Four abnormal states associated with HYPOXAEMIA?
Ventilation / Perfusion imbalance - V/Q
Diffusion impairment
Alveolar
Hypoventilation
Shunt
What happens when alveolar oxygen tension falls?
All vessels constrict if there is arterial hypoxaemia (localised)
A protective mechanism
Do not send blood to alveoli short of oxygen!
What is the effect of constriction of the heart?
Right ventricle has to pump harder
What is the cause of Hypoxaemia?
Ventilation / Perfusion abnormality (•LOW V/Q is COMMONEST cause of hypoxaemia encountered clinically) (mismatch) Bronchitis / Bronchopneumonia
Shunt (Severe bronchopneumonia Lobar pattern with large areas of consolidation) - no ventilation of abnormal alveoli
What causes Low V/Q?
In some alveoli arises due to local alveolar hypoventilation due to some, focal disease
•Hypoxaemia due to low V/Q responds well to even small increases in FIO2
Why is normal V/Q 0.8?
Normally breathe about 4 litres per minute
Cardiac output is 5 litres per minute
What is Shunt?
•Blood passing from Right to Left side of Heart WITHOUT contacting ventilated alveoli
How can shunt arise from congenital heart disease and pulmonary disease?
Pathological shunt in arteriovenous malformations
What makes the alveoli good for allowing the diffusion between air and blood?
Alveolar walls, rich with capillaries
