30 Gas Transport and Ventilation Flashcards
Gas Law–The pressure of a gas =?
the sum of the partial pressure of all its constitutes
4 important gases in the body?
N2, O2, CO2, H2O
In the air, the atmospheric pressure is approximately equal to the sum of which two pressures?
N2 and O2
Atmosphere is approximately % N and % O?
79% N and 21% O
Atmospheric pressure at sea level mmHg?
760 mmHg
Is the PCO2 greater within the alveoli or in room air?
Much greater in alveoli
What is Henry’s Law?
Quantity of dissolved gas= partial pressure x solubility coefficient
What are the 3 forms carbon dioxide is transferred in the blood?
dissolved (5%), as bicarbonate (77%), and as carbamino compounds (18%)
What drives the diffusion of gases?
a pressure or concentration gradient
Does CO2 or O2 have a greater solubility?
CO2
Is the CO2 bound to hemoglobin bond strong?
No its weak.
What do red blood cells contain that facilitate combination of Co2 and water?
carbonic anhydrase
CO2 and water combine to form?
carbonic acid—dissociates to proton and bicarbonate
Does the bicarbonate stay in the RBC where it is formed?
no, it diffuses out because of concentration differences
What diffuses into RBC in order to maintain electroneutrality when bicarb diffuses out?
chloride—hence the chloride shift
What is the volume of gas inspired or expired with each breath?
Tidal Volume
What is the minute ventilation?
tidal volume x respiratory rate
What is the portion of minute ventilation that does not participate in gas exchange?
dead space ventilation
What are the two types of dead space ventilation?
anatomical and physiological
What is the portion of minute ventilation that does participate in gas exchange called?
Alveolar ventilation
What is alveolar ventilation + dead space ventilation?
minute ventilation
What 2 things result in the level of CO2 in the alveolus?
- How much CO2 is delivered.
2. How much CO2 is eliminated
Alveolar PO2 is determined by what 2 factors?
Alveolar ventilation and oxygen consumption
What type of motion is it when each molecule moves with random?
Brownian Motion
Ficks law of diffusion takes in account which three factors?
- driving pressure
- properties of gas
- properties of the membrane
How long is each blood cell in contact with alveolus?
.75 seconds– only needs .25 seconds to equilibrate
Do thick alveolar walls indicate diffusion limitation in the case of hypoxemia?
No- real mechanism is mismatch of ventilation and perfusion
O2 content of blood and cardiac output combined is equal to?
O2 delivery
What is the shape of the dissociation curve for hemoglobin and oxygen?
sigmoid shaped due to cooperative binding
What are the two pools of oxygen being carried in the blood?
Hb bound O2 (98%) + dissolved O2 (2%)
Is it more popular to judge blood oxygenation by saturation or PO2?
saturation
What occurs if O2 content falls and tissue oxygen delivery cannot be maintained?
Tissue hypoxia
What are the 2 most popular reasons O2 content falls?
- low arterial 02 saturation
2. low hemoglobin concentration
Is the diffusion distance in tissues much greater than in lung?
yes
What provides a storage tank for oxygen in the muscle?
myoglobin
What increases release of oxygen in the tissues (right shift of curve)?
lowered pH, increased pCO2, increased temp, and increase in 2,3-DPG
When does 2,3 DPG get released more?
accumulation of glycolytic intermediates
what is true rate limiting step of O2 Transport?
diffusion distance
what is the most effective way of increasing oxygen delivery to a given tissue?
recruiting or construction of additional capillaries
Gases with a similar solubility in blood and diffusion barrier are said to be what?
perfusion limited
Gases with very different solubility in blood and a diffusion barrier are said to be?
diffusion limited
True or False: Both oxygen and carbon dioxide are diffusion-limited in tissues
true
