Carbon dioxide is produced continuously as the body's cells respire, and this CO2 will accumulate rapidly if the lungs do not adequately expel it through alveolar ventilation.

Hypoventilation in COPD involves multiple mechanisms, including decreased responsiveness to hypoxia and hypercapnia, increased ventilation-perfusion mismatch leading to increased dead space ventilation, and decreased diaphragm function secondary to fatigue and hyperinflation.

[citation needed] Chronic respiratory acidosis also may be secondary to obesity hypoventilation syndrome (i.e., Pickwickian syndrome), neuromuscular disorders such as amyotrophic lateral sclerosis, and severe restrictive ventilatory defects as observed in interstitial lung disease and thoracic deformities.

[citation needed] Alveolar ventilation is under the control of the respiratory center, which is located in the pons and the medulla.

[citation needed] Diagnoses can be done by doing an ABG (Arterial Blood Gas) laboratory study, with a pH <7.35 and a PaCO2 >45 mmHg in an acute setting.

Patients with COPD and other Chronic respiratory diseases will sometimes display higher level of PaCO2 with HCO3- >30 and normal pH.