Effects of Hyperbaric Oxygen Therapy on Glucose Homeostasis in Patients Living With Diabetes Mellitus
Phase: NA
Conditions: Diabetes Mellitus, Type 2, Diabetes Mellitus, Type 1
Sponsor: Legacy Health System

December 4, 2019 
 
1 
 
Proposal for Research 
Investigators 
Enoch Huang, MD; Davut Savaser, MD; Chae Bliss, CHT, Jessica Castle, MD; Shaban 
Demirel, PhD 
Title 
Effects of hyperbaric oxygen therapy on glucose homeostasis in patients living with 
diabetes mellitus (Protocol HB-002) 
Background 
Diabetes mellitus (DM) is an epidemic of global proportion with a steadily rising 
prevalence of disease. It is believed at least 15% of people living with diabetes will 
develop a lower extremity foot ulcer during their lifetime.1,2 The annual incidence of 
foot ulcer development is 5-6% among patients living with diabetes.1-3 Patients with 
diabetes mellitus often require hyperbaric oxygen (HBO2) for treatment of diabetic foot 
ulcers (DFU)4. Hyperbaric oxygen is thought to affect blood glucose (BG) levels,5-7 
leading to treatment protocols that rely on pre-HBO2 BG to determine whether patients 
can be safely treated that day or not.8  
 
Mechanisms to explain the drop in BG associated with HBO2 include a rise in serum 
insulin levels, increased sensitivity to insulin, and inhibition of anti-insulin hormones 
such as glucagon.9 An alternative theory as to why patients with DM have lowered blood 
glucose after HBO2 is the fact that they may have a decreasing trend in their BG prior to 
starting HBO2 that is then exacerbated by the fact that they are sequestered for up to 
120 minutes in the hyperbaric chamber without easy access to additional carbohydrate 
sources.5,9 A single fingerstick BG prior to HBO2 is insufficient to determine whether a 
patient’s BG is stable, trending up, trending down, or changing rapidly. Continuous 

December 4, 2019 
 
2 
 
glucose monitoring (CGM) offers a unique opportunity to monitor BG before, during, 
and after HBO2.  
 
We previously studied the reliability of a commercially available Dexcom G6 CGM 
(Dexcom, Inc., San Diego, CA) under hyperbaric oxygen conditions in healthy volunteers 
who did not have diabetes. This showed an increase of 3.76 mg/dL (3.72%, p<0.001) 
while patients were breathing HBO2 at 2.4 atmospheres absolute (ATA) and an increase 
of 4.12 mg/dL (4.13%, p=0.015) when comparing pre-HBO2 and post-HBO2 values. The 
increase in EGV may have been related to increases in interstitial fluid temperature 
related to the HBO2, but that was not measured. While this was statistically significant, it 
was not felt to be clinically relevant. The Dexcom G6 CGM was felt to be accurate and 
reliable for use with patients without DM receiving HBO2. The goal for this proposed 
study is to look at multiple CGMs in patients with DM receiving HBO2. 
Research Goals 
Specific Aim 1 – Determine whether the Dexcom G6 CGM accurately estimates blood 
glucose under hyperbaric oxygen conditions 
 
Specific Aim 2 – Determine whether a single HBO2 treatment affects blood glucose in 
patients with diabetes mellitus 
 
Specific Aim 3 – Determine whether glucagon varies in relationship with HBO2 
Materials and Methods 
Study Design and Timeline 
This will be a prospective, controlled trial comparing a standard HBO2 treatment vs. a 
control period. Each patient will serve as their own control. 
 

December 4, 2019 
 
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Recruitment 
We will recruit individuals who are living with type 1 or type 2 diabetes and are willing 
to undergo a single hyperbaric exposure to 2.4 ATA while breathing 100% oxygen. 
Participants will provide their informed consent after the risks of the study have been 
explained to them (e.g., HBO2 possibly decreasing BG) and the risks of HBO2 (e.g., 
barotrauma, confinement anxiety, oxygen toxicity, and fire). Upon enrollment in to the 
study, participants will have a commercial G6 CGM inserted in the subcutaneous tissue 
of their abdomen and a research G6 data logger inserted in the subcutaneous tissue on 
the back of the arm. Participants will return >36 hours after insertion for their study 
exposures.  
 
Compensation up to $400 will be pro-rated to encourage completion of all study 
sessions (Figure 1): 
• Implantation of CGM loggers - $50 
• Completion of control study session - $50 
• Completion of HBO2 study sessions- $100 
• Completion of follow-up data collection - $200 
 
Figure 1. Study Timeline and Compensation Schedule 
 
 
Commercial CGMs have a 10-day lifespan and data loggers have a 14-day lifespan, but 
all study sessions should be completed within 10 days of insertion (Figure 2). The color 
coding represents whether or not participants and staff will have to come in over the 
weekend for a control or HBO2 session (red), to insert CGMs or remove CGMs (yellow), 
or if they won’t have to come in over the weekend at all (green).  
Day
Day 1
36 hour interval
Day 3
Day 4
Day 5-9
Day 10
Payment
$50
$50
$100
$250
Event
Consent Placement 
of CGM
Control Exposure - 3 hours 
HBO2 Treatment - 3 hours
Return for CGM Removal
Event Log
Meals and Medication Times
Meals and Medication Times
Meals and Medication Times
Meals and Medication Times
Home Testing
4 capillary measurements per 
day at home
4 capillary measurements per day 
at home
4 capillary measurements per day 
at home
4 capillary measurements per 
day at home
Study Testing
UCG
Fingerstick measurement - POC x 12 Fingerstick measurement - POC x 12
Venous glucose - laboratory x 12
Venous glucose x 12
Glucagon x 3
Glucagon x 3
Hba1c x 1
G6 CGM
G6 CG Logger
Estimated Glucose Value
Interstitial Temperature

December 4, 2019 
 
4 
 
 
Figure 2. Weekly schedule of events  
 
 
We will plan for recruitment of 24 individuals. Half will be patients living with type 1 
diabetes and half will be patients living with type 2 diabetes. 
 
Inclusion Criteria 
• Diagnosis of type 1 or type 2 diabetes 
• Willing to have 2 subcutaneous glucose monitors for 10 days 
• Willing to be NPO after midnight on the day of the study session 
• Willing to come to the hyperbaric facility on successive days (one control session 
and one hyperbaric treatment), spending approximately 3 hours in the facility on 
each day of testing 
• Willing to undergo multiple fingersticks on the days of testing 
• Willing to have a peripheral intravenous catheter placed for blood sampling 
• Willing to perform four daily fingerstick blood glucose checks throughout the 
study period 
 
Exclusion Criteria 
• Contraindication to HBO2 as determined by the study investigator (e.g., 
pregnancy) 
• Previous treatment with HBO2 within 30 days of enrollment 

December 4, 2019 
 
5 
 
• Current use of CGM is not an exclusion, but participants must use study 
equipment during the study 
• Current use of an insulin pump 
• Known allergy to medical-grade adhesives 
• Extensive skin changes/disease that preclude wearing the sensor on normal skin 
(e.g. extensive psoriasis, recent burns or severe sunburn, extensive eczema, 
extensive scarring, extensive tattoos, dermatitis herpetiformis)  
 
Control Protocol (Figure 3) 
Because the effects of HBO2 may extend longer than one day, participants will first be 
exposed to a 2-hour control period where they will simulate an HBO2 exposure. Patients 
must be NPO after midnight of the day prior to the control study period. Participants in 
a control session will sit quietly (as they would in the hyperbaric chamber) and will not 
be allowed to consume carbohydrates unless directed to by the hyperbaric department 
hypoglycemia protocol. The timing of the blood draws (Figure 5) will be parallel to that 
of the HBO2 exposure. 
 
Figure 3. Control Testing Protocol 
 
 
Hyperbaric Oxygen Therapy (Figure 4) 
The day after the control study period, participants will undergo a standard HBO2 
treatment breathing 100% oxygen at 2.4 ATA with 3 x 30 min O2 periods and 5 min air-
breaks between O2 periods. Patients must be NPO after midnight of the day prior to the 
HBO2 period. Participants will not be allowed to consume carbohydrates during the 
treatment unless directed to by the hyperbaric department hypoglycemia protocol. 
 

December 4, 2019 
 
6 
 
Figure 4. HBO2 Testing Protocol 
 
 
Modification of hypoglycemia medication regimen 
Because participants are being asked to remain NPO after midnight, they will be asked 
to modify their normal hypoglycemic medications as follows: 
• Oral hypoglycemic medications should be held until after they eat their first meal 
of the day 
• Patients with meal-time doses of insulin should hold their meal-time boluses 
until they eat their first meal of the day 
• Patients who require a correction dose of insulin the morning of study session 
(control of HBO2) because of a blood glucose >250 mg/dL should take their 
normal dose of insulin and document it in their medication log 
• Patients who use long-acting insulin should modify their doses as follows 
o Patients who are on BID long-acting insulin to take their normal dose in 
the morning, but 2/3 of their dose the night before 
o Patients who are on night-time long-acting insulin to take 2/3 their 
normal dose the night before 
o Patients who are on morning long-acting insulin to take 2/3 of their 
normal dose in the morning 
Study investigators will review insulin doses and provide additional instructions for 
adjustment if needed for safety. 
 
Modification of the Hyperbaric Department Glucose Protocol 
The hyperbaric department currently follows a protocol to provide supplemental 
carbohydrates to patients with a pre-HBO2 BG <100 mg/dL whether they are 

December 4, 2019 
 
7 
 
symptomatic or not. We will be following the hyperbaric department protocol and 
obtaining pre-HBO2 fingerstick blood sugars, but we will not provide mandatory 
supplemental carbohydrate for BG <100 mg/dL unless participants complain of 
symptoms they associate with hypoglycemia. If participants are documented to have 
hypoglycemia – defined by the American Diabetes Association (ADA) as a BG ≤ 70 
mg/dL10  – before or during study periods, we will institute the hyperbaric department’s 
hypoglycemia protocol and provide 15 grams of supplemental carbohydrate. 
Hypoglycemia risk to the patient is mitigated because we will be able to monitor blood 
sugar in real time using CGM, however clinical decisions will be made using the 
fingerstick GDH-based POC glucometer. 
 
Transcutaneous Oxygen Monitoring during HBO2 exposures 
We will obtain concurrent transcutaneous oximetry measurements (TCOM) using a 
Clarke electrode (Radiometer America, Brea, CA) attached no farther than 3 cm from 
the commercial CGM on the abdomen to measure tissue oxygenation in the region of 
the CGM only during HBO2 exposure. The TCOM value closest to the time of each blood 
draw will be used for analysis. The average pre-HBO2 TCOM measurements will be used 
as a surrogate for the control day TCOM. 
 
Hemoglobin A1c 
We will obtain a single Hba1c measurement using the central laboratory chemistry 
analyzer (AU680 Chemical Chemistry Analyzer, Beckman Coulter, Inc., Brea, CA) at the 
first blood draw to establish baseline control of their DM. 
 
Blood glucose (central laboratory) 
We will use the central laboratory chemistry analyzer (AU680 Chemical Chemistry 
Analyzer, Beckman Coulter, Inc., Brea, CA) to measure blood glucose at each of the time 
points (Figure 4). This analyzer uses a hexokinase reaction that is insensitive to blood 
oxygen levels and will serve as the reference for CGM and POC glucometers. 
 

December 4, 2019 
 
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Glucagon (send-out to OHSU) 
We will draw blood glucagon before (Timepoint 1), during (Timepoint 9), and after 
(Timepoint 12) actual or simulated HBO2 (Figures 2-4) in order to determine whether 
there are any effects of HBO2 on glucagon. The protocol for the glucagon handling is 
described below. 
 
