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<p><b>New page</b></p><div>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Administration of free-radical scavengers (vitamins C and E) before oxygen diving did not improve eustachian tube ventilatory function.</span>'''<br />
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<span style="border-color: windowtext; border-style: solid; border-width: 1.5pt; display: block; padding: 1pt 4pt;"><br />
<span style="padding-bottom: 0cm; padding-left: 0cm; padding-right: 0cm; padding-top: 0cm;">'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Clinical Bottom Line:</span>'''<br />
<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">1. Administration of vitamins C and E promoted negative middle ear pressures after oxygen diving.<br />
2. The magnitude of middle ear negative pressure was less after the second dive in both groups.</span></span><br />
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**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Appraised by:</span>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;"> Mike Bennett, Dept. of Diving and Hyperbaric Medicine, Prince of Wales Hospital, Sydney; Sunday, 17 September 2000</span><br />
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**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Clinical Scenario:</span>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;"> A diver exposed to hyperbaric oxygen displayed negative middle ear pressures.</span><br />
**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Three-part Question:</span>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;"> In divers using high inspired oxygen, does the administration of vitamins C and E, compared to placebo, prevent negative middle ear pressure after diving?</span><br />
**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Search Terms:</span>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;"> Middle ear, eustachian tube</span><br />
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**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">The Study:</span>'''<br />
<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Double-blinded concealed randomised controlled trial with intention-to-treat.</span><br />
<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Fit volunteer naval divers</span><br />
**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Control group</span>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;"> (N = 8; 8 analysed): Placebo medication at least three hours before diving (oxygen rebreather at 4m for 30 minutes average) on two consecutive days. </span><br />
**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Experimental group</span>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;"> (N = 7; 7 analysed): 1g vitamin C and 600 IU of vitamin E at least three hours prior to diving (same exposure).</span><br />
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**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">The Evidence:</span>'''<br />
{| <br />
| <span style'''"line-height: normal; margin-bottom: 0pt;">'''Non-event outcomes'''</span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">'''Time to outcome'''</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">'''Placebo group'''</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">'''Vitamin group'''</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style="display: block; text-align: center;">'''P-value'''</span></span> <br />
|-<br />
| <span style'''"line-height: normal; margin-bottom: 0pt;">'''Middle ear impedance (1st dive)'''</span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">24 hours</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">-5 daPa</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">-17.5 daPa</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style="display: block; text-align: center;">0.017</span></span> <br />
|-<br />
| <span style'''"line-height: normal; margin-bottom: 0pt;">'''Middle ear impedance (2nd dive)'''</span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">24 hours</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">-2.5 daPa</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style'''"display: block; text-align: center;">-7.5 daPa</span></span> || <span style'''"display: block; line-height: normal; margin-bottom: 0pt; text-align: center;"><span style="display: block; text-align: center;">0.64</span></span> <br />
|-<br />
|}<br />
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**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Comments:</span>'''<br />
<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">1. Administration of vitamins was associated with significantly worse eustachian tube function- this finding was the reverse of that hypothesised.</span><br />
<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">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.</span><br />
<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">3. Report in abstract only</span><br />
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**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">Expiry date:</span>'''<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;"> June 2020</span><br />
**<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">References: </span>'''<br />
<span style="font-family: &#39;Times New Roman&#39;,&#39;serif&#39;; font-size: 16px;">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.</span><br />
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