Brief but high-yield question-based approach to differential diagnosis in hypercapnic failure.

Analyzing the differentials and management options based on the formula of Alveolar Minute Ventilation:

Alveolar Minute Ventilation = Respiratory Rate x (Tidal Volume - Dead Space Volume)

VA = RR x (Vt-Vd)

DDxing of hypercapnia includes low RR (e.g. opiate use), Low Vt (e.g restrictive lung disease) or high Vd (COPD).