Physiology of Respiration Pt 2 (Week 4)

Question 1

What happens after the spirometer tap is closed after inhalation?

Answer 1

The subject relaxes the respiratory muscles

Question 2

How can the curve for lung and chest wall compliance be explained?

Answer 2

By the addition of the individual lung and chest wall curves

Question 3

What happens to airway resistance if the airway wall becomes more ‘floppy’?

Answer 3

Airway resistance can change

Question 4

Why do people with COPD often breathe at higher FRC/residual volumes?

Answer 4

Higher FRC helps keep narrowed airways open

Question 5

What occurs when you breathe out and the airways get smaller?

Answer 5

Gas velocity increases

Question 6

According to the Bernoulli principle, what happens to pressure when air moves faster?

Answer 6

Lower pressure is created on the airway walls

Question 7

What increases during expiration that affects airway resistance?

Answer 7

Intrapleural pressure increases

Question 8

What is the Bernoulli principle?

Answer 8

An increase in the speed of a fluid occurs simultaneously with a decrease in pressure

Question 9

What happens to small airways during expiration due to increased velocity?

Answer 9

Narrowing and collapse of small airways occur

Question 10

What is Dalton’s Law?

Answer 10

Each gas in a mixture develops its own pressure independent of all other gases

Question 11

What is the partial pressure of a gas?

Answer 11

The pressure of an individual gas in a mixture

Question 12

What does the difference between pulmonary artery blood and aorta blood indicate?

Answer 12

The alveolar–arterial oxygen gradient (A–aO2) exists due to venous admixture

Question 13

What factors affect the rate of gas diffusion through the respiratory membrane?

Answer 13

• Thickness of the membrane
• Surface area of the membrane
• Diffusion coefficient of the gas
• Partial pressure difference

Question 14

What occurs to the thickness of the respiratory membrane in conditions like edema?

Answer 14

Thickness occasionally increases

Question 15

What does Fick’s Law state about gas transfer?

Answer 15

The amount of gas transferred is proportional to area and pressure difference, inversely proportional to thickness

Question 16

What is the diffusing capacity of the lung (DL)?

Answer 16

The volume of gas transferred per minute divided by the mean partial pressure gradient

Question 17

What does the Hb dissociation curve represent?

Answer 17

Oxygen saturation or content plotted against the partial pressure of oxygen

Question 18

What does an increase in P50 indicate?

Answer 18

Lower binding affinity for oxygen

Question 19

What effect does carbon monoxide have on the oxyhemoglobin equilibrium curve?

Answer 19

It causes a leftward shift of the curve

Question 20

How is carbon dioxide primarily transported in the blood?

Answer 20

In three forms: * Physically dissolved (10%)
* HCO3− (major proportion, ~ 70%)
* Carbamino-hemoglobin (30%)

Question 21

What is the Haldane effect?

Answer 21

The effect of increased O2 tension that shifts the carbon dioxide equilibrium curve

Question 22

The point where the inward elastic recoil of the lungs equals the outward elastic recoil of the chest wall

Answer 22

Resting respiratory level (FRC)

Question 23

At lower lung volumes, airway resistance is _______ (low/high) due to the reduced calibre of airways (narrower airways increase resistance)

Answer 23

high

Question 24

What is the reciprocal of airway resistance?

Answer 24

Conductance

Note: Higher conductance means airflow in the airways is LESS restricted

Question 25

In emphysema, there is a loss of ____________, resulting in less elastic pull

Answer 25

elastin

Note: elastin keeps small airways open

Question 26

As airway velocity increases (moreso during expiration), the pressure against the walls fo the small airway drops.

This is known as the __________ effect

Answer 26

Bernoulli effect

Question 27

True or False: In emphysema, collapse point is in bronchioles (where there is NO cartilage), whereas in healthy lungs, collapse point is in bronchi (where there is cartilage)

Answer 27

True

Note: “collapse point” = where intrapleural pressure equals intra-airway pressure

Note: cartilage prevents airway collapse by providing support to the bronchi

Question 28

breakdown of partial pressures in atmospheric air (at sea level)

Answer 28

Nitrogen (N₂) → ~78% → ~593 mmHg

Oxygen (O₂) → ~21% → ~160 mmHg

Other gases (e.g., CO2, argon, etc.) → 1% → 7mmHg

Note: If oxygen has a partial pressure of 160mmHg, we are good to diffuse it into our bloodstream. However, as altitudes increase, the partial pressure of oxygen drops (becomes less than 160 mmHg), reducing its availability for diffusion

Question 29

When is the partial pressure of O2 in the blood highest?

Answer 29

when it leaves the lungs

Question 30

When is the partial pressure of CO2 in the blood highest?

Answer 30

when it enters the lungs

Question 31

How do oxygen and carbon dioxide travel across the alveolar-capillary membrane?

Answer 31

diffusion

Question 32

If D_L
is _________ (low/high), then oxygen transport is impaired

Answer 32

low

Question 33

the PO2 value at which hemoglobin is 50% saturated with oxygen

Answer 33

P50

Question 34

At arterial PO2 (100 mmHg), hemoglobin (Hb) is approximately _____ % saturated

Answer 34

100%

Note: maximal oxygen delivery to tissues

See Point A in image

Question 35

At venous PO2 (40mmHg), hemoglobin (Hb) is approximately _______ % saturated

Answer 35

75%

See point V in image

Question 36

What factors can shift the Hb Dissociation Curve?

Answer 36

• pH
• CO2
• temperature
• 2,3-DPG (Bohr effect)

Thus all of these can affect oxygen affinity

Question 37

How does P50 influence the Hb Dissociation Curve?

Answer 37

LOWER p50 –> higher affinity (curve shifts to LEFT)

HIGHER p50 –> lower affinity (curve shifts to RIGHT)

Question 38

How do pH, CO2, temperature, and 2,3-DPG affect the Hb Dissociation Curve?

Answer 38

Increased temp, DPG, PCO2 = SHIFTS RIGHT

Decreased pH = SHIFTS RIGHT

Question 39

If the Hb Dissociation Curve shifts to the RIGHT, this means it takes _________ (less/more) oxygen to saturate the hemoglobin

Answer 39

more

This means it’s harder to saturate the Hb. A shift to the right means hemoglobin (Hb) has a lower affinity for O₂, making it easier to release O₂ to tissues but harder to load O₂ in the lungs

Question 40

In anemia, hemoglobin levels are reduced, lowering the total oxygen content in the blood to _____ % of normal

Answer 40

40% of normal

Note: the overall shape of the curve is unchanged but the height of the curve is LOWER

Question 41

True or False: When the blood is 60% saturated with carbon MONOXIDE (HbCO), O2 content is reduced (height of curve is lower) and there is also a leftward shift of the Hb dissociation curve

Answer 41

True

Note: Carbon monoxide (CO) binds to Hb with 200x more affinity than oxygen; this is how CO poisoning can happen

Question 42

the main transporter of carbon dioxide

Answer 42

bicarbonate (HCO3-)

Note: accounts for 70% of how CO2 is transported

Question 43

When oxygen levels increase, increasing the partial pressure of O2, the CO2 association curve shifts right and downwards. This means that hemoglobin binds less CO2 in oxygen-rich environments (e.g., lungs), facilitating CO2 unloading for exhalation.

This PO2 effect on the CO2 association curve to Hb is known as the ____________ effect

Answer 43

Haldane effect