Hyperbaric Oxygen Therapy for Nonhealing Wounds-A Long-term Retrospective Cohort Study.

OBJECTIVE: To analyze wound healing results of hyperbaric oxygen therapy (HBOT) for a variety of different wound types. METHODS: This retrospective cohort study included all patients treated with HBOT and wound care at a single hyperbaric center between January 2017 and December 2020. The primary outcome was wound healing. Secondary outcome measures were quality of life (QoL), number of sessions, adverse effects, and treatment cost. Investigators also examined possible influencing factors, including age, sex, type and duration of wound, socioeconomic status, smoking status, and presence of peripheral vascular disease. RESULTS: A total of 774 treatment series were recorded, with a median of 39 sessions per patient (interquartile range, 23-51 sessions). In total, 472 wounds (61.0%) healed, 177 (22.9%) partially healed, 41 (5.3%) deteriorated, and 39 (5.0%) minor and 45 (5.8%) major amputations were performed. Following HBOT, median wound surface area decreased from 4.4 cm 2 to 0.2 cm 2 ( P < .01), and patient QoL improved from 60 to 75 on a 100-point scale ( P < .01). The median cost of therapy was €9,188 (interquartile range, €5,947-€12,557). Frequently recorded adverse effects were fatigue, hyperoxic myopia, and middle ear barotrauma. Attending fewer than 30 sessions and having severe arterial disease were both associated with a negative outcome. CONCLUSIONS: Adding HBOT to standard wound care increases wound healing and QoL in selected wounds. Patients with severe arterial disease should be screened for potential benefits. Most reported adverse effects are mild and transient.

Hyperbaric oxygen therapy for nonhealing wounds: Treatment results of a single center.

The present article evaluates the results of the treatment with adjuvant hyperbaric oxygen therapy (HBOT) of patients with nonhealing, chronic wounds. In the period 2013 to 2016, 248 patients were referred from various hospitals because of chronic wounds that were recalcitrant in healing despite standard wound care as described in national and international guidelines. After inclusion, all patients were treated with HBOT and subjected to a weekly standard wound care treatment. During each HBOT session, 100% O2 was administered for 75 minutes under increased pressure of 2.4 ATA. Wounds and quality of life were assessed before and after the total treatment period. A total of 248 patients have been evaluated. Diabetic foot ulcers were present in 134 patients, the remainder (114 patients) showed a variety of wound locations and etiologies. The number of HBOT treatments amounted to an average of 48 (range 20-68) sessions. Before referral to our clinic, 31% of all wounds had existed for at least 18 months (72 patients). After HBOT, 81% of all wounds were near complete healing or completely healed, in 13% of the cases the wound was stable, and in 2% minor or major amputation had to be carried out. The mean treatment time for wounds pre-existing fewer than 6 weeks ("early referrals") was 67 days, and 119 days for wounds pre-existing more than 18 months ("late referrals"). A majority of the patients in our study referred with nonhealing wounds clinically improved when adjuvant HBOT was added to standard wound care protocols. No differences in success rate were seen between diabetic and nondiabetic wounds. It showed that HBOT is a well-tolerated treatment.

Hyperbaric oxygen treatment for University of Texas grade 3 diabetic foot ulcers: a retrospective cohort study.

AIM: Hard-to-heal diabetic foot ulcers (DFUs) may increase the risk of amputation. This study reports the positive influence of hyperbaric oxygen therapy (HBOT) on hard-to-heal DFUs involving underlying bone. METHOD: A single-centre, retrospective cohort study reporting the results of HBOT and wound care on hard-to-heal University of Texas grade 3 DFUs (i.e., involving underlying bone) between 2013 and 2019. Outcome measures were primarily (near-) complete wound healing (i.e., ≥80% ulcer surface area reduction) and amputation rate (minor or major), and secondarily the number of hyperbaric sessions and improvement in quality of life (QoL) and pain score. RESULTS: The study included 206 patients, of whom 74 (36%) achieved complete wound healing, and 75 (36%) near-complete healing. Amputations were performed in 27 patients (13%): 12 (6%) minor and 15 (7%) major. The median number of HBOT sessions was 42. Participants who achieved complete healing received a median of 43 sessions, compared with 10 for those who required major amputation. Patients with at least 30 sessions were less likely to undergo amputation (odds ratio: 0.08; 95% confidence interval (CI): 0.03-0.21). Mean QoL increased by 7.6 points (95%CI: 3.9-11.3; p<0.01) and median pain score fell from 3 to 1 (0-3) (p<0.01). CONCLUSIONS: The addition of HBOT to standard wound care may lead to a decreased amputation risk, improved wound healing and increased QoL for people with a University of Texas grade 3 DFU. An adequate number of HBOT sessions is required to achieve optimal clinical results. Objective selection criteria and shared decision-making are suggested to improve dropout rates.

A systematic review and meta-analysis of hyperbaric oxygen therapy for diabetic foot ulcers with arterial insufficiency.