Blood sampling schedule (Figure 4) 
We will obtain a venous blood glucose sample on all participants at the following time 
points during the study (±2 min): 
1. 30 minutes prior to starting (NBAir) 
2. 15 minutes prior to starting (NBAir) 
3. Immediately prior to study session (NBAir) 
10-minute compression  
4. 15 minutes into O2 period 1 (HBO2) 
5. 30 minutes into O2 period 1 (HBO2) 
6. 15 minutes into O2 period 2 (HBO2) 
7. 30 minutes into O2 period 2 (HBO2) 
8. 15 minutes into O2 period 3 (HBO2) 
9. 30 minutes into O2 period 3 (HBO2) 
5-minute decompression 
10. Immediately after reaching 1 ATA (NBAir Post-HBO2) 
11. 15 minutes after reaching 1 ATA (NBAir Post-HBO2) 
12. 30 minutes after reaching 1 ATA (NBAir Post-HBO2) 
 
Figure 4. Timeline of testing 
 
Control/HBO2
1
2
3
4
5
6
7
8
9
10
11
12
Time ± 2min
T-30
T-15
T0
T+25
T+40
T+60
T+75
T+95
T+110
T+115
T+130
T+145
CGM EGV
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CGL EGV
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Interstitial T°
•
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•
Lab Glucose
•
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•
•
•
•
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NovaStat
•
•
•
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•
•
•
•
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•
AccuChek
•
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•
•
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•
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TCOM
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Glucagon
•
•
•
Pre-HBO2
HBO2
Post-HBO2

December 4, 2019 
 
9 
 
 
Because we are using a saline-locked peripheral IV with a 4-way stopcock for blood 
sampling, our protocol for each blood draw will be as follows: 
• Draw approximately 4 ml of venous blood from distal port of the IV catheter, 
leaving the syringe in place; 
• Withdraw 2 ml of venous blood and place in purple top for measurement of 
glucagon; 
• Return the 4 ml of venous blood through proximal port and flush with 10-20 ml 
of normal saline until line is clear of blood; 
• Cap the port with a clean 1 ml syringe; 
 
For glucagon processing 
• Prechill a lavender top (EDTA) with aprotonin tube at 4°C before drawing the 
specimen 
• Draw the prechilled lavender (EDTA) top tube and process 2.0 mL of EDTA 
plasma as follows:  
o Sample should be mixed by inverting gently 6-7 times; 
o Chill lavender (EDTA) top tube in wet ice for 10 minutes; 
o Centrifuge in a refrigerated centrifuge (4 °C) or in chilled centrifuge cups; 
o Spin at ≈2600 RPM in the centrifuge with samples balanced; 
o Aliquot plasma into appropriate number cryo-tubes using a separate 
transfer pipette for each tube; 
o Freeze samples ASAP in freezer 
 
A runner will process each glucagon sample immediately after removal from the 
hyperbaric chamber. Frozen glucagon samples will be batched and transported to the 
OHSU laboratory on dry ice for processing. 
 

December 4, 2019 
 
10 
 
Fingerstick point-of-care glucose testing 
Because we have not established that CGMs are reliable under HBO2 conditions, we will 
collect POC glucose measurements using the hospital’s standard GOx-based NovaStat 
POC glucometer (Nova Biomedical, Waltham, MA) and a GDH-based AccuChek Inform II 
POC glucometer (Roche Diagnostics, Indianapolis, IN) at each testing point. We will 
compare the POC glucometer readings against the laboratory readings to generate a 
mean absolute relative difference (MARD) for each glucometer. Because GOx-based 
POC glucometers are known to underestimate BG while GDH-based POC glucometers do 
not, we will primarily use the AccuChek GDH-based POC glucometer for clinical decision 
making. 
 
Fingerstick protocol 
1. Clean the subject's fingertip with soap and water and allow to dry. 
2. Puncture the skin with one quick stroke with the lancet to achieve a good flow of 
blood.  
3. Wipe away the first drop of blood as it may be contaminated with plasma or 
debris. 
4. Blood collection - Avoid squeezing the finger too tightly as this will dilute the 
specimen with plasma and increase the probability of hemolysis.  
a. At 1 ATA - gently squeeze the finger and apply blood to the test strip.  
b. At 2.4 ATA - gently squeeze the finger and collect blood in micro-pipette.  
5. When the blood collection procedure is complete, apply firm pressure to the site 
to stop the bleeding.    
 
