©THEBRIGHT 2024/2025 ALL RIGHTS RESERVED 10:15AM A+
HMX Physiology Exam Questions And
Answers |Latest 2025 | Guaranteed Pass.
A healthy 21 year old man is mountain climbing in Nepal and is at an altitude of approximately
3,000 meters. Barometric pressure is 530 mm Hg. He is feeling short of breath and the climbing
is becoming more difficult. The partial pressure of oxygen in the air he is breathing is
approximately:
150 mm Hg
220 mm Hg
110 mm Hg
35 mm Hg - Answer✔110 mm Hg
Explanation:
Atmospheric pressure at sea level is 760 mmHg or one atmosphere (atm). As we ascend, the
pressure decreases (~0.012 atm or 9mmHg per 100 meters) and thus the partial pressures of
atmospheric gases drop (even though the composition or percentages remain the same). Partial
pressure of a gas is calculated as the concentration (percentage) of that gas multiplied by the
atmospheric pressure (Pgas = Patm (Fgas) ). Air is composed of 78% nitrogen (N2) and 21%
oxygen (O2) and 1% other gases (these values are sometimes simplified to 79% N2 and 21% O2
for calculations). Thus the PO2 or partial pressure of oxygen is 0.21 X 530 = 111.3 or about
110mmHg.
It's New Year's Eve and you are eager to drink some champagne. Unable to wait until midnight,
you open a bottle and pour yourself a glass. Your date comes by and tells you to recork the
bottle, which you promptly do. Several minutes later the champagne is no longer "bubbling."
The partial pressure of carbon dioxide in the bottle above the champagne is now:
1
,©THEBRIGHT 2024/2025 ALL RIGHTS RESERVED 10:15AM A+
The same as in the partial pressure of CO2 in the atmosphere
The same as the partial pressure of CO2 in the champagne
Less than the partial - Answer✔The same as the partial pressure of CO2 in the champagne
Explanation:
Carbon dioxide (CO2) is dissolved in solution under high pressures as in a champagne bottle.
When the cork is removed the high pressure in the bottle begins to equalize with atmospheric
pressure outside the bottle. As the pressure rapidly decreases in the bottle, CO2 begins to come
out of solution and is represented as bubbles. When the cork is reinserted into the bottle, CO2
coming out of solution begins to accumulate as a gas in the bottle and the PCO2 in the gaseous
state increases. When the bubbling ceases, the partial pressure of CO2 in the gaseous state in
the bottle equals the PCO2 dissolved in the liquid (champagne). Consequently, the PCO2 in the
bottle is greater than the PCO2 in the atmosphere (where it is essentially zero). We cannot
know with certainty how much greater the PCO2 is in the gaseous phase in the bottle compared
to the atmosphere.
Imagine you are on the planet Venus where the atmospheric pressure is ~92 atm (1 atm = 760
mmHg). What are the partial pressures of the component atmospheric gases, given gas
fractions of 96.5% CO2 and 3.5% N2?
PCO2 96.5 atm; PN2 3.5 atm
PCO2 88.8 atm; PN2 3.2 atm
PCO2 0 atm; PN2 78 atm
PCO2 73.3 atm; PN2 26.6 atm - Answer✔PCO2 88.8 atm; PN2 3.2 atm
Explanation:
Partial pressure of a gas is calculated as the concentration (percentage) of that gas multiplied
by the atmospheric pressure (Pgas = Patm (Fgas)). For CO2 on Venus, the calculation would be
PCO2 = 0.965 X 92 = 88.8 atm; for N2, PN2 =.035 X 92 = 3.2 atm. The partial pressures of the
component gases added together equals the total pressure in the system, in this case 92 atm.
