Chapter Three - Repiratory Function and Gas Exchange Flashcards
What is the normal tidal volume, dead space volume, and what proportion of the tidal air remains in the conducting airways? So that leaves what volume of fresh gas that goes into the lungs? Knowing that, now describes what happens during shallow breathing.
Left panel: Tidal inspiration pushes anatomical dead space volume back into the alveoli. At end-inspiration, 1/3 third of the tidal air remains in the conducting airways so that alveoli receive only 300 mL of fresh gas.
Right panel: Shallow breathing. The tidal inspiration equals the anatomical dead space volume. Theoretically, no fresh gas enters the alveoli. However, in reality, some gas mixing does occur.
What is the difference between the conduction zone and the respiratory zone? What is the “dead space” and what is it’s normal volume?
Conduction zone: no gas exchange, respiratory zone: gas exchange
Volume of the conducting zone: around 150 mL. We call it «dead space». Not all air that goes into your lungs is fresh and filled with oxygen, we breathe in a certain amount of “dirty” air that has already taken place in gas exchange.
Give the definition of tidal volume. How much fresh air do we get during quiet respiration?
Tidal volume: volume of air that we breathe in or out, in a single breath, during quiet respiration. So that leaves us with 300 mL (450 - 150 mL) of fresh air
Give the definition of residual volume.
Residual volume = volume of air that we cannot exhale, but we do not need to go there
Why is a tracheostomy usually better than a ventilator, in the ICU?
In the ICU: tracheostomy = better because there is less dead space than a ventilator
What is the effect of more shallow ventilation, or panting? Give the equation that allows us to see the relationship between the tidal volume and alveolar ventilation.
The total volume of gas being inhaled per minute looks the same, but the volume of each inhale is small (because there is a bigger proportion of dead space air), so Va is very small with panting
Equation: Va = (Vt - Vd) x f, where Va = alveolar ventilation, Vt = tidal volume, Vd = volume of dead space, and f = frequency
Panting is NOT like exercise where you breathe quickly and deeply, but rather shallowly and rapidly (panting)
How is oxygen transported in the blood?
Oxygen travels in our blood through red blood cells, bound to hemoglobin molecules
The more oxygen is bound to hemoglobin, the higher its affinity to oxygen becomes
Draw the oxygen-Hb dissociation curve with all its details, including two different y axis. What happens at the top of the curve? What does the slope of the curve represent? What is the pO2 of the blood at the tissue level? What does that allow?
At the top of the curve, most of the oxygen is not dissolved, most of it is bound to hemoglobin (total vs combined = not a big difference)
The slope represents how easily the oxygen is going to leave the hemoglobin (if the slope is high, a small change makes a big difference on how much O2 in bound to the hemoglobin)
The more oxygen dissolved in blood, the more oxygen on the hemoglobin. The high O2 drives a pressure for the hemoglobin to bind to oxygen
At the tissue level, the pO2 of the blood is about 40, so that allows the oxygen to good feed the cells instead of staying with te hemoglobin
(A-V) O2 difference: on your O2-Hb dissociation curve, draw the lines for:
- Veinous blood in exercise
- Normal veinous blood
- Normal arterial blood
- Veinous blood in exercise: 15 mm Hg
- Normal veinous blood: 40 mm Hg
- Normal arterial blood: 95 mm Hg
Decribe the Bohr effect. Use the O2-Hb dissociation curve to explain. What makes the curve move to the right, and what does that imply? To the left? How does a rising or lowering in blood temperature affect the curve?
Happens when CO2 concentration is rising, so pH is going down = suggests a problem with gas exchange, so it would be helpful for the hemoglobin to release its O2 to the tissue more easily (ex: exercise = increase in temperature = tissue more hungry for O2 = decrease in affinity is helpful)
The pH of the blood will cause your hemoglobin saturation curve to move left and right, and that has implication on how easily oxygen leaves hemoglobin for the tissue. Shift to the right = less affinity of the hemoglobin for oxygen, shift to the left = more affinity for O2
Pink line = normal pH of the blood, retaining CO2 (gas exchange not working well), the pH drops (blue line), and the hemoglobin is less saturated at a given pO2, the hemoglobin is giving up its oxygen more easily
Temperature does the same thing, increase in CO2, decrease in pH, and an increase in temperature, will all move the curve to the RIGHT
Describe the many ways in which carbon dioxide (CO2) can be transported through the body. Be specific
CO2 is carried in many ways through the body:
- 90% of the CO2 in the body is managed by the red blood cells, and some of it (10%) gets dissolved in the blood (which gives us the pCO2)
- Part of it can be dissolved (a small proportion)
- Some of it can go through the chemical reaction that results in bicarbonate, but most of it is turned into bicarb, because of carbonate anhydrase (CO2 + H2O ->//
- Another way is for CO2 to combine with plasma proteins (ex: hemoglobin), or proteins in general
With the help of a graph, explain the CO2 carrying capacity of hemoglobin. Include the physiological CO2 range and the normal resting CO2 range. How is it different than the relationship between Hb and O2?
Relationship between pCO2 and the total CO2 in the blood: axis are the same as the pO2 curve. Similar relationship: as the pCO2 increases, so does the total amount of CO2 in the blood, but its a linear relationship: we don’t have the affect of hemoglobin affinity for CO2. So it is EASIER to offload CO2 than O2
With a brief description AND the help of a graph, explain the haldane effect.
A smaller pO2 means that we can load up more CO2 on the hemoglobin. That’s the Haldane effect, and it is helpful for gas exchange. When we get closer to the tissues, the O2 levels lower, and that allows Hb to capture more CO2 and get it back to the lungs, to get it out of the body during expiration.
Basically it says that the amount of CO2 that is carried in the blood (most of it is with Hb in the red blood cells) is lower if the pO2 is high. Which means that when we have lots of O2 on hemoglobin, then we will not be able to carry as much CO2. So there is a competition between CO2 and O2 to get carried around, and O2 wins
Hemoglobin still has a higher affinity for CO2 than it does for O2.
