Saturday, April 28, 2007

U.S. Navy Flying After Diving Introduction - DAN Medical Research

U.S. Navy Flying After Diving Study
DAN Medical Research

Research into Flying After Diving (FAD) has been conducted at Duke University for many years. The current USN FAD study is designed to test dive-flight profiles that are of interest to the U.S. Navy. This current project is the second phase of the DAN Flying After Diving Study.

U.S. Navy (USN) divers undertake both training and missions that may require flying soon after diving. To reduce the risk of decompression sickness (DCS) as a result of flying after diving (FAD), guidelines were published in the USN Diving Manual that specify how long a diver should wait between dive and flight. The Navy guidelines were developed in part with data from previous FAD studies for recreational divers done at Duke (Vann et al., in prep). Additional testing is required to evaluate profiles not previously tested. These include some very long dives and decompression dives. In addition, studies will be conducted to investigate the possibility of decreasing preflight surface intervals by breathing oxygen before flight.

U.S. Navy Flying After Diving : Project Overview


The four specific goals of the U.S. Navy (USN) Flying After Diving project are:

1. Test air dive-flight profiles included in the USN flying after diving tables that would benefit from additional validation.

2. Use existing data and data generated from Aim 1 to develop a decompression model capable of computing risk of DCS for altitude exposures following air dives.

3. Use the resultant decompression model to (a) compute a comprehensive set of flying after diving guidelines for air diving; (b) make predictions for dive-altitude exposures for nitrogen oxygen mixtures other than air; and (c) make preliminary predictions for diving at altitude procedures.

This study will not repeat exposures tested in previous Duke studies. However, all previous Duke exposure data as well as germane exposures from other sources will be included with those from the present study to form a decompression model calibration data set.


This study will be limited to tests of only a few specific dive-altitude combinations because of time and cost considerations. A comprehensive medical screening questionnaire and medical examination by a physician will ensure that subjects meet the physical requirements for diving. Air dives in a dry hypo- / hyperbaric chamber with resting subjects will be followed by a interval at ground level up to 29 hours in duration, and then an 8,000-feet / 2,438-meter altitude exposure for four hours. The 8,000-foot altitude is the allowable lower limit of cabin pressures in commercial airliners. Dive depths between 60 and 100 fsw (feet of sea water; 18 and 30 msw, or meters of sea water) will be used with bottom times selected from the U.S. Navy dive tables.

The outcome of each experimental dive-surface interval-flight profile will be evaluated statistically to determine the next profile to be tested. Three alternatives are possible: (1) accept the surface interval without additional testing and begin testing a shorter surface interval; (2) reject the surface interval from further testing and begin testing a longer surface interval; or 3) test a different dive-surface interval-flight profile.

Two experiments, with up to 10 subjects per experiment, are conducted monthly. Subjects are dry and at rest throughout the dives and dry and at rest during the flight. Subjects are certified scuba divers or experienced in hypo- / hyperbaric exposures who are qualified upon completion of: 1) a medical history review and physical examination by a Hyperbaric Center physician; 2) body composition assessment; and 3) baseline ultrasonic measure. Subjects will be monitored for bubbles throughout the study with precordial Doppler (sound only) and transthoracic echocardiographic (two-dimensional picture) ultrasound for the presence of bubbles in the circulation.


Participant Eligibility Requirements

Participants must be:

between 18–60 years of age;
certified scuba divers, or have experience with hyperbaric exposure (they may be a student diver if accompanied by their instructor);
in good physical condition (subjects must not be over 40% of their ideal weight, or risk disqualification on the physical exam. Body composition will be assessed with a skin-fold caliper); and
healthy, without any disqualifying conditions:
Pregnancy - females of child-bearing age must submit to blood drawing for serum pregnancy determination, or have a statement from a physician verifying sterility;
Asthma that is active and requires medication (check with study physician);
Chronic seizure disorder;
Chronic diseases (e.g., heart condition, migraine, diabetes, hypertension) – check with study physician; or
Recent joint surgery (within 6 months of study date)
Subjects are eligible for more than one study as the profiles change, but a subject may participate only once in a given dive / surface interval/flight profile.

Restrictions prior to the study:

No diving 48 hours prior to study dive and after study flight.
No flying 24 hours prior to the study dive and / or 48 hours after the study flight.
No organized sports or other intense exercise less than 72 hours prior to the test.
No prescription or over-the-counter medication including aspirin other than those identified to the Study Physician within one week prior to the test.


