Pathology of Respiratory Tract Infection Flashcards
What is croup?
Acute Laryngotracheobronchitis - Upper respiratory tract infection
What infective agents can cause acute epiglottitis?
Group A beta-haemolytic Streptococci
Haemophilus influenzae
*Rarely caused by Parainfluenza virus type 4 - other viruses may also be responsible
List common upper respiratory tract infections
Coryza - common cold Sore throat syndrome Croup Laryngitis Sinusitis Acute Epiglottitis
List common lower respiratory tract infections
Bronchitis
Bronchiolitis
Pneumonia
What structures and systems work as respiratory tract defence mechanisms
Macrophage-mucocilliary escalator system
General immune system (humoral and cellular)
Respiratory tract secretions acting as filters
Failure in any of the respiratory tract defence mechanisms results in what?
Increased risk of respiratory tract infections
What three components make up the macrophage-mucocilliary escalator system/
Alveolar macrophages
Muscociliary escalator
Cough reflex
How does particle clearance from the lungs work in the terminal bronchioles/proximal alveoli?
Clearance by alveolar macrophages phagocytosis
Interstitial pathways via lymph to lymph nodes
How does particle clearance from the lungs work in the conducting airways?
Clearance by the mucociliary escalator - expelled by cough or swallow reflexes
What are the aetiological types of pneumonia?
Community acquired pneumonia Hospital acquired (nosocomial) pneumonia Pneumonia in the immunocompromised Atypical pneumonia Aspiration pneumonia Recurrent pneumonia
What is bronchopneumonia?
Pneumonia arising in the bronchi
What is lobar pneumonia?
Pneumonia localised to a lobe of the lung
What is meant by the term hypostatic pneumonia?
Refers to pneumonia characterised by collection of fluid in the dorsal regions of the lungs
What are the outcomes of pneumonia?
Most resolve
Pleurisy, Pleural effusion and emphysema (puss in pleural cavity)
Organisation
Lung abscess
Bronchiectasis (widened lungs which fill with sputum; characterised by productive cough)
Organisation of pneumonia can result in what three outcomes?
Mass lesion
Cryptogenic organising pneumonia (COP)/BOOP
Constrictive bronchiolitis
What are the two types of respiratory failure?
Type 1 PaO2 <8kPa
Type 2 PaCO2 >6.5kPa
What are the four abnormal states associated with hypoxaemia?
Ventilation/Perfusion mismatch
Diffusion impairment
Alveolar hypoventilation
Shunt
What does hypoxaemia lead to?
Pulmonary vascular changes
What are the pulmonary vascular changes associated with hypoxaemia?
Physiological pulmonary arteriolar vasoconstriction - pulmonary hypertension - occurs as a result of a fall in oxygen tension
What is the most common cause of hypoxaemia clinically?
Vent/Perf mismatch
What is the normal V/P value?
.8
What is a cause of local low V/P?
Local alveolar hypoventilation due to local disease
How is hypoxaemia typically treated?
Responds well to even a small increase in FiO2 (Fraction of inspired oxygen)
When does shunt occur in the lungs?
When there is no ventilation of alveoli
What is shunt?
Blood passing from right to left side of heart without contacting ventilated alveoli
What is the normal percentage of shunt?
2-4%
What can be the cause of pathological shunt?
Arteriovenous malformations
Congenital heart disease
Pulmonary disease (Our important one for this topic)
