Pathology of pulmonary infection 1 Flashcards
Types of microorganism pathogenicity
-Primary(most dangerous)
-Facultative ( needs little
help to establish infection)
-Opportunistic ( doesn’t normally cause infection, but it does in the immunocompromised)
What determines the capacity of an individual to resist infection?
- State of the host defence mechanisms
- Age of patient
State types of Upper respiratory tract infections (URTI)
SALSAC
- Coryza (common cold)
- Sore throat syNdrome
- Acute Laryngotracheobronchitis ( Croup)
- Laryngitis
- Sinusitis
- Acute epiglottiitis
What bacterias can be responsible for acute epiglottitis?
- Haemophilus infuenzae ( type b - Hib)
- Group A beta-haemolytic streptococci
- Parainfluenza virus type 4 (rarely)
State examples of lower respiratory tract infections
- Bronchitis (infection of bronchi)
- Bronchiolitis ( ‘’ ‘’ of bronchioles)
- Pneumonia( infection involving alveolar air space/air sacs + fluid)
State the respiratory tract defence mechanisms
- Macrophage-mucociliary escalator system: main mechanism that sterilises LRT
- General immune system ( humoral and cellular immunity)
- RT secretions(mucous) + upper RT acting as a ‘filter’
- failure of these will increase risk of RTI
Describe the macrophage-mucociliary escalator system
- Alveolar macrophages ( englufs particles that reaches alveolar space>interstitial pathway via lymph to lymph nodes)
- Mucociliary escalator (system of moving mucous from lower RT>throat)
- cough reflex ( aspirtate/swallow)
State the aetiological classifications of pneumonia
CHAAIR
-Community Acquired Pneumonia
-Hospital Acquired (Nosocomial) Pneumonia (may have antibiotic resistance)
-Pneumonia in the
Immunocompromised (opportunistic pathogens can establish lung infection)
- Atypical Pneumonia (unusual organisms)
- Aspiration Pneumonia(vomit or other aspirated particles)
- Recurrent Pneumonia(patient keeps getting it in same region)
Patterns of pneumonia
- Bronchopneumonia
- Segmental
- Lobar
- Hypostatic ( lung secretions accumulating)
- Aspiration
- Obstructive, retention, endogenous lipid
Features of bronchopneumonia
- acute inflammation of bronchioles/bronchi
- bilateral basal
- patchy opacification relating to the nature of consolidation
- high neutrophil count, ocalised in small airways and alveolated tissue, Does not reach pleura so no pleural complications unlike other types of pneumonia
State the outcomes/complications of pneumonia
- pleurisy(inflammation of pleura), pleural effuision (fluid builds up between pleural membranes) effusion and empyema ( pus accumulates in pleural cavity)
-organisation(production of scar/fibrous tissue)
: mass lesion, COP (cryptogenic organising pneumonia BOOP), constricive bronchitis
-lung abscess
-bronchiectasis
Lung abscess
-obstructed bronchus: tumour(can be mistaken by this)
Caused by
- aspiration
- particular organism ( S.aureus, pneumococci, klebsiella)
- metastatic in pyaemia
- nectrotic lung ( secondary infection)
What is Bronchiectasis?
- pathological dilation of bronchi due to :
- severe infective episode
- reduccrent infections
- proximal bronchial obstruction
- lung parenchymal destruction
Symptoms of Bronchiectasis
- 75% starts in childhood
- cough, abundant sputum, haemopytis, signs of chronic infection
- course crackles, clubbing
- thing sectrion CT ( previously bronchography)
- postural drainage, antibiotics, surgery
Complications of Bronchiectasis
-Haemorrage
Causes of aspiration pneumonia
- vomiting
- oesophageal lesion
- obstretic anaesthesia
- neuromuscular disorders
- sedation
What is Opportunistic infections ?
- increased chance of ‘ordinary ‘ infections
- infection by organisms not normally capaeble of producing disease in patients with intact lung defences
Types of opportunistic lung infections
- Low grade bacterial pathogens
- CMV
- pneumocystis jirovecii
- other fungi + yeasts
State the four abnormal states associated with hypoxaemia(Low O2 in blood)
- ventilation/perfusion imbalance - V/Q ratio
- diffusion impairment
- alveolar hypoventilation
- shunt ( ventilation
Pulmonary vascular changes in hypoxia
-physiological pulmonary arteriolar vasoconstriction: when alveolar oxygen tension falls, can be localised effect. All vessels constrict if there is arterial hypoxaemia
Why does pneumonia cause hypoxaemia
- ventilation/perfusion abnormality ( bronchitis/bronchopneumonia) < Most common! : some ventilation of abnormal alveoli but just not enough
- shunt ( in severe bronchopneumonia) : no ventilation of abnormal alveoli
Signs of shunt/severe bronchopneumonia on lobes
lobar pattern with large areas of consolidation
Shunt
Blood passing from Right to Left side of Heart WITHOUT contacting ventilated alveoli
Normally 2-4% shunt
Pathological shunt in AV malformations, congenital heart disease and PULMONARY DISEASE
Large shunts respond poorly to increases in FI O2
Blood leaving normal lung is already 98% saturated
Why does COPD cause hypoxaemia?
- Airway Obstruction
- Reduced Respiratory Drive
- Loss of Alveolar Surface Area
- Only during acute exacerbation
Alveolar hypoventilation
- insufficient air moved in + out lungs
- increases PACO2 + decreases PAO2
How is fall in PaO2 due to hypoventilation corrected?
-by raising FIO2 ( fraction of inspired air which is O2RR
Why is there pulmonary hypertension in hypoxic cor pulmonale
- pulmonary vasoconstriction
- pulmonary arterioles ; muscle hypertrophy + intima fibrosis
- loss of capillary bed
- secondary polycythaemia
- bronchopulmonary arterial anastomoses
What is Chronic (hypoxic) cor pulmonale
-hypertrophy of right ventricle resulting from disease affecting the function and/or structure of the lung, except where diseases primarily affect the left side of the heart/congenital HD
