Bispectral index in hypercapnic encephalopathy associated with COPD exacerbation: a pilot study.

Background: Hypercapnic encephalopathy is relatively frequent in severe exacerbations of COPD (ECOPDs), with its intensity usually being evaluated through clinical scales. Bispectral index (BIS) is a relatively new technique, based on the analysis of the electroencephalographic signal, which provides a good approximation to the level of consciousness, having already been validated in anesthesia.

Objective: The objective of the study was to evaluate the utility of BIS in the assessment of the intensity of hypercapnic encephalopathy in ECOPD patients.

Patients and methods: A total of ten ECOPD patients were included, and the level of brain activity was assessed using BIS and different scales: Glasgow Coma Scale, Ramsay Sedation Scale (RSS), and Richmond Agitation-Sedation Scale. The evaluation was performed both in the acute phase and 3 months after discharge.

Results: BIS was recorded for a total of about 600 minutes. During ECOPD, BIS values ranged from 58.8 (95% CI: 48.6-69) for RSS score of 4 to 92.2 (95% CI: 90.1-94.3) for RSS score of 2. A significant correlation was observed between values obtained with BIS and those from the three scales, although the best fit was for RSS, followed by Glasgow and Richmond ( r =-0.757, r =0.701, and r =0.615, respectively; P <0.001 for all). In the stable phase after discharge, BIS showed values considered as normal for a wake state (94.6; 95% CI: 91.7-97.9).

Conclusion: BIS may be useful for the objective early detection and automatic monitoring of the intensity of hypercapnic encephalopathy in ECOPD, facilitating the early detection and follow-up of this condition, which may avoid management problems in these patients.