RESP 4 Flashcards
What is the % of hemoglobin saturated with O2 in the pulmonary veins (SvO2)?
75%
What is the % of hemoglobin saturated with O2 in the pulmonary arteries (SaO2)?
97%
___ of O2 reversibly binds to
hemoglobin inside of the RBC
98%
___ of total oxygen content is
dissolved in plasma
2%
Iron must be in __________ state to bind O2
ferrous (Fe2+)
The amount of oxygen bound to Hb depends on:
- Plasma PO2
- Number of binding sites in RBCs depends on the Hb amount per RBC
What is CaO2?
ml of O2carried by oxyhemoglobin plus ml of O2 carried dissolved in plasma
What is the average CaO2?
19.782 ml O2/ 100 ml blood
What is positive cooperativity?
At a high PO2, hemoglobin’s affinity for O2 is highest.
The lower the PO2, the ____ likely O2 will dissociate from hemoglobin.
more
2,3-BPG binds to Beta subunits of deoxy HB and ________ its O2 affinity
decreases
What is the bohr effect?
Oxyhemoglobin Dissociation Curve Shifts to the RIGHT
What does a right shift in the Oxyhemoglobin Dissociation Curve cause?
- DECREASED affinity between hemoglobin and oxygen
- oxygen is MORE likely to dissociate
from Hemoglobin.
When do levels of 2,3-BPG increase?
- exercise
- hypoxia from high altitude
- pregnancy
- chronic lung disease
What causes a right shift in the Oxyhemoglobin Dissociation Curve?
- increased hydrogen ions (lower pH)
- increased CO2
- increased temperature
- increased BPG
What does a left shift in the Oxyhemoglobin Dissociation Curve cause?
- INCREASED affinity between oxygen and hemoglobin
- oxygen is LESS likely to dissociate from hemoglobin
What causes a left shift in the Oxyhemoglobin Dissociation Curve?
– Decreased PCO2
– Increased pH
– Decreased temperature
– Decreased 2,3-BPG
Carbon Monoxide has a ______ greater affinity for Hemoglobin than Oxygen.
250X
CO bound to hemoglobin _______ Hb’s affinity for O2.
increases
- left-ward shift
What is the treatment for carbon monoxide poisoning?
- Pure oxygen
- 5% CO2
What are the variants of hemoglobin?
- Methemoglobin
- Hemoglobin F (fetal hemoglobin)
- Hemoglobin S (sickle cell)
How does fetal hemoglobin differ from HbA?
- left shift
- no B chains
- higher affinity for oxygen
How is methemoglobin different from HbA?
- Heme with Fe3+ does not bind O2 as readily (reduced
affinity) - Causes any heme groups in the same Hb molecule with heme in the Fe2+ state to have have higher affinity for bound O2 ➔ net effect is reduced O2 delivery to the tissues
What causes methemoglobin to form?
- Ferrous to ferric
- occur due to G6PDH deficiency or upon exposure to some local anesthetics
How does hemoglobin S (sickle cell) differ from HbA?
– Normal α units, abnormal B units
– When deoxygenated, RBCs form sickle shapes, obstructing small vessels
– O2 has lower affinity
What are the causes of hypoxemia?
- decreased FiO2
- hypoventilation
- diffusion defects
- V/Q defects
What is wrong with the A-a gradient in each of these causes of hypoxemia?
- decreased FiO2 = normal gradient
- hypoventilation = normal gradient
- diffusion defects = increased gradient
- V/Q defects = increased gradient
How does PaO2 change in all of the causes of hypoxemia?
decreased PaO2
What are the three ways carbon dioxide is transported in the blood?
- Dissolved CO2
- Carbamino-hemoglobin (CO2Hgb)
- Bicarbonate (HCO3-)
What is the main way of CO2 transport?
bicarb
What is the bicarb equation?
What is the haldane effect in systemic capillaries?
Deoxygenated Hb promotes increased binding of CO2 to Hb.
What is the haldane effect in the pulmonary capillaries?
Oxygenated Hb promotes dissociation of CO2 from Hb.
Which way does CO2 move in the systemic capillaries?
- tissue
- capillary walls
- plasma
- erythrocyte
Which way does CO2 move in the pulmonary capillaries?
- erythrocyte
- plasma
- capillary wall
- alveolus
What are the causes of methemoglobinemia?
- acquired (exposure to chemicals that cause oxidative stress)
- inherited (deficiency in NADH-MetHb reductase)
How can you treat acquired Methemoglobinemia?
methylene blue and dextrose infusion
- cofactor for the NADPH-MetHb Reductase Pathway, but this is contraindicated in patients with G6PD deficiency
How does methylene blue stop oxidative stress and methemoglobinemia?
uses NADPH to create for HbFe2+ instead of 3+
The only way RBCs make NADPH is
through a pathway catalyzed by what pathway?
Glucose 6-Phosphate Dehydrogenase (G6PD)
If someone has a Glucose 6-Phosphate Dehydrogenase deficiency what will methylene blue cause?
more damage since it is an oxidant that can lead to hemolysis
