The purpose of this Research Study is:

1. To determine the reliability and performance of the Dexcom G6® continuous glucose
monitoring (CGM) system in patients with diabetes undergoing hyperbaric oxygen (HBO2)
exposure. The study-specific blood glucose meter and CGM system are approved by the FDA
(U.S. Food and Drug Administration).

2. To determine whether HBO2 exposure causes blood glucose to drop as a result of the
treatment.

3. To determine whether HBO2 causes a change in blood glucagon (a hormone that raises blood
glucose).

Investigators will be comparing changes in blood glucose and glucagon in volunteers with
diabetes who will be exposed to a single hyperbaric oxygen treatment (pressurization to 2.4
atmospheres absolute for 90 minutes) to a control period of 2 hours where volunteers will
simulate a hyperbaric treatment while sitting in an examination room breathing room air at
sea level pressure. Investigators will be measuring blood glucose with a variety of devices
including a continuous glucose monitor, two point-of-care glucometers, and the hospital
inpatient laboratory measurement of venous blood.