Physio block 4

What is hypoxemia?

reduction of oxygen in blood

what is hyperoxemia?

high oxygen in blood

what can cause hypoxemia using v/q? ex of each

Low V/Q from poor ventilation and normal perfusion (ex: asthmma,bronchitis, airway obstruction)

High V/Q from good ventilation and poor profusion (oxygen cant enter blood)(ex: pulmonary embolism, severe reduction in pulmonary blood flow)

What is the most common cause of hypoxemia in clinical medicine?

Low V/Q from poor ventilation while have normal profusion

What is the most severe low V/Q situation? what us V/Q like and what happens?

Shunt

V/Q=0

no ventilation and normal perfusion

what is high carbon dioxide in blood called?

hypercapnia

what is hypoventilation?

ventilation is insufficient relative to metabolic needs

What are 3 ex of things that cause hypoventilation?

CNS depression

Anesthesia

Neromuscular disease

what does hypoventilation lead to?

hypoxemia and hypercapnia

what is diffusion imparement? 3 ex?

membrane thickens so oxygen diffusion becomes more difficult

-fibrosis

-pulmonary edema

-severe pneumonia

what does diffusion imparement lead to?

hypoxemia

what is hypoxia?

low oxygen in tissues

How many types of hypoxia? what called? what problem in each?

4

-hypoxemic: not enough oxygen in blood

-anemic: not enough hemoglobin

-ischemic: not enough blood flow

-histotoxic: cells cant use oxygen

which is the only type of hypoxia related to gas exchnage?

Hypoxemic

what is the most common cause of cyanosis?

Hypoxemic hypoxia

what else does cyanosis depend on besides oxygen levels?

hemoglobin

what is main way blood carries oxygen for transport?

hemoglobin

What is hemoglobin made up of?

4 globin subunits each mad eof a heme group that can bind ONE oxygen each

what call when no oxygen bound to hemoglobin?

deoxyhemoglobin

what call it when hemoglobin is 25%,50%,75% or 100% saturated with oxygen?

oxyhemoglobin

what is main factor that influences oxygen saturation of hemoglobin?

partial pressure of oxygen in blood

what is positive coopertivity?

hemoglobins affinity for oxygen increases as it binds more oxygen. Very hard to bind first oxygen but gets easier every after as changes hemoglobins conformation which impacts its affinity.

what is shape of hemoglobin curve? why this way? whats it do?

sigmoid

-positive coopertivity makes it harder for hemoglobin saturation to increase at first

-lower pressure promotes oxygen release and high pressure promotes oxygen binding

What is P50?

the pressure needed for hemoglobin to be half saturated

what 4 factors affect hemoglobins affinity for oxygen?

carbon dioxide

temperature

pH

2,3 DPG (diphosphoglyceric acid)

If tissues are in a high metabolic state where using lots of oxygen what happens to oxygen curve? why?

Shift to right

-hemoglobin release oxygen easier as tissues need it sinc eusing lots of oxygen

what is co2, temp, pH and 2,3 DPG like in high metabolic state? what does this do?

high co2

high temp

low pH

high 2,3 DPG

-shifts curve to right

how does 2,3 DPG affect hemoglobin affinity for oxygen? when happen? how does this be helpful?

2,3 DPG binds 2 hemes changing hemoglobin conformation and therefore decreasing affinity for oxygen

Happens when oxygen delivery is difficult when in situations like high altitude, chronic anemia and chronic hypoxemia

makes unloading oxygen easy which is good as have 2,3 DPG when dont have lots of oxygen so this means the hemoglobin will be getting oxygen to cells that need it

If tissues are in a low metabolic state where using lots of oxygen what happens to oxygen curve? why?

curve shits to left

-affinity for oxygen increases as is in situation where tissues are not actively using oxygen so they dont need as much

what is co2, temp, pH and 2,3 DPG like in low metabolic state? what does this do?

low co2

low temp

higher pH

low 2,3 DPG

-shifts curve to left

When curve shifts right what does hemoglobin do to oxygen? what about when shifts left?

right: release more oxygen

left:hold on/bind to more oxygen

what does it mean if oxygen saturation curve shifts right? left?

right: need higher ppO2 to reach P50

left:need lower ppO2 to reach P50

If a racehorse’s exercising muscles are producing large amount sof CO2 and heat, what effect would this have on hemoglobin?

right shift with enhanced oxygen delivery

how is carbon dioxide transported in blood?

dissolved in plasma

bound to hemoglobin

AS BICRABONATE ← main way

what is Bohr effect?

