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.