Continuous glucose monitor 
We will use both a commercial Dexcom G6 (Dexcom, Inc., San Diego, CA) CGM and a 
CGM logger for continuous glucose monitoring. A CGM logger differs from a 
commercially available CGM in that it does not provide feedback to the patient, but it 
records data that a commercially available CGM does not (e.g., interstitial fluid 
temperature). Data can be retrieved from the logger at the end of the study period for 

December 4, 2019 
 
11 
 
analysis. The G6 CGM will be inserted in the subcutaneous tissue of the abdomen 
according to the manufacturer's directions. The G6 CGM logger will be inserted in the 
subcutaneous tissue on the back of the arm according to the manufacturer’s directions. 
We will allow at least 48 hours of runtime before hyperbaric exposure in order to allow 
equilibration of CGM readings. The CGM will be considered the primary data source for 
EGV, with the CGM logger providing a backup in case of data loss. 
 
Home glucose monitoring 
In order to verify that the CGM is working before and after HBO2 exposure, we will have 
participants obtain fingerstick BG using a POC Contour One glucometer and test strips 
(Ascensia Diabetes Care, Parsipanny, NJ) that will be provided to them. This will be done 
a minimum of 4 times a day throughout the study period. Data from the POC 
glucometer will be downloaded at the end of the study period for comparison with the 
CGM data. 
 
Ancillary Data collection 
We will provide all participants a log to document the time of their meals and the time 
of any medications taken throughout the study period.  
Risks of hyperbaric oxygen (HBO2) therapy 
HBO2 is an FDA approved treatment modality for many different conditions. It is 
administered in a rigid-hulled hyperbaric chamber that either accommodates a single 
patient (monoplace chamber) or multiple patients (multiplace chamber). Monoplace 
chambers are compressed with 100% oxygen while patients breathe the ambient 
atmosphere. Multiplace chambers are compressed with air (21% oxygen) while patients 
breathe 100% oxygen from a face mask or an oxygen hood. Treatment pressures range 
from 2.0 atmospheres absolute (ATA) to 2.5 ATA and include at least 90 minutes of 
oxygen breathing. Treatment protocols include periods of air breathing (air breaks) of 5-
10 minutes duration interspersed between 30-minute oxygen breathing periods. The 
treatments start by increasing pressure during the compression phase of the treatment, 

December 4, 2019 
 
12 
 
which lasts between 5-10 minutes. Once reaching the prescribed treatment pressure, 
patients will be maintained at the prescribed treatment pressure for three 30-minute 
oxygen breathing periods and two 5-minute air breaks. At the completion of the final 
oxygen breathing period, the decompression phase of the treatment will reduce the 
ambient pressure until reaching sea level pressure. Treatment protocols for HBO2 
typically range between 30 sessions to 60 sessions offered daily on a Monday-Friday 
basis.  
 
In this study, participants will be treated in our multiplace hyperbaric chamber for a 
single HBO2 session between Monday-Friday. Participants will be pressurized to 2.4 ATA 
for three 30-minute oxygen breathing periods separated by two 5-minute air breaks. 
Patients will breathe oxygen from clear plastic hoods fitted over a neck ring with a 
rubber gasket. Study treatments will occur concurrently with non-study patients during 
daily hyperbaric operations.  
 
The primary risks to participants from treatment in a hyperbaric chamber are related to 
the increased partial pressure of gasses in the chamber. The most common risk is 
middle-ear and sinus barotrauma and confinement anxiety (incidence included in Table 
1). Very rare risks include oxygen related seizures, pneumothorax, arterial gas emboli, 
and decompression sickness.  
 
Ear and sinus barotrauma: Some individuals may have difficulty equalizing the 
pressures within the middle ears or sinuses which may cause ear or sinus discomfort. 
Participants will be screened for ear problems, and an ear exam, using an otoscope, will 
be done before any hyperbaric exposure. Participants will be given a thorough 
orientation at the time of their consent and instructed on ear clearing maneuvers. If a 
participant is unable to equalize their ears, the exposure will be discontinued, and they 
may be referred for myringotomy before continuing in the study. If the participant has 
any significant otoscopic findings in the eardrum after the study exposure to hyperbaric 

December 4, 2019 
 
13 
 
treatment, appropriate follow up will be arranged if needed. Follow up will be covered 
by participant’s insurance if necessary.  
 
