Final answer:
In COPD patients, the respiratory drive is dependent on carbon dioxide levels due to a shift in the body's regulation mechanism from oxygen to carbon dioxide, strongly influencing hemoglobin affinity and blood pH.
Step-by-step explanation:
In patients suffering from Chronic Obstructive Pulmonary Disease (COPD), carbon dioxide levels, rather than oxygen levels, are the primary driver for the respiratory drive. This is because these patients often have chronically high levels of oxygen in their blood, and the responsiveness of their respiratory centers to oxygen levels declines. The body then primarily relies on elevated carbon dioxide levels to regulate breathing. Increased levels of carbon dioxide lead to a decrease in blood pH, causing the affinity of hemoglobin for oxygen to reduce, as indicated by a shift to the right in the oxygen-hemoglobin dissociation curve. Hence, more oxygen is needed for hemoglobin to achieve the same level of saturation as it would at a higher pH. Conditions such as COPD severely affect this balance, and the respiratory system's response shifts accordingly to maintain blood gas and pH homeostasis.