Intro to respiratory system (physiology)

Question 1

What is the difference between external and internal respiration?

Answer 1

External respiration - between air and blood

Internal respiration - between blood and cells

Question 2

What is pulmonary ventilation?

Answer 2

The movement of air into and out of lungs

Question 3

What does ventilation rely on?

Answer 3

A pressure gradient along the airways

Question 4

What is the equation for flow pressure and resistance? (like Ohm’s Law)

Answer 4

Flow = pressure gradient/resistance

Question 5

What is a low flow rate caused by?

Answer 5

Low pressure gradient/high resistance

Question 6

What must be the relationship between the atmospheric pressure and the alveolar pressure for inspiration to occur?

Answer 6

Atmospheric pressure (at mouth/nose) must be greater than alveolar pressure

Question 7

What is Boyles law?

Answer 7

The pressure of a fixed number of molecules is related to the volume of the container.
ie pressure and volume are inversely related - decreasing the volume increases the pressure and vv.

Question 8

What mechanically couples the lungs to the chest wall?

Answer 8

The pleural fluid

Question 9

What prevents the lungs from collapsing inwards?

Answer 9

The outward recoil of the chest wall

Question 10

What pressure is the intrapleural space held at resting end expiration?

Answer 10

Negative pressure (-5cm H20)

Question 11

Which thoracic structure wants to recoil outwards and which inwards?

Answer 11

Lungs want to spring inwards
Chest wall wants to spring outwards
2 opposite elastic forces
These forces are exactly equal just before inspiration

Question 12

What happens during inspiration?

Answer 12

Contract respiratory muscles to increase volume of thoracic cavity
Decreases the intrapleural pressure - becomes more negative
Lung expands even further (pressure lower inside than outside) –> air moves in

Question 13

At rest, is expiration active or passive?

Answer 13

Passive

Question 14

Are pressures given absolute in respiratory physiology?

Answer 14

No - relative to atmospheric pressure

Question 15

Is inspiration active or passive?

Answer 15

Always active - inspiratory muscles contract (diaphragm esp important)

Question 16

Name the obligate inspiratory muscles

Answer 16

Diaphragm
External intercostal muscles
Scalenes
Parasternal intercostal muscles

Question 17

Name the accessory inspiratory muscles

Answer 17

Sternocleidomastoids

Question 18

Name the expiratory muscles

Answer 18

Internal intercostals
Rectus abdominis
External oblique
Internal oblique
Transversus abdominis

Question 19

What is Ppl?

Answer 19

Intrapleural pressure

Question 20

What is PA?

Answer 20

Alveolar pressure

Question 21

What is Pb?

Answer 21

Barometric pressure

Question 22

How do you calculate transmural pressures?

Answer 22

Pressure differential of the inside compartment minus the outside

Question 23

What is PL and how do you calculate it?

Answer 23

Transpulmonary pressure/distending pressure that inflates the lung
PL = PA - Ppl

Question 24

What is PL at rest?

Answer 24

+5 (0–5)

Positive pressure holding the lung open (‘distending pressure’)

Question 25

What happens to PL during inspiration?

Answer 25

It increases

Question 26

When may the intrapleural pressure become positive?

Answer 26

During forced expiration

Question 27

What is a pneumothorax?

Answer 27

After a chest wall puncture - air is sucked into the pleural space Collapse of the lung due to elastic recoil inwards Chest wall springs outwards

Question 28

What is a respiratory cycle?

Answer 28

A single cycle of inhalation and expiration

Question 29

What is the term for the volume of air moved in 1 respiratory cycle?

Answer 29

Tidal volume

Question 30

What is a normal value for a tidal volume?

Answer 30

500ml

Question 31

What is FRC?

Answer 31

Functional residual capacity | Volume of air that you start breathing in from

Question 32

What is the vital capacity?

Answer 32

The difference between the maximum amount of inspired air and the volume after a maximum expiration

Question 33

What is TLC?

Answer 33

Total lung capacity (total volume of long)

Question 34

What is the expiratory reserve volume?

Answer 34

Difference between the vital capacity and the inspiratory capacity (volume left over after a normal breath out)

Question 35

What is the inspiratory reserve volume?

Answer 35

Volume that you have left to breath into after a normal breath in to take you up to the vital capacity

Question 36

What is the inspiratory capacity?

Answer 36

Difference between functional residual capacity and total lung capacity

Question 37

What is the residual volume?

Answer 37

The volume of air left in the lungs after forced expiration that cannot be breathed out

Question 38

Which lung volumes cannot be measured directly by spirometry?

Answer 38

Total lung capacity Residual volume Functional residual capacity

Question 39

What is dead space? (Vd)

Answer 39

Airway volume with no gas exchange

Question 40

What is anatomic dead space?