Confinement anxiety: Some individuals can experience confinement anxiety due to 
being in the chamber or wearing the oxygen hood or mask. To minimize this risk, we will 
screen potential participants for a history of confinement anxiety or other psychiatric 
disorders. Participants will always be accompanied in the chamber and will be reassured 
by highly trained staff. The chamber is very large (23 feet long and 7 feet in diameter) 
and is similar in size to a small aircraft cabin. Participants can terminate the exposure at 
any time and be removed from the chamber with a simple request. Participants can 
terminate the exposure and be removed from the chamber even there are non-study 
patients in the chamber at the same time.  
 
Hypoglycemia: HBO2 has been reported to decrease blood glucose in patients with DM. 
The hyperbaric department will follow their hypoglycemia protocol and provide 
supplemental carbohydrates if blood glucose is low either before or during HBO2  
 
Oxygen related seizure: Seizures occurring while someone is in a hyperbaric chamber 
are extremely uncommon and range from 0.02% - 0.04% in patients undergoing 
hyperbaric oxygen treatments at 2.0 to 2.5 ATA (Camporesi, E.M., 2014; Jokinen-
Gordon, et al., 2017). The risk of seizures is increased with baseline neurologic disease 
and prior history of seizures. Screening will be done to determine if there is any 
increased risk by way of history taking and physical exam. A spontaneous oxygen 
seizure, should it occur, is self-limited and does not result in any long-term neurologic 
sequelae. The risk of seizure is only while someone is in the chamber and breathing 
oxygen. There is no risk after the hyperbaric exposure.  
 
Oxygen related visual acuity changes: Hyperoxic myopia is a phenomenon that occurs 
after repeated hyperbaric exposures to 100% oxygen and is not a risk for study 

December 4, 2019 
 
14 
 
participants as it does not typically present until individuals have had several weeks of 
HBO2.  
 
Pneumothorax: Pneumothorax, or collapsed lung, occurs in the extremely rare 
instances when individuals who have air-filled cysts in the lungs are exposed to rapidly 
changing pressures. Potential participants will be screened to make sure they have no 
history of lung disease. Pneumothorax is an extremely rare situation that requires 
medical and/or surgical treatment, such as inserting a tube through the skin into the 
chest to re-expand the collapsed lung.  
 
Arterial gas emboli: Arterial gas emboli can form if an individual holds their breath 
while the pressure in the chamber is reduced, causing lung air sacs to rupture, releasing 
gas bubbles into the chest, neck, and blood. The gas bubbles may travel through the 
arteries and cause a blockage of blood-flow to the heart, brain, or other organs, and a 
heart attack or stroke may occur. Arterial gas emboli are extremely rare in the 
hyperbaric chamber because of the control and monitoring of change of depth and can 
be successfully treated by prompt recompression with hyperbaric oxygen.  
 
Fire hazard: A risk unique to the hyperbaric chamber is the risk of injury due to fire as a 
result of elevated oxygen levels. Because of this, there are limits around what electronic 
devices are allowed in the hyperbaric chamber. Due to this inherent risk, our research 
team has taken measures to minimize risk of fire. Participants will not be allowed to 
take any electronic device (phone, computer, pager, etc.) into the chamber. The 
hyperbaric chamber has fire suppression equipment and the staff is trained how to 
respond in the event of this extremely rare event.  
 
There has never been a fire in a clinical multiplace chamber in the United States.  

December 4, 2019 
 
15 
 
 
Risks of Continuous Glucose Monitoring 
The Dexcom Continuous Glucose Monitoring System described in this protocol is 
considered by the Sponsor to be of non-significant risk as it does not meet the definition 
of a significant risk device per 21 CFR 812.3(m), in that: 
• It is not an implant nor presents a potential for serious risk to the health, safety 
or welfare of a subject; 
• CGM devices are not purported or represented to be for use in supporting or 
sustaining human life and thus do not present a potential for serious risk to the 
health, safety, or welfare of a subject; or 
• Use of CGM devices does not present a potential for serious risk to the health, 
safety or welfare of a subject.  
There is a very low risk of developing a local skin infection at the site of the sensor 
placement and a very low risk of sensor breakage. The participant will be instructed to 
notify study staff if they develop swelling, redness, or pain at the sensor insertion site. 
Adverse Events 
We will catalog adverse events associated with HBO2 (e.g., otic/sinus barotrauma, O2 
toxicity, confinement anxiety) or severe hypoglycemia (BG < 70 mg/dL) associated with 
HBO2. We will report any complications related to the insertion of the CGM or 
fingersticks related to home glucose testing. Asymptomatic patients with a BG <100 

