Electroencephalographic and evoked potential monitoring in the hyperbaric environment

Abstract

The purpose of this study was to investigate brain bioelectrical activity during hyperbaric oxygenation by continuous and simultaneous monitoring of electroencephalographic and bimodal (auditory, somatosensory) evoked potentials. Multivariable recordings (electroencephalogram, brainstem auditory evoked potentials, early somatosensory evoked potentials, heart rate, heart rate variability, and transcutaneous partial pressure of oxygen) were measured with a new technique in 12 healthy male volunteers 26 to 52 years old (mean +/- SD, 35.9 +/- 9.5 years). Recordings were obtained while the subjects breathed (1) air at normal atmospheric pressure, (2) 100% oxygen at normal atmospheric pressure, (3) air at 2 atm (10 meters sea water [msw]), and (4) 100% oxygen at 2 atm (10 msw). Spontaneous brain electrical activity, somatosensory evoked potentials, and heart rate variability were not significantly affected during hyperbaric oxygenation, whereas the heart rate showed a significant decrease (paired t test, P less than 0.05). Alterations in brainstem auditory evoked potentials were seen under hyperbaric conditions and did not reach statistical significance (increase of the I-V interpeak latency by paired t test; P less than 0.2). All subjects showed insignificant increases in dominant alpha frequency and decreases in delta frequency under hyperbaric situations.

Heart rate variability in healthy volunteers during normobaric and hyperbaric hyperoxia

“…Litscher et al . (1990 ) found an increased HRV with a time domain analysis with oxygen breathing but no differences between normobaric and hyperbaric oxygen.…”

“…However, atropine abolished bradycardic response during 100% oxygen breathing at ambient pressure in healthy volunteers ( Daly & Bondurant 1962). In another study, HRV and RR‐intervals did not change significantly during HBO therapy in volunteers, compared with 100% oxygen breathing at normal ambient pressure ( Litscher et al . 1990 ).…”

Functional MRI during hyperbaric oxygen: Effects of oxygen on neurovascular coupling and BOLD fMRI signals

“…Spontaneous activities of the theta, alpha, beta and gamma bands decreased under HBO compared to NB, while the delta band showed a decreasing trend but did not reach statistical significance. Previous studies have reported reduced oxygen consumption in brain slices (Mulkey et al, 2001) and reduced glucose consumption in the pig brain in vivo (van Hulst et al, 2003), but no changes in delta and theta band activity in humans (Litscher et al, 1990) under HBO. These differences could be due to difference in species and/or anesthesia.…”

Continuous Brainstem Auditory Evoked Potential Monitoring During Nocturnal Sleep

“…The subjects arrived at the sleep laboratory at approximately 10:00 p.m. and the recording sessions started between 11:00 and 12:00 p.m. Sleep polysomnography was done with a system developed at the Department of Medical Informatics, Graz University of Technology (Litscher, Friehs, Maresch & Pfurtscheller, 1990;Pfurtscheller, Schwarz, Schroettner, Litscher, Maresch, Auer & List, 1987;Steller, Litscher, Maresch & Hurtscheller, 1990). The system can record and process signals with high-frequency components (e.g., electroencephalograms (EEG), electrooculograms (EOG), electromyograms (EMG), BAEPs) as well as those with low-frequency components (e.g., respiration, oxygen saturation, temperature).…”