Respiratory Physiology 3

Question 1

Describe the term ventilation

Answer 1

Movement of air in and out of lungs
Can be described in two ways - pulmonary ventilation and alveolar ventilation

Question 2

Describe pulmonary (minute) ventilation

Answer 2

Total air movement into/out of lungs - relatively insignificant
L/min

Question 3

Describe Alveolar ventilation

Answer 3

Fresh air getting to alveoli so therefore available for gas exchange - more functionally significant
L/min

Question 4

Percentage that tidal breathing is effective and why?

Answer 4

75%
When inhaling 500ml (tidal volume), only 350ml of fresh air enters the alveoli as 150ml of dead space stale air enters the alveoli. At end of the inspiration the dead space is filled with fresh air which is exhaled out with 350ml of air from the alveoli

Question 5

What is hypoventilation

Answer 5

When the alveolar ventilation is lower (3000ml/min) than the normal 4200ml/min
Happens when someone has a low tidal volume and high respiratory rate
Total pulmonary ventilation is the same

Question 6

What is hyperventilation

Answer 6

Alveolar ventilation is higher than normal (4800ml/min)
Larger Tidal volume of 750ml at a slower respiratory rate
Same total pulmonary ventilation

Question 7

What id Dalton’s Law

Answer 7

States that total pressure of gas mixture is a sum of the individual gases

Question 8

What does Partial Pressure mean

Answer 8

The pressure of a gas in the mixture of gases is equivalent to the percentage of that particular gas in the mixture multiplied by the pressure of the whole gaseous mixture

Question 9

What happens to the alveolar ventilation during hyperventilation?

Answer 9

There is increased alveolar ventilation
Partial pressure of O2 rises to 120mm Hg and partial pressure of CO2 falls to 20mm Hg

Question 10

What happens to alveolar ventilation during hypoventilation?

Answer 10

There is decreased alveolar ventilation
Partial pressure of O2 falls to 30mm Hg and partial pressure of CO2 rises to 100mg

Question 11

What happens to the alveolar ventilation from the base of the lung to the apex of the lung?

Answer 11

Declines with height from base to the apex
Compliance is lower at the apex due to being more inflated at FRC. At the base the lungs are slightly compressed by the diaphragm hence more compliant on inspiration

Question 12

What does the pulmonary artery carry?

Answer 12

Carries deoxygenated blood away from the heart and towards the lungs

Question 13

What does the pulmonary vein carry?

Answer 13

Carries oxygenated blood away from the lungs and towards the heart

Question 14

What is the bronchial circulation?

Answer 14

Supplied via pulmonary arteries arising from systemic circulation to supply oxygenated blood to the lung tissues.
Comprises 2% of left heart output. Blood drains to left atrium via pulmonary veins.

Question 15

What is the pulmonary circulation?

Answer 15

Consists of Left and right arteries originating from the right ventricle. Entire cardiac output is from the RV. Supplies the dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein
Is a high flow but low pressure system

Question 16

Describe gas exchange at the alveoli and the tissues - partial pressure

Answer 16

Air diffuses across the membranes down partial pressure gradient
In alveoli: O2 moves from 100 - 40mm Hg and CO2 moves from 46 - 40 mm Hg
In tissues: opposite happens

Question 17

What does the PACO2 mean?

Answer 17

Partial pressure of carbon dioxide in alveolar air

Question 18

What does the PaO2 mean?

Answer 18

Partial pressure of oxygen in arterial blood

Question 19

Explain gas exchange in the lungs

Answer 19

Gas will move across the membrane that is permeable, down its partial pressure gradient (similar to conc.). Will continue to do so until equilibrium is reached

Question 20

What is the rate of diffusion across membrane proportional to?

Answer 20

Directly proportional to partial pressure gradient
Directly proportional to gas solubility
Directly proportional to the available surface area
Inversely proportional to the thickness of the membrane
Most rapid over short distances

Question 21

What does partial pressure in alveoli correspond to?

Answer 21

Partial pressure in systemic arterial blood

Question 22

What does the partial pressures in pulmonary arterial blood (deoxygenated blood) correspond with?

Answer 22

Partial pressure at tissues

Question 23

Explain how O2 and CO2 diffuse at similar rates

Answer 23

O2 diffuses at 250ml/min and CO2 at 200ml/min
O2 diffuses slightly faster due to its PP having bigger difference
CO2 still diffuses as it is more soluble in water than O2

Question 24

What are 3 parts of the lung that help maximise gas exchange?