Increase in Co2 in tissues causes hemoglobin to release oxygen more easily

what does bohr effect ensure?

ensures oxygen delivery increases exactly where co2 production is high so cells that need oxygen recive it which directly links oxygen transport to metabolic activity

what is haldane effect?

explains deoxygenated hemoglobin has higher affinity for co2 so when hemoglobin releases oxygen it chnages conformation to easilky bind co2

what call it when hemoglobin is carrying co2?

carbaminohemoglobin

what enxyme use to convert co2 to bicarbonate? whats the reaction?

carbonic anhydrase

CO2+H2O ←>Carbonic acid ←> hydrogen+ bicarbonate

what is the system of converting CO2 to bicarbonate important for?

maintaining blood pH

what is chloride shift?

after bicarbonate is formed using carbonic anhydrase in hemoglobin cl is brought into hemoglobin in ecchange for moving bicarbonate out of hemoglobin

what happens to bicarbonate when blood reaches pulmonary capillaries?

bicarbonate brought back into hemoglobin and cl taken out. Then bicarbonate made back into CO2 in the reverse direction of the reaction. The co2 is then released into alveoli to be exhaled

whata re the 4 main categories of problems for gas transport?

-hemoglobin related problems (oxygen carrying capacity problems)

-impared oxygen delivery

-impared oxygen utilization

co2 transportproblems

what are 4 things we talked about that can cause hypoxia? how?

low hemoglobin ← low amount of hemoglobin so less oxygen transported

carbon monoxide poisoning ← carbon dioxide binds hemoglobin stronger than oxygen so less oxygen transported

methemoglobinemia ← hemoglobin oxidized from ferrous form to ferric form so it cant hold oxygen so oxygen not transported, and oxygen that is held has harder time being unloaded

Heinz bodies ← oxidative damage destroys RBC so less hemoglobin a sit denatures and precipitates so less hemoglobin to transport oxygen

what two things see cause hypoxia in acetominophen poisoning in cats?

heinz bodies

methemoglobinemia

what is blood flow related way in which oxygen transport is lessened?

when things like shock, heart failure and thrombosis reduce blood flow (reduced circulation) so tissues do not get enough oxygen leading to ischemic hypoxia

what do disorders affecting CO2 transport typically involve alterations to?

hemoglobin function or acid base balance

why do disorders impacting CO2 transport rarely lead directly to hypoxia?

CO2 can be transported in multiple forms the main consequence is altered buffering and pH regulation rather than oxygen delivery

What does hypercapnia primarily result from?

impaired ventilation

While increased CO2 can lead to respiratory acidosis what may it indirectly impact? why?

Oxygen delivery by affecting hemoglobin affinity

-Bohr effect

If the key mechanism is failure of CO2 removal what is any associated hypoxia due to? what not due to?

Associated with ventilation defects rather than transport abnomalities

what are the three types of hypoxia that are not hypoxemic best understood to be?

gas transport and utilization problems

What general problem causes anemic hypoxia?

hemoglobin problem as oxygen can not be carried efficiently

What general problem causes ischemic hypoxia?

Blood flow problem as oxygen can not be delivered to tissues

What general problem causes histotoxic hypoxia?

cellular problem as oxygen can not be used by cells

When trying to determine if get right shift or left shift for a situation, what steps go through to determine?

1. first determine if its a lung problem. If the lungs are damaged/impacted will get V/Q mismatch, from there determine what O2 is like in blood and CO2. If CO2 increased get lower pH which will lead to right shift, if decreased CO2 get higher pH resulting in left shift.

2. If not lung problem need to look at what Oxygen is doing. If PO2 normal its a transport or delivery problem, if PO2 decreased its a lung issue so go back to step 1

3. If PO2 normal then can determine problem by looking at blood flow. If not delivering well its ischemic hypoxia, if low amount of hemoglobin its anemia. If the hemoglobin function is abnormal than its a structural problem.

4. If all that is not true and hemoglobin is normal then may be a shift. so look at temp, pH, Co2, 23DPG. If low cO2,high pH and low temp get left shift where high CO2,low pH and high temp get right shift.

5. If everything above is normal that its a tissue issue

Does hemoglobin shift left/right due to V/Q mismatch?

no, it shifts due to chnages in CO2,pH, temp and 23BPG. Changes in those things may result from mismatch and therefore them resulting from mismatch may get left or right shift due to those factors chnaging

Can you get right/left shift without V/Q mismatch?

yes

-the shift results from abnormal gas transport which doesnt always have to do with lungs (v/q is lung thing)

If have V/Q mismatch how determine what shift results from it? what result in for hemoglobin?

Look at what happens to CO2. If co2 increased then pH should increase due to the bicarbonate reaction so get right shift. if co2 decreased get lower pH due to bicarbonate reaction so get left shift. -if right shift affinity for oxygen is high so have hemoglobin unload less o2/binding oxygen very strongly

-if left shift affinity for oxygen is lower so hemoglobin unload more o2/not binding oxygen well