Transport of O2 and CO2 and the Regulation of Ventilation Flashcards
Factors that shift to the right the O2-Hb dissociation curve
- ⬆️ CO2 (Bohr effect)
- ⬆️ H (⬇️ pH)
- ⬆️ Temperature
- ⬆️ 2,3-BPG
What happen when the shift of the O2-Hb dissociation curve doesn’t change the affinity of Hb to O2 (P50 remains normal) and at PO2=100 mm Hg saturation is still close to 100%? What is the the most probably change?
Carrying capacity (HbO2 content vol%)
What is the effect of shift (right or left) the O2-Hb dissociation curve on the transport of oxygen?
- shift left: ⬇️ P50 ▶️ ⬆️ affinity Hb to O2 ▶️ load O2
- shift right: ⬆️ P50 ▶️ ⬇️ affinity Hb to O2 ▶️ unload O2
*at PO2=100 mmHg there is close 20% vol HbO2 content, it wouldn’t affect saturation nor carrying capacity, just affinity.
In what cases is the carrying capacity of the blood for O2 changed?
- Anemia: ⬇️ [Hb] ▶️ ⬇️ carrying capacity (⬇️ O2 content)
- Polycythemia: ⬆️ than normal [Hb] ▶️ ⬆️ carrying capacity (⬆️ O2 content)
*P50 (affinity), saturation (O2 per g Hb) doesn’t changed
Effects of carbon monoxide on oxygen transport
- shift left Hb-O2 dissociation curve (⬆️ affinity Hb for O2)
- ⬇️ P50
- ⬇️ % saturation (O2 per g Hb)
- ⬇️ O2 content (vol%)
*affects both; carrying capacity and affinity
What is the haldane effect
Remove O2 from Hb facilitates formation of HCO3 in RBC
*because deoxygenated Hb is better buffer
What is the function of the chloride shift at the RBC
Maintain neutrality of RBC when HCO3 moves to plasma
*change Cl by HCO3
What happen with ventilation in case of acute rise of arterial H+ (⬇️ pH)?
No change in ventilation - BBB is not permeable to H+
*there isn’t stimulation of central chemoreceptors. They sense H+ in CSF through CO2 (cross BBB)
Main or total drive for ventilation under resting conditions at sea level is accomplished by
CO2
How does the anemia stimulate ventilation if there’s normal PO2 and saturation%?
⬇️ HbO2 content ▶️ ⬇️ O2 delivery ▶️ ⬆️ lactic acid (H+) ▶️ stimulate chemoreceptors
*indirect stimulation
Uses of the hyperbaric oxygen
- carbon monoxide poisoning
- compromised tissue graphs
- gas gangrene
The largest quantity of carbon dioxide in venous blood is transported as
HCO3-
Which factor would tend to reduce the increase in ventilation at high altitude?
Alkalosis
*At high altitude, hypoxia stimulates ventilation through the arterial chemoreceptors. This decreases arterial PCO2 (hypocapnia) and causes alkalosis. Alkalosis inhibits ventilation.
Central chemoreceptors of the medulla respond most directly to which substance in the cerebrospinal fluids and extracellular fluid?
H+
What quantity of transfused blood is required to cause hypocalcemia and why does it happen?
More than 5 to 6 liters over 24 hours
Citrate (store blood contain as anticoagulant)