Participants will receive pro-rated compensation for a total of $120 per trial. Completion of the study is required for full payment. This includes the follow-up interview at the Hyperbaric Center on the third day and the call-in 48 hours after the study flight. The medical outcome is just as important as the dive. Pro-rated compensation is $45 for the dive day, $45 for the flight day, $15 for the morning-after on-site health check, and $15 for 48-hour telephone health check (note: volunteers disqualified after completing the baseline evaluations but before beginning the dive will receive a total of $20 compensation).

DAN membership and Preferred Plan insurance will be provided for participants who complete the dive phase of the study if they are not currently covered (current DAN members with lesser insurance coverage will have their level increased to Preferred for the remainder of their annual membership cycle).

Meals will be provided at the chamber during the study, and some meals may be compensated up to $7 for lunch and $13 for dinner.

Individuals living outside a 60-minute driving radius from Duke University are asked to stay overnight following the dive and flight (room cost is covered by the study on a shared basis).

Sign Up or Ask Questions

If you would like to participate in this study, you will need to complete a Medical History Form (PDF: 33 KB) and return it by e-mail to, by fax to +1-919-493-3040, or mail to DAN Research, 6 West Colony Place, Durham, NC 27705.

For additional information, contact DAN Research at +1-919-684-2948 x260 or send a message.

Frequently Asked Questions (FAQs)

What is the study about?

The USN Flying After Diving Study is designed to evaluate the effect of altitude exposure following diving on the production of circulating bubble production and / or the development of decompression sickness.

Where do we go diving?

This study involved a dry chamber dive followed by a chamber flight to 8,000 feet / 2,438 meters after a surface interval. All trials are conducted at the Center for Hyperbaric Medicine and Environmental Physiology (Hyperbaric Center) in Duke University Medical Center, Durham, NC.

Do I bring any gear? What should I wear?

Dive gear is not required for this dry chamber study. Cotton "scrubs" (pants and shirt) will be issued to all subjects to wear in the chamber. We ask that females wear a two-piece bathing suit, shorts and halter top or aerobic-type top and bottoms. The abdomen, front and back and the chest and legs need to be exposed for the physical examination. The abdomen and as much of the rib cage as possible need to be accessible to facilitate the ultrasound monitoring.

How do we receive our compensation?

Participants are paid by check sent to the address supplied on the Compensation Form (DUMC Research Subject Registration Form). Usually, you may expect checks to arrive within four to five weeks.

What is a typical study like?

Participants will need to be at the Hyperbaric Center on Friday for physical examination, briefing, and body composition and ultrasound assessments. The dive follows, usually three hours from arrival. There is a one-hour medical watch after the dive. The flight is scheduled for Saturday. There is a four-hour medical watch after the flight. There also will be an interview on Sunday morning, in person, with the study physician.

Medical / Physical evaluations are conducted prior to the dive (baseline), immediately post-dive, four hours post-dive, the morning after the dive, and Sunday morning. All interviews are conducted in person with the study physician on the dive and flight days and the morning following the flight. The 48-hour interview will be by phone.

What can I bring inside the chamber?

You may bring a limited amount of reading material (excluding newsprint), but no electronic devices (e.g., pagers, cell phones, computers, CD players, or electronic games).

What if I develop symptoms?

The Hyperbaric Center conducts both clinical and research exposures. Any research subject developing symptoms associated with the study during or following the dive / flight exposures will receive immediate medical care at no cost to them. Protocols are in place to ensure the timely response and management of cases.

What is a typical trial schedule?

Experiments can take one or two days plus follow-up. The dive and flight activities are combined into a single day when short surface intervals are being tested.

Example Study Schedule (based on a long [24-hour] surface interval). Please be advised that this is a sample schedule. The study schedule that you will be participating in will be sent to you by DAN Research at least one week prior to the study date.

Day 1
8:00 Subjects assemble at the lab
8:00 - 8:30 Complete paperwork, dress in scrubs
8:30 - 9:00 Study Brief
9:00 - 10:00 Physicals and Baseline Doppler exams
10:00 - Chamber briefing and commence dive
13:00 - End dive / Start medical watch
13:30 - 14:00 Doppler
14:00 - Lunch
16:00 - Interview with physician and release

Day 2
12:00 - Subjects assemble at the lab
12:00 - 13:00 Interview with physician
13:00 - Start flight
17:00 - End flight
17:30 - 19:30 - Dinner
20:00 - Interview with physician and release

Day 3
AM interview with physician at the Center for Hyperbaric Medicine and Environmental

Physiology Day 4
Phone interview

Project Supporters

The U.S. Naval Sea Systems Command is funding this research program.

Please email if you are interested or want additional information.

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