Joe and John are identical twins. John had a bleeding ulcer last week and is anemic with a
hemoglobin level of 10 grams/100 ml of blood; Joe has a hemoglobin level of 14 grams/100 ml
of blood (normal range is 13.5-17 grams/100 ml). Both are completely healthy, with the
exception of John's recent ulcer. The partial pressure of oxygen in the twin's blood is:
2
,©THEBRIGHT 2024/2025 ALL RIGHTS RESERVED 10:15AM A+
The same
Higher in Joe than John
Higher in John than Joe
You need more information to make the determination. - Answer✔The same
Hemoglobin is a protein carried in the blood that is responsible for the large oxygen carrying
capacity of the blood. As oxygen enters the blood some is carried on hemoglobin and some is
dissolved in "solution" or the plasma component of blood. Partial pressure only measures
dissolved oxygen in the bloodstream, not oxygen bound to hemoglobin. When we measure
hemoglobin in blood it is measured as grams of the protein per 100 milliliters of blood volume.
This question drives at the difference between oxygen content (i.e. dissolved oxygen + oxygen
bound to hemoglobin) and partial pressure of oxygen (i.e. reflective of dissolved oxygen only).
Partial pressure of oxygen in the blood is independent of the hemoglobin or oxygen carrying
capacity of the blood. Thus regardless of the amount of hemoglobin in the blood the partial
pressure of oxygen is the same between the twins.
Carbon monoxide, a product of combustion, is a toxic gas that has an extremely high affinity for
hemoglobin (much higher than that of oxygen for hemoglobin); consequently, as soon as it
dissolves in the liquid part of blood at low partial pressure, it diffuses quickly into red blood
cells and binds to hemoglobin. In carbon monoxide (CO) poisoning, even with very low partial
pressure of inspired CO, CO rapidly binds to hemoglobin (Hgb), leaving a lower fraction of
oxygen binding sites on Hgb avai - Answer✔Normal PO2
Explanation:
The person's arterial PO2 is likely to be normal. Remember that the O2 content of the blood
consists of dissolved O2 and O2 bound to Hgb. The partial pressure of O2 in the blood is
determined by the O2 dissolved in the liquid portion of the blood and does not depend on the
amount of Hgb or the availability of oxygen binding sites on Hgb. The partial pressure of
inspired CO is usually low in CO poisoning and does not change the PO2 in the inspired air;
therefore, oxygen will reach the same equilibrium between its gaseous state in the alveolus and
its dissolved state in the alveolar capillary blood during carbon monoxide poisoning. However,
oxygen content (dissolved oxygen + oxygen bound to hemoglobin) decreases because of carbon
monoxide's interaction with hemoglobin (taking up oxygen binding spots). This interaction also
causes hemoglobin-bound oxygen to be more tightly bound, thereby impairing oxygen release
at the tissues. These factors contribute to decrease
3
, ©THEBRIGHT 2024/2025 ALL RIGHTS RESERVED 10:15AM A+
Why do the lungs not decrease in volume even as you move the scuba diver deeper under the
water?
The diver is breathing pressurized gas, the pressure of which matches the surrounding water
pressure.
The scuba diver is holding his breath, so no air can get in or out and the volume stays the same.
The diver is able to keep the lungs at a normal volume just using the muscles of the chest wall,
without any assistance. - Answer✔The diver is breathing pressurized gas, the pressure of which
matches the surrounding water pressure.
Explanation:
The diver is breathing pressurized gas, the pressure of which matches the surrounding water
pressure. As mentioned in the Dive Descent - Explained Video, without breathing pressurized
gas matched by the scuba regulator to the surrounding water pressure, divers would be unable
to exert sufficient force with muscles to overcome the surrounding water pressure. For
example, trying to breathe through a long tube that extends to the surface while lying on the
bottom of a pool would be futile; even at relatively shallow depths, the pressure exerted by the
water on the chest wall would be too much.
At 66 feet of depth, the scuba diver is breathing air at 3.00 atm of pressure. What is the
inspired fraction of oxygen at that point? Try to answer without re-visiting the diagram.
63%
42%
21%
7% - Answer✔21%
Explanation:
Although the total inspired pressure changes and the PO2 in the inspired air rises
proportionally, the fraction of inhaled oxygen does not change. Most recreational scuba dives
are done using compressed air. If this is unclear, review the diagram and make sure to select
the information icon in the lower right to see a more in-depth explanation.
