Decompression SicknessNCT03390335
Decompression Tables for Diving at Altitude
A study testing Pressure and Breathing Gas in people with Decompression Sickness and Acute Mountain Sickness, run by Duke University at 1 site in United States.
Trial summary
The aims of this proposal are to test current USN procedures for adjusting decompression procedures during air diving at 8,000 and 10,000 ft altitude and to provide a decompression algorithm for no-stop dives to 100 feet of sea water (fsw) at 10,000 and 12,000 ft altitude using enriched O2 (PO2=1.3 ATM). Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Decompression Sickness, Acute Mountain Sickness
- What is being tested?
- Pressure and Breathing Gas
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 103 participants
- Where
- 1 siteUnited States
- Study dates
- 13 Feb 2018to 29 Oct 2021
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- -
Who cannot join
- smoking, cardiorespiratory disease (including hypertension, airways obstruction), seizure disorder, pregnancy, history of middle ear or sinus disease or high altitude cerebral or pulmonary edema (HACE, HAPE), inability to perform middle ear autoinflation, anemia, sickle cell disease and sickle cell trait. Individuals with VO2peak <35 mL.kg-1.min-1 (males) and <30 mL.kg-1.min-1 (females)
Trial locations and contacts
1 site in 1 country.
United States1 site
Duke University Hospital
Durham, North Carolina, 27710
About this study
Official title: Development of Decompression Tables for Diving at Altitude
The aims of this proposal are to test current USN procedures for adjusting decompression procedures during air diving at 8,000 and 10,000 ft altitude and to provide a decompression algorithm for no-stop dives to 100 feet of sea water (fsw) at 10,000 and 12,000 ft altitude using enriched O2 (PO2=1.3 ATM). Additionally, the experiments will determine whether a period of hyperbaric hyperoxia, such as would be experienced during a dive at altitude, reverses altitude acclimatization, resulting in a return of acute mountain sickness (AMS) symptoms.
Read the detailed description
Three different types of experiments will be performed:
(A). Testing of Cross corrections breathing air at 8,000 (0.743 ATA) and 10,000 ft (0.688 ATA). Subjects will be decompressed in a hypobaric chamber to one of the altitudes above. A no-stop dive to 60 fsw will be tested at each altitude (2.82 ATA at sea level, 2.56 ATA at 8,000 ft, 2.51 ATA at 10,000 ft). Using the Cross corrections, the virtual depth for both altitudes is 90 fsw, for which the no-stop time is 30 minutes. During the dive the subject will be immersed/submersed at rest/mild exercise in 28°C water. Ascent rate will be 30 fsw/min. Upon surfacing the diver will be monitored for 12 hours for symptoms of decompression sickness and transthoracic echocardiography (rest and leg/arm motion) to examine for venous gas embolism (VGE) at 5, 15, 30, 60 and 120 minutes after surfacing. After that, measurements will be continued until no bubbles are detected.
(B). Testing of a no-stop dive to 100 fsw at 10,000 ft and 12,000 ft breathing 35% O2. For this series of experiments all subjects will remain at altitude for 48 hours before diving, in order to allow for resolution of AMS symptoms. Appropriate depth-time profiles have been assessed by calculating the equivalent sea level air depth for each of these dives (PN2 values 2.42 and 2.36 ATM, respectively). These yield equivalent air depths of 68 and 66 fsw, respectively. Cross corrected virtual depths would therefore be 99 and 104 fsw, yielding no-stop times of 25 and 20 minutes, respectively. The Cross correction method will be used in this instance because, although largely untested, it is presently in use by the Navy. As with the air dives described above, the more provocative dives (12,000 ft) will be completed before the ones at 10,000 ft, which will increase the confidence for the bottom time used at the lower altitude.
