Chapter 12: The Respiratory System

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[Laura_2707]

Hi,

Just wondering if you could go through how you got the solution for q13, I understand the meaning of the graph but am not sure why you need to do the calculations when the info is on the graph and why the answer is B and not C!

Thanks

[goldstanda3269]

Hi,

Just wondering if you could go through how you got the solution for q13, I understand the meaning of the graph but am not sure why you need to do the calculations when the info is on the graph and why the answer is B and not C!

Thanks

Please explain how you arrived at answer choice C.

(please keep in mind that the caption in Figure 2 says "... as a function of altitude above sea level" so, if we are at sea level, then we must be looking at an altitude of 0, look again at the y-axis on the far right)

[horbowiec.7527]

This is regarding Biology Chapter 12 Worked solution for Q11 (BIO-235):

A little stuck on this explanation:

Heimlich Maneuver includes upward abdominal thrust - forcible maneuver which suddenly increases size and pressure in thoracic cavity.
How come if size is increased pressure increases? I thought it's the opposite...

If you apply upward pressure to abdominal cavity you will notice that your chest (thoracic) size increases. Of course, your thoracic volume is decreasing due to abdominal contents entering the chest cavity.
How come size is increasing and volume is decreasing in the same time? If abdominal content is entering chest cavity, wound't size and volume of thoracic cavity be decreasing?

Regards,
Ania

[horbowiec.7527]

This is regarding Biology Chapter 12 Worked solution for Q13 (BIO-237):

I have looked at bottom x axis on Volume Percent Oxygen in Atmosphere and assumed 90-100% is optimal (as passage said below 90% is low) and that corresponds to around 30-35 for sea level equivalent and then I just looked at Total pressure psia which was around 4 psia for that level and chose B because of that.

I know now that passage refereed to "Saturation percent" from first graph not "Volume percent" from second graph, so I got right answer by luck, not by understanding it.

I can see worked solutions derive this answer completely differently and I am confused why those calculations and how based on passage I were to know this calculations?

Regards,
Ania

[goldstanda3269]

This is regarding Biology Chapter 12 Worked solution for Q13 (BIO-237):

I have looked at bottom x axis on Volume Percent Oxygen in Atmosphere and assumed 90-100% is optimal (as passage said below 90% is low) and that corresponds to around 30-35 for sea level equivalent and then I just looked at Total pressure psia which was around 4 psia for that level and chose B because of that.

The passage refers to 90% oxygen saturation of Hg. Note the difference: less than 90% oxygen saturation of Hg is low, but Figure 2 shows that 90% oxygen in the atmosphere at sea level is far beyond "Maximum tolerable". Somewhere in the back of your mind should be that 99% of the air you are breathing (CHM 1.1) is just nitrogen (N2, 78%) and oxygen (O2, 21%, far below 90%).

I can see worked solutions derive this answer completely differently and I am confused why those calculations and how based on passage I were to know this calculations?

Actually, sometimes questions will say "based on the information in this passage" OR "based on the information in this passage and Figure X"; but this question said "Based on Figure 2" and that means that is all that you need. Of course, you should be applying the Gold Standard 5-step technique to assess graphs (GM 3.6). The altitude is the y-axis at the far right and you have no choice but to choose 0 ft above sea level (because the question stem said: "at sea level").

Now we need to understand the other 2 axes. The x-axis is clearly telling us how much oxygen is any given volume. This is an indicator of the concentration of oxygen in the atmosphere. But we are asked for the amount of pressure due to oxygen (i.e. partial pressure of oxygen). So we need to know what the total pressure of all of the gases would be and then multiply that by the concentration of oxygen. The y-axis at the far left provides the information about the total pressure of all of the gases in the atmosphere.

This is 100% graph analysis which improves with practice.

[goldstanda3269]

This is regarding Biology Chapter 12 Worked solution for Q11 (BIO-235):

A little stuck on this explanation:

Heimlich Maneuver includes upward abdominal thrust - forcible maneuver which suddenly increases size and pressure in thoracic cavity.
How come if size is increased pressure increases? I thought it's the opposite...

If you apply upward pressure to abdominal cavity you will notice that your chest (thoracic) size increases. Of course, your thoracic volume is decreasing due to abdominal contents entering the chest cavity.
How come size is increasing and volume is decreasing in the same time?

That is a typo: The thoracic volume is increasing.

Your thoracic volume is increasing due to the abdominal contents entering the space normally occupied by the lungs. This will be updated within 24 hours.

[horbowiec.7527]

Thank you that is very helpful!

Ania

[horbowiec.7527]

Sorry still not quite understanding it:
you say: "The fact that the Heimlich Maneuver includes an upward abdominal thrust means that it is a forcible maneuver which suddenly increases the size and pressure in the thoracic cavity thus dislodging the food."
How come if size or volume of thoracic cavity is increased the pressure increases? I thought it's the opposite...

Ania

[goldstanda3269]

Sorry still not quite understanding it:
you say: "The fact that the Heimlich Maneuver includes an upward abdominal thrust means that it is a forcible maneuver which suddenly increases the size and pressure in the thoracic cavity thus dislodging the food."
How come if size or volume of thoracic cavity is increased the pressure increases? I thought it's the opposite...

You are correct to assume that during normal breathing "if size or volume of thoracic cavity is increased" then the pressure decreases. But this is not a normal situation. There is a blockage preventing air from leaving.

Imagine a balloon that is partially inflated on a table (of course, air is blocked from leaving the balloon). Push your fist downwards against the balloon and naturally the balloon widens. This is equivalent to the abdominal contents pushed up against the lungs with a blocked airway leading to expansion of the chest.

If you keep pushing your fist down to the table, the pressure in the balloon might get so high that the balloon will pop. Similarly, for the lung, the pressure (hopefully) rises enough to 'pop' the obstruction out of the airway so normal breathing can resume.

[KatherineDever]

Hello,
I was wondering if you could explain the reasoning behind question 14 as I am a little stuck with the graph in the worked solutions.

Thank you very much.

[goldstanda3269]

Hello,
I was wondering if you could explain the reasoning behind question 14 as I am a little stuck with the graph in the worked solutions.

The worked solution refers to 2 different graphs: Figure 1 and Figure 2. Can you please specify which graph or what numerical interpretation in the worked solution needs clarification? We will be happy to help, thanks for your patience.

[emstevens46670]

Hey,
I was just wondering how you determine the answer for question 4?
I have looked at the worked solutions however I am still extremely confused.
Thank you so much,
Em

[goldstanda3269]

Hey,
I was just wondering how you determine the answer for question 4?
I have looked at the worked solutions however I am still extremely confused.
Thank you so much,
Em

To have the minimum difference between the 2 values, the higher value (oxygen) needs to be as low as possible, and the lower value (carbon dioxide) needs to be as high as possible. Be careful because the left y axis has a different scale as compared to the right y axis. Also, be sure to follow the correct lines as stated below the graph “partial pressures of oxygen (pO2, solid line) and carbon dioxide (pCO2, dashed line) ”

Thus the minimum difference can be identified in Figure 1 at approx. 0.75 seconds, approximate values: pO2 93 – pCO2 40 = 53 mmHg.

Going Deeper: Consider other values from the graph . . .
• At 2 seconds, approximate values: pO2 98 – pCO2 35 = 63 (the lower value is as low as it can go and the higher value is as high as it can go making the largest difference possible)