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Phys2 resp undr strs

How does altitude affect inspired PO2 INVERSELY proportional. As altitude Inc, inspired PO2 dec. **due to barometric pressure decreasing at higher altitudes
Does the concentration of O2 in the atmosphere change with altitude? NO it is always 20.93%
4 mechanisms contributing to acclimatization 1.Hyperventilation. 2.Polycythemia. 3.Changes to O2 dissociation curve. 4.Circulatory changes.
Hyperventilation's affect on acclimatization Occurs as a result of Dec arterial PO2 stimulating peripheral chemoreceptors. **this will Inc alveolar PO2 & dec alveolar PCO2 in an effort to maximize alveolar PO2.
Alveolar PCO2 as a result of Hyperventilation lowered to 8mmHg. **This in turn INCREASES alveolar PO2 thru the eq: PAO2=PIO2-(PACO2/R)
2 stages of hypoxia induced hyperventilation 1.Respiratory alkalosis limits Hypervent: Inc vent due to peripheral chemoreceptors, alkalosis sensed by CENTRAL chemoreceptors causing a vent slow down). 2.Arterial & CSF pH corrects, ventilation now Inc further
what is Polycythemia Increased hematocrit
Why is Polycythemia useful at high altitudes? Icreases the total O2 content but not the PO2 or Hb sat%. **higher O2 content for a given PO2
Erythropoietin Hormone responsible for the Inc RBC production at high altitudes. **Makes O2 dissociation curve STEEPER so that a slight dec in PO2 will release more O2 to the tissues.
What is a big danger with polycythemia (& erythropoietin) Increases BL viscocity which increases vascular resistance making the heart work harder (BAD NEWS)
At what altitude will there be a RIGHT shift of the O2 dissociation curve? Moderate altitude, caused by production of 2,3BPG by the RBC. **Decreases the Hb affinity for O2 for a given PO2.
At what altitude will there be a LEFT shift of the O2 dissociation curve? Extreme altitude, due to ensuing respiratory alkalosis that follows the hyperventilation in response to dec PO2. **Helps Hb scavenge any O2 possible in the lungs at lower PO2s.
Are changes in pulmonary circulation helpful at high altitudes? NO
What circulatory changes occur as a result of acclimatization? Systemic circulation: 1.Inc capillary density. 2.Inc in mitochondrial enzyme production. **Helps with O2 delivery to the cells
How does Increased capillary density aid in O2 delivery during acclimatization? reduces the diffusion distance for O2 which INCREASES rate of diffusion
How does Increased mitochondrial enzyme expression aid in O2 delivery during acclimatization? Depletes diffused O2 to enhance and maintain the Partial Pressue gradient for O2 in cells.
HAPE High Altitude Pulmonary Edema.
What causes HAPE? generalized vasoconstriction due hypoxia will lead to HTN and edema. **This also increases the work of the Right Ventricle leading to R sided HF.
Why is prolonged breathing of pure O2 toxic? Causes: 1.Convulsions. 2.Pulmonary edema (inc capillary leakiness). 3.Dec vital capacity (due to absorption atelectasis).
What function does N2 serve in the alveoli nitrogen normally does not diffuse from the alveoli into the blood, and the N2 just stays there in the alveoli. This helps to keep the alveoli open.
What causes Absorption atelectasis With prolonged breathing of O2, N2 content is depleted from the alveoli and BL. This produces a large difference in the total partial pressure between the alveoli and BL. Therefore if the airway is blocked the alveoli will collapse.
What is the normal alveolar PN2? 573mmHg
Why is hyperbaric O2 therapy useful in carbon monoxide poisoning? Since Hb is bound to CO, the only way to get sufficient O2 into the BL is by increasing the PO2 (amt of O2 dissolved)
Why is the placenta not very efficient for the fetus? B/c the placenta is in parallel with the rest of it's organs, so its BL mixes w/ deoxygenated BL leaving other organs.
What is the main function of the Foramen Ovale in the fetus' circulation Directs BL from inferior vena cava into the left atria and then to the HEART and BRAIN.
What is the main function of the Ductus Arteriosus in the fetus' circulation Shunts BL away from the unused unused lungs, allowing it to flow from the pulmonary arteries directly into the descending aorta.
Why is the placenta not very efficient for gas exchange? B/c the maternal BL flows haphazardly in the placenta.
2 things that cause a new born to switch from placental breathing to lung breathing 1.Hypoxemia. 2.Hypercapnia (sensitization of the chemoreceptors).
Is the intraplueral pressure More or Less negative in a newborn? MORE NEGATIVE (-40cm H2O), b/c their alveoli are filled with fluid and have a very high surface tension, making it hard to inflate their lungs. **This is why Surfactant is necessary and Premature babies struggle due to a lack of surfactant production.
What is responsible for infant BF being redirected to the lungs? 1.Dec pulmonary vascular resistance (loss of hypoxic vasoconstriction & Inc lung vol->Inc radial traction->Inc radius of pulm A & V). 2.Ductus arteriosus constricts (Inc PO2 & prostaglandin release). 3.Foramen Ovale closes (Inc L atrial pressure).
Created by: WeeG



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