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  1. Where does gas exchange occur (2 structures) during external respiration?
  2. Where does gas exchange occur (2 structures) during internal respiration?

  1. external- alveolus and pulmonary capillaries
  2. internal- systemic capillaries and systemic tissues



What types of physiologic parameters are measured during a blood gas analysis of arterial or venous blood? (5)

  1. pH
  2. PO2
  3. PCO2 
  4. HCO3-
  5. BE (Base Excess)


which blood gas is best to evaluate lung function

arterial blood gas


what is important about FiO2 when interpreting PaO2?

If giving animal 100% oxygen the PaO2 will increase 


if there is an increase in altitude what will happen to PIO2?

decreases PIO2


what is ficks law?

rate of diffusion across a membrane


Regarding ficks law, what do the following symbols stand for

  1. ∆P

  2. A

  1. D – Rate of gas diffusion
  2. ∆P – Partial pressure difference
    • Want to move from high to low pressure
  3. A – cross-sectional area of surface



Regarding ficks law, what do the following symbols stand for

  1. S
  2. X
  3. MW

  1. S – Solubility of gas in the fluid

  2. X – Diffusion Coefficient, distance of diffusion path  

    • ex. Pneumonia would have an increased distance of diffusion

  3. MW– Molecular weight of gas


what does this stand for

The rate of gas movement between the alveolus and the blood in the pulmonary capillary EXTERNAL RESPIRATION


what is dalton's law

Each gas in a mixture of gases exerts its own pressure, as if all other gases were not present


regarding dalton's law what does everything stand for

  1. Px= partial pressure of a certain gas
  2. Fx= fractional concentration of a gas 
  3. Pt= total pressure, sum of all partial pressures


why is dalton's law important in respiration?

The changes in gas( ie- O2 or CO2) partial pressures from high to low concentration drives the gas into the blood for diffusion to occur.


  • How would you calculate PO2 at atmospheric pressure using dalton's law

Px= Fx x Pt

  • FIO2 = 0.21  (inspired air has 21% oxygen)
  • PO2  = 0.21 x 760 mmHg = 160 mmHg


as temperature increases what happens to vapor pressure?



how does the partial pressure of water vapor PH20 effect PO2

  • During inhalation, air is warmed to body temperature and humidified in the conducting airways. 
  • The concentration of oxygen and other gases is reduced by the presence of water vapor molecules-
  • Increased temperature = increased water vapor = diluted or decreased PO2


Example: 37°C, PH20   = 47 mmHg

PO2 = FIO2 x (PB - PH20 ) = 0.2094 x (760-47) = 149 mm Hg

Example: 38°C, PH20  = 50 mmHg

PO2 = FIO2 x (PB - PH20 ) = 0.209 x (760 - 50) = 148 mmHg


What if body temperature increases a little?   

  1. what will happen to PO2
  2. what happens with gas exchange?

  1. P H20 will dilute PO2 (decrease)
  2. will have dificult time with gas exchange


what is henry's law

  • Content (quantity) of gas dissolved in a liquid,

e.g. oxygen dissolved in plasma


regarding henry's law what does everything stand for?

Cx = βx Px

  1. C = Concentration or Content
    •Volumes percent = ml gas / 100 ml liquid
  2. β = solubility coefficient
  3. P = partial pressure in mmHg


Does CO2 diffuse at the same rate as O2?

CO2 diffuses 20 times faster than O2


Why does CO2 diffuses 20 times faster than O2

  • solubility coefficient for oxygen is lower than CO2

Oxygen = 0.00364 ml O2 . dl-1 . mmHg-1
CO2 (solubility)= 0.72


How is solubility related to temperature

solubility decreases as temperature increases


What is hyperbaric oxygenation and what is the physiologic principle?  

  • Hyperbaric chamber pressure raised to 3 to 4 atmospheres so that tissues absorb more O2
  • Breathing O2 under increased pressure dissolves more O2 in the blood


What types of problems can be treated with this type of therapy? (7)

  1. Treatment for patients with anaerobic bacterial infections (tetanus and gangrene)
    • Anaerobic bacteria die in the presence of O2
  2. Used to treat heart disorders,
  3. CO poisoning,
  4. cerebral edema,
  5. bone infections,
  6. gas emboli
  7. crush injuries


Compare and contrast the PO2 and PCO2 of alveolar gas, arterial blood, and venous blood

(what are the values for each)


why is there such a low amount of PO2 in venous blood?

oxygen has been transfered to the tissues


Is the total pressure the same or different compared with atmospheric air- PB of PO2 and PCO2 of alveolar gas, venous blood and arterial blood.

the same


Describe the Alveolar ventilation rate and effect on PAO2 and PACO2 

PAO2 increases as PACO2 decreases and vice versa


what is the normal alveolar ventilation rate?

4 L/min


during hyperventilation what will happen to...

  1. PAO2  
  2. PACO2


  1. PAO2  ↑
  2. PACO2 ↓