Lecture 11 - COPD pathophysiology

Question 1

COPD is the __ leading cause of death

Answer 1

4th

Question 2

Traditional definition of COPD

Answer 2

• 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

Question 3

Type A COPD

Answer 3

• Predominant emphysema
• tend to be lean with no fluid retention
• maintained gas exchange through incresaed ventilatory effort
• Often exhibiting mild hypoxemia only

Question 4

Type B COPD

Answer 4

• 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

Question 5

COPD diagnostic criteria according to GOLD

Answer 5

• 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

Question 6

EMphysema

Answer 6

• abnormal permanent enlargement of airspaces distal to the terminal bronchioles with destruction of their walls and without obvious fibrosis

Question 7

• Chronic bronchitis

Answer 7

• 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

Question 8

Small airways disease in COPD

Answer 8

• 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

Question 9

Pure chronic bronchitis characteristics

Answer 9

• large airways: mucus hypersecretion, inflammation, +- chronic bronchitis
• small airways: peribronchiolar fibrosis, airway obstruction, chronic bronchiolitis

Question 10

Pure emphysema characteristic

Answer 10

• Acinus: loss of elastic recoil, emphysema

Question 11

Emphysema: centrilobular (centriacinar)

Answer 11

• 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

Question 12

Emphysema: Panlobular (Panacinar)

Answer 12

• 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

Question 13

Emphysema: Paraseptal

Answer 13

• distal acinar emphysema, preferentially involves the distal airway structures, alveolar ducts and alveolar sacs
• localized around the septa of the lungs or pleura

Question 14

Airway limitation is attributed to three different mechanisms

Answer 14

• 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

Question 15

Loss of elastic recoil in emphysema

Answer 15

• chest wall natural tendency is to move outwards
• lung natural tendency is to move inwards
• these forces are at equilibrium at rest

Question 16

Flow limitation: effects on operating lung volumes

Answer 16

• 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

Question 17

Vital capacity

Answer 17

• = inspiratory capacity + Expiratory reserve volume

- = inspiratory reserve volume + tidal volume + expiratory reserve volume

Question 18

In obstructive diseases what happens to the lung capacities?

Answer 18

• FRC increases

- RV increases a lot

Question 19

Positive effects of hyperinflation

Answer 19

• 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

Question 20

Negative effects of hyperinflation

Answer 20

• overall recoil pressure to drive respiratory flow is reduced
• puts respiratory muscles at a disadvantage

Question 21

Equal pressure point

Answer 21

• flow is determined by the differene between alveolar and intrapleural pressure difference
• point where intrapleural pressure and alveolar pressure are equal - flow stops

Question 22

Equal pressure point and lung movements

Answer 22

• 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

Question 23

3 step process of COPD

Answer 23

• airway collapse: increased RV, air trapping
• Greater traction on the airway enlarging their diameter: increased FRC, hyperinflation
• Chest wall remodeling: Barrel chest, Hoover sign

Question 24

Spirometry in COPD

Answer 24

• necessary to make a diagnosis
• not a good predictor of patient-centred outcomes
• morbidity and mortality better predicted by BODE index

Question 25

- BODE index

Answer 25

- B: Body mass index - O: Airway obstruction (FEV1) - D: Dyspnoea (MMRC dyspnoea scale) - E: Exercise capacity (6 min walk test)

Question 26

Lung volumes in COPD

Answer 26

- a lot of increase in RV - moderate increase in FRC - mild increase in TLC

Question 27

Airway obstruction

Answer 27

- decrease FEV1, FVC and the ratio

Question 28

Importance of lung volumes in COPD

Answer 28

- 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