Administration
of free-radical scavengers (vitamins C and E) before oxygen diving did not
improve eustachian tube ventilatory function.
Clinical Bottom Line:
1.
Administration of vitamins C and E promoted negative middle ear pressures
after oxygen diving.
2.
The magnitude of middle ear negative pressure was less after the second dive
in both groups.
Appraised
by: Mike Bennett, Dept. of Diving and
Hyperbaric Medicine, Prince of Wales Hospital, Sydney; Sunday, 17 September 2000
Clinical
Scenario: A diver exposed to hyperbaric
oxygen displayed negative middle ear pressures.
Three-part
Question: In divers using high inspired
oxygen, does the administration of vitamins C and E, compared to placebo,
prevent negative middle ear pressure after diving?
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Terms: Middle ear, eustachian tube
The
Study:
Double-blinded concealed
randomised controlled trial with intention-to-treat.
Fit volunteer naval divers
Control
group (N = 8; 8 analysed): Placebo
medication at least three hours before diving (oxygen rebreather at 4m for 30
minutes average) on two consecutive days.
Experimental
group (N = 7; 7 analysed): 1g vitamin
C and 600 IU of vitamin E at least three hours prior to diving (same exposure).
The
Evidence:
Outcomes
Time to outcome Placebo
group
Vitamin group
P-value
Middle
Ear
24 hrs
-5 daPa
-17.5 daPa
0.017
Impedance
(1st dive)
Middle
Ear
Impedance
(2nd dive)
24hrs
-2.5 daPa
-7.5 daPa
0.64
Comments:
1. Administration of vitamins
was associated with significantly worse eustachian tube function- this finding
was the reverse of that hypothesised.
2. The putative action of
vitamins was to reduce free-radical mediated mucosal damage that might explain
the development of negative middle ear pressures after oxygen diving.
3. Report in abstract only
Expiry
date:
July
2002
References:
1. Mutzbauer T, Mueller P,
Tetzlaff K et al. Is eustachian tube ventilatory function (ETVF) impairment
after oxygen diving mediated by free radicals? Undersea and Hyperbaric Medicine
2000; 27(suppl):16.
