Pathology of Pulmonary Infections Flashcards
Healthy people are mainly infected by what kind of microorganisms?
Viruses/aggressive organisms
What are the different categories of pathogens?
- primary
- facultative
- opportunistic
The capacity of a host to resist infection depends on what factors?
- State of host defence mechanisms
- Age of patient
What effect will being immunocompromised have on a patient’s likelihood to have an infection?
It increases the patient’s susceptibility (particularly from opportunistic pathogens)
What are the most common upper respiratory tract infections?
- Coryza (common cold)
- Sore throat syndrome
- Acute Laryngotracheobronchitis (croup)
- Laryngitis
- Sinusitis
- Acute Epiglottitis
As a result of vaccination, what pathogen is increasing responsible for epiglottitis?
Group A beta-haemolytic streptococci
What are the most common lower respiratory tract infections?
- Bronchitis
- Bronchiolitis
- Pneumonia
Aside from the general immune system and respiratory tract infections, what is the main respiratory tract defence mechanism?
The macrophage-mucociliary escalator system
In normal conditions, is the lower respiratory tract sterile or non-sterile?
Sterile
What cells are responsible for trapping dirt allowing it to be removed from the lower respiratory tract?
Alveolar Macrophages
What is the function of ciliated cells in the respiratory tract?
To carry a layer of mucous upwards on the mucociliary escalator from the lower respiratory tract to the larynx
What happens to the mucous layer containing any dirt or foreign particles once it is swept by the mucociliary escalatory into the larynx?
It is swallowed or spat out
What kind of infection is often fatal to people in a flu epidemic due to disruption of the mucociliary escalator?
Secondary bacterial infection
What is the danger of cellular bronchitis, especially in small children?
Inflammatory exudate produced during infection can close off the airway very rapidly
Pneumonia can be classed in what three categories?
- Anatomical
- Aetiological
- Microbiological
Microbiological classification can be used to do what?
Confirm what organism is causing infection and allow a suitable treatment to be given
Under what headings can pneumonia be classed, aetiologically?
- Community acquired
- Hospital Acquired
- Pneumonia in the Immunocompromised
- Atypical
- Aspiration
- Recurrent
What is the most common aetiological classification of pneumonia?
Community acquire pneumonia
What two aetiological classes of pneumonia are generally caused by aggressive organisms?
Community acquired
Hospital acquired
What aetiological class of pneumonia is caused by abnormal organisms?
Atypical
A pneumonia infection in a patient with another condition e.g. cardiac failure can lead to what in the lungs making it difficult to clear the infection?
Accumulation of secretions
What anatomical distributions of pneumonia are there?
- Bronchopneumonia
- Segmental Pneumonia
- Lobar Pneumonia
What form of pneumonia shows acute inflammation at a pathological level and spots of infection and formation of pus in the lungs?
Bronchopneumonia
What is often seen on a chest x-ray of a patient with bronchopneumonia relating to the focal nature of consolidation?
Bilateral basal patchy opacification
What is consolidation?
The replacement of air in the lungs by another substance
What is seen in lobar pneumonia?
Consolidation/infection of an entire lobe
The extensiveness of lobar and broncho-pneumonia is dependent on what feature of the causative organism?
The aggressiveness
Give a complication of pneumonia
- Pleurisy
- Pleural effusion
- Empyema
- Lung abscess
- Bronchiectasis
- Organising pneumonia (mass lesion/cryptogenic organising pneumonia/constrictive bronchiolitis)
What is the cause of Organising Pneumonia?
Bronchopneumonia turning into fibrosis
10% of patients presenting with a lung abscess will have what?
An underlying tumour
Lung abscess can result from the obstruction of what structure?
Bronchus
What 3 pathogens most commonly cause lung abscesses?
- Staphylococcus Aureus
- Klebsiella
- some Pneumococci
What is Bronchiectasis?
