Hyperbaric oxygen for sudden hearing loss: Influence of international guidelines on practice in Australia and New Zealand.

INTRODUCTION: Idiopathic sudden sensorineural hearing loss (ISSHL) is an otolaryngologic emergency. The Undersea and Hyperbaric Medicine Society (UHMS) revised practice guidelines in 2014 adding ISSHL to approved indications. This study investigated whether the UHMS guidelines influenced referral and practice in Australia and New Zealand. METHODS: Retrospective review of 319 patient referrals in two time periods (five years prior to addition of ISSHL to indications (T-PRE) and three years post (T-POST)). RESULTS: Seven of eight participating hyperbaric facilities provided data down to the level of the indication for HBOT for analysis. In T-PRE 136 patients were treated with HBOT for ISSHL, representing between 0% and 18% of the total cases to each facility. In the T-POST period 183 patients were treated for ISSHL, representing from 0.35% to 24.8% of the total patients in each facility. Comparison between the two periods shows the proportion of patients treated with ISSHL among all indications increased from 3.2% to 12.1% (P < 0.0009). One facility accounted for 74% (101/136) of ISSHL patients receiving HBOT in T-PRE and 63% (116/183) in T-POST. ISSHL case load at that facility increased from 18% to 24.8% (P = 0.009) after the UHMS guideline publication. Three of the seven units had a significant increase in referrals after the guideline change. CONCLUSION: There remains equipoise regarding HBOT in the management of ISSHL. Only three out of seven units had a significant increase in ISSHL patients after the UHMS guidelines publication. Without well controlled RCTs to develop guidelines based on good evidence this is unlikely to change and practice variation will continue.

Hyperbaric oxygen treatment for the management of radiation-induced xerostomia.

INTRODUCTION: Hyperbaric oxygen therapy (HBOT) is widely used for the treatment of the late effects of radiation therapy. We report a prospective observational cohort study of 51 patients designed to examine the effectiveness of hyperbaric oxygen treatment (HBOT) for xerostomia following radiotherapy. METHODS: Objective (saliva volume) and subjective (quality of life scoring and visual analogue scale (VAS) of discomfort) measurements associated with xerostomia were compared prior to commencement of HBOT, after 30 sessions (over 6 weeks) of HBOT at 243 kPa for 90 minutes daily for five days per week and at 6-week review (12 weeks from commencement). RESULTS: One hundred and one courses of treatment in 99 patients were examined. For 53 (53%) courses in 51 patients, data were recorded before and after HBOT and so could be included in the analysis. Thirty-four (34%) of these patients had complete data for all three time points. The unit of study was per treatment course, not per person. There were no major complications to HBOT. There was a statistically significant difference in saliva volume following HBOT (P = 0.016). The mean saliva volume increase was 0.9 mL over a 5-min collection period (95% CI 0.2-1.5). There was also a statistically significant improvement in discomfort after HBOT (P < 0.001) and QOL (P < 0.001). The mean visual analogue scale for discomfort (VAS on a 0-10 scale) score decreased by 1.4 units (95% CI 0.7-2.1), whilst the mean QOL score was 10 points lower after treatment (95% CI 5.9-14.4). CONCLUSION: Hyperbaric oxygen therapy may be a safe and effective treatment for symptoms of xerostomia after radiation therapy and should be considered when available.

Audit of practice in Australasian hyperbaric units on the incidence of central nervous system oxygen toxicity.