(C). Testing to determine whether a high PO2 dive would reverse altitude acclimatization and re-establish susceptibility to AMS. Subjects will ascend in the chamber to 15,000 ft in a graded fashion over 12 hours (15,000 ft has been chosen due to extensive Duke experience with this altitude). Then, after 48 hours they will simulate a hyperoxic dive by breathing 100% O2 for 120 minutes at 1.3 ATA. This will simulate, for example, a 2 hour dive at 12,000 ft to 65 fsw breathing 50% O2. The diver will then return to 15,000 ft and remain at that altitude for 24 hours to allow for AMS symptoms to recur (if indeed they do). Lake Louise AMS scores will be collected every 8 hours. AMS symptoms will be treated with acetaminophen, NSAIDs and anti-emetics as needed. Subjects will be assessed clinically every 12 hours for high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Occurrence of either HAPE or HACE will require that the subject be returned immediately to 1 ATA and treated appropriately.
- Conditions
- Decompression Sickness, Acute Mountain Sickness
- Being tested
- Pressure, Breathing Gas
- Medical subject headings
- Decompression Sickness, Altitude Sickness
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PressureOther
Subjects undergo altitude exposure, diving exposure, and return to altitude. Altitudes: 8,000, 10,000, 12,000, or 15,000 feet Dives: 60 or 100 feet of sea water
Breathing GasOther
Subjects will breathe air, 35% Oxygen, Balance Nitrogen, or 100% Oxygen during the diving exposure
| Study group | Role | What they receive |
|---|---|---|
| Altitude Dive Altitude profile | Experimental | Subjects are exposed to Pressure profiles (Altitude followed by a Dive with a return to Altitude) and Breathing Gases during dive exposures. Receives: Other: Pressure; Other: Breathing Gas |
What is being measured
The primary outcome is the main question the study is designed to answer.
Decompression Sickness
Subjects will be evaluated for symptoms of decompression sickness when returning to the initial altitude following a dive exposure.
Measured: 12 hours
Maximum Acute Mountain Sickness (AMS) Score Change
Lake Louise Scoring System for Acute Mountain Sickness. Subjects will fill out a six-question questionnaire (0 - 3, higher scores are worse symptoms) and a three-question clinical assessment (0-4, 0-4, 0-2, higher score is worse a assessment). The total score of all questions and assessments (0 - 28, higher is worse AMS), is determined every eight hours for 48 hours at altitude pre-dive and 24 hours at altitude post-dive.
Measured: 48 hour, 72 hours
Secondary outcomes (1)
Venous Gas Emboli
2D ultrasound will be used to assess right ventricular bubble score at 5, 15, 30, 60 and 120 minutes and hourly until no bubbles are detected using the following scale: Modified Eftedal-Brubakk Scale for Venous Gas Embolism (VGE)
Grade Definition 0 No observable bubbles
- Occasional bubbles
- At least 1 bubble every 4 heart cycles
- At least 1 bubble every heart cycle
- A Continuous bubbling, 1-2 bubbles per cm2 in every image
4B Continuous bubbling, at least 3 bubbles per cm2 in every image 4C Almost complete whiteout in the right heart, individual bubbles can still be discerned 5 "White out", single bubbles cannot be discriminated
Measured: 12 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Jan 2018
- Study start13 Feb 2018
- Primary completion29 Oct 2021
- Study completion29 Oct 2021
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Decompression SicknessStudies of the same condition, open and under way.
- More trials run by Duke UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Prevention
- Allocation
- Not applicable
- Intervention model
- Sequential
- Model description
- This design is a two factor, incomplete block design - three altitudes (8,000, 10,000, and 12,000 feet) and 2 breathing gases (air, 35% O2-N2). The investigators expect to see 0 events in the combinations tested, calculated by the Bayesian Method. If the rate of events is larger than expected, the investigators will use logistic regression to assess if the main effect Air (Air vs. 35% O2-N2) or altitude (8,000, 10,000 or 12,000 feet) or the interaction of these 2 factors imparts relative increased risk. The investigators will set a Type-I error rate of 0.05 (two-tailed).In the presence of 'zero cells', the investigators will either (1) collapse cells into reasonable groups, or (2) add a very small set of constants to the frequency and assess the impact on the effect sizes and tests of significance.1 In the absence of an interaction effect, main effects will be reported.
