Decompression Tables for Diving at Altitude

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Brief Title

Decompression Tables for Diving at Altitude

Official Title

Development of Decompression Tables for Diving at Altitude

Brief 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). 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 Type

Interventional

Primary Outcome

Decompression Sickness

Secondary Outcome

 Venous Gas Emboli

Condition

Decompression Sickness

Intervention

Pressure

Study Arms / Comparison Groups

 Altitude Dive Altitude profile
Description:  Subjects are exposed to Pressure profiles (Altitude followed by a Dive with a return to Altitude) and Breathing Gases during dive exposures.

Publications

* Includes publications given by the data provider as well as publications identified by National Clinical Trials Identifier (NCT ID) in Medline.

Recruitment Information

Recruitment Status

Other

Estimated Enrollment

120

Start Date

February 13, 2018

Completion Date

November 1, 2021

Primary Completion Date

November 1, 2021

Eligibility Criteria

        Inclusion Criteria:

        -

        Exclusion Criteria:

          -  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)

Gender

All

Ages

18 Years - 40 Years

Accepts Healthy Volunteers

Accepts Healthy Volunteers

Contacts

Richard Moon, MD, 919-668-0017, [email protected]

Location Countries

United States

Location Countries

United States

Administrative Informations

NCT ID

NCT03390335

Organization ID

Pro00087803

Responsible Party

Sponsor

Study Sponsor

Duke University

Collaborators

 United States Department of Defense

Study Sponsor

Richard Moon, MD, Principal Investigator, Duke Universtiy Health System

Verification Date

September 2021