The severe dilatation of bronchi
What are the causes of Bronchiectasis?
- Severe infective episode
- recurrent infections
- proximal bronchial obstruction
- lung parenchymal destruction
Is Bronchiectasis most common in adult life or childhood?
Childhood
What are the symptoms of chronic bronchiectasis infection?
- cough
- abundant purulent sputum
- haemoptysis
What are the main treatments for bronchiectasis?
- postural drainage
- antibiotics
- surgery
What might cause local bronchial obstruction and lead to recurrent lung infection?
- tumour
- foreign body
What local pulmonary damage is a common cause of recurrent lung infections?
Bronchiectasis
What generalised lung disease is a common cause of recurrent lung infection?
- Cystic Fibrosis
- COPD
In what kind of patients might non-respiratory disease cause recurrent lung infection?
- Immunocompromised
What is the cause of Aspiration Pneumonia?
Vomit travelling down the oesophagus into the lung
What section of the lung is most common affected by aspiration pneumonia?
Apical segment of the right lower lobe
What type of pneumonia might affect someone after excessive alcohol consumption?
Aspiration pneumonia
What is an opportunistic lung infection?
An infection caused by organisms not normally capable of producing disease in patients with functioning lung defences
Opportunistic infections are most common in what patients?
Immunocompromised
Bulk flow in airways can be _ or _
Laminar
Turbulent
What does turbulent flow in the upper respiratory tract do to inhaled air?
Humidifies/warms it
Pulmonary gas exchange occurs at what barrier?
Blood-air barrier
Gas moves by diffusion beyond
terminal bronchioles
What is Type I respiratory failure?
Failure to maintain arterial oxygen concentration above 8 kPa
What is Type II respiratory failure?
Inability to get rid of carbon dioxide
What four abnormal states are associated with Hypoxaemia?
- Ventilation/Perfusion imbalance
- Diffusion impairment
- Alveolar Hypoventilation
- Shunt
What pulmonary vascular change occurs in hypoxia?
Pulmonary arteriolar vasoconstriction
Pulmonary arteriolar vasoconstriction occurs when
Oxygen tension falls in pulmonary tissue
In Hypoxia, what changes will occur in the amount of blood going to the abnormal lung?
Amount of blood going to abnormal lung will be greatly reduced compared to normal
Other than in lung disease, when might hypoxia occur?
At high altitudes
Severe bronchopneumonia can cause what abnormal state associated with Hypoxaemia?
Shunt
Bronchitis and Bronchopneumonia can cause what abnormal state associated with Hypoxaemia?
Ventilation/Perfusion mismatch
To what abnormal state would treating with 100% oxygen make no difference due to no ventilation?
Shunt
What is the most common cause of hypoxaemia encountered clinically?
Low V/Q mismatch
Hypoxaemia due to low V/Q responds well to small increases in what?
FIO2
What is Shunt?
Blood passing from the right to left side of the heart without contacting ventilated alveoli
What are the common causes of Hypoxaemia in COPD?
- Ventilation/Perfusion abnormality
- alveolar hypoventilation
- diffusion impairment
- shunt
What would the cause of hypoxaemia likely be in a patient with chronic COPD?
Alveolar hypoventilation (as breaths per minute are decreased and CO2 retained)
What is Alveolar Hypoventilation?
An insufficient amount of air moved in and out of the lungs
What effect does hypoventilation have on PACO2, PaCO2, PAO2 and PaO2?
PACO2 - increases
PaCO2 - increases
PAO2 - decreases
PaO2 - decreases
Fall in PaO2 due to hypoventilation can be corrected by raising what?
FIO2
Why can chronic hypoxia lead to pulmonary hypertension?
Causes bone marrow to produce more red blood cells which makes blood more viscous and difficult to move through blood vessels and lungs
What is Chronic Cor Pulmonale?
Hypertrophy of the right ventricle resulting from disease affecting the function and/or structure of the lung