respiratory system, gas exchange

Question 1

Describe the relationship stating that if the volume of gas increases the pressure decreases.

Answer 1

V=1/P

if the volume of a container of gas changes, the pressure of the gas will change in ana inverse manner: P1V1=P2V2

Question 2

What is the term defining the individual pressure exerted by a particular gas within a mixture.

Answer 2

Partial pressure (Px), x= location of measurement

Question 3

determine the parial pressure in the following conditions

1. Water vapor
   
   1. 25c, dry air
   2. 25C, 100% humidity
   3. 37c, 100 humidity
2. P02:
   
   1. 25C, dry air, at sea level
   2. 25C, 100% humiditiy, sea level
   3. 37C, 100% humidity,

Answer 3

Pgas=(Patm-Ph2o)(%of gas)

The trick is you need to know the water vapor pressure at these temperatures.

37c = 47mmHg, most important b/c this is body temp (alveolar humidity=100)

1. PO2
   
   1. (760-0)(.21)=160
   2. (760-24)(.21)=155
   3. (760-47)(.21)=150

Question 4

describe the Po2 and PCO2 for alveolar air and expired air. explain findings

Answer 4

1. alveolar air
   
   1. Po2 = 104mmHg
   2. PCO2 = 40mmHg
   3. alveolar air is only partially replaced by atmospheric air
      
      1. breathed in = 500. take away 150 as the dead space that move into the lungs. leaving a fraction of the inhaled air to make it to the alveoli.
   4. O2 and CO2 are constantly diffusing from the alveoli intor blood
2. expired air
   
   1. Po2=120mmHg
   2. PCO2=27 mmHg
   3. alveolar air is mixed with dead space atmospheric air
   4. note
      
      1. [O2] higher in the atmosphere compared to alveoli
      2. [CO2] higher in lower atomosphere compared to alveoli

Question 5

what explains the [O2] being higher in the alveoli compared to an ABG while both are under the same pressure?

what happens when CO2 and O2 are in the same concentration in a fluid?

Answer 5

Henry’s law

1. at equilibrium the partial pressure of O2 in the liquid phase equals the partial pressure in the gas phase
2. this does not mean concentration is the same in air and water

If two gases are present in a fluid at the SAME concentration the less soluble gas will display a higher parial pressure relative to the more soluble gas. CO2 is 20x’s more soluble than O2

Question 6

Jerry’s results came back: ABG 100mmHg

knowing that O2 solubility is 0.003, what is the concentration?

Answer 6

Cx =Px(solubility). 0.3(mL gas/100mL blood)

C=concentration

P=partial pressure

x=location

Question 7

define the following

1. daltons law
2. partial pressure
3. partial pressure in humid environment
4. movement of gases
5. boyles law

Answer 7

1. the toal pressure of a mixture of gases is the sum of the pressure of the individual gases (daltons law)
2. partial pressure: Pgas=Patm(%gas)
3. partial pressure with humidity Pgas=(Patm-Ph2o) (%gas)
4. gases, singly or in a mixture, move from areas of higher pressure to areas of lower pressure
5. if the volume of a container of gas changes, the pressure of tthe gas will change in an inverse manner
   
   1. P1V1=P2V2

Question 8

define the normal steady state of PAO2 (alveolar partial pressure of O2)

how can you determine new O2 rate of entry?

Answer 8

normal steady state= 102mmHg

Pao2=Pio2 - (Paco2/R)

where R=0.8 ( combination of O2 used by diet: fats,proteins and carbs)

Paco2= obtained from ABG

Pio2 = Fio2 (Patm-Ph20)

• remember:.21(760-47)
  
  • Ph2o and 37c = 47
    
    • 760-47
  • Fio2= fraction of O2 inhaled = 0.21 or 21%