Freedman's tangent

Question 1

What is PO2 at sea level? At peak of Mt Everest? What is the general equation at play here?

Answer 1

PO2 = .21 (760-47);
PO2 = .21 (255 -47);
Pi = Fi (PT - PH2O)

Question 2

What are mild symptoms of hypoxemia at high altitude? What causes these symptoms?

Answer 2

Drowsiness and muscular fatigue, occasional headache or nausea, sometimes euphoria, gradual decline in cognition; inadequate response to hypoxemia resulting in reduced blood flow to brain

Question 3

What does arterial hypoxemia stimulate? What is reduced?

Answer 3

Peripheral chemoreceptors, leading to increased symp drive, leading to tachy (increased HR and contractility, Increased CO) and alveolar ventilation increases to 1.7 times normal;
PCO2 and H+ concurrently reduced with increased ventilation

Question 4

_____ stimulates respiration, ______ inhibits it; Initial hyperventilation causes _______ which inhibits _________; what restores normal pH? How quickly do compensations work for metabolic acidosis and alkalosis relative to their respiratory counterparts?

Answer 4

acidic pH; alkaline pH;
respiratory alkalosis; respiratory drive;
Immediate, so they are quicker (respiratory compensation through kidneys could last days!!!!)

Question 5

With chronic hypoxia, what are adaptations?

Answer 5

1. Increased CO and vasodilation
2. Increased hematocrit
3. Increased 2,3-DPG synthesis lowering Hb-O2 affinity
4. Pulmonary hypertenion (hypoxic vasoconstriction)

Question 6

With DPG, how does the Hb-O2 dissociation curve shift?

Answer 6

To the RIGHT!!!

Question 7

What are long-term adaptations to high altitude?

Answer 7

Hypoxia-inducible factor 1 (HIF-1):

1. Hematocrit up to >55% (renal hypoxia stimulates EPO production and release)
2. Increased pulmonary diffusing capacity by 2-3 x (more blood volume in capillaries and more capillary surface area in lungs)
3. Increased tissue vascularity
4. More expression of oxidative enzymes in mito (extract O2 better!!)

Question 8

What is acute mountain sickness attributed to? Symptoms?

Answer 8

Cerebral vasodilation (cerebral edema) and hypoxic pulmonary vasoconstriction (pulmonary edema);
Headache and muscular fatigue, dizziness, dyspnea, sleep disturbance, peripheral edema, nausea and vomiting

Question 9

What can chronic mountain sickness lead to? What built up to this?

Answer 9

CHF of R heart:

1. Crit >60%, increasing blood viscosity and vascular resistance
2. Increased thrombosis risk
3. Increased pulmonary VR and increased blood viscosity increases afterload on R heart