- Masking
- None (open label)
- Enrolment
- 103 participants (actual)
Sponsor and investigators
- Lead sponsor
- Duke University
- Sponsor type
- University, hospital or other
- Collaborators
- United States Department of Defense
- Responsible party
- Sponsor
- Investigators
- Richard Moon, MD, Principal investigator, Duke Universtiy Health System
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03390335
- Sponsor's protocol ID
- Pro00087803
- Status last verified
- Nov 2021
- First submitted
- 28 Dec 2017
- Last updated
- 14 Dec 2021
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 14 Dec 2021. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Development of Decompression Tables for Diving at Altitude
- ClinicalTrials.gov ID
- NCT03390335
- Acronym / sponsor ID
- Pro00087803
- Conditions
- Decompression Sickness, Acute Mountain Sickness
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 103 participants (actual)
- Lead sponsor
- Duke UniversityUniversity, hospital or other
- Collaborators
- United States Department of Defense
- Study start
- 13 Feb 2018 (actual)
- Primary completion
- 29 Oct 2021 (actual)
- Study completion
- 29 Oct 2021 (actual)
- First posted
- 4 Jan 2018 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The aims of this proposal are to test current USN procedures for adjusting decompression procedures during air diving at 8,000 and 10,000 ft altitude and to provide a decompression algorithm for no-stop dives to 100 feet of sea water (fsw) at 10,000 and 12,000 ft altitude using enriched O2 (PO2=1.3 ATM). Additionally, the experiments will determine whether a period of hyperbaric hyperoxia, such as would be experienced during a dive at altitude, reverses altitude acclimatization, resulting in a return of acute mountain sickness (AMS) symptoms.
Detailed description
Three different types of experiments will be performed:
(A). Testing of Cross corrections breathing air at 8,000 (0.743 ATA) and 10,000 ft (0.688 ATA). Subjects will be decompressed in a hypobaric chamber to one of the altitudes above. A no-stop dive to 60 fsw will be tested at each altitude (2.82 ATA at sea level, 2.56 ATA at 8,000 ft, 2.51 ATA at 10,000 ft). Using the Cross corrections, the virtual depth for both altitudes is 90 fsw, for which the no-stop time is 30 minutes. During the dive the subject will be immersed/submersed at rest/mild exercise in 28°C water. Ascent rate will be 30 fsw/min. Upon surfacing the diver will be monitored for 12 hours for symptoms of decompression sickness and transthoracic echocardiography (rest and leg/arm motion) to examine for venous gas embolism (VGE) at 5, 15, 30, 60 and 120 minutes after surfacing. After that, measurements will be continued until no bubbles are detected.
(B). Testing of a no-stop dive to 100 fsw at 10,000 ft and 12,000 ft breathing 35% O2. For this series of experiments all subjects will remain at altitude for 48 hours before diving, in order to allow for resolution of AMS symptoms. Appropriate depth-time profiles have been assessed by calculating the equivalent sea level air depth for each of these dives (PN2 values 2.42 and 2.36 ATM, respectively). These yield equivalent air depths of 68 and 66 fsw, respectively. Cross corrected virtual depths would therefore be 99 and 104 fsw, yielding no-stop times of 25 and 20 minutes, respectively. The Cross correction method will be used in this instance because, although largely untested, it is presently in use by the Navy. As with the air dives described above, the more provocative dives (12,000 ft) will be completed before the ones at 10,000 ft, which will increase the confidence for the bottom time used at the lower altitude.
