1 COPD Flashcards
Define COPD
Chronic Obstructive Pulmonary Disease
- Consists of a combination of emphysema and chronic bronchitis
Some patients with COPD have chronic asthma with an element of fixed airway obstruction (but treat as asthma)
Define emphysema
Air space destruction
- permanent enlargement of all or part of the respiratory unit
- it targets the respiratory units, including bronchioles, alveolar ducts, and alveoli
List the causes of emphysema
- smoking (most common cause)
- a1-antitrypsin (AAT) deficiency
List the 2 types of emphysema
- Centriacinar (centrilobular)
- Panacinar emphysema
Describe centriacinar (centrilobular) emphysema
- most common type of emphysema
- can be due to the destruction of distal terminal bronchioles/RB; upper lobes
- primarily involves the apical segments of the upper lobes
Describe panacinar emphysema
- Targets distal terminal bronchioles/entire respiratory unit; lower lobe
Describe the pathogenesis of emphysema
Increased compliance and decreased elasticity
- changes are due to an imbalance between destructive elastase and anti-elastases (e.g. AAT)
- there is an imbalance between oxidants (free radicals and antioxidants)
- elastase and oxidants derive from neutrophils and macrophages
- cigarette smoke: chemotactic to neutrophils
- Free radicals in cigarette smoke inactivate AAT and antioxidants, hence a functional AAT deficiency
Describe the normal function of elastic tissue in the lungs
…and hence describe the effect of the destruction of these elastic tissues to the airways
- Fibres attach to the outside wall of small airways
- These airways apply radial traction to keep airway lumens open
So, destruction of elastic tissue means:
- loss of radial traction in the respiratory unit
- small airways collapse, particularly on expiration
- air trapping behind collapsed distal terminal bronchioles
What observations can be made on a chest X-ray for a patient with emphysema?
- Hyperlucency
- Vertically orientated heart
- Depressed diaphragms
What are the observations made in the blood gas and lung function tests in a patient with emphysema?
- Increased TLC due to an increase in RV - lungs are hyperinflated
- Decreased FEV1
- Decreased FVC
- Decreased FEV1/FVC ratio
- Decreased PaO2 develops late in the disease
- Normal to decreased arterial PCO2 (respiratory alkalosis, “pink puffer”
What are the clinical findings in emphysema?
- Progressive dyspnoea (severe) and hyperventilation
- Emphysema: pink puffer; blow off CO2 (respiratory alkalosis), breathlessness, hyperinflation, and mild hypoxemia
- Hypoxemia occurs late in the disease (takes time for the destruction of respiratory units)
- Hyperinflation causes diminished breathing sounds
- Cor pulmonale is uncommon
- Centriacinar emphysema frequently coexists with Chronic Bronchitis
Define chronic bronchitis
Conducting airway inflammation
What is the clinical diagnosis for Chronic bronchitis?
a productive cough for at least 2 months for 2 years
What are the causes of chronic bronchitis?
- Smoking cigarettes
- Cystic fibrosis
What is the pathogenesis of chronic bronchitis? (chronic cough with mucous)
- Hypersecretion of mucus occurs in the bronchus and its subdivisions
- Obstruction to airflow occurs from mucus plug located in the segmental bronchi and proximal bronchioles - block the exodus of CO2
- Irreversible fibrosis may occur in chronically inflamed segmental bronchi and bronchioles
- Acute inflammation (neutrophils) often superimposed on chronic inflammation
- Loss of ciliated epithelium and presence of squamous metaplasia
What is a mucus plug?
- It allows air to move around in inspiration as the airway is expanding
- CAn expand around plug, but clocks expiration
- Prevents egress of CO2
- This produces respiratory acidosis and potentially wheeze as air is squeezed around the obstruction
What are the clinical findings in emphysema?
- Dyspnoea occurs late in the disease
- Hypoxemia and respiratory acidosis occurs early in the disease, blue bloaters, restain CO2, develop cyanosis from a decrease in O2 saturation
- Tend to be stocky or obese
- Shoulders tend to be higher up, use it for forced breathing (accessory muscles)
- Expiratory wheeze and rhonchi
- Cor pulmonale is commonly present
Describe the observations made in blood gas and lung function tests for a patient with chronic bronchitis
- Less increase in TLC and RV than emphysema
- Chronic respiratory acidosis/hypoxemia
(-arterial PCO2 > 45mmHg)
(-Bicarbonate > 30mEq/L) - Moderate to severe hypoxemia early in the disease
