| Question | Answer |
| 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). |
