Gas Transport 4 Flashcards
Oxygen is transported in what 2 forms in the body?
How to calculate total oxygen content in the boddy
PO2 (partial pressure) in the bloodstream determines
How much oxygen will dissolve in plasma and physically combine with hemoglobin
Dissolved oxygen is determined by
O2 solubility (coefficient) in plasma
O2 solubility is proportional to
partial pressure of O2 (called Henry’s LAw)
Hemoglobin
What is globin and what can bind to it
What state does O2 bind to hemoglobin
Is oxygenation of hemoglobin a reversible process?
Yes, because oxygen can also be given to tissue
How many oxygens can bind to a hemoglobin?
4
What kind of an event is the process of oxygenation of hemoglobin?
Cascade event, as more oxygen bind it becomes easier and easier for the other oxygen molecules to bind until 4 have been bound to 1 hemoglobin
What is full saturation of hemoglobin
When all 4 sites are bound
What is our oxygenation capacity
How to calculate oxygen saturation
Are partial pressure of oxygen and oxygen saturation different?
Yes, the amount of O2 combined with hemoglobin varies with oxygen partial pressure. Oxygen that is bound with hemoglobin does not exert partial pressure ONLY dissolved oxygen in the plasma. (partial pressure is about gas molecules vs saturation is how much oxygen is bound to hemoglobin and available in the blood)
Describe the oxyhemoglobin dissociation curve
Sigmoid shape
-In the alveoli (far right) we need a significant drop in PO2 before oxygen loading will be affected (need high affinity/attraction in lungs so oxygen binds to hemoglobin in lungs)
-As we drop down in partial pressure (tissues) we want lower affinity/attraction of oxygen to hemoglobin, so oxygen will offload and be delivered to the tissues (not much change in partial pressure to drop to deliver more and more oxygen)
Describe the difference between an adult and fetal oxyhemoglobin dissociation curve
In the fetal curve, the slope is steep and plateau happens sooner, therefore a much lower partial pressure is needed for hemoglobin to be fully saturated with oxygen because its receiving oxygen from a placenta and not the lungs
Name the effects of RBC count have on the oxyhemoglobin dissociation curve
Only changed the content of oxygen and number of RBC available to carry it. Doesn’t impact shape of curve, but does effect carrying capacity
What are the effects of carbon monoxide on the oxyhemoglobin dissociation curve
Name 8 symptoms of carbon monoxide poisoning (as it worsens)
Really low levels can cause us to faint (doesnt take much)
What is the P50 value
What are factors that can shift the oxyhemoglobin dissociation curve left or right
Left shift: LESS carbon dioxide and increased pH (basic) = loading of oxygen becomes easier in the lungs (but offloading becomes more difficult = want to stay bound) -> can look at p50 (normative value = 28, in this graph = 20) so we need partial pressure to drop more to have greater offloading of oxygen
Right shift: More Co2, acidic, increased temperature decreases oxygens affinity to cause mor oxygen offloading in the tissue. It takes more pressure to load the oxygen now (but less pressure to offload) -> p50 is closer to 30
How much oxygen do we have in our blood at arterial blood and resting venous blood
What 3 forms is carbon dioxide transported into in the body?
**CO2 has much higher solubility so there should be more CO2 in plasma than oxygen
Describe the Haldane effect
Higher CO2 in blood when O2 is lower
Describe the carbon dioxide dissociation curve
**Body can carry infinite amount of CO2 compared to oxygen is a finite value
Do we need oxygen and carbon dioxide to work together
Yes
Describe the difference in normal vs abnormal gas exchange
**PA vs Pa and Ca
Describe the ideal lung (single compartment model of pulmonary gas exchange)
All inspired air and pulmonary vessels participates in gas exchange
Describe the real lung (three compartment model of pulmonary gas exchange)
1st compartment (wasted ventilation): Some inspired air participates in gas exchange while others go into dead space (eg. blocked or collapsed alveoli) or in conducting zones (eg. trachea or bronchi)
2nd compartment (gas exchange): Alveolar gas is matched with the capillary blood not the venous blood (where gas exchange is actually occurring
3rd compartment (wasted perfusion): Not all our blood participates in gas exchange resulting in wasted perfusion
What are 4 mechanisms of hypoxemia
A-a: alveolar arterial gradient
Describe normal ventilation
We breathe because we want to blow off CO2 from body not because we need more oxygen
Hyperventilation: Too little CO2
Hypoventilation: Too much CO2
Describe alveolar hypoventilation
Mechanisms of hypoventilation -> therefore hypoxemia
1) Alcohol poisoning/drug overdoses
2) Spinal cord injury
3) Chest wall/respiratory muscle weakness
4) Stiff lungs
5) Loss of neuromuscular junction
Describe ranges of P(A-a) O2 for FiO2 changes
As we increase FiO2 we increase the amount of oxygen tremendously in the alveolar-arterial gradient
What causes diffusion impairment of gases
1) Thickened blood gas barrier -> rate of diffusion is slow (may only be evident during exercise not at rest because of increased blood flow rate decreasing time for gas exchange)
Describe V/Q (ventilation/perfusion) mismatching and shunts -> atelectasis (alveolar collapse) vs normal vs dead space
High V/Q = q is smaller
Low V/Q = v is smaller -> severe hypoxemia (no air entry due to poor ventilation)
What value is considered a V/Q mismatch
Any number that is not 0.8
