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What is respiration?
Process of getting O2 into the body for tissue utilization and removing CO2
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Where does CO2 build up? Where does it go after?
CO2 is built up in the tissues because of metabolism then diffuses into the capillary blood before being carried to the lungs for exchange with alveolar gases
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What is gas movement between the lungs and tisse called?
Simple diffusion: The diffusion gradient for CO2 is the opposite of O2
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Where is partial pressure of CO2the highest? Lowest?
- Highest in the cells, approx 60mmHg
- Lowest in Room Air, 1mmHg
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What is the normal PaCO2?
35-45mmHg
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What is the primary determinant of PAO2?
FIO2
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What is the equation for PAO2?
PAO2 = FIO2 x (PB - 47) - (PACO2/0.8)
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If a PT is breathing 60% or more O2 what happens to the 0.8 or RQ?
RQ will be dropped
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What is the equation for Pan2?
Pan2 = PB - (PAO2 + PACO2 + PH2O)
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What mmHg should never exceed during hyperventilation?
Should never be higher then 120mmHg when breathing room air or it will be called, an error.
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What are the 3 barriers of gas diffusion?
- Alveolar epithelium
- Interstitial space
- Capillary endothelium
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What is Fick's Law?
The greater the surface area, diffusion constant and pressure gradient, the more diffusion.
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CO2 diffuses 20x faster across the A/C membrane than O2 because?
It's higher solubility in plasma
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How long is pulmonary blood exposed to alveolar gas normally? during exercise?
- 0.75 secs normally
- With exercise, 0.25 secs
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How long does it take for normal equilibriation?
0.25 secs
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PaO2 is normally ______ less than calculated PAO2 due to the presence of anatomic shunts.
5-10mmHg
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What are the 2 right-to-left anatomical shunts called?
- Bronchial Venous Drainage
- Thesbian Venous Drainage
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What are anatomical shunts for?
Picks up poorly oxygenated blood and moves it into arterial circulation, called venous admixture. This action lowers the O2 content of arterial blood.
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What accounts for 3/4's of the normal difference between PAO2 and PaO2?
Anatomical shunts: Bronchial and Thesbian Venous Drainage
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What are 2 ways O2 is carried in the blood?
- Dissolved: in plasma
- Bound: in hemoglobin
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What is the normal value for hemoglobin saturation?
SaO2 is 95%-100%
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Why does the steep portion drop happen in capillaries during hemoglobin saturation?
A small drop in PO2 causes a large drop in SaO2 indicating a lessening affinity for O2.
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What is the normal O2 content of blood?
16-20ml/dl
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What is the normal adult QT or cardiac output for Fick's equation?
4-8L/min
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What are the 3 types of abnormal hemoglobins?
- Sickle cell HbS
- Methemoglobin metHb
- Carboxyhemoglobin HbCo
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What can sickle cell (HbS) lead to?
Hemolysis, Thrombi and acute chest syndrome can be the most common cause of death
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What has abnormal iron, cannot bind with O2 and alters HbO2 affinity Left shift?
Methemoglobin
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What is methemoglobin commonly caused by?
Nitric Oxide (NO), nitroglycerin and lidocaine
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Which abnormal Hb binds with CO, having a 200x greater Hb affinity than O2?
Carboxyhemoglobin
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What is the treatment for Carboxyhemoglobin?
Hyperbaric therapy
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What is it called when HCO3- (bicarbonate) diffuses out of RBCs in exchange for Cl- (chloride)?
Chloride shift or Hamburger phenomenon
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What happens when HbO2 increases and Caco2 decreases?
Haldane effect
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What does DO2 stand for?
Impaired O2 delivery
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When DO2 is inadequate, what starts to ensue?
Tissue Hypoxia
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What does hypoxemia mean?
Abnormally low or inadaquate PaO2
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The most common cause of V/Q mismatch is?
Hypoxemia
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What can occur with a normal CaO2 if Qt is low?
Hypoxia
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What is a form of hypoxia which the cellular uptake of O2 is abnormally decreased?
Dyoxia
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What is acid base balance?
Refers to phsoilogic mechanisms that keep the H+ of body fluids in a range of compatible life
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What is the normal pH to sustain life?
7.35-7.45
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What are volatile acids made out of?
Carbonic acid (H2CO3) and HCO3
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What are fixed or nonvolatile acids made up of?
Phosphates and proteins including Hb
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What is the avg fixed acid production?
50-70 mEq/day
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Define Acid?
Compound that yields H+ ions when placed in an aqueos solution
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Define Base?
- A compound that yields OH (Hydroxide) when placed into an aqueos solution.
- AKA substance that is capable of inactivating acids
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Why is Bicarbonate buffer system also called, Open Buffer system?
H2CO3 is in equilibrium with dissolved CO2 which is readily removed by ventilation
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Why does Bicarbonate buffer or Open system have the greatest buffering capacity?
It functions in an open system
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What is the back up buffer system called?
Nonbicarbonate buffer or closed system
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Why is nonbicarbonate also called, Closed buffer system?
All of the components of acid-base reactions remain in the system
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What is the Henderson-Hasselbach equation? Think pH
pH = HCO3- (kidneys) / PaCO2 (lungs)
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When pH is low it will be?
Acidic
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When pH is high is will be?
Alkalytic
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How much acid excretion do lungs remove daily?
~24000 mmol/L CO2 removed daily
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How much acid do the kidneys excrete daily?
< 100mEq fixed acid per day
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