Recording respiratory parameters in patients with epilepsy.

Anecdotal evidence and data from small studies suggest that respiratory changes occur in both complex partial and generalized seizures. Our understanding of sudden unexpected death in epilepsy (SUDEP) may be furthered by recording and analyzing these changes. Investigators at the Jules Thorn Telemetry Unit at the National Hospital for Neurology and Neurosurgery have documented a range of respiratory parameters (respiratory effort, airflow, oxygen saturation) in conjunction with time-locked audio-video electroencephalograms and electrocardiograms to provide a more complete picture of the physiologic changes that occur during seizures. Cardiorespiratory information on 79 seizures (70 complex partial, nine generalized) in 37 patients (20 male, 17 female) is presented. Whereas tachycardia was a common ictal feature, bradycardia was seen only rarely and tended to follow a period of apnea. Apnea occurred in 100% of generalized seizures and 39% of complex partial seizures. Apnea was predominantly central and lasted for 10-75 s (mean duration 29 s). Central apnea may be one of the major, although by no means exclusive, ictal events predisposing to SUDEP.