Pathology of respiratory tract infection Flashcards
what common viruses can cause URTI
rhinoviruses, adenoviruses,
parainfluenza, influenza and EB virus
what determines the capacity of a patient to resist infection
state of host defence mechanisms
age of the patient
name some common URTI’s (6)
Coryza - common cold Sore throat syndrome Acute Laryngotracheobronchitis (Croup) Laryngitis Sinusitis Acute Epiglottitis
which 2 main organisms cause acute epiglottitis
caused by beta-haemolytic streptococci
or haemophilus influenzae
name some common LRTI’s
Bronchitis
Bronchiolitis
Pneumonia
4 main respiratory tract defence mechanisms?
Macrophage-mucociliary escalator system
General immune system (Humoral and cellular immunity)
Respiratory tract secretions
Upper respiratory tract as a ‘filter’
what 3 parts are involved in the macrophage mucociliary escalator system
alveolar macrophages
mucociliary escalator
cough reflex
process of particle clearance from the lungs
clearance by alveolar macrophage phagocytosis
interstitial pathway via lymph to the lymph nodes
then from the nodes to the trachea- clearance via the mucociliary escalator
what is the mucociliary escalator
whole process of cilia beating secreted mucus with foreign particles within it up the trachea towards the laryngopharynx. It is then either swallowed (it goes to stomach where acidity helps neutralise foreign particles) or it is coughed up
what different classes of pneumonia exist? (6)
Community Acquired Pneumonia Hospital Acquired (Nosocomial) Pneumonia Pneumonia in the Immunocompromised Atypical Pneumonia Aspiration Pneumonia Recurrent Pneumonia
spatial patterns of pneumonia? (3)
bronchopneumonia
segmental
lobar
patterns in characteristics of pneuomonia? (3)
hypostatic
aspiration
obstructive, retention, endogenous lipidq
outcome/complications of pneumonia
most resolve
pleurisy, pleural effusion and empyema
organisation (mass lesion, constrictive bronchiolitis)
lung abscess
bronchiectasis
pneumonia is still a potentially fatal disease
lung abscess
often caused by aspiration
staph aureus, some pneumococci and klebsiella
bronchiectasis is dilatation of Bronchi which can be caused by what? (4)
Severe Infective Episode
Recurrent Infections
Proximal Bronchial Obstruction
Lung Parenchymal Destruction
Bronchiectasis disease profile
75% start in childhood
cough, abundant purulent (pus) sputum
coarse crackles, clubbing
treatment/ investigations for Bronchiectasis
thin section CT
postural drainage antibiotics
surgery
how do recurrent lung infections occur?
Local Bronchial Obstruction - Tumour, Foreign body
Local Pulmonary Damage - Bronchiectasis?
Generalised Lung Disease - Cystic Fibrosis? COPD?
Non-Respiratory Disease -Immunocompromised (HIV, other)?, Aspiration?
what is normal pulmonary gas exchange
air flow in airways - bulk flow and depends on pressure difference
beyond the terminal bronchiole - diffusion occurs
O2 gets pulled into blood by haemoglobin
CO2 is v soluble and rapidly equilibrates between blood and air
what are the 4 abnormal states associated with hypoxaemia?
ventilation/perfusion imbalance
diffusion impairment
alveolar hypoventilation
shunt
type 1 respiratory failure values
NORMAL
PaO2 10.5-13.5 kPa
FAILURE
PaO2 <8 kPa (PaCO2 normal or low)
type 2 respiratory failure values
NORMAL
PaCO2 4.8 – 6.0 kPa
FAILURE
PaCO2 >6.5 kPa (PaO2 usually low)
differentiation between type 1 and 2 respiratory failure?
type 1 and 2 are different based on whether there is a high carbon dioxide level or not
what pulmonary vascular changes occur in hypoxia
pulmonary arteriolar vasoconstriction (when alveolar O2 tension falls)
what do all vessels do if there is arterial hypoxaemia?
constrict
so that blood is not sent to alveoli that are short of oxygen
what is the most common cause of hypoxaemia enzountered in clinic?
low V/Q which can arise due to local alveolar hypoventilation due to some focal disease
what is V/Q
ratio of the amount of air reaching the alveoli per minute to the amount of blood reaching the alveoli per minute
Hypoxaemia due to low V/Q responds well to
small increases in FIO2 (fraction of inhaled O2)
shunt and pneumonia?
can be caused by severe bronchopneumonia
shunt means no ventilation of abnormal alveoli
define shunt
Blood passing from Right to Left side of Heart WITHOUT contacting ventilated alveoli
why do large shunts not responde well to increases in FIO2?
because the blood leaving a normal lung is already 98% saturated (haemoglobin) so can’t increase it much more)
how is a fall in PaO2 due to hypoventilation corrected?
by raising FIO2
where is there deposition?
on the conducting airways
on the terminal bronchioles/proximal alveoli
what is bronchopneumonia?
inflammation of the lungs, arising in the bronchi or bronchioles
what is hypoxic cor pulmonale
a maladaptive response to pulmonary hypertension
croup/epiglottitis
definition signs symptoms diagnosis/investigation management
epiglottitis
inflammation of the upper portion of the larynx or the epiglottis
symptoms - sudden onset of sore throat, stridor, muffled voice, dry cough, pain swallowing, drooling, fever
diagnosis/investigation - do nnot examine with tongue depressor!! due to risk of laryngeal obstruction; rather, they should be urgently referred for laryngoscopy
management - augmentin/cephalosporin
may require intubation
croup
inflammation inside wind pipe
signs - barking cough, stridor, difficulty breathing, no drooling
diagnosis/investigation - clinical diagnosis by ruling out other conditions (diagnosis by exclusion)
management - oral steroids, O2 therapy
what is ottitis media
a common complication of URTI
inflammatory disease of the middle ear
signs - erythema (redness of the skin or mucous membranes), bulging ear drum
symptoms- painful ear, history of URTIs, discharge from ear
diagnosis/investigation - examination of ear
management - painkillers or antibiotics if severe or bilateral
What is coryza (common cold) caused by?
inflammation and irritation of the mucous membranes
