|A.||The shift of normal respiratory drive to hypercapnic drive|
Renal compensation to maintain near-normal pH
Maintenance of the ventilation-perfusion (V/Q) ratio by compensatory renal vasodilation
Maintenance of pH by pulmonary vasoconstriction
Pulmonary vasoconstriction to preserve the V/Q ratio, renal compensation to maintain near-normal pH, and hypoxic drive are the important compensatory measures in patients with chronic obstructive pulmonary disease (COPD).
The target oxygen pulse oximetry in patients with COPD is important. It is 88% to 92%. Increasing oxygen saturation beyond 92% negatively affects the compensatory measures.
The kidneys compensate by retaining more bicarbonate and, hence, neutralizes the acidity due to hypercapnia in these patients.
The chemoreceptors become tolerant to chronically elevated carbon dioxide in patients with COPD. Therefore, low oxygen plays a major role in the stimulation of chemoreceptors and maintains the respiratory drive.