December 4, 2019 
 
16 
 
mg/dL will not be considered an adverse outcome associated with HBO2 but will be 
counted for analysis. 
Analysis 
Endpoint 1 
In order to determine the accuracy of the G6 CGM in patients with diabetes who are 
receiving HBO2, we will compare CGM values to laboratory results in the pre-HBO2 NBAir 
(1-3), HBO2 (4-9), and post-HBO2 NBAir (10-12) phases. We will compare the mean 
absolute relative difference (MARD), which is listed at 9.9% in the Dexcom G6 user guide 
and has a standard deviation of 7.99 mg/dL. If we are trying to detect a difference of 5 
percentage points in MARD (9.9% in room air up to 14.9% in HBO2) with a standard 
deviation of 8 mg/dL, alpha level (p<0.05), and a power of 0.80, we will require a 
minimum sample size of 18 patients.  
 
Endpoint 2 
We will compare CGM and venous blood glucose readings before (1-3), and after (10-12) 
each study session and use this to determine if there is any effect of session type (HBO2 
vs control) on BG. Each individual will serve as their own control, which will improve the 
study’s power. We will determine if the BG changes observed during HBO2 sessions are 
greater than those observed when the participants are sitting quietly outside the 
chamber during the control sessions. Linear mixed effects regression (LMER) analyses 
will be used to account for the clustering of data within an individual while also allowing 
for the main effect (difference in pre- vs. post- by session type) to be determined. 
 
Endpoint 3 
We will evaluate whether a single HBO2 treatment affects glucagon levels by comparing 
control glucagon levels with the pre-, intra-, and post-HBO2 glucagon levels. 

December 4, 2019 
 
17 
 
Estimated time to conduct study 
• Once approved, we will begin recruiting participants and anticipate 2 weeks 
before the first individual is enrolled. 
• We will be able to accommodate up to 2-4 participants per week, which should 
allow us to complete testing in 12-24 weeks. 
• We estimate a total time to complete the study of approximately 30 weeks. 
 
 
 

December 4, 2019 
 
18 
 
Budget 
 
Description
Unit Price
Quantity
Total
Equipment
Dexcom G6 CGM Sensors and CGM
24
-
$                     
Dexcom G6 Data Sensors and Logger
24
-
$                     
Oxygen Hoods and Neck Rings (1 per subject)
125.00
$          
24
3,000.00
$          
Laboratory Glucose Testing (24 per subject)
5.11
$               
576
2,943.36
$          
Laboratory Glucagon Testing (6 per subject)
20.00
$             
144
2,880.00
$          
Laboratory Hba1c (1x per subject)
15.00
$             
24
360.00
$              
Subtotal
8,823.36
$          
Administrative Fees
IRB Initial Application Fee
2,500.00
$       
1
2,500.00
$          
IRB Preparation Fee
750.00
$          
1
750.00
$              
IRB Closure Fee
750.00
$          
1
750.00
$              
Stipend for research subjects
400.00
$          
24
9,600.00
$          
Subtotal
13,600.00
$       
Salary Support
Research Coordinator subject recruitment (20 hours)
45.00
$             
20
900.00
$              
Research Coordinator (Informed consent - 1 hr, data collection 
6 hrs, data entry 1 hr) = 8 hrs/subject x 24
45.00
$             
192
8,640.00
$          
Research Coordinator (IRB and Consent Preparation - 10 hrs)
45.00
$             
10
450.00
$              
Laboratory Runner for Glucagon Samples ($25/specimen x 3)
75.00
$             
24
1,800.00
$          
Biostatistician support (Demirel) and manuscript writing
86.32
$             
64
5,524.48
$          
Legacy Research Institute Overhead (35% of salary support)
6,060.07
$       
1
6,060.07
$          
Hyperbaric Chamber Operator - 3 hours per subject per 
exposures x 24
30.00
$             
72
2,160.00
$          
Hyperbaric Outside Observer - 4 hours per subject x 24
30.00
$             
72
2,160.00
$          
Hyperbaric Inside Observer (RN) for phlebotomy - 3 hours per 
subject x 24
60.00
$             
72
4,320.00
$          
Research Coordinator (RN) for phlebotomy during control 
period - 3 hours per subject x 24
60.00
$             
72
4,320.00
$          
Investigator Support (Huang) @ $150/hour (Supervision of 
hyperbaric exposure x 3 hours per subject [24] x 1 HBOT or 
control sessions, plus primary manuscript writing - 20 hrs)
150.00
$          
92
13,800.00
$        
Investigator Support (Savaser) @ $150/hour (Supervision of 
hyperbaric treatment x 3 hours per subject [24] x 1 HBOT or 
control sessions, plus manuscript writing)
150.00
$          
72
10,800.00
$        
Investigator Support (Castle) @ $150/hour (Consultation, 
manuscript writing)
150.00
$          
20
3,000.00
$          
Subtotal
63,934.55
$       
Total
86,357.91
$       

December 4, 2019 
 
19 
 
References 
1. 
Margolis DK MD, Hoffstad, OJ. Prevalence of diabetes, diabetic foot ulcer, and 
lower extremity amputation among Medicare beneficiaries, 2006 to 2008. 
Diabetic Foot Ulcers. Data Points #1 (prepared by the University of Pennsylvania 
DEcIDE Center, under Contract No. HHSA29020050041I). Agency for Healthcare 
Research and Quality.;2011. 
2. 
Margolis DK MD, Hoffstad, OJ. Incidence of diabetic foot ulcer and lower 
extremity amputation among Medicare beneficiaries, 2006 to 2008. Data Points 
#2 (prepared by the University of Pennsylvania DEcIDE Center, under Contract 
No. HHSA29020050041I). Agency for Healthcare Research and Quality;2011. 
3. 
Boyko EJ, Ahroni JH, Cohen V, Nelson KM, Heagerty PJ. Prediction of diabetic 
foot ulcer occurrence using commonly available clinical information: the Seattle 
Diabetic Foot Study. Diabetes care. 2006;29(6):1202-1207. 
4. 
Huang ET, Mansouri J, Murad MH, et al. A clinical practice guideline for the use 
of hyperbaric oxygen therapy in the treatment of diabetic foot ulcers. Undersea 
Hyperb Med. 2015;42(3):205-247. 
5. 
Stevens SL, Narr AJ, Claus PL, et al. The incidence of hypoglycemia during HBO2 
therapy: A retrospective review. Undersea Hyperb Med. 2015;42(3):191-196. 
6. 
Al-Waili NS, Butler GJ, Beale J, et al. Influences of hyperbaric oxygen on blood 
pressure, heart rate and blood glucose levels in patients with diabetes mellitus 
and hypertension. Arch Med Res. 2006;37(8):991-997. 
7. 
Trytko B. Does hyperbaric oxygen affect blood sugar levels in diabetics? (Abstract 
only). South Pacific Underwater Medicine Society (SPUMS) Journal. 2002;32(3):1. 
8. 
Stevens SL, Sorita A, Narr AJ, et al. Applying quality improvement methods in a 
hyperbaric oxygen program: reducing unnecessary glucose testing. Undersea 
Hyperb Med. 2016;43(4):427-435. 
9. 
Heyboer M, Wojcik SM, Swaby J, Boes T. Blood glucose levels in diabetic patients 
undergoing hyperbaric oxygen therapy. Undersea and Hyperbaric Medicine. 
2019;46(4):437-445. 
10. 
Seaquist ER, Anderson J, Childs B, et al. Hypoglycemia and diabetes: a report of a 
workgroup of the American Diabetes Association and the Endocrine Society. 
Diabetes Care. 2013;36(5):1384-1395.