BACKGROUND: Diabetic foot ulcers (DFUs) are frequently associated with peripheral arterial occlusive disease (PAOD) and may ultimately lead to amputations of the lower extremity. Adjuvant hyperbaric oxygen treatment (HBOT) might foster better wound healing and lower amputation rates in patients with DFU and PAOD. A systematic review was conducted to assess the effects of HBOT as an adjunctive therapy to standard treatment for patients with DFUs with PAOD. METHODS: Systematic review using the MEDLINE, EMBASE, and Cochrane CENTRAL databases (from inception to October 2018). All original, comparative studies on the effect of HBOT on DFUs with PAOD were eligible. The primary outcome measures were amputation rate, amputation-free survival, complete ulcer healing, and mortality. RESULTS: Eleven studies, totaling 729 patients, were included for analysis, including 7 randomized clinical trials, 2 controlled clinical trials, and 2 retrospective cohorts. Four were used for quantitative synthesis. Meta-analysis showed a significantly fewer major amputations in the HBOT group (10.7% vs 26.0%; risk difference, -15%; 95% confidence interval [CI], -25 to -6; P = .002; number needed to treat, 7; 95% CI, 4-20). No difference was found for minor amputations (risk difference, 8%; 95% CI, -13 to 30; P = .46). Three studies reporting on complete wound healing showed contrasting results. No significant difference was found for mortality or amputation-free survival. CONCLUSIONS: Current evidence shows that adjuvant HBOT improves major amputation rate, but not wound healing, in patients with DFUs and PAOD. Given the wide range of patients included in the trials, better patient selection may help define which patients with DFUs and PAOD benefit most from HBOT as standard adjunctive treatment.

Hyperbaric oxygen therapy for nonischemic diabetic ulcers: A systematic review.

Diabetic foot ulcers are a common complication of diabetes, which affects 25% of patients and may ultimately lead to amputation of affected limbs. Research suggests hyperbaric oxygen therapy improves healing of these ulcers. However, this has not been reflected in previous reviews, possibly because they did not differentiate between patients with and without peripheral arterial occlusive disease. Therefore, we performed a systematic review of published literature in the MEDLINE, Embase, and Cochrane CENTRAL databases on nonischemic diabetic foot ulcers with outcome measures including complete ulcer healing, amputation rate (major and minor), and mortality. Seven studies were included, of which two were randomized clinical trials. Two studies found no difference in major amputation rate, whereas one large retrospective study found 2% more major amputations in the hyperbaric oxygen group. However, this study did not correct for baseline differences. Two studies showed no significant difference in minor amputation rate. Five studies reporting on complete wound healing showed no significant differences. In conclusion, the current evidence suggests that hyperbaric oxygen therapy does not accelerate wound healing and does not prevent major or minor amputations in patients with a diabetic foot ulcer without peripheral arterial occlusive disease. Based on the available evidence, routine clinical use of this therapy cannot be recommended. However, the available research for this specific subgroup of patients is scarce, and physicians should counsel patients on expected risks and benefits. Additional research, focusing especially on patient selection criteria, is needed to better identify patients that might profit from this therapy modality.

Massive gas embolisms in diving fatalities visualized by radiology and neuropathology.

Massive vascular gas embolism is a feared and often lethal symptom of decompression illness, resulting from diving accidents. The aim of this case report was to correlate post-mortem computed tomography scan (PMCT) findings with autopsy in cases of massive vascular gas embolism. Two cases of fatal diving accidents were retrospectively selected from a forensic radiological pathological database. The PMCT results were initially shared with the forensic pathologist prior to autopsy, enabling a more accurate overall assessment. Both cases were in retrospect thoroughly studied to compare the PMCT findings with the autopsy results. In general, intra- and extra-vascular gas collections are easily detected on PMCT in all body regions. We focused on abundant intravascular gas collections, mainly in the large brain vessels. General autopsy findings are described in both cases, and in one case we elaborate on specific intracerebral changes found at autopsy. Both cases were diagnosed as pulmonary barotrauma with subsequent vascular gas embolisms. We conclude that PMCT excels in the detection of macroscopic gas collections in the body, whereas microscopic gas collections identified at autopsy aid in the differentiation between decompression sickness and pulmonary barotrauma followed by vascular gas embolism. The presented cases highlight the advantages of using both PMCT and autopsy in the post-mortem evaluation of fatal diving accidents.

Hyperbaric oxygen therapy in patients suffering from wounds in calciphylaxis: a narrative review.

Background: Calcific uremic arteriolopathy (calciphylaxis) is a rare and highly lethal vascular disease. Vascular calcification with calcium depositions lead to ischemic ulcers associated with gangrene, severe pain and poor healing. Although hyperbaric oxygen (HBO2) therapy has been used in the treatment of calciphylaxis, evidence of its effectiveness is limited. Objective: To determine whether HBO2 therapy has a beneficial effect in the healing of calciphylaxis ulcers. Methods: A search was made in PubMed using a comprehensive strategy to identify the effect of HBO2 on calciphylaxis wounds. Included in the analysis were studies published up to October 2018 involving a minimum of four patients receiving HBO2 therapy. Results: Ten retrospective (case) series were included. This review included a total of 131 patients with calciphylaxis who were treated with HBO2 therapy; of these, 58 patients (45%) had full response on HBO2 with complete wound closure. Regarding partial response, 17 of the patients (13%) experienced substantial wound improvement on different wound scale scores. Conclusion: Patients with calcific uremic arteriolopathy can benefit from HBO2. More research is needed using standardized wound scores. Outcomes related to quality of life and pain relief should also be assessed.

Double-blind trials in hyperbaric medicine: A narrative review on past experiences and considerations in designing sham hyperbaric treatment.

Background Hyperbaric oxygen therapy, which consists of breathing 100% oxygen under a higher atmospheric pressure than normal, is utilized worldwide in the treatment of several diseases. With the growing demand for evidence-based research, hyperbaric oxygen therapy has been criticized for delivering too little high-quality research, mainly in the form of randomized controlled trials. While not always indispensable, the addition of a sham-controlled group to such a trial can contribute to the quality of the research. However, the design of a sham (hyperbaric) treatment is associated with several considerations regarding adequate blinding and the use of pressure and oxygen. This narrative review discusses information on the sham profile and the blinding and safety of double-blind trials in hyperbaric medicine, irrespective of the indication for treatment. Methods MEDLINE, Embase and CENTRAL were searched for sham-controlled trials on hyperbaric oxygen therapy. The control treatment was considered sham if patients were blinded to their allocation and treatment took place in a hyperbaric chamber, with no restrictions regarding pressurization, oxygen levels or indication. Studies involving children or only one session of hyperbaric oxygen were excluded. Information on (the choice of) treatment profile, blinding measures, patient's perception regarding allocation and safety issues was extracted from eligible studies. Results A total of 42 eligible trials were included. The main strategies for sham treatment were (1) use of a lower pressure than that of the hyperbaric oxygen group, while breathing 21% oxygen; (2) use of the same pressure as the hyperbaric oxygen group, while breathing an adjusted percentage of oxygen; and (3) use of the same pressure as the hyperbaric oxygen group, while breathing 21% oxygen. The advantages and disadvantages of each strategy are discussed using the information provided by the trials. Conclusion Based on this review, using a lower pressure than the hyperbaric oxygen group while breathing 21% oxygen best matches the inertness of the placebo. Although studies show that use of a lower pressure does allow adequate blinding, this is associated with more practical issues than with the other strategies. The choice of which sham profile to use requires careful consideration; moreover, to ensure proper performance, a clear and detailed protocol is also required.

An observational study ascertaining the prevalence of bullae and blebs in young, healthy adults and its possible implications for scuba diving.

Introduction: Intrapulmonary air-filled cavities, e.g., bullae, blebs, and cysts, are believed to contribute topulmonary barotrauma (PBT) and arterial gas embolism (AGE) in divers. However, literature is unclear about the prevalence of bullae in healthy adults, ranging from 2.3-33.8%. While this could in part be explained due to increasing quality of radiologic imaging, such as computed tomography (CT) scans, other methodological factors may also affect these findings. This study aims to ascertain the prevalence of bullae in young and healthy adults. Methods: This single-center cross-sectional observational study re-assessed the CT scans of adults (aged 18-40) performed for a clinical suspicion for pulmonary embolism, from 1 January 2016 to 1 March 2020. Presence of bullae was recorded in an electronic database. Chi-square and Fisher exact tests were used for statistical analyses. Additionally, a multivariate logistic regression analysis was performed to study the independent predictive value of identified risk factors. Results: A total of 1,014 cases were identified, of which 836 could be included. Distribution amongst age groups (18-25, 26-30, 31-35, and 36-40) was almost equally, however, 75% of the population was female. Of the male proportion, 41% smoked, compared to 27% in females. In 7.2% (95% CI 5.6-9.1) bullae were identified. The prevalence increased with increasing age (p < 0.001), with odd ratios up to 5.347 (95% CI 2.164-13.213, p < 0.001) in the oldest age group. Males and smokers had higher odds ratios for bullae of 2.460 (95% CI 1.144-4.208; p = 0.001) and 3.406 (95% CI 1.878-6.157, p < 0.001), respectively. Similar results were seen in the multivariate logistic regression analysis, where age, male sex and smoking were all statistically significant independent risk factors for bullae. Discussion: Bullae were seen in 7.2% of a healthy population up to 40 years old. Increasing age, smoking, and being male were identified as statistically significant risk factors, both in independent and in multivariate logistic regression analyses. Our observations may warrant a re-evaluation of the contribution of bullae to PBT and AGE, as the latter two occur very rarely and bullae appear to be more frequently present than earlier assumed.

Chain of events analysis in diving accidents treated by the Royal Netherlands Navy 1966-2023.

Introduction: Diving injuries are influenced by a multitude of factors. Literature analysing the full chain of events in diving accidents influencing the occurrence of diving injuries is limited. A previously published 'chain of events analysis' (CEA) framework consists of five steps that may sequentially lead to a diving fatality. This study applied four of these steps to predominately non-lethal diving injuries and aims to determine the causes of