Hypoventilation → CO₂ retention → acidaemia.
Compensation
- • Acute: HCO₃ rises 1 per 10 ΔPaCO₂
- • Chronic: HCO₃ rises 3.5 per 10 ΔPaCO₂
Causes
- • CNS depression (opioids, sedatives, stroke)
- • Neuromuscular (GBS, MG, ALS, NM blockade)
- • Airway (COPD, asthma, OSA, obstruction)
- • Chest wall (kyphoscoliosis, flail, obesity hypoventilation)
- • Pulmonary (severe pneumonia, ARDS late)
Treatment
- • Reverse cause (naloxone if opioid)
- • Optimise ventilation; NIV (BiPAP) for type 2 RF
- • Intubate if drowsy, exhausted, pH <7.25 despite NIV
- • Avoid over-rapid CO₂ correction (cerebral alkalosis)