Answer 24

Large surface area of alveoli
Minimal diffusion difference
Thin walled membranes (Type I alveolar cells, capillary cell)

Question 25

What is emphysema?

Answer 25

Destruction of the alveoli reduces surface area for gas exchange PO2 is normal or low in alveoli PO2 is low in veins

Question 26

What is Fibrotic lung disease?

Answer 26

Thickened alveolar membrane that slows gas exchange. Loss of lung compliance which can decrease alveolar ventilation as stretch of lungs affected. PO2 is normal or low in alveoli PO2 is low in the veins

Question 27

What is pulmonary oedema?

Answer 27

Fluid in the interstitial space increases the diffusion distance. The PCO2 may be normal as CO2 solubility in water. PO2 is normal in alveoli PO2 is low in veins

Question 28

What is asthma?

Answer 28

Increased airway resistance which decreases airway ventilation. The bronchioles are constricted and does not affect diffusion. PO2 is low in the alveoli so PO2 is low in the veins

Question 29

What does the fibrotic tissue in fibrotic lung disease cause?

Answer 29

Makes the alveoli resistant to stretch so low compliance Resists the expansion of lungs during inspiration so can have impact on ventilation. Also impedes diffusion

Question 30

What characteristics does an emphysemic lung have?

Answer 30

Loss of elasticity as smoking can produce the enzyme elastase that breaks down the fibres. Loss of surface area Low compliance so expiration and muscles need to be used to get air out

Question 31

Explain obstructive lung disease

Answer 31

Obstruction of air flow especially on expiration

Question 32

Explain Restrictive lung disease

Answer 32

Restriction of lung expansion Loss of lung compliance More effort in the inspiration

Question 33

What are obstructive lung disorders?

Answer 33

Asthma - reduction in radius COPD - chronic bronchitis which is inflammation of bronchi so reduction in airway. Emphysema - destruction of alveoli so elastic recoil is damaged and air cant be pushed out through airways.

Question 34

What are restrictive lung disorders?

Answer 34

Fibrosis - creates stiff lung. Can be idiopathic (cause unknown) or asbestosis. Infant respiratory distress syndrome - insufficient surfactant production Oedema Pneumothorax

Question 35

What is pneumothorax?

Answer 35

Air is introduced into the pleural cavity which pushes the pleural membranes apart. Lung is no longer related to the chest wall and diaphragm Now independent - no expansion or contraction

Question 36

What is spirometry?

Answer 36

measuring the volume of air that is inspired and expired. Can be static or dynamic measurements

Question 37

Explain static measurements

Answer 37

Where the only consideration made is the volume exhaled

Question 38

Explain dynamic measurements

Answer 38

Where the time taken to exhale a certain volume is what is being measured

Question 39

What volumes of lung capacity can be measured with the spirometer?

Answer 39

Measures where the residual volume is not a component TV, IRV, ERV, IC, VC

Question 40

What is FEV1?

Answer 40

Forced expiratory volume in 1 second - in fit healthy males: 4L So how fast air can be pushed out

Question 41

What is FVC?

Answer 41

Forced vital capacity Total amount o air you can expire over whatever time In fit healthy males: 5L

Question 42

What is the FEV1/FVC?

Answer 42

80%

Question 43

Describe the pressure-volume relationship and compliance during inspiration

Answer 43

There is a decrease in pressure before there is an increase in volume Compliance increases during inspiration Requires greater change in pressure to reach a particular lung volume Requires more negative intrapleural pressure

Question 44

Describe the pressure-volume relationship and compliance during expiration

Answer 44

Requires less of a change in pressure to maintain the volume in expiration Low compliance at start of expiration

Question 45

Why does inspiration require a greater change in pressure to reach particular volume compared to expiration?

Answer 45

Overcome ling inertia during inspiration - reluctance for tissues to change shape Overcome surface tension - wants alveoli to collapse During expiration compression of airways means more pressure is required for air to flow along them

Question 46

Give examples of when inspiration and expiration require more effort

Answer 46

Emphysema - loss of elastic tissue means expiration is more difficult as muscles have to force air out, not elastic recoil Fibrosis - inert fibrous means more effort on inspiration as thickened alveoli walls meaning lower compliance

Question 47

Describe inspiration and expiration when someone has asthma?

Answer 47

Inspiration - airways are pulled open by physical forces of inspiration Expiration - airways are compressed by physical forces of expiration so more effort is needed to expire