6. [Total: 9pts] Chemical regulation of ventilation

An investigator wants to investigate the effect of exercise on ventilation and Pacoz in a healthy

volunteer. Assume that the baseline ventilatory response to CO₂ and the subject's metabolic

hyperbola prior to participating in the study yields an operating point labeled "BL" in the figure

below. In order to measure ventilation during the exercise study, when the volunteer has to be on a

treadmill, she has to wear a face mask connected to a long breathing tube which is then connected

to a device used to measure ventilation. This device does not provide any ventilation support, but it

can provide different levels of inhaled oxygen. The graph below shows metabolic hyperbolas and

ventilatory response to CO₂ under different conditions.

в с

VdotE or VdotC (l/min)

BL

A

Measures

ventilation

PACO₂ or P

or Pacoz (mmHg)

O

E

F

a) [3 pts] First, the subject's ventilation and Pacoz are measured while she is standing at rest on the

treadmill and she breathes in air (21% O₂). Considering the long tube in this experimental setup,

which curve (A, B, C, D, E or F) best represents this situation? Briefly explain your selection. Label

on the figure "a", the new steady state equilibrium values of Pacoz and ventilation for the

volunteer at rest.