Physiology Flashcards
Your climbing in the alps when you feel short of breath and while taking a break your friend asks you what physiological mechanism is triggering your increased breathing rate and why; what’s your explanation?
What’s a side effect of hyperventilation? How does your body compensate for this?
Decreased PO2 at this altitude is such that the carotid chemoreceptors sensed a deficiency and stimulated my phrenic nerve so that the diagphram picks up the respiration rate so as to increase O2.
Bad news is your CO2 is also decreasing and you’re going into respiratory alkalosis. Kidneys will try to excrete more bicarbinate.
What changes take place to the pulmonary blood flow due to high altitude, what drugs could you use to treat this theoretically?
Pulmonary htn, increased pulmonary arterial pressure, this could lead to right heart failure.This is from vasoconstriction of the capillary in the lungs, due to lack of O2.
Treat with any of the pulmonary htn drugs.
When Hb levels decrease how is the concentration of O2 affected and why?
It will also decrease b/c its a combination of HbO2 and dissolved O2
The binding capacity of the blood is determined by which factors?
Total Hb content and the %saturation
If the PaO2 is 100mmHg and the PvO2 is 40mmHg why is the gradient of 60mmHg not represented in the tissues as changing from the original PO2 of 40mmHg?
This is because of the dynamic equilibrium of the tissues which are both receiving O2 and using it simultaneously. That’s why unless someone is exercising this value is relatively constant.
Why is there such a large difference between the PO2 in arterial blood (60mmHg) compared to the PCO2 (5mmHg)?
The CO2 is more soluble than O2 in blood.
At high altitude the PO2 is greatly decreased and carotid chemoreceptors stimulate the diaphragm leading to hyperventillation, causeing both a decrease in CO2 and increase in O2, leading potentially to respiratory alkalosis. Which way will someones O2 Hb dissociation curve shift and why?
R shift. Although the decrease in CO2 would suggest a Left shift, the increase in 2,3-DPG from anaerobic metabolism due to hypoxia will play a greater role in shifting the curve.
What is cyanosis and what causes it?
Blue color of the skin and mucous membranes from increased amounts of reduced (deoxiginated) HB in the capillaries supplying an area. It’s suggestive of hypoxia but it can be present without cyanosis.
Define Hypoxia and Hypoxemia
Hypoxia-signs and symptoms of inadequate O2 supply of the tissues; this can be present w/o Hypoxemia.
Hypoxemia Deficient PaO2
Is it more or less difficult to detect cyanosis in someone with Polycythemia compared to anemia? What about fetal Hb?
Less difficult to detect cyanosis is someone with a high volume of Hb. These people maybe cyanotic without being hypoxic.
With fetal Hb hypoxia maybe present even with mild cyanosis.
Why do patient with asthma have a increased residual volume?
When these patients exhale some of their alveoli collapse and air is trapped inside the lungs. This increases the residual capacity (& FRC) and is a classic sign of an obstructive disease; as is a decreased FEV1/FVC ratio.
How does a decreased V/Q ratio lead to decreased PaO2?
Blood will shunt from less oxygenated alveoli due to vasoconstriction of the capillaries in response to hypoxia. This blood will then mix with well oxygenated blood and decrease the overall PaO2
Why do asthmatics having an attack have a predisposition to progress from respiratory alkalosis to respiratory acidosis?
Initially they have trouble breathing due to increased lung volumes and patchy alveolar collapse which increases the work of breathing. They start to hyperventilate when their O2 sat drops below 60 mmHg due to chemoreceptors in the carotid sinus. This leads to respiratory alkalosis. Over time though the amount of alveolar collapse can increase leading to rising PaCO2 despite an attempt to compensate through hyperventilation.
The V/Q mismatch increased the A-a gradient.
