Lecture 11 - COPD pathophysiology Flashcards
1
Q
COPD is the __ leading cause of death
A
4th
2
Q
Traditional definition of COPD
A
- encompasses chronic bronchitis and emphysema
- A COPD phenotype is a single or combination of disease attributes that describe differences between individuals with COPD as they relate to clinically meaningful outcomes
3
Q
Type A COPD
A
- Predominant emphysema
- tend to be lean with no fluid retention
- maintained gas exchange through incresaed ventilatory effort
- Often exhibiting mild hypoxemia only
4
Q
Type B COPD
A
- predominant bronchitis with cough and sputum production
- allowed their gas exchange to deteriorate
- poorer prognosis with the onset of fluid retention and cor pulmonale
- worse hypoxemia and hypercapnia as the disease progressed
5
Q
COPD diagnostic criteria according to GOLD
A
- any patient who has dyspnea, chronic cough or sputum production, and a history of exposure to risk factors for the disease
- spirometry is required to make the diagnosis in this clinical context
- the presenxe of a post-bronchodilator FEV1/FVC
6
Q
EMphysema
A
- abnormal permanent enlargement of airspaces distal to the terminal bronchioles with destruction of their walls and without obvious fibrosis
7
Q
- Chronic bronchitis
A
- productive cough on most days for at least 3 consecutive months over not less than 2 consecutive years
- not necessarily associated with airflow limitation
- but in the presence of obstruction leads to more exacerbations and more rapid decline of lung
8
Q
Small airways disease in COPD
A
- importance of small airway function in COPD
- Respiratory bronchiolitis recognised as early lesion in young smokers
- chronic inflammatory immune cell infiltration, tissue repair and remodeling process leads to increase resistance in airways
9
Q
Pure chronic bronchitis characteristics
A
- large airways: mucus hypersecretion, inflammation, +- chronic bronchitis
- small airways: peribronchiolar fibrosis, airway obstruction, chronic bronchiolitis
10
Q
Pure emphysema characteristic
A
- Acinus: loss of elastic recoil, emphysema
11
Q
Emphysema: centrilobular (centriacinar)
A
- primarily the upper lobes
- occurs with loss of respiratory bronchioled in the proximal portion of the acinus,with sparing of distal alveoli
- this pattern is most typical for smokers
12
Q
Emphysema: Panlobular (Panacinar)
A
- involves all lung fields, particularly the bases
- occurs with loss of all portions of the acinus from the respiratory bronchiole to the alveoli
- this pattern is typical for a-1-antitrypsin deficiency
13
Q
Emphysema: Paraseptal
A
- distal acinar emphysema, preferentially involves the distal airway structures, alveolar ducts and alveolar sacs
- localized around the septa of the lungs or pleura
14
Q
Airway limitation is attributed to three different mechanisms
A
- Partial block of the lumen
- thickening of the airway wall, which occurs because of edema or muscle hypertrophy
- abnormality of the tissue surrounding the airways
15
Q
Loss of elastic recoil in emphysema
A
- chest wall natural tendency is to move outwards
- lung natural tendency is to move inwards
- these forces are at equilibrium at rest
16
Q
Flow limitation: effects on operating lung volumes
A
- airflow during exhalation is the result of the balance between the elastic recoil of the lungs promoting flow and resistance of the airways that limits flow
- in flow limited patients, the time available for lung emptying during spontaneous breathing is often insufficient to allow lung volume to decline to its natural relaxation volume
- this leads to lung hyperinflation
17
Q
Vital capacity
A
- = inspiratory capacity + Expiratory reserve volume
- = inspiratory reserve volume + tidal volume + expiratory reserve volume
18
Q
In obstructive diseases what happens to the lung capacities?
A
- FRC increases
- RV increases a lot
19
Q
Positive effects of hyperinflation
A
- greater traction on the airways enlarging their diameter
- holds open collateral channels in lung parenchyma allowing ventilation past occluded airways and improve gas exchange
- shifting the lung’s pressure volume relationship
20
Q
Negative effects of hyperinflation
A
- overall recoil pressure to drive respiratory flow is reduced
- puts respiratory muscles at a disadvantage
21
Q
Equal pressure point
A
- flow is determined by the differene between alveolar and intrapleural pressure difference
- point where intrapleural pressure and alveolar pressure are equal - flow stops
22
Q
Equal pressure point and lung movements
A
- Forced exhalation: pleural pressure becomes positive
- Increased respiratory effort: increasing IP moves the EPP and the site of airway compression closer to the alveoli
- in COPD, the equal pressure point is very distal - air gets trapped
23
Q
3 step process of COPD
A
- airway collapse: increased RV, air trapping
- Greater traction on the airway enlarging their diameter: increased FRC, hyperinflation
- Chest wall remodeling: Barrel chest, Hoover sign
24
Q
Spirometry in COPD
A
- necessary to make a diagnosis
- not a good predictor of patient-centred outcomes
- morbidity and mortality better predicted by BODE index
25
Q
- BODE index
A
- B: Body mass index
- O: Airway obstruction (FEV1)
- D: Dyspnoea (MMRC dyspnoea scale)
- E: Exercise capacity (6 min walk test)
26
Q
Lung volumes in COPD
A
- a lot of increase in RV
- moderate increase in FRC
- mild increase in TLC
27
Q
Airway obstruction
A
- decrease FEV1, FVC and the ratio
28
Q
Importance of lung volumes in COPD
A
- respiratory muscles are inefficient at high lung volumes
- COPD is characterised by gas trapping and hyperinflation - work of breathing is increased
- volume response to bronchodilator is more important than airway response
- Volume response correlates with improvements in dyspnea, exercise capacity and QOL
- basis of LVRS treatment for emphysema
