How would the partial pressures of O2 and CO2 change in an exercising muscle?

Answer 1

Although venous levels change, arterial Pco2 and Po2 levels remain surprisingly constant during exercise. In fact, Pco2 may even decline to below normal and Po2 may rise slightly because of the efficiency of the respiratory adjustments. Increased blood flow does not cause a change in gas pressures. the only way to change gas pressures is by altering atmospheric pressure, ie. Scuba diving, or changing elevation. Partial pressure of any blood born gas is always directly proportional to atmospheric pressure as evidenced by Dalton's law of partial pressures. However in exercising muscle metabolic processes temporarily increase Pco2 and decrease Po2 until equalized by sufficiently oxygenated arterial blood. So the short answer to your question is that intramuscular Pco2 pressures would increase and Po2 would decrease, but the partial pressures in the blood would remain constant.