4
HMX Physiology Exam Questions And
Answers |Latest 2025 | Guaranteed Pass.
A healthy 21 year old man is mountain climbing in Nepal and is at an altitude of approximately
3,000 meters. Barometric pressure is 530 mm Hg. He is feeling short of breath and the climbing
is becoming more difficult. The partial pressure of oxygen in the air he is breathing is
approximately:
150 mm Hg
220 mm Hg
110 mm Hg
35 mm Hg - Answer✔110 mm Hg
Explanation:
Atmospheric pressure at sea level is 760 mmHg or one atmosphere (atm). As we ascend, the
pressure decreases (~0.012 atm or 9mmHg per 100 meters) and thus the partial pressures of
atmospheric gases drop (even though the composition or percentages remain the same). Partial
pressure of a gas is calculated as the concentration (percentage) of that gas multiplied by the
atmospheric pressure (Pgas = Patm (Fgas) ). Air is composed of 78% nitrogen (N2) and 21%
oxygen (O2) and 1% other gases (these values are sometimes simplified to 79% N2 and 21% O2
for calculations). Thus the PO2 or partial pressure of oxygen is 0.21 X 530 = 111.3 or about
110mmHg.
It's New Year's Eve and you are eager to drink some champagne. Unable to wait until midnight,
you open a bottle and pour yourself a glass. Your date comes by and tells you to recork the
bottle, which you promptly do. Several minutes later the champagne is no longer "bubbling."
The partial pressure of carbon dioxide in the bottle above the champagne is now:
1
,©THEBRIGHT 2024/2025 ALL RIGHTS RESERVED 10:15AM A+
The same as in the partial pressure of CO2 in the atmosphere
The same as the partial pressure of CO2 in the champagne
Less than the partial - Answer✔The same as the partial pressure of CO2 in the champagne
Explanation:
Carbon dioxide (CO2) is dissolved in solution under high pressures as in a champagne bottle.
When the cork is removed the high pressure in the bottle begins to equalize with atmospheric
pressure outside the bottle. As the pressure rapidly decreases in the bottle, CO2 begins to come
out of solution and is represented as bubbles. When the cork is reinserted into the bottle, CO2
coming out of solution begins to accumulate as a gas in the bottle and the PCO2 in the gaseous
state increases. When the bubbling ceases, the partial pressure of CO2 in the gaseous state in
the bottle equals the PCO2 dissolved in the liquid (champagne). Consequently, the PCO2 in the
bottle is greater than the PCO2 in the atmosphere (where it is essentially zero). We cannot
know with certainty how much greater the PCO2 is in the gaseous phase in the bottle compared
to the atmosphere.
Imagine you are on the planet Venus where the atmospheric pressure is ~92 atm (1 atm = 760
mmHg). What are the partial pressures of the component atmospheric gases, given gas
fractions of 96.5% CO2 and 3.5% N2?
PCO2 96.5 atm; PN2 3.5 atm
PCO2 88.8 atm; PN2 3.2 atm
PCO2 0 atm; PN2 78 atm
PCO2 73.3 atm; PN2 26.6 atm - Answer✔PCO2 88.8 atm; PN2 3.2 atm
Explanation:
Partial pressure of a gas is calculated as the concentration (percentage) of that gas multiplied
by the atmospheric pressure (Pgas = Patm (Fgas)). For CO2 on Venus, the calculation would be
PCO2 = 0.965 X 92 = 88.8 atm; for N2, PN2 =.035 X 92 = 3.2 atm. The partial pressures of the
component gases added together equals the total pressure in the system, in this case 92 atm.
