PHYSIOLOGY
11. A subject is connected at FRC to a bag containing 2L of 8% He, 92% O2. He rebreathes from the bag until mixing is complete; at which time the fraction of He is 4.6%. What is the value of FRC?
A. 1.15L
B. 1.48L (can you please explain this answer)
C. 2.48L
D. 3.48L
E. It cannot be calculated from the information given
The minimum time it takes a normal person to go from residual volume (RV) to total lung capacity (TLC) is less than the minimum amount of time to go from TLC to RV. The most probable explanation for this effect is:
A. the chest wall tends to spring outward when the respiratory system is at RV.
B. the chest wall is less compliant at RV.
C. inspiratory muscles are stronger than expiratory muscles.
D. the lungs have less recoil at TLC.
E. the airways tend to collapse during forced expiration. (can you please explain why this is the answer)
Two gases, A and B have the same partial pressure difference across the alveolar capillary barrier. Gas A has a molecular weight of 36 and solubility of 24 while gas B has a molecular weight of 16 and solubility of 2. What is the rate of diffusion of gas A through the barrier compared to gas B?
A. 12:1
B. 8:1 (can you explain why B is the answer?)
C. 6:4
D. 4:1
E. They are the same.
If an individual with a tidal volume of 500 ml and a dead space volume of 100 ml were to exercise and double the CO2 production, with no change in respiratory rate, what tidal volume would be required to maintain their original PCO2 of 40 mm Hg?
A. 1200 ml
B. 1100 ml
C. 1000 ml
D. 900 ml (can you explain why the answer is D?)
E. 800 ml
39. What is the total amount of oxygen in the arterial blood (in ml O2 /100ml blood) of an individual who has PO2=90mm Hg, PCO2=40mm Hg, Hb=15g/100ml, hemoglobin saturation = 95%, (solubility coefficient of O2=0.003 ml O2/100 ml blood/mm Hg; at saturation Hb binds 1.34 ml O2/g)
A. (0.95 x 15) + (95 x 0.003)
B. (90 x 1.34 x 15) + (95 x 0.003)
C. ((90 - 40) x 1.34 x 0.95) + (90 x 0.003)
D. (0.95x 1.34 x 15) + (90 x 0.003) (can you explain why the answer is D?)
E. none of the above