Session 3: Case Studies Flashcards
If a gas mixture has a total pressure of 100 kPa and consists of 21% oxygen and 40% helium with the balance being nitrogen. What is (i) the pO2 and (ii) the pNw in the gas mixture?
(i) 21 kPa
(ii) 39 kPa
If the same gas mixture is saturated with water vapour at 37 degrees celsius in the upper respiratory tract, what now is the pO2 of the moist inspired air? (SVP of water at 37 degrees celsius = 6.28 kPa)
100 - 6.28 = 93.72 kPa
93.72 x 0.21 = 19.7 kPa
What will be the pH2O in alveolar gas when breathing air at 100kPa?
6.28 kPa as it stays constant.
It is only dependant on temperature.
What will be the pO2 of moist inspired air, if atmospheric air was being breathed at the top of Mount Everest where the atmospheric pressure is 35kPa?
35 kPa - 6.28 kPa = x
x * 0.21 = 6.03 kPa
What will be the partial pressure of oxygen in blood exposed to a gas mixture containing 14% oxygen at a total pressure of 101.1 kPa, at 37 degrees saturated with water vapour?
101.1 kPa - 6.28 = x
x * 0.14 = 13.3 kPa
If the pO2 of a patient’s blood is measured at 27.3 kPa what might you conclude about the (i) pO2 of alveolar air and (ii) pO2 of gas mixture he or she is breathing?
(i) 27.3 kPa
(ii) roughly doubled
What will happen to the amount of nitrogen dissolved in blood if air is breathed at twice normal pressure?
It will increase
A 24 year old man is noted to be hyperventilating. What is likely to happen to his alveolar pO2 and pCO2?
Alveolar pO2 will increase slightly but more or less stay the same
Alveolar pCO2 will decrease by a significant amount
A 22 year old man was found in a semiconscious state. A narcotic overdose is suspected. His breathing is slow and shallow. What is likely to have happened to his alveolar pO2 and pCO2?
Alveolar pO2 will decrease significantly
Alveolar pCO2 will increase significantly
