Hypercapnia-induced cerebral oedema in a patient with COPD exacerbation: a rare and under-recognised entity

A 56-year-old Caucasian woman with severe chronic obstructive pulmonary disease (COPD) on home oxygen presented with a severe exacerbation. Vitals included a blood pressure of 111/73 mm Hg, a pulse of 102/minute, respiratory rate of 13/minute and O2 saturation of 84% on oxygen of 2–3 L/minute by nasal cannula. She was lethargic, confused and was wheezing. She was placed on bi-level positive airway pressure (BiPAP) but her mentation continued to deteriorate. White cell counts were normal. Chest X-ray showed hyperinflated lungs but no infiltrates. Arterial blood gases revealed severe hypercapnic respiratory acidosis with a pH of 7.26, pCO2 of 100.1 mm Hg, pO2 of 187 mm Hg and bicarbonate of 47 mmol/L. In spite of BiPAP, her acidosis worsened with a pCO2 of 131 mm Hg. …