Answer 40

All of airway except alveoli and respiratory bronchioles, e.g. trachea

Question 41

What is physiologic dead space?

Answer 41

Anatomic plus areas where gas exchange is dysfunctional

Question 42

Which kind of dead space increases in respiratory disease e.g. emphysema?

Answer 42

Alveolar dead space (therefore physiologic dead space)

Question 43

What is the equation for physiologic dead space?

Answer 43

Physiologic dead space = anatomical dead space + alveolar dead space

Question 44

What is the relationship between alveolar and anatomical dead space in a healthy individual?

Answer 44

They should be approximately equal

Question 45

What is a typical total ventilation rate?

Answer 45

7500ml/min

Question 46

What is a typical anatomical dead space?

Answer 46

150ml

Question 47

What is a typical alveolar gas volume?

Answer 47

3000ml

Question 48

What is a typical pulmonary capillary blood volume?

Answer 48

70ml

Question 49

What is a typical ventilation frequency (resps)?

Answer 49

15/min

Question 50

What is a typical pulmonary blood flow rate?

Answer 50

5000ml/min

Question 51

What is the equation for alveolar ventilation?

Answer 51

Minute ventilation - dead space ventilation

Question 52

What is a typical value for alveolar ventilation?

Answer 52

5250ml/min

Question 53

What is important about the values for alveolar ventilation and pulmonary blood flow rate?

Answer 53

It is well matched (both around 5000 ml/min)

Question 54

What are the two main sources of resistance to breathing?

Answer 54

1. Elastic resistance of the lung (due to elastic tissues and air-liquid interface in alveoli) 2. Airway resistance to airflow (due to friction from air flowing within tube)

Question 55

What is dyspnoea?

Answer 55

Breathlessness

Question 56

What is lung compliance?

Answer 56

Stretchiness of the lung

Question 57

What is the equation for lung compliance?

Answer 57

Change in long volume/change in transmural pressure gradient (V/P)

Question 58

What is the equation for airway resistance?

Answer 58

Airway resistance = alveolar pressure-mouth pressure/flow at mouth

Question 59

What are the two types of flow?

Answer 59

Laminar or turbulent

Question 60

What is turbulent flow?

Answer 60

Disruption of laminar flow due to hitting a branch point etc - more oscillations of airflow (wheeze) Increases resistance

Question 61

What causes a wheeze?

Answer 61

Oscillations of airflow (turbulent flow) down a narrow airway

Question 62

What could a silent wheeze from an asthmatic suggest?

Answer 62

Very severe obstruction - insufficient airflow to generate wheeze

Question 63

What determines airway resistance?

Answer 63

Poiseuille's law (R is proportional to 1/r^4) | Radius has largest effect on resistance

Question 64

What are the main sites of airway resistance?

Answer 64

Wherever the tubes get narrower Nose, pharynx, larynx Medium bronchi

Question 65

Which part of the airway contributes most to airway resistance?

Answer 65

Medium bronchi at generation 3-5

Question 66

What are the two main factors causing variations in airway resistance (RAW)?

Answer 66

Factors within the airways, e.g. bronchial SM tone | Pressure across airway wall (if collapsing the airway down)

Question 67

What effect does CO2 have on bronchial muscle tone?

Answer 67

Relaxes

Question 68

What effect do NANC nerves have on bronchial muscle tone?

Answer 68

Relax

Question 69

What effect does B2 receptor stimulation have on bronchial muscle tone?

Answer 69

Relaxes

Question 70

What does salbutamol do?

Answer 70

B2 agonist | Relaxes bronchial SM in ashtmatics

Question 71

What effect does histamine and prostaglandins have on the bronchial SM?

Answer 71

Contract SM

Question 72

What affect does activation of airway irritant receptors have?

Answer 72

Contraction via brainstem pathway | inhibited by pulmonary stretch receptors

Question 73

What occurs during dynamic compression of the airways?

Answer 73

Positive pressure in alveoli during forced expiration (due to expiratory muscles contracting plus inward recoil of lungs) +38 within alveoli At some point this alveolar pressure decreases below the intrapleural pressure so there is a positive pressure pushing the lung in --> airway collapse

Question 74

Where is dynamic compression of the airways most likely to occur?

Answer 74

Bronchi at generation 3/4 | those without collagen/cartilage

Question 75

What does dynamic compression of the airways limit?

Answer 75

Forced expiration - it is effort independent at low lung volume (can't decrease the volume anymore)

Question 76

What causes dynamic compression of the airways?

Answer 76

High intrapleural pressures

Question 77

What is the problem with dynamic compression of airways in lungs with RAW?

Answer 77

It causes marked limitation in airflow and slow expiration | - low peak flow, wheeze and air trapping