(C). Testing to determine whether a high PO2 dive would reverse altitude acclimatization and re-establish susceptibility to AMS. Subjects will ascend in the chamber to 15,000 ft in a graded fashion over 12 hours (15,000 ft has been chosen due to extensive Duke experience with this altitude). Then, after 48 hours they will simulate a hyperoxic dive by breathing 100% O2 for 120 minutes at 1.3 ATA. This will simulate, for example, a 2 hour dive at 12,000 ft to 65 fsw breathing 50% O2. The diver will then return to 15,000 ft and remain at that altitude for 24 hours to allow for AMS symptoms to recur (if indeed they do). Lake Louise AMS scores will be collected every 8 hours. AMS symptoms will be treated with acetaminophen, NSAIDs and anti-emetics as needed. Subjects will be assessed clinically every 12 hours for high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Occurrence of either HAPE or HACE will require that the subject be returned immediately to 1 ATA and treated appropriately.
Study design
- Primary purpose
- Prevention
- Allocation
- Not applicable
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- This design is a two factor, incomplete block design - three altitudes (8,000, 10,000, and 12,000 feet) and 2 breathing gases (air, 35% O2-N2). The investigators expect to see 0 events in the combinations tested, calculated by the Bayesian Method. If the rate of events is larger than expected, the investigators will use logistic regression to assess if the main effect Air (Air vs. 35% O2-N2) or altitude (8,000, 10,000 or 12,000 feet) or the interaction of these 2 factors imparts relative increased risk. The investigators will set a Type-I error rate of 0.05 (two-tailed).In the presence of 'zero cells', the investigators will either (1) collapse cells into reasonable groups, or (2) add a very small set of constants to the frequency and assess the impact on the effect sizes and tests of significance.1 In the absence of an interaction effect, main effects will be reported.
| Arm | Type | Receives |
|---|---|---|
| Altitude Dive Altitude profile | Experimental | Other: Pressure, Other: Breathing GasSubjects are exposed to Pressure profiles (Altitude followed by a Dive with a return to Altitude) and Breathing Gases during dive exposures. |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (1 listed)
- -
Key exclusion criteria (1 listed)
- smoking, cardiorespiratory disease (including hypertension, airways obstruction), seizure disorder, pregnancy, history of middle ear or sinus disease or high altitude cerebral or pulmonary edema (HACE, HAPE), inability to perform middle ear autoinflation, anemia, sickle cell disease and sickle cell trait. Individuals with VO2peak <35 mL.kg-1.min-1 (males) and <30 mL.kg-1.min-1 (females)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PressureSubjects undergo altitude exposure, diving exposure, and return to altitude. Altitudes: 8,000, 10,000, 12,000, or 15,000 feet Dives: 60 or 100 feet of sea water | Other | Altitude Dive Altitude profile |
| Breathing GasSubjects will breathe air, 35% Oxygen, Balance Nitrogen, or 100% Oxygen during the diving exposure | Other | Altitude Dive Altitude profile |
Primary outcome
Decompression Sickness
Time frame: 12 hours
Subjects will be evaluated for symptoms of decompression sickness when returning to the initial altitude following a dive exposure.
Maximum Acute Mountain Sickness (AMS) Score Change
Time frame: 48 hour, 72 hours
Lake Louise Scoring System for Acute Mountain Sickness. Subjects will fill out a six-question questionnaire (0 - 3, higher scores are worse symptoms) and a three-question clinical assessment (0-4, 0-4, 0-2, higher score is worse a assessment). The total score of all questions and assessments (0 - 28, higher is worse AMS), is determined every eight hours for 48 hours at altitude pre-dive and 24 hours at altitude post-dive.
1 secondary outcome
Venous Gas Emboli
Time frame: 12 hours
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 14 Dec 2021.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Richard Moon, MD principal investigator
Duke Universtiy Health System
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Pressure and Breathing Gas in people with Decompression Sickness and Acute Mountain Sickness, run by Duke University at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 1 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 14 Dec 2021. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Decompression Sickness (time frame: 12 hours). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 14 Dec 2021.