One
hour of simulated descent in a hyperbaric chamber improved immediate clinical
state in patients with mild acute mountain sickness, but did not significantly
improve patients in the longer term.
Clinical
Bottom Line:
1.
One hour of treatment by simulated descent was associated with significant
clinical improvement.
2.
There was no significant improvement in clinical state at twelve hours
following treatment, although fewer hyperbaric patients received anti-emetics
in the 12 hours following treatment.
Appraised
by:
Mike Bennett, Dept. of Diving and Hyperbaric Medicine, Prince of Wales Hospital,
Sydney; Monday, 5 April 1999
Clinical
Scenario:
A patient with acute mountain sickness for treatment. We wondered if simulated
descent using an inflatable hyperbaric chamber would improve symptoms.
Three-part
Question:
In the treatment of mild acute mountain sickness, does the administration of
hyperbaric air to simulate descent, compared to bed rest, result in any
improvement in symptoms or rate of recovery?
Search
Terms:
altitude sickness, hyperbaric air.
The
Study:
Non-blinded
concealed randomised controlled trial without intention-to-treat.
Mountaineers
suffering from mild mountain sickness with headache and at least one of
dizziness, nausea, insomnia, facial oedema or ataxia. Patients with symptoms of
high altitude pulmonary oedema were excluded.
Control
group (N = 33; 33 analysed): Rest and mild analgesia. Two groups of control, one
not pressurised and resting in the chamber for one hour, the other compressed to
sham hyperbaric treatment by application of about 20mbar for one hour.
Experimental
group (N = 31; 31 analysed): As above, but treated for one hour at 193mbar in
the chamber (equivalent to a descent of 2,250m).
The
Evidence:
|
Outcome |
Time
to Outcome |
Control
group |
Pressure
group |
Relative
risk reduction |
Absolute
risk reduction |
NNT |
|
Analgesia
after treatment period |
12
hours |
0.697 |
0.581 |
17% |
0.12 |
9 |
|
95%
CI: |
|
|
|
-17%
to 50% |
-0.12
to 0.35 |
NNT=3
to INF NNH=8 to
INF |
|
Anti-emetics
after treatment period |
12
hours |
0.242 |
0.065 |
73% |
0.18 |
6 |
|
95%
CI: |
|
|
|
3%
to 100% |
0.01
to 0.35 |
3
to 142 |
Non-Event
Outcomes
Time to outcome
Control group
Pressure group
P-value
Clinical
severity
Score
1 hour
1.4
2.7
<0.001
Clinical
severity
score
12 hours
2.7
2.5
0.29
Comments:
1.
Control group treatment changed during study due to apparent clinical effect of
placebo compression. Suggests no outcome blinding.
2.
Beneficial short-term effect is probably due to improved oxygenation.
3.
Efficacy of longer or more frequent treatments at pressure remains unknown.
4.
Fewer anti-emetics required here in the active group when two control groups
analysed together, not reported in paper.
Expiry
date: April
2003
References:
1. Bartsch P, Merki B, Hofstetter D, Maggiorini M, Kayser B,
Oelz O. Treatment of acute mountain sickness by simulated descent: a randomised
controlled trial. British Medical Journal 1993; 306:1098-1101.
