Lecture 4 - ventilation, lung mechanisms and disorders Flashcards

1
Q

Functional residual capacity in patient with emphysema

A

Increases - air filled alveolar spaces

Chest wall expansion has a greater force than lung elastic recoil

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2
Q

Functional residual capacity in patient with pulmonary fibrosis

A

Decreases

Elastic recoil greater than compliance

Therefore can’t stretch as much

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3
Q

Bronchus structure

A

Small islands of cartilage

Glands in submucosa

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4
Q

Bronchiole structure

A

No cartilage or glands in submucosa

Thin walls

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5
Q

Radial traction

A

Outward tugging force exerted by surrounding alveoli on the bronchioles to prevent collapse during expiration when the pressure increases.

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6
Q

What type of cells are type II pneumocytes?

A

Cuboidal

Type I is simple squamous

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7
Q

What can arise if there is an inability to expand the chest?

A

Hypoventilation
CO2 increases
O2 decreases - Type 2 respiratory failure

e.g. in Duchene’s muscular dystrophy

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8
Q

Pneumothorax

A

Air in pleural space with loss of pleural seal therefore lung collapse as loss of negative pressure

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9
Q

Conditions where there is decreased compliance

Restrictive

A

Interstitial lung disease - increased collagen in alveolar walls therefore stiffer

Respiratory distress syndrome - decrease in surfactant increases surface tension

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10
Q

Conditions where there is decreased elasticity

obstructive

A

Asthma - narrowed airways therefore increased resistance and loss of elastin

COPD - emphysema - loss of elastic recoil and alveoli are distended

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11
Q

Why are problems with air flow worse in expiration?

A

During expiration, pressure increases as airways decrease in volume as compressed.

Therefore more likely to collapse e.g. due to loss of radial traction

Passive so not controlled by muscles

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12
Q

Interstitial lung disease

A

Diffuse lung fibrosis - thicker pulmonary interstitium, increasing the diffusion pathway

  • Stiffer lungs
  • Reversible and irreversible fibrosis
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13
Q

Pathophysiology of interstital lung disease

A
  1. Deposition of fibrous tissue in the interstitium
  2. Lungs are less complaint
  3. Elastic tissue is replaced by collagen therefore decreased compliance as stretch less
  4. Elastic recoil increases therefore SA decreases
    (airways are not narrowed as the alveolar still exert radial traction)
  5. Restrictive ventilatory defect as chest expansion is reduced as greater elastic recoil force
  6. Thickening of the alveolar walls increases the diffusion pathway
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14
Q

What type of ventilation defect is interstitial lung disease

A

Restrictive

FVC decreased

FEV1/FVC - normal or greater than 70%

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15
Q

Symptoms of intersitial lung disease

A

Shortness of breath (dyspnea)
Dry cough
Reduced exercise tolerance
Fatigue

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16
Q

Signs of interstitial lung disease

A
Tachypnoea
Tachycardia
Coarse crackles
Finger clubbing
Reduced bilateral chest movement 

Pleural effusions

17
Q

What does the interstitium contain?

A

Fibroblasts
Elastin fibres
Collagen fibres

18
Q

What can cause interstitial lung disease?

A

Exposure to:

  • Asbestos
  • Drugs - methotrexate
  • Radiation
  • Mouldy hay

Autoimmune- mediated inflammation - sarcoidosis

Connective tissue disorder:
SLE
Rheumatoid arthritis

Idiopathic pulmonary fibrosis

19
Q

Neonatal respiratory distress syndrome

A

Do not produce surfactant in babies less than 30 weeks

Increased surface tension
Decreased lung expansion
Some alveoli collapse therefore no gas exchange
Impaired ventilation

20
Q

Presentation of neonatal respiratory distress syndrom

A
Grunting
Nasal flaring
Intercostal and subcostal retractions
Tachypnoea
Central cyanosis
21
Q

How to treat respiratory distress syndrome

A

Give steroid in utero

Give surfactant in ventilator when 34 weeks old

22
Q

COPD

A

Chronic
Impaired airflow
Irreversible

Emphysema and chronic bronchitis

Mucus hypersecretion - mucous plugging
Reduced cilia - mucous not cleared
Obstructive ventilation

23
Q

Clinical diagnosis of COPD

A

Productive cough for more than 3 months for more than once a year

24
Q

Cause of COPD

A

Smoking

Inhaled pollutants

25
Pre COPD
Impaired airflow but no clinical symptoms yet with normal spirometry. High risk of COPD in 5 years
26
Causes of mucous hypersecretion on COPD
Loss of cilia Decreased PEF Airway occlusion ``` Increased production: Oxidative stress Viral infection Inflammatory celss Bacterial infection ```
27
Chronic bronchitis
Increased mucus production in bronchi
28
Emphysema
Loss of elastin (destruction) in alveolar walls therefore loss of elastic recoil and radial traction. Increased compliance Permanent enlargement of air spaces distal to the terminal bronchioles (air trapping) Dried mucus plug block - Inflammatory cells accumulate which releases elastases and oxidants, destroying alveolar walls and elastin + protease-mediated destruction (alpha 1 antitrypsin deficiency) Increased lung volume and takes longer to completely expel air Barrel chest
29
Asthma
Reversible airway obstruction triggered by a stimulus Smooth muscle hypertrophy - thicker airway walls Bronchoconstriction Mucosal oedema In bronchi and bronchioles
30
Emphysema on CXR
Flattened diaphragm | Hyperinflated lungs - air trapping
31
Difference between emphysema and pulmonary fibrosis
Emphysema: - Loss of elastin - Decreased elastic recoil and increased compliance - Hyperinflated lungs (Barrel chest) - Small airways collapse during expiration due to loss of radial traction - Air trapping - Obstructive Pulmonary fibrosis: - Increased collagen deposition - Increased elastic recoil and decreased compliance - Lungs are stiffer and harder to expand - Smaller lungs - Decreased functional residual capacity - Restrictive
32
Causes of atelectasis
Respiratory distress syndrome Compression collapse: - Pneumothorax - Pleural effusion Compression from abdominal distension - after major abdominal surgery don't want to take deep breaths Resorption collapse: Tumour in bronchioles - obstructed airway
33
How to treat pneumothorax
Chest drain using an underwater seal - prevents fluid or air from entering the pleural seal
34
Resorption collapse
The airway is obstructed Air downstream is slowly absorbed into the bloodstream but new air cannot enter distal to the site of blockage - Alveoli collapse
35
Causes of hypoventilation
``` Duchene's muscular dystrophy RDS Opiates Head injury Guillain Barre syndrome Myasthenia gravis Pneumothorax Severe asthma End-stage COPD Foreign body Pulmonary fibrosis Kyphoscoliosis Severe obesity ```
36
Cough reflex
Coordinated by the cough centre in the medulla oblongata - Deep inspiration - Glottis is closed due to adduction of the vocal cords - Strong contraction of expiratory muscles - Increase in intra-pulmonary pressure - Sudden opening of the glottis by abduction of the vocal cords causes an explosive discharge of air