Final answer:
After acclimation, submaximal pulmonary ventilation plateaus at approximately 50% higher than at sea level to compensate for lower oxygen availability and pressure at high altitudes.
Step-by-step explanation:
After acclimation, submaximal pulmonary ventilation plateaus around 50% higher than at sea level. This increase is due to the body's physiological response to lower atmospheric pressure at high altitudes, which reduces the partial pressure of oxygen and makes it more difficult to achieve the same level of oxygen saturation as at sea level. To compensate for the lower oxygen availability, pulmonary ventilation must increase once the individual has acclimatized to the new altitude, allowing for a higher uptake of oxygen into the bloodstream. At extreme altitudes, such as 19,000 feet above sea level, hemoglobin saturation can be as low as about 67 percent, compared to approximately 98 percent at sea level, illustrating the body's need to adapt its pulmonary ventilation to maintain adequate oxygenation.