The crashing COPD patient is not simply a patient with a high carbon dioxide level.
They are often fighting several physiologic battles at once.
Ventilation is impaired. Work of breathing is high. Dynamic hyperinflation may be developing. Gas exchange is inefficient. The right ventricle may be strained.
COPD increases airway resistance and prolongs expiratory time constants. Air leaves the lungs slowly.
When respiratory rate rises, exhalation may become incomplete before the next breath begins. Air trapping develops. End-expiratory lung volume rises. Intrinsic PEEP accumulates.