title: Proof of concept evaluation of the electroencephalophone as a discriminator between wakefulness and general anaesthesia.
abstract: BACKGROUND
  Depth of anaesthesia (DOA) monitors based on the electroencephalogram (EEG) are commonly used in anaesthetic practice. Their technology relies on mathematical analysis of the EEG waveform, generally resulting in a number which corresponds to anaesthetic depth. We have created a novel method of interpreting the EEG, which retains its underlying complexity. This method consists of turning the EEG into a sound: the electroencephalophone (EEP).
  
  
  METHODS
  In a pilot study, we recorded awake and anaesthetized EEGs from six patients. We transformed each EEG into an audio signal using a ring buffer with a write frequency of 1 kHz and a read frequency of 48 kHz, thus elevating all output frequencies by a factor of 48. In essence, the listener hears the previous 12 s of EEG data compressed into 250 ms, updated every 250 ms. From these data, we generated a bank of 5 s audio clips, which were then used to train and test a sample of 23 anaesthetists.
  
  
  RESULTS
  After training, 21 of the 23 anaesthetists were able to use the EEP to correctly identify the conscious state of >5 of 10 randomly selected patients (P<0.001). The median score was 8 out of 10, with an inter-quartile range of 7-9.
  
  
  CONCLUSIONS
  The EEP shows promise as a DOA monitor. However, extensive validation would be required in a variety of clinical settings before it could be accepted into mainstream clinical practice.
authors.affiliation: Southern General Hospital, Glasgow, UK. johnglen@doctors.org.uk
authors.forename: J
authors.initials: J
authors.lastname: Glen
authors.forename: B
authors.initials: B
authors.lastname: Porr
authors.forename: R
authors.initials: R
authors.lastname: Hamilton
authors.forename: L
authors.initials: L
authors.lastname: Tait
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D000328:Adult; D000768:Anesthesia, General / Q000379:methods*; D004569:Electroencephalography / Q000379:methods*; D006801:Humans; D016343:Monitoring, Intraoperative / Q000295:instrumentation* / Q000379:methods*; D010865:Pilot Projects; D012815:Signal Processing, Computer-Assisted; D014851:Wakefulness / Q000187:drug effects*
keywords: consciousness monitors; electroencephalography; monitoring, intraoperative