Respiratory Physiology Part 3

Question 1

if transmural pressure is positive

Answer 1

expanding pressure on the lung

Question 2

if transmural pressure is negative

Answer 2

collapsing pressure on the lung

Question 3

At rest of breathing cycle

Answer 3

• diaphragm at equilibrium
• alveolar pressure = atmospheric pressure
• no airflow b/c no pressure difference
• intrapleural space is negative
• FRC

Question 4

During Inspiration of breathing cycle

Answer 4

• diaphragm contracts
• lung volume increases
• pressure in lung decreases
• intrapleural space becomes more negative
• dynamic compliance

Question 5

Halfway through inspiration of breathing cycle

Answer 5

alveolar pressure falls below atmospheric

this drives airflow into lung until atmospheric pressure = 0

Question 6

expiration of breathing cycle

Answer 6

• alveolar pressure becomes positive

- air flows out & returns to FRC

Question 7

Forced expiration of the breathing cycle

Answer 7

• contraction of expiration muscles raises intrapleural pressure
• if transmural pressure is positive the airways and lungs will remain open

Question 8

patients with emphysema forced expiration

Answer 8

• airways can collapse
• lung compliance increases
• alveolar & airway pressure lower than normal
• resistance increases (expiration more difficult)
• expire more slowly

Question 9

O2 in gas exchange

Answer 9

alveolar gas into pulmonary capillary

delivered to tissues

systemic capillary blood into cells

Question 10

CO2 in gas exchange

Answer 10

delivered from the tissue to venous blood to pulmonary capillary blood

alveolar gas to be expired

Question 11

Dalton’s Law of Partial Pressure

Answer 11

the partial pressure of gas in a mixture of gases is the pressure that gas would exert if it occupied the total volume of the mixture

Question 12

barometric pressure

Answer 12

sume of partial pressures
O2
CO2
N2
H2O

Question 13

percentages of gases in dry air at barometric pressure

Answer 13

O2 = 21%

N2 = 79%

CO2 = 0%

Question 14

since air is humidified in the airways, the water pressure is ___

Answer 14

obligatory and equal to 47 mmHG at 37 degrees

Question 15

Henry’s Law for Concentration of Dissolved Gases

Answer 15

used to convert the partial pressure of gas in the liquid phase to the concentration of gas in the liquid phase

Question 16

at equilibrium, the partial pressure of a gas in the liquid phase =

Answer 16

the partial pressure in the gas phase

Question 17

diffusion of gases - fick’s law

Answer 17

transfer of gases that occurs by simple diffusion

Question 18

rate of transfer by diffusion is directly proportional to

Answer 18

driving force
diffusion coefficient
surface area available for diffusion

Question 19

rate of transfer by diffusion is inversely proportional to

Answer 19

the thickness of membrane barrier

Question 20

the driving force for diffusion of a gas is the ___

Answer 20

partial pressure difference of the gas across membrane

Question 21

the diffusion coefficient of gas is a combination of ___

Answer 21

usual diffusion coefficient and the solubility of gas difusion

Question 22

gas concentration

Answer 22

dissolved gas + bound gas + chemically modified gas

Question 23

dissolved gas

Answer 23

contribute to partial pressure

Question 24

N2 as a dissolved gas

Answer 24

can only be carried in dissolved form and is never bound or chemically modifies

Question 25

bound gases

Answer 25

O2, CO2, and CO are bound to proteins in blood

Question 26

chemically modified gas

Answer 26

CO2 –> HCO3 in RBC by action carbonic anhydrase

Question 27

gas transport in the lungs

Answer 27

Mixed venous enters the pulmonary capillary

Oxygen is added to pulmonary capillary blood

CO2 is removed from it by transfer across the alveolar/capillary barrier

Systemic arterial blood leaves the pulmonary capillary

Question 28

dry inspired air

Answer 28

PO2 = 160 mmHg

Question 29

Humidified tracheal air

Answer 29

air saturated w/ water vapor

O2 reduced
No CO2

humidified air enters alveoli

Question 30

alveolar air

Answer 30

O2 decreases (going in blood)

CO2 increases (enters alveolar air)

Question 31

mixed venous blood

Answer 31

blood entering pulmonary capillary - blood returned from tissue to heart

Question 32

systemic arterial blood

Answer 32

blood that leaves pulmonary capillary that has been oxygenated

Question 33

diffusion-limited gas exchange

Answer 33

total amount of gas transported across alveolar-capillary barrier that is limited by diffusion process

Question 34

perfusion limited

Answer 34

total amount of gas transported across alveolar/capillary barrier is limited by blood flow

Question 35

how to increase the amount of gas transported?

Answer 35

increase blood flow

Question 36

oxygen is carried in 2 forms

Answer 36

dissolved

bound to hemoglobin

Question 37

dissolved oxygen

Answer 37

insufficient to meet the demands of the tissues

needs hemoglobin

Question 38

oxygen bound to Hgb

Answer 38

98% of total O2 content is reversibly bound Hgb

Question 39

4 subunits of Hgb

Answer 39

4 molecules of O2 per molecule of Hgb

Question 40

The O2 content of blood is primarily determined by

Answer 40

Hgb and the O2 binding capacity of hgb

Question 41

amount of O2 delivered to tissues is determined by

Answer 41

blood flow and O2 content of blood ( dissolved O2 + O2-Hgb)

Question 42

CO2 is carried in blood in 3 forms

Answer 42

• dissolved CO2
• carbaminohemoglobin (CO2 bound to hemoglobin)
• bicarbonate (CO2)