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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
Incidence of Middle Ear Barotrauma In Staged Versus Linear Chamber Compression During Hyperbaric Oxygen Therapy: A Double Blind, Randomized Clinical Trial
Scientific title
All New Patient Receiving Hyperbaric Oxygen Therapy Using Staged Or Linear Chamber Compression And The Incidence Of Middle Ear Barotrauma
Secondary ID [1] 280785 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Middle Ear Barotrauma 286845 0
Condition category
Condition code
Ear 287164 287164 0 0
Other ear disorders

Study type
Description of intervention(s) / exposure
Staged Chamber Compression using the compression protocol as below:

(atm = atmosphere; min = minutes)

i)Compress from 1atm to 1.28atm @ 1.4meters/min for 2 mins, hold pressure for 1min
ii)Compress from 1.28atm to 1.7atm @ 1.4meters/min for 3mins, hold pressure for 1min
iii)Compress from1.7atm to 2.4atm @ 1.4meters/min for 5mins
Total descent time = 12mins
Intervention code [1] 285214 0
Treatment: Other
Comparator / control treatment
Standard Linear Chamber Compression using standard compression protocol as below:

Compression from 1 atm to 2.4atm @ 1.1meters/min
Total descent time = 12mins 43 secs
Control group

Primary outcome [1] 287465 0
Incidence of middle ear barotrauma.

Both tympanic membranes of each participant will be photographed pre and post hyperbaric treatment with a Welch Allyn Digital Macroview Otoscope by trained staff members using standard mode (no magnification) and auto white balance producing pictures with a resolution of 1280x1024 megapixel in jpeg format.

One set photograph of each ear with a complete view of the tympanic membrane will be taken immediately prior to entering the hyperbaric chamber. Another set of photographs (left and right ears) will be taken within 10mins of the participant exiting the hyperbaric chamber. Each photograph will be assigned a random number.

Any ear wax impeding the view will be removed during the pre treatment assessment i.e. before any photograph is taken.

Middle ear barotrauma is defined as an increase in tympanic membrane (TM) score in one or both ears by at least one grade. The TM score used is based on the modified Teed's score. Photographs of all TMs will be assessed and graded by one single experienced and blinded Otolaryngologist not involved in the clinical care of the participants.
Timepoint [1] 287465 0
Immediately after first hyperbaric oxygen therapy session.
Secondary outcome [1] 298217 0
Number of interrupted treatments. An interrupted treatment is defined as a pause in the compression protocol due to a participant experiencing ear pain / discomfort but successfully arriving at prescribed depth (2.4atm).

Any interrupted treatment will be recorded and the number of interrupted treatments of both arms compared.
Timepoint [1] 298217 0
During the first hyperbaric oxygen therapy session
Secondary outcome [2] 298227 0
Number of aborted treatments. An aborted treatment is defined as a treatment terminated before reaching the prescribed depth (2.4atm) due to the inability of the participant to equalize the ears despite repeated attempts. The protocol for the inability to equalize ears follow that of the Hyperbaric Medicine Unit, Townsville Hospital, Emergency Protocol 18 (EP18)

Any aborted treatment will be recorded and the number of aborted treatments of both arms compared.
Timepoint [2] 298227 0
During the first hyperbaric oxygen therapy session
Secondary outcome [3] 298228 0
Pain score. A subjective pain score rated directly after reaching the prescribed depth will be recorded by each participant on a numerical rating scale with supporting adjectives at both extreme ends.

Median pain scores of both arms will be compared.
Timepoint [3] 298228 0
During the first hyperbaric oxygen therapy session

Key inclusion criteria
All adults aged 18 or above with indication for hyperbaric oxygen therapy
Minimum age
18 Years
Maximum age
99 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Previous hyperbaric oxygen therapy, contraindications for hyperbaric oxygen therapy, patient with grommets, active otological conditions, tympanic membrane rupture, unconscious patient, prescribed hyperbaric treatment table other than 2.4ATA

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
The allocation sequence will be concealed from the hyperbaric doctors enrolling and assessing participants in sequentially numbered, opaque, sealed and stapled envelopes. Corresponding envelopes will be opened only after the enrolled participant is inside the hyperbaric chamber and the chamber door closed.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
A balanced, blocked randomisation procedure will be employed by generating the allocation list based on a random seed using a statistical package and produced by an investigator with no clinical involvement in the trial .

From the allocation list, sequentially numbered, opaque, sealed and stapled envelopes containing the random allocation for the single participants will be produced.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 285580 0
Name [1] 285580 0
The Townsville Hospital
Address [1] 285580 0
100 Angus Smith Drive, Douglas 4814 QLD
Country [1] 285580 0
Primary sponsor type
Queensland Health
The Townsville Hospital, 100 Angus Smith Drive, Douglas, 4814 Queensland
Secondary sponsor category [1] 284416 0
Name [1] 284416 0
Address [1] 284416 0
Country [1] 284416 0

Ethics approval
Ethics application status
Ethics committee name [1] 287589 0
Townsville Health Service District Human Research Ethics Committee
Ethics committee address [1] 287589 0
100 Angus Smith Drive, Douglas, 4814 QLD
Ethics committee country [1] 287589 0
Date submitted for ethics approval [1] 287589 0
Approval date [1] 287589 0
Ethics approval number [1] 287589 0

Brief summary
All new patients presenting for hyperbaric oxygen therapy meeting the eligibility criteria will be randomized to either a Staged Compression Protocol (Trial regimen) or a Linear Compression Protocol (standard regimen) during their first hyperbaric chamber compression. Both protocols will achieve the treatment depth of 14 meters within 12-13 minutes. The Staged Protocol has a slightly faster compression rate (1.4 meters/min vs 1.1 meters/min) and has 2 holding stage with no pressure change to allow for patient to catch up with their ear equalization. The rate of compression and depth at the holding stages were choosen based on Boyle's Law calculation that middle ear volume will not change more than 30%.

Photographs of the tympanic membranes will be taken pre and post the first session of hyperbaric oxygen therapy. The number of interrupted or aborted treatment and subjective pain score will also be recorded. The photographs will be assessed by a blinded experienced otolaryngologist for middle ear barotrauma grade. Primary outcome is incidence of middle ear barotrauma in staged versus linear protocols. Secondary outcomes are number of interrupted and aborted treatments and patient's comfort from the pain score.

The hyperbaric doctors, hyperbaric nurses and the otolargyngologist assessor will all be blinded to protocol used. Only the chamber operator (who is not involved in the clinical management / assessment of the participants) will be aware of the protocol used.

Sample size calculation require 50 participants per arm for a power of 80% to detect a difference. The department received on average 10 new patients per month and the research is anticipated to take one year.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 34398 0
Dr Andrew Wei Aun Ng
Address 34398 0
Hyperbaric Medicine Unit, The Townsville Hospital, 100 Angus Smith Drive, Douglas 4814 QLD
Country 34398 0
Phone 34398 0
Fax 34398 0
Email 34398 0
Contact person for public queries
Name 17645 0
Dr Dr Andrew Ng
Address 17645 0
Hyperbaric Medicine Unit, The Townsville Hospital, 100 Angus Smith Drive, Douglas 4814 QLD
Country 17645 0
Phone 17645 0
Fax 17645 0
Email 17645 0
Contact person for scientific queries
Name 8573 0
Dr Dr Andrew Ng
Address 8573 0
Hyperbaric Medicine Unit, The Townsville Hospital, 100 Angus Smith Drive, Douglas 4814 QLD
Country 8573 0
Phone 8573 0
Fax 8573 0
Email 8573 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary