Lung Ventilation

Question 1

Define ventilation

Answer 1

The process of inspiration and expiration

Question 2

What are the parts of the respiratory tract?

Answer 2

• conducting portion: anatomical dead space
• respiratory portion

Question 3

Outline the process of passive expiration

Answer 3

• muscles used in inspiration relax
• diaphragm moves up
• thoracic cavity volume reduces
• volume of lungs reduces and return to original
  volume
• intrapulmonary pressure increases
• air expelled

Question 4

What makes up the conducting portion of the respiratory tract

Answer 4

Nasal cavity to the terminal bronchioles

• nasal cavity
• pharynx
• larynx
• trachea
• primary + secondary bronchi
• bronchioles
• terminal bronchioles

Question 5

What makes up the respiratory portion of the respiratory tract?

Answer 5

• respiratory bronchioles
• alveolar ducts
• alveoli

Question 6

What is anatomical dead space?

Answer 6

The volume of air in the conducting airways

Question 7

What is alveolar dead space?

Answer 7

Air in alveoli which do not take part in gas exchange
e.g. damaged alveoli

Question 8

What is physiological dead space?

Answer 8

PDS = anatomical DS + alveolar DS

Question 9

How do you calculate tidal volume?

Answer 9

TV = anatomical dead space + alveolar ventilation

Question 10

How do you calculate the total pulmonary ventilation?

Answer 10

TPV = tidal volume x respiratory rate

Question 11

What is the pressure inside the lungs called?

Answer 11

Intrapulmonary pressure

Question 12

Outline the process of inspiration

Answer 12

• external intercostal muscles contract
• diaphragm contracts + flattens
• intrathoracic volume increases
• intrapulmonary pressure decreases below atmospheric pressure
• elastic tissue in alveoli is stretched
• air pushed into lungs

Question 13

What are the accessory muscles involved in forced inspiration?

Answer 13

• sternocleidomastoid
• scalene muscles
• serratus anterior
• pectoralis major + minor

Question 14

What accessory muscles are used in forced expiration?

Answer 14

• internal intercostals
• abdominal wall muscles

Question 15

Describe the pleural seal

Answer 15

• the surface tension of the pleural fluid creates a film that coats the lungs + the thoracic cavity > when chest cavity expands so do the lungs
• the film prevents the lungs from collapsing + allows for expansion and contraction when breathing

Question 16

Describe the pleural membranes of the thorax

Answer 16

• Parietal pleura lines the inside of each hemi-thorax
• Visceral pleura lines the lungs

Question 17

What does parietal pleura line?

Answer 17

Parietal pleura lines each hemi-thorax

Question 18

What is the hemi thorax?

Answer 18

The bony thoracic cage, diaphragm + mediastinal surfaces

Question 19

What is the intrapleural space?

Answer 19

Space between visceral and parietal pleura

Question 20

What does visceral pleura line?

Answer 20

Visceral pleura lines the lungs

Question 21

What is functional residual capacity?

Answer 21

Volume of air remaining after passive expiration

Question 22

What is compliance?

Answer 22

A measure of how distensible the lungs are

Question 23

How do you calculate compliance?

Answer 23

C = change in volume / change in pressure

Question 24

What is emphysema?

Answer 24

• condition in which destruction of the terminal bronchioles + distal air spaces occurs via the breakdown of elastin
• permanent enlargement of air spaces (bullae)

Question 25

What is the opposite of compliance?

Answer 25

Lung elastic recoil

Question 26

What is elastic recoil in respiratory system?

Answer 26

The ability of something to return to its original size

Question 27

What is elastic recoil directly related to?

Answer 27

- connective tissue surrounding alveoli ( elastic fibres) - alveolar fluid surface tension

Question 28

What does lungs returning to their original volume depend on?

Answer 28

Elastic recoil

Question 29

Where do interstitial lung disease occur?

Answer 29

The interstitium between alveolar epithelium + capillary endothelium

Question 30

What happens in pulmonary fibrosis in terms of compliance and elastic recoil?

Answer 30

- stiff lungs > **compliance is reduced** - **elastic recoil is increased** > resting lung volume is smaller - restrictive disease

Question 31

What impact does surface tension have on compliance?

Answer 31

Surface tension decreases compliance

Question 32

What issue can occur in premature babies <35 weeks in relation to the alveoli?

Answer 32

**Surfactant respiratory distress syndrome** - not enough lung surfactant has been produced > alveoli collapse - exogenous lung surfactants are needed

Question 33

Clinical features of neonatal respiratory distress syndrome?

Answer 33

- grunting - nasal flaring - intercostal +subcostal retractions (use of accessory muscles) - tachypneoa - cyanosis

Question 34

Treatment for neonatal respiratory distress syndrome

Answer 34

- surfactant replacements via endotracheal tube - O2/assisted ventilation

Question 35

At how many weeks do babies have enough surfactant?

Answer 35

35 weeks

Question 36

How could you calculate the patient’s total pulmonary ventilation?

Answer 36

Tidal volume x respiratory rate

Question 37

What is the negative intrapleural pressure?

Answer 37

- **lungs** have a natural **inward elastic recoil** - **chest wall** has a natural **outward elastic recoil** - opposing forces create a negative pressure in the intrapleural space

Question 38

Role of negative intrapleural pressure

Answer 38

Keeps alveoli/lungs from fully collapsing with each expiration

Question 39

How does intrapulmonary pressure change between inspiration and expiration relative to the atmosphere

Answer 39

- **inspiration**: intrapulomnary pressure in negative relative to atmosphere > air pushed in - **expiration**: intrapulmonary pressure is positive relative to atmosphere

Question 40

How does intrapleural pressure change during inspiration and expiration?

Answer 40

ALWAYS negative

Question 41

What is transpulmonary pressure?

Answer 41

Intrapulmonary pressure - intrapleural pressure

Question 42

What type of lung disease is pulmonary fibrosis?

Answer 42

Restrictive

Question 43

How do bronchioles stay open in expiration?

Answer 43

**Radial traction** Of the surrounding alveolar walls on bronchioles

Question 44

Describe airways resistance across the lung

Answer 44

Individual resistance is high Altogether is low

Question 45

Is there lower resistance in the upper or lower airways? Why?

Answer 45

**lower airways** - connective branches create alternative routes - combined resistance of downstream branches is less than higher up - it’s easier for air to flow deeper into lungs

Question 46

Compare the structure of a bronchus compared to a bronchiole

Answer 46

- **bronchus**: has cartilage + glands - **bronchioles**: no cartilage (require radial traction to stay open) or glands

Question 47

What is Gillian Barre syndrome?

Answer 47

Autoimmune condition where the body attacks its own peripheral nerves.

Question 48

What is the function of the plerual seal?

Answer 48

To ensure the lungs expand as the thoracic cavity does using the surface tension of the pleural fluid

Question 49

What types of cells produce surfactant?

Answer 49

Type II pneumocytes

Question 50

What happens to compliance and elastic recoil in a patient with emphysema?

Answer 50

- **Compliance increases** - **Elastic recoil decreases** - Due to breakdown of elastin > less pull in

Question 51

What is interstitial lung disease?

Answer 51

Umbrella term for disease that cause fibrosis + inflammation to lungs Collagen is deposited into interstitium

Question 52

What happens to compliance and elastic recoil in a patient with interstitial lung disease?

Answer 52

**Compliance decreases** **Elastic recoil increases**

Question 53

Function of surfactant

Answer 53

- decreases surface tension of alveoli - prevents small alevoli collapsing into larger alveoli