Outcomes of hyperbaric oxygen treatment for central and branch retinal artery occlusion at a major Australian referral hospital.

Introduction: This study analysed the treatment outcomes of patients that received hyperbaric oxygen treatment (HBOT) for retinal artery occlusion (RAO) at the Royal Brisbane and Women's Hospital in Brisbane, Australia between 2015 and 2021. Methods: Retrospective study from patient records including 22 eyes from 22 patients that received HBOT for either central RAO (17 patients) or branch RAO (five patients). Patients received the Royal Brisbane and Women's Hospital RAO protocol for their HBOT. Analysis included best corrected visual acuity pre- and post-treatment, subjective improvements, side effects and patient risk factors were also recorded. Results: Improvement in best corrected visual acuity was LogMAR -0.2 for central RAO on average with 8/17 (47%) experiencing objective improvement, 5/17 (29%) experienced no change and 4/22 (24%) experienced a reduction in best corrected visual acuity. Subjective improvement (colour perception or visual fields) was reported in an additional 4/17 patients, resulting in 12/17 (71%) reporting improvement either in visual acuity or subjectively. There was no improvement in the best corrected visual acuity of any of the five patients suffering from branch RAO. Cardiovascular risk factors present in the cohort included hypertension, hypercholesterolaemia, previous cardiovascular events, cardiac disease and smoking. Limited side effects were experienced by this patient cohort with no recorded irreversible side effects. Conclusions: Hyperbaric oxygen treatment appears a safe, beneficial treatment for central RAO. No benefit was demonstrated in branch RAO although numbers were small. Increased awareness of HBOT for RAO resulting in streamlined referrals and transfers and greater uptake of this intervention may further improve patient outcomes.

Contemporary practices of blood glucose management in diabetic patients: a survey of hyperbaric medicine units in Australia and New Zealand.

Introduction: Blood glucose levels may be influenced by hyperbaric oxygen treatment (HBOT). Patients with diabetes mellitus commonly receive HBOT but there is a lack of standardised blood glucose management guidelines. We documented relevant contemporary practices applied for patients with diabetes treated in hyperbaric medicine units. Methods: A survey was administered in 2022 to the directors of all 13 accredited hyperbaric units in Australia and New Zealand to identify policies and practices related to management of patients with diabetes receiving HBOT. Results: Twelve of the 13 units routinely managed patients with diabetes. Three-quarters (9/12) used < 4 mmol·l-1 as their definition of hypoglycaemia, whereas the other three used < 5, < 3.6, and < 3 mmol·l-1. Units reported 26% (range 13-66%) of their patients have a diagnosis of diabetes of which 93% are type 2. Ten (83%) units reported specific written protocols for managing blood glucose. Protocols were more likely to be followed by nursing (73%) than medical staff (45%). Ten (83%) units routinely tested blood glucose levels on all patients with diabetes. Preferred pre-treatment values for treatments in both multiplace and monoplace chambers ranged from ≥ 4 to ≥ 8 mmol·l-1. Seven (58%) units reported continuation of routine testing throughout a treatment course with five (42%) units having criteria-based rules for discontinuing testing for stable patients over multiple treatments. Two-thirds of units were satisfied with their current policy. Conclusions: This survey highlights the burden of diabetes on patients treated with HBOT and identifies considerable variability in practices which may benefit from further study to optimise management of these patients.

The effectiveness of hyperbaric oxygen therapy for healing chronic venous leg ulcers: A randomized, double-blind, placebo-controlled trial.

Over 30% of venous leg ulcers do not heal despite evidence-based treatment. This study aimed to determine the effectiveness of Hyperbaric Oxygen Therapy (HBOT) as an adjunct treatment for nonhealing venous leg ulcers. A randomized, double-blind, parallel group, placebo-controlled trial was undertaken in three hyperbaric medicine units. Adults with a venous leg ulcer, Transcutaneous Oxygen Measurement indicative of a hypoxic wound responsive to oxygen challenge, and without contraindications for HBOT; were eligible. Of 84 eligible patients, 10 refused and 74 enrolled. 43 participants achieved over 50% ulcer Percent Area Reduction (PAR) after four weeks of evidence-based care and were thus excluded from the intervention phase. Thirty-one participants were randomized to either 30 HBOT treatments (100% oxygen at 2.4 atmospheres absolute (ATA) for 80 minutes), or 30 "placebo" treatments, receiving a validated "sham" air protocol, initially pressurized to 1.2ATA, then cycled between 1.05-1.2ATA for eight minutes before settling at 1.05ATA. The primary outcome was numbers in each group completely healed. Secondary outcomes were ulcer PAR, pain and quality of life, 12 weeks after commencing interventions. The participants' mean age was 70 years (standard deviation (SD) 12.9) and median ulcer duration at enrolment was 62 weeks (range 4-3120). At 12 weeks, there was no significant difference between groups in the numbers completely healed. The HBOT intervention group had a mean of 95 (SD 6.53) ulcer PAR, compared to 54 (SD 67.8) mean PAR for the placebo group (t = -2.24, p = 0.042, mean difference -40.8, SE 18.2) at 12 weeks. HBOT may improve refractory healing in venous leg ulcers, however patient selection is important. In this study, HBOT as an adjunct treatment for nonhealing patients returned indolent ulcers to a healing trajectory.

Hyperbaric oxygen therapy in the treatment of sudden sensorineural hearing loss: a retrospective analysis of outcomes.

OBJECTIVE: To analyse predictive factors affecting outcome after treatment with hyperbaric oxygen (HBOT) in patients with idiopathic sudden sensorineural hearing loss (ISSHL). METHODS: This is a retrospective audit of outcome in 77 consecutive patients referred for consideration of HBOT for ISSHL for either adjunctive treatment or after failure of steroid therapy. The hearing measured from the pre- and post-HBOT pure-tone audiogram (PTA4) at four frequencies; 500 Hz, 1 kHz, 2 kHz and 4 kHz, was averaged and compared. The PTA4 score was classified into three groups: complete improvement (≤ 25 dB residual hearing loss); moderate improvement (11-50 dB gain) and no improvement (≤ 11dB gain). Data were also analysed using mean residual loss on completion as the outcome measure. RESULTS: Seventy-six patients underwent 1,029 HBOT sessions. Twenty five of 78 ears (33%) had complete resolution of deafness after HBOT. A further 31 (40%) had a significant improvement in PTA4. Delay (〉 28 days) and older age were associated with worse outcomes in PTA4 improvement. Those with less severe hearing loss and short delay (〈 15 days) had the best outcome (mean residual loss 28 dB). Eight of nine patients who were delayed 〉 28 days had no improvement in PTA4. CONCLUSIONS: Fifty-six of 76 (74%) patients had complete (25) or moderate (31) improvement in hearing loss after HBOT. Short delay to HBOT, a severer degree of hearing loss and younger age were the best predictive factors of improved PTA4. Outcome was poor if treatment was delayed over 28 days. Well-designed randomised controlled trials are needed to clarify the role of HBOT and steroids.