Question

In this experiment, increasing amount of carbon dioxide in inhaled air from 0.04% to 4% resulted in an 8% increase in arterial partial pressure of carbon dioxide. Decreasing amount of oxygen in inhaled air from 20.9% to 15% oxygen resulted in an 8% decrease in arterial partial pressure of oxygen. Which of the following statements concerning affect of arterial partial pressure of carbon dioxide and oxygen on minute ventilation is true?

Decreasing arterial partial pressure of oxygen by 8% and increasing the arterial partial pressure of carbon dioxide by 8% had no effect on minute ventilation

Decreasing arterial partial pressure of oxygen by 8% and increasing the arterial partial pressure of carbon dioxide by 8% caused minute ventilation to increase by the same amount.

Increasing arterial partial pressure of carbon dioxide by 8% caused a greater increase in minute ventilation than decreasing arterial partial pressure of carbon oxygen by 8%

Decreasing arterial partial pressure of oxygen by 8% caused a greater increase in minute ventilation than increasing arterial partial pressure of carbon dioxide by 8%

Answer 1

Increasing arterial partial pressure of carbon dioxide by 8% caused a greater increase in minute ventilation than decreasing arterial partial pressure of oxygen by 8%.

Blood carbon dioxide (PaCO2) levels generally vary inversely with minute volume.For example, a person with increased minute volume (e.g. due to hyperventilation) should demonstrate a lower blood carbon dioxide level. The healthy human body will alter minute volume in an attempt to maintain physiologic homeostasis. A normal minute volume while resting is about 5–8 liters per minute in humans. Minute volume generally decreases when at rest, and increases with exercise. For example, during light activities minute volume may be around 12 litres. Riding a bicycle increases minute ventilation by a factor of 2 to 4 depending on the level of exercise involved. Minute ventilation during moderate exercise may be between 40 and 60 litres per minute.