Joe and John are identical twins. John had a bleeding ulcer last week and is anemic with a
hemoglobin level of 10 grams/100 ml of blood; Joe has a hemoglobin level of 14 grams/100 ml
of blood (normal range is 13.5-17 grams/100 ml). Both are completely healthy, with the
exception of John's recent ulcer. The partial pressure of oxygen in the twin's blood is:
2
,©THEBRIGHT 2024/2025 ALL RIGHTS RESERVED 10:15AM A+
The same
Higher in Joe than John
Higher in John than Joe
You need more information to make the determination. - Answer✔The same
Hemoglobin is a protein carried in the blood that is responsible for the large oxygen carrying
capacity of the blood. As oxygen enters the blood some is carried on hemoglobin and some is
dissolved in "solution" or the plasma component of blood. Partial pressure only measures
dissolved oxygen in the bloodstream, not oxygen bound to hemoglobin. When we measure
hemoglobin in blood it is measured as grams of the protein per 100 milliliters of blood volume.
This question drives at the difference between oxygen content (i.e. dissolved oxygen + oxygen
bound to hemoglobin) and partial pressure of oxygen (i.e. reflective of dissolved oxygen only).
Partial pressure of oxygen in the blood is independent of the hemoglobin or oxygen carrying
capacity of the blood. Thus regardless of the amount of hemoglobin in the blood the partial
pressure of oxygen is the same between the twins.
Carbon monoxide, a product of combustion, is a toxic gas that has an extremely high affinity for
hemoglobin (much higher than that of oxygen for hemoglobin); consequently, as soon as it
dissolves in the liquid part of blood at low partial pressure, it diffuses quickly into red blood
cells and binds to hemoglobin. In carbon monoxide (CO) poisoning, even with very low partial
pressure of inspired CO, CO rapidly binds to hemoglobin (Hgb), leaving a lower fraction of
oxygen binding sites on Hgb avai - Answer✔Normal PO2
Explanation:
The person's arterial PO2 is likely to be normal. Remember that the O2 content of the blood
consists of dissolved O2 and O2 bound to Hgb. The partial pressure of O2 in the blood is
determined by the O2 dissolved in the liquid portion of the blood and does not depend on the
amount of Hgb or the availability of oxygen binding sites on Hgb. The partial pressure of
inspired CO is usually low in CO poisoning and does not change the PO2 in the inspired air;
therefore, oxygen will reach the same equilibrium between its gaseous state in the alveolus and
its dissolved state in the alveolar capillary blood during carbon monoxide poisoning. However,
oxygen content (dissolved oxygen + oxygen bound to hemoglobin) decreases because of carbon
monoxide's interaction with hemoglobin (taking up oxygen binding spots). This interaction also
causes hemoglobin-bound oxygen to be more tightly bound, thereby impairing oxygen release
at the tissues. These factors contribute to decrease
3
, ©THEBRIGHT 2024/2025 ALL RIGHTS RESERVED 10:15AM A+
Why do the lungs not decrease in volume even as you move the scuba diver deeper under the
water?
The diver is breathing pressurized gas, the pressure of which matches the surrounding water
pressure.
The scuba diver is holding his breath, so no air can get in or out and the volume stays the same.
The diver is able to keep the lungs at a normal volume just using the muscles of the chest wall,
without any assistance. - Answer✔The diver is breathing pressurized gas, the pressure of which
matches the surrounding water pressure.
Explanation:
The diver is breathing pressurized gas, the pressure of which matches the surrounding water
pressure. As mentioned in the Dive Descent - Explained Video, without breathing pressurized
gas matched by the scuba regulator to the surrounding water pressure, divers would be unable
to exert sufficient force with muscles to overcome the surrounding water pressure. For
example, trying to breathe through a long tube that extends to the surface while lying on the
bottom of a pool would be futile; even at relatively shallow depths, the pressure exerted by the
water on the chest wall would be too much.
At 66 feet of depth, the scuba diver is breathing air at 3.00 atm of pressure. What is the
inspired fraction of oxygen at that point? Try to answer without re-visiting the diagram.
63%
42%
21%
7% - Answer✔21%
Explanation:
Although the total inspired pressure changes and the PO2 in the inspired air rises
proportionally, the fraction of inhaled oxygen does not change. Most recreational scuba dives
are done using compressed air. If this is unclear, review the diagram and make sure to select
the information icon in the lower right to see a more in-depth explanation.
4
