Test 5 Study Guide Part 3 Flashcards
Blood gas machines:
- Calibration:
- Measures:
- Provides a good index of what why?
- Calibration:
Done with a gas tank of known partial pressure of O2 - Measures:
pO2 in the plasma, not in the blood (cannot measure within RBCs) - Provides a good index of what why?
Lung function, because it measures how close to atmospheric oxygen partial pressure it is reaching
How much of oxygen in RBC vs plasma?
RBC: 19.7 ml of O2 (98.5% blood O2)
Plasma: .3 ml of O2 (1.5% blood O2)
Why does breathing 100% O2 not significantly increase RBC O2 level?
What about plasma O2 conc?
Because hemoglobin is 97% saturated at 100 mmHg pO2.
It will increase, but since plasma O2 is only 1.5% of blood O2 content, even if it triples only an increase of 3% is is seen
In increase in plasma pO2 will cause an increase in what?
Ability to diffuse blood to tissues. Does not greatly increase blood level in the blood
After systemic circulation:
Pco2 is 46 mmHg
Po2 is 40 mmHg
What is it after leaving the lungs?
40 Pco2
100 Po2
Arterial blood Po2 and Pco2 is measured to determine the health of what?
The lungs
Results from breathing 100% oxygen at above 2.5 atmospheres of pressure, radically increasing blood Po2:
Oxygen toxicity
Oxygen toxicity results in what?
Damage the CNS from oxidation of enzymes. Coma and death.
Gas mixture (oxygen + inert gas) are used for what reason?
To avoid oxygen toxicity from pure O2 at >2.5 atm.
Toxicity felt in the depths, which jacques cousteau called “rapture of the deep” is medically referred to as?
Nitrogen Narcosis
Nitrogen narcosis symptoms:
- Cause:
- Symptoms:
- Cause:
Very high Pn2 while under water - Symptoms:
narcotic like state
A diver at depth for a sufficient period of time will have a high Pn2.
- Slow rising?
- Rapid rising?
- Slow rising?
Nitrogen is slowly lost from blood stream as the pressure decreases. Nitrogen remains in solution and concentrations fall. - Rapid rising?
Nitrogen rapidly leaves solution, forming a gas in the vessels and causing gas emboli
The bends:
- Alternative name:
- Cause:
- Treatment:
- Alternative name:
Decompression sickness - Cause:
N2 gas emboli (blood blocked small arteries) - Treatment:
Hyperbaric oxygen chamber (increase pressure, drive nitrogen back into solution)
What sets the rhythm for diaphragm other muscles of respiration?
The rhythmicity (respiratory) center of the medulla oblongata (unconscious control) The cerebral cortex (conscious control of respiration)
Sensory information from the peripheral chemoreceptors is conveyed back to the rhythmicity (respiratory) center by which nerves?
Cranial nerve IX (glossopharyngeal)
Cranial nerve X (vagus)
The rhythmicity (respiratory) center has intrinsic rhythmicity…
True
Effect of: Hyperventilation: - PO2 level: - PCo2 level: Hypoventilation: - PO2 level: - PCo2 level:
Hyperventilation: - PO2 level: increases - PCo2 level: decreases Hypoventilation: - PO2 level: decreased - PCo2 level: increases
When enzyme catalyzes this reaction in the blood?
What is its significance
CO2 + H2O -> H2CO3 -> H+ + HCO3-
Carbonic Anhydrase
CO2 levels rising will drop pH
Why is pH/CO2 used instead of oxygen as the measure O2 regulator?
- During hyperventilation:
- During hypoventilation:
CO2/pH will vary more and do so before O2 levels vary. Which means the body never need be oxygen deprived to know it needs to breath more or less.
- During hyperventilation:
O2 stays almost constant (due to high hemoglobin saturation), but CO2 increases significantly
- During hypoventilation:
O2 levels fall more slowly because it is stored in hemoglobin, but CO2 levels rapidly rise
What causes the newborn to take its first breath?
CO2 build up -> decreased pH -> peripheral or central chemoreceptors -> respiratory (rhythmicity) center -> breathing
Diaphragmatic nose breather:
Babies do this, breath mainly with the diaphragm
Eucapnia:
Arterial CO2 of 40 mmHg
Elevated CO2 levels are and are called:
Low Co2 levels are and are called:
> 45 mmHg, hypercapnia
< 35 hypocapnia
Someone hyperventilates before swimming.
Blood hemoglobin is already saturated, so does not increase.
Blood CO2 levels drop, pH rises, the urge to breath decreases
Someone blacks out because they do not feel the need to breath
Shallow water blackout:
How does peripheral chemoreceptor response differ from central chemoreceptor response?
Peripheral to pH changes in the blood. It’s response is IMMEDIATE.
the blood brain barrier is not permeable to H+, CO2 must diffuse into interstitial fluid, be converted to HCO3- + H+, increase interstitial pH for activation. SLOWER more longterm effect.
Synopsis of response:
- peripheral chemoreceptor:
- central chemoreceptor:
- peripheral chemoreceptor: Faster (responds to plasma pH) Smaller effect Located in carotid and aortic bodies - central chemoreceptor: Slower (responds to interstitial fluid pH) Larger effect located in medulla oblongata
Any increase in acid will decrease pH and stimulate hyperventilation. Name two such acids in the body:
Lactic acid
Ketone bodies
Po2 fall as a breathing stimulus:
- Strength:
- What is it called:
- Strength:
weak stimulus - What is it called:
hypoxic drive
Cells in the carotid body which detect the changes in plasma pH
Glomus cells:
effect on CO2 regulation:
- Hypoxia (low Po2):
- hyperoxia (elevated Po2):
- Hypoxia (low Po2):
increase sensitivity to pH changes - hyperoxia (elevated Po2):
decreased sensitivity to pH changes
Patients with emphysema (and other COPDs) are driven by Po2 levels instead of PCo2 levels:
- Why?
chronically high CO2 blunts the body to CO2 changes:
increased bicarbonate production in the choroid plexus, increased secretion into CSF.
increased buffer on CSF (and possibly blood) pH.
A large change in pH is needed to be detected, at least by the central chemoreceptor
Patients with emphysema (and other COPDs) are driven by Po2 levels instead of PCo2 levels:
- This causes what when given oxygen?
Respiratory arrest
Where is Po2 levels detected?
By the peripheral chemoreceptors
- How many subunits are in hemoglobin?
- How many hemoglobins are in a RBC?
- How many subunits are in hemoglobin?
2 beta, 2 alpha (4 oxygen molecules/hemes between them) - How many hemoglobins are in a RBC?
280 million
Oxyhemoglobin:
Hemes on erythrocytes with bound O2 to Fe2+
deoxyhemoglobin:
- Define:
- Alternative Name:
- Coloration:
- Define: Hemes on erythrocytes without bound O2 to Fe2+ - Alternative Name: reduced hemoglobin - Coloration: Maroon
Methemoglobin:
- define:
- Coloration:
- define: Fe3+ on hemes instead of Fe2+ Cannot bind oxygen because it lacks the e- which would normally bind it - Coloration: Bluish color
Carboxyhemoglobin:
- define:
- Coloration:
- define:
hemoglobin bound to CO, the bond is 210 x stronger then the bond with O2. - Coloration:
cranberry juice color
Can a pulse oximeter differentiate from a oxihemoglobin and carboxyhemoglobin?
No it cannot.
Percentage oxygen saturation change:
smokers 2-4% lower
CO poisoning 20 - 40% lower
Percent oxyhemoglobin at 100 mmHg:
Percent oxyhemoglobin at 40 mmHg:
Significance?
97%
75%
Only 22% of O2 is given in the tissues normally
The amount of oxygen your blood and lungs can carry:
Oxygen carrying capacity
- Anemia:
- Polycythemia
- Effect on oxygen carrying capacity?
- Anemia: Low RBC - Polycythemia High RBC - Effect on oxygen carrying capacity? Think about it
Red blood cell production is promoted by:
Erythropoietin
Androgens
Binding of O2 to hemoglobin (occurs in lungs)
release of O2 from hemoglobin (occurs in systemic capillaries)
- driven by diffusion
Loading reaction:
Unloading reaction:
Oxyhemoglobin disassociation curve shows what?
The percentage of hemoglobin saturation vs Po2 (mmHg)
- it is sigmoidal (changes between 40 - 20 mmHg results in large changes)
How long can a person last without O2?
4-5 minutes without CPR
CPR recirculates residual oxygen
Since percent hemaglobin saturation is based on Po2 how will oxygen affect it?
It will lower percent hemaglobin saturation (but not by much over small elevation changes)
How much oxygen is unloaded in mild exercise:
How much oxygen is unloaded in heavy exercise:
97% -> 58% = 39% unloaded
97% -> ~20% = ~80% unloaded
High pH (low CO2) effect on Oxygen dissociation curve?
Left shift, less oxygen is given to tissues
Low pH (High CO2) effect on Oxygen dissociation curve?
Right shift, more oxygen is given to tissues
