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what are the 2 ways by which O2 is transported in the blood?
dissolved in the plasma (1.5%) or bound to hemoglobin (98.5%)
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define henry's law
how much of the gas that will dissolve depends on the partial pressure of that gas
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what is the solubility factor for dissolved oxygen in the plasma
.003 mL/mmHg O2 in 100mL of blood
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describe the structure of hemoglobin
Hb has 2 alpha chains and 2 beta chains mainly made up of amino acids. 4 heme portions contrain the iron ion and these are what grabs onto the oxygen. the iron groups can be in 2 states Fe+2 (Ferrous) and Fe+3 (Ferric). the iron needs to be in the Ferrous state because the Ferric state does not carry the O2 and is known as methemoglobin.
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what is the normal amound of hemoglobin in males?
14-16 g/100mL blood
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what is the normal amount of Hb in females
12-15 g/100mL blood
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What effect on oxygen carrying does CO poisoning have?
CO has 210x the affinity of O2 for Hb and reduces the Hb O2 carrying capacity
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what effect on oxygen carrying does methhemoglobin have?
methhemoglobin is the changing of the iron molecule in the heme from the ferrous state to the ferric state, resulting in an inability to transport O2
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what effect on oxygen carrying does sickle cell anemia have?
the RBCs become crescent shaped and unable to carry as many O2 molecules as normal RBCs
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what effect on oxygen transport does anemia have?
anemia is a condition in which there is a deficiency of Iron which will lead to Hb's ability to transport O2 to be eliminated
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what is the difference between oxygen content and oxygen capacity?
oxygen content is how much oxygen is actually bound to the Hb while oxygen capacity is how many O2 molecules can be bound to Hb is SaO2 were to actually be 100%
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explain the term vol% of O2
Vol% represents the amount of O2 in mm that is in 100mL of blood.
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what is the oxygen dissociation curve?
part of a nomogram that graphically illustrats the percentage of Hb that is chemically bound to oxygen at each oxygen pressure with a second scale that gives the precise oxygen content that is carried by the Hb at each oxygen pressure.
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what shape is the oxygen dissociation curve?
S
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explain the relationship between PO2 and the Sat% of Hb
as Po2 increases % saturation of Hb increases
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explain the clinical significance of the flat portion of the oxygen dissociation curve
it illustrates that Hb has an excellent safety zone for loading of O2.
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explain the clinical significance of the steep portion of the oxygen dissociation curve
when PO2 continues to fall below 60mmHg the quantity of O2 delivered to the tissues, and any small disease in PO2 causes O2 to be released from Hb to the tissues
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define P50
the partial pressure of O2 that causes 50% saturation of normal Hb.
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how do you recognize a right or left shift of the O2-Hb dissociation curve using P50?
- 27mmHg = P50
- If < 27mmHg it causes a left shirt
- If > 27mmHg it causes a right shift
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what are the factors that can cause the O2-Hb curve to shift its behavior?
pH, temp, PCO2, and DPG
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explain why the factors that change the behavior of the O2-Hb curve cause these effects.
a decrease in any of the factors will cause a right shift and illustrate the behavior of Hb that means the Hb releases O2 more easily and does not hold onto oxygen as well. an increase will cause a left shift and illustrate the behavior of Hb and means Hb does not release O2 as easily or it holds onto O2 more strongly
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explain the clinical significance for the lungs and tissues of the shifts
a right shift in the behavior of Hb is bad for the lungs but good for the tissues. a left shift in the behavior of Hb is good for the lungs but bad for the tissues. local is good, systemic is bad because in the lungs Hb won't bind as well
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explain the concept of total oxygen delivery
how much O2 is being delivered to the tissues by all the blood in one minute
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explain the concept of arterial-venous oxygen content difference
the oxygen contect of arterial blood minus oxygen content of venous blood = how much blood is consumer by the tissues
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explain the concept of oxygen consumption
the amount of oxygen extracted by the tissued in one minute
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explain the concept of oxygen extraction ratio
the amount of O2 extracted divided by the amount of oxygen delivered
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explain the concept of mixed venous oxygen saturation
how much O2 the patient is actually using (@ rest 75%, 65% is acceptable)
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what is the formula for calculating total oxygen delivery
DO2 = QT x (CaO2 x 10) where Qt = cardiac output, CaO2 = content of oxygen in arterial blood, and 10 = a conversion factor
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what is the formula for calculating CaO2
CaO2 = (Hb x 1.34 x SaO2) + (PaO2 x .003)
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what is the formula for calculating CvO2
CvO2 = (Hb x 1.34 x SvO2) + (PvO2 x .003)
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what is the formula for calculating arterial-venous oxygen content difference?
C(a-v)O2
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what is the formula for calculating oxygen consumption?
VO2 = QT[C(a-v)O2 x 10]
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what is the formula for calculating the oxygen extraction ratio?
O2ER = C(a-v)O2 / CaO2
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define the term pulmonary shunting
a portion of the cardiac output that bypasses the respiratory membrane
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describe the effect of a shunt
to re-route blood flow
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explain the difference between true shunts and shunt-like effects
true shunts cause the blood to miss the alveoli completely, resulting in absolutely no gas exchange. shunt-like effects happen when there is SOME but not an adequate amount of ventilation
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what are the 2 types of true shunts?
anatomic and capillary
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explain anatomic shunts
true shunt, caused by non-oxygenated blood completely bypassing the alveoli and entering either the pulmonary vascular system or the left atrium through the thebesian veins. in both cases this is the mixing of richly oxygenated blood with poorly oxygenated blood so the overall oxygen levels decrease, can be caused by congenital heart disease, intrapulmonary fistula, and vascular lung tumors
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explain capillary shunts
caused by either atelectasis, edema, or alveolar consolidation
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what causes shunt-like effects?
hypoventilation of the alveoli, ventilation-perfusion mismatching, or alveolar-capillary diffusion defects
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explain venous admixture
a mixture of shunted, non-oxygenated blood mixed with reoxygenated blood distal to the alveoli. when this occurs it increases the PO2 in the non-reoxygenated blood but is an overall decrease in the PO2 in blood
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what is the formula for the shunt equation?
- QS/QT
- QS = CcO2 - CaO2
- QT = CcO2 - CvO2
- where QS is the portion that is shunting and CcO2 is the theoretic perfect oxygenation
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explain the clinical significance of pulmonary shunting
- lower than 10% reflects normal lung status
- 10-20% indicated intrapulmonary abormality
- 20-30% indicates significant intrapulmonary disease and may be life threatening with limited cardiovascular function
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explain hypoxia
low O2 levels in the tissues
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what are the different causes of hypoxia?
low PAO2 (environmental or hypoventilation), diffusion defects (decrease in surface area or increase in wall thickness), ventilation-perfusion mismatching (not matching airflow to blood flow), and shunting
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define cyanosis
blue-gray or purplish discoloration seen on the mucus membranes, fingertips, and toes. occurs when these areas have only 5g% reduced Hb
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define polycythemia
increased level of RBC
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