L10.1 Lung Function in Health and Disease

Question 1

define obstructive lung diseases

Answer 1

difficulty with exhalation ; increased airway resistance e.g. asthma, emphysema, chronic bronchitis, cystic fibrosis

Question 2

define restrictive lung diseases

Answer 2

difficulty with inhalation; impaired lung expansion e.g. pleural effusion/pleurisy, atelectasis, fibrosis

Question 3

what are some possible causes of restrictive diseases

Answer 3

impaired expansion of the lung could be due to…

• damage to lung tissue
• disease of pleura/chest wall
• neuromuscular disease

Question 4

define pulmonary fibrosis and causes

Answer 4

restrictive disease resulting in reduced lung compliance; inflammed lung tissue becomes ‘scarred’
causes: exposure to irritants (e.g. asbestos, silica)

Question 5

define chronic bronchitis and causes

Answer 5

• hypersecretion and mucus and chronic productive cough for at least 3 months of the year for at least 2 consecutive years
• increased in inflammation of the lungs that results in swelling of the airways and a production of mucus
• causes: cigarette smoking, air pollutants

Question 6

what is the pathophysiology of chronic bronchitis

Answer 6

• chronic inflammation
• bronchial oedema and increased mucous production
• impaired mucous clearance
• mucous accumulation in lungs and recurrent infections

Question 7

define emphysema and causes

Answer 7

• permanent enlargement of airways in the respiratory region
• causes: cigarette smoking and pollutants

Question 8

what is the pathophysiology of emphysema

Answer 8

• increased enzymatic activity -> breakdown of lung elastic fibres
• reduced elastic recoil (decrease elastic fibres and decrease surface tension)
• difficulty during expiration
• air trapping (increase residual volume)

Question 9

what are the anatomical changes caused by emphysema

Answer 9

• in normal lung the alveolar walls are complete and the lung has a continuous network of elastic fibres
• with emphysema the alveolar walls are broken and often large air sacs are present (elastic networks have been destroyed). Lungs can expand, and deflate poorly

Question 10

define asthma

Answer 10

• periods of increased airway resistance
  1. inflammation- thickening of airway walls
  2. increased mucous secretion
  3. airway hyperresponsiveness- bronchoconstriction
• reduced airway radius in the bronchioles = increases resistance to air flow

Question 11

what are COPD symptoms

Answer 11

• obstruction: bronchoconstriction/collapse; excess mucus
• difficulty during expiration: early small airway closure causing air trapping
• reduced gas exchange: reduced surface area (emphysema); increased diffusion distance (chronic bronchitis)
• ventilation- perfusion mismatch: imbalance between air in the alveolus and blood in surrounding capillaries

Question 12

airways remain ___ during normal quiet breathing

Answer 12

airways remain OPEN during normal quiet breathing

• resistance to airflow is low
• frictional loss of airway pressure is minimal
• airway pressure higher than intrapleural pressure

Question 13

describe dynamic airway closure

Answer 13

• intra-pleural and intra-alveolar pressure increase
• at low lung volume- loss of pressure in the airways
• dynamic airway closure- equal pressure in airways and pleural sac

Question 14

describe early small airway closure

Answer 14

• in obstructive diseases: equal pressure point reached at higher lung volume = more air gets trapped in the lungs
• airways small airway closure causes air trapping and increased residual volume
• early small airway closure is caused by: increased resistance to airflow (decreased airway diameter, asthma); increased intrapleural pressure (decreased elastic recoil, emphysema)

Question 15

what is spirometry?

Answer 15

• measures volume and flow of air

- two read outs: volume-time curve, flow-volume loop

Question 16

what is volume-time curve?

Answer 16

FVC = maximum volume forcefully exhaled after maximum inspiration
FEV1= forced expiratory volume in 1 second
FEV1/FVC= provides info about resistance to airflow

Question 17

what is flow volume loop?

Answer 17

• maximum inspiration beforehand
• maximum fast expiration followed by maximum fast inspiration
• measures: PEF (peak expiratory flow rate); FVC (forced vital capacity); PIF (peak inspiratory flow rate)

Question 18

what are the factors affecting lung function results?

Answer 18

• healthy population: age, height/build, gender

- pathological factors