INTRODUCTION: Central nervous system oxygen toxicity (CNS-OT) is an uncommon complication of hyperbaric oxygen treatment (HBOT). Different facilities have developed local protocols in an attempt to reduce the risk of CNS-OT. This audit was performed to elucidate which protocols might be of benefit in mitigating CNS-OT and to open discussion on adopting a common protocol for Treatment Table 14 (TT14) to enable future multicentre clinical trials. METHODS: Audit of CNS-OT events between units using different compression profiles for TT14, performed at 243 kPa with variable durations of oxygen breathing and 'air breaks', to assess whether there is a statistical diference between protocols. Data were collected retrospectively from public and private hyperbaric facilities in Australia and New Zealand between 01 January 2010 and 31 December 2014. RESULTS: Eight of 15 units approached participated. During the five-year period 5,193 patients received 96,670 treatments. There were a total of 38 seizures in 33 patients when all treatment pressures were examined. In the group of patients treated at 243 kPa there were a total of 26 seizures in 23 patients. The incidence of seizure per treatment was 0.024% (2.4 per 10,000 treatments) at 243 kPa and the risk per patient was 0.45% (4.5 in 1,000 patients). There were no statistically significant differences between the incidences of CNS-OT using different TT14 protocols in this analysis. CONCLUSION: HBOT is safe and CNS-OT is uncommon. The risk of CNS-OT per patient at 243 kPa was 1 in 222 (0.45%; range 0-1%) and the overall risk irrespective of treatment table was 0.6% (range 0.31-1.8%). These figures are higher than previously reported as they represent individual patient risk as opposed to risk per treatment. The wide disparity of facility protocols for a 243 kPa table without discernible influence on the incidence of CNS-OT rates should facilitate a national approach to consensus.

ECHM Consensus Conference and levels of evidence.

The ECHM Consensus Conference on indications for hyperbaric oxygen treatment (HBOT) was a welcome update of the evidence for HBOT use. However, clarification is requested in relation to how the GRADE system (Grades of Recommendation, Assessment, Development and Evaluation) was modified and how levels of evidence were applied in the case of idiopathic sudden sensorineural hearing loss (ISSHL). GRADE has a low kappa value for inter-observer agreement, so is modification valid? The original GRADE criteria, using consensus, grades evidence (defined as high, low and very low) and uses this to adjust the strength of recommendations. Randomised controlled trials (RCTs) score highly. The ECHM have modified the GRADE system without explanation, assigning grades as levels 1 to 4 and have asserted that RCTs which are double-blinded constitute level 1 or 2 evidence. This has important implications for HBOT research. The term double-blinded is not used in the abstract, which leads the reader to wonder; where do RCTs which are not double-blinded fit in? The ECHM, by including the term double blinded as a requirement for level 1 or 2, has lifted the evidence bar. Does this constitute a form of research "bracket creep"? Double-blinding is viewed by many to require a 'sham' treatment in hyperbaric research. Many conditions require multiple doses requiring daily hospital attendance with associated costs of lost time from work and daily transport costs. Even with a crossover after the sham, a requirement of many ethics committees, the lost time for a patient is a considerable burden. Delaying HBOT until crossover in those randomised to the control group in a disease that has a narrow therapeutic temporal window, such as idiopathic sudden sensorineural hearing loss (ISSHL), may affect the chance of recovery. Double blinding is logistically difficult with HBOT. A sham treatment may be achieved by using air instead of oxygen; however, this exposes the non-intervention group to a risk that the intervention group does not have, that of decompression sickness (DCS). This may be considered to be unethical. Researchers have used hypoxic air mixtures to compensate for the higher oxygen partial pressure at depth as the control, but this is complex and increases the nitrogen load (and thus the risk of DCS). RCTs which control by other methods should still be considered high level evidence (as the original GRADE system recognised). Many indications for HBOT have multiple therapies against which to compare, which could act as a control. The requirement for double-blinding to achieve level 1 or 2 evidence may hamper research; an unintended negative consequence. There is lack of consistency of definitions in relation to levels of evidence used by the ECHM. The authors state that for clinical research the levels of evidence are; levels A to F, which they defined. The ECHM jury used a grading scale of level 1 to 4. For ISSHL, this results in a recommendation to treat based on level B evidence. Is this the same as level 2 in their modified system? This is confusing. The authors have not explained why they modified the GRADE system which is itself non-validated. The lack of references to the publications which provide the foundation for the strength of the recommendations leaves the reader unable to determine the true strength of the evidence. The GRADE system has been criticised as it dissociates recommendations from the evidence that the recommendation is founded upon. Further, the application of the GRADE system has been questioned when strong recommendations are made with it as this may cause ethics committees to question whether equipoise exists, further hampering research. How do we present a well-designed trial for ISSHL to an ethics committee when a strong recommendation has already been made despite the Cochrane review on ISSHL concluding there is a need for large, well designed RCTs in this area?

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.