Fig. 2.

A, hypercapnic encephalopathy syndrome: 65-year-old man with a previous history of left pneumonectomy. Impairment of vigilance, mutism. At admittance, the day of the EEG, PaCO₂ 127 mmHg, PaO₂ 134 mmHg, pH 7.15, natremia 151 mmol/L, serum creatinine 55 μmol/L. The EEG shows numerous muscular artifacts, especially on the left temporal region. Eyes are open. Periodic paroxysms with a variable interval. The activity is diffuse. The paroxysms have no typical triphasic morphology. B, hypoxemia: 56-year-old woman, impaired vigilance. Arterial blood gas: PaO2 48 mmHg, PaCO2 38 mmHg, pH 7.47, Hb 8.4 g/L. No metabolic change. The EEG shows diffuse periodic activity with triphasic morphology, sharply contoured at the end of the plate.