Pathophysiology of Respiratory Disease 2 (COPD & Pneumonia) Flashcards
What does COPD stand for?
COPD - chronic obstructive pulmonary disease
Describe what COPD is
COPD is an umbrella term used for a mixture of chronic bronchitis and emphysema and encompasses a long term, progressive and accelerated decline in respiratory function
State some facts to do with the link between COPD and smoking
90% of COPD is associated with long term tobacco smoke exposure
30% of long term smokers develop COPD
Other factstate or may be genetic and environmental hazards
Describe how smoking reduces respiratory function and causes COPD
- Tobacco smoke contains noxious chemicals and reactive oxygen species that are then inhaled
- This then leads to tissue damage
- This then leads to an inflammatory response whereby IL-8 and TNF alpha are produced (types of cytokines)
- This then leads to macrophage and neutrophil activation and trafficking
- This increases the levels of cytotoxic enzymes like proteases into the local environment which causes more tissue damage
- The chemicals in tobacco smoke can inactivate antiprotease enzymes and so this tissue damage effect is further increased
- The tissue damage then means that there is impaired mucociliary clearance which causes more frequent respiratory infections and so further exacerbates the inflammatory responses
- Over a long period of time this leads to tissue remodelling which causes decreased respiratory function
Describe the features of chronic bronchitis
- Chronic bronchitis -
- Damage to cilia
- Mucus hypersecretion due to increased goblet cells and mucus gland activation
- Inflamed swollen airway tissue and oedema
- Weakened airway structure due to a loss of elastin and a loss of patency causing airway collapse
- Causes -
- Impaired mucociliary clearance - increased risk of infection which leads to recurrent infections
- Irritation of sensory neurons causing a cough
- Decreased luminal area increasing airway resistance and obstruction
Describe how emphysema impacts lung function in COPD (enlargement)
- There is an enlargement of the airspaces in the lungs
- This decreases the surface area and perfusion
- This then decreases gas exchange
- There is a loss of elastin fibres which increases compliance and decreases recoil
Describe the effects of chronic respiratory failure on the body
- Leads to chronic alveolar hypoxia
- Leads to widespread hypoxic vasoconstriction which increases pulmonary vascular resistance
- This leads to pulmonary hypertension
- There is increased right ventricular afterload which leads to hypertrophy of right ventricle
- There is then right heart failure
- It also causes hypoxaemia, hypercapnia and acidemia which means the person has reduced exercise tolerance, fatigue and a decreased quality of life overall
Describe what pneumonia is
- Infection of the lung parenchyma - results in inflammation and oedema
- It is classified into different types based on the infectious agent e.g. whether it is bacterial, viral, fungal and tissues effects
Describe the pathophysiology of pneumonia
- There is weakening of host defences e.g. following viral infection damage to epithelium or immune suppression
- This causes the alveoli to become colonised by pathogens
- There is activation of macrophages and cytokine release (IL-6, IL-8 and TNF alpha)
- There is then recruitment of neutrophils into alveolar space, release of proteases and reactive oxygen species
- Injury to alveolus and surrounding structures
Describe how alveolar injury leads to impaired gas exchange and hypoxaemia in pneumonia
- After alveolar injury there is deposition of dead cells and proteins in the alveolar wall which impairs gas exchange and leads to hypoxaemia
- It also causes disruption of the endothelium and basement membrane
- This causes fluid to accumulate in the alveoli and or interstitium which can cause lung sounds like crackles and lung opacity on x ray - causes impaired gas exchange and hypoxaemia
- Hypercapnia is avoided due to a reflex increase in ventilation in better functioning areas of the lung
