When
performing visual evoked potential studies on the macula, rate of recovery of
P100 amplitude after dazzling may be altered following repeated hyperbaric
exposures.
Clinical Bottom Line:
1.
Vague findings of unknown significance.
Appraised
by: Mike Bennett, Dept. of Diving and
Hyperbaric Medicine, Prince of Wales Hospital
Sydney; Saturday, 21 August 1999
Clinical
Scenario: A patient receiving hyperbaric
oxygen for retinal ischaemic pathology.
Three-part
Question: For patients having hyperbaric
oxygen therapy for retinal ischaemic pathology, does rate of recovery of a
visual evoked potential (VEP) after dazzling usefully indicate any benefit of
hyperbaric therapy?
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Terms: Visual evoked potential,
retinal ischaemia
The
Study:
Double-blinded randomised
controlled trial intention-to-treat probable.
Volunteers, men and women.
Control group (N = 8; 8 analysed):
One session breathing air at 2.5ATA for 90 minutes.
Experimental group (N = 7; 7
analysed): One session breathing 100% oxygen at 2.5ATA for 90 minutes
The
Evidence:
Non-Event
Outcomes
Time to outcome
Control group
HBO group P-value
P100
latency
and
amplitude
before and after
unchanged
unchanged
Not given
Amplitude
recovery
after
?unchanged
?unchanged
Not Sig
Comments:
1. No quantitative results
given.
2. Some subjects had multiple
exposures, it is not known how many. It appears from the text it is these
patients that may have shown a difference in rate of recovery of P100 amplitude.
3. Methodology and results not
presented clearly.
4. Authors conclusions do not
seem to clearly follow from results.
Expiry date: October 2003
References:
1. Oriani G, Magni R, Musini A,
Meazza D, Brancato R. A new electrophysiological test to assess ophthalmological
benefits of hyperbaric therapy. Proceedings of the 10th International Congress
on Hyperbaric Medicine, Amsterdam. Best Publishing, Flagstaff, Arizona
1992:104-109.
