Alternative Uses of Hyperbaric Oxygen Therapy in Military Medicine: Current Positions and Future Directions
Authors: Biggs Adam T , Littlejohn Lanny F , Dainer Hugh M 
Published: February 2021

ABSTRACT

Introduction
Hyperbaric oxygen therapy (HBOT) is a commonly used treatment for a variety of medical issues, including more than a dozen currently approved uses. However, there are alternative proposed uses that have significant implications among an active duty military or veteran population as treatments for PTSD, mild traumatic brain injury (mTBI), and traumatic brain injury (TBI). These applications have seen a recent groundswell of support from the operator and veteran communities, raising the visibility of using HBOT for alternative applications. The current review will cover the existing evidence regarding alternative uses of HBOT in military medicine and provide several possibilities to explain the potential conflicting evidence from empirical results.

Materials and Methods
There were no inclusion or exclusion criteria for articles addressing currently approved HBOT uses as covered under the military health system. These references were provided for comparison and illustration as needed. For alternative HBOT uses, the review focuses explicitly upon three alternative uses in PTSD, mTBI, and TBI. The review addresses any piece of case study evidence, observational data, quasi-experimental design, or randomized-controlled trial that explored any or a combination of these issues within an active duty population, a veteran population, or a civilian population.

Results
The existing medical evidence does not support a consensus viewpoint for these alternative uses of HBOT. Based on the literature review, there are four competing positions to explain the lack of consistency among the empirical results. These possibilities are described in no particular order. First, an explanation suggests that the results are because of placebo effects. The combination of participant expectations and subjective symptom reporting creates the potential that reported improvements are because of placebo rather than casual mechanisms. Second, another position suggests that experiments have utilized sham conditions which induced therapeutic benefits. If sham conditions have actually been weakened active treatment conditions, rather than placebo controls, it could explain the lack of observed significant differences in randomized clinical trials. Third, there has been a substantial amount of heterogeneity both in the symptoms treated and the treatments applied. This heterogeneity could explain the inconsistency of the data and the difficulty in reaching a consensus viewpoint. Fourth, the HBOT treatments may actively treat some tangential medical issue the patient is having. The treatment would thus promote an environment of healing without directly treating either PTSD, mTBI, or TBI, and the reduction in orthogonal medical issues facilitates a pathway to recovery by reducing tangential medical problems.

Conclusions
The mixed empirical evidence does not support recommending HBOT as a primary treatment for PTSD, mTBI, or TBI. If applied under the supervision of a licensed military medical professional, the consistently safe track record of HBOT should allow it to be considered as an alternative treatment for PTSD, mTBI, or TBI once primary treatment methods have failed to produce a benefit. However, the evidence does warrant further clinical investigation with particular emphasis on randomized clinical trials, better placebo controls, and a need to develop a consistent treatment protocol.