Skip to main content

Research Repository

Advanced Search

Responsiveness of the frontal EMG for monitoring the sedation state of critically ill patients

Walsh, Timothy S; Lapinlampi, T P; Ramsay, Pamela; S�rkel�, M O K; Uutelo, K; Vierti�-Oja, H E


Timothy S Walsh

T P Lapinlampi

Pamela Ramsay

M O K S�rkel�

K Uutelo

H E Vierti�-Oja


Background. Excessive sedation is associated with adverse patient outcomes during critical illness, and a validated monitoring technology could improve care. We developed a novel method, the responsiveness index (RI) of the frontal EMG. We compared RI data with Ramsay clinical sedation assessments in general and cardiac intensive care unit (ICU) patients.
Methods. We developed the algorithm by iterative analysis of detailed observational data in 30 medical–surgical ICU patients and described its performance in this cohort and 15 patients recovering from scheduled cardiac surgery. Continuous EMG data were collected via frontal electrodes and RI data compared with modified Ramsay sedation state assessments recorded regularly by a blinded trained observer. RI performance was compared with EntropyTM across Ramsay categories to assess validity.
Results. RI correlated well with the Ramsay category, especially for the cardiac surgery cohort (general ICU patients r¼0.55; cardiac surgery patients r¼0.85, both P,0.0001).
Discrimination across all Ramsay categories was reasonable in the general ICU patient cohort [PK¼0.74 (SEM 0.02)] and excellent in the cardiac surgery cohort [PK¼0.92 (0.02)]. Discrimination between ‘lighter’ vs ‘deeper’ (Ramsay 1–3 vs 4–6) was good for general ICU patients [PK¼0.80 (0.02)] and excellent for cardiac surgery patients [PK¼0.96 (0.02)].
Performance was significantly better than EntropyTM. Examination of individual cases suggested good face validity.
Conclusions. RI of the frontal EMG has promise as a continuous sedation state monitor in critically ill patients. Further investigation to determine its utility in ICU decision-making is warranted.


Walsh, T. S., Lapinlampi, T. P., Ramsay, P., Särkelä, M. O. K., Uutelo, K., & Viertiö-Oja, H. E. (2011). Responsiveness of the frontal EMG for monitoring the sedation state of critically ill patients. British Journal of Anaesthesia, 107, 710-718.

Journal Article Type Article
Acceptance Date Jun 18, 2011
Online Publication Date Jul 28, 2011
Publication Date Jul 28, 2011
Deposit Date Jun 29, 2016
Print ISSN 0007-0912
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 107
Pages 710-718
Keywords critical care; diagnostic techniques; neurological; electroencephalogram; monitoring; physiologic; sedation; deep;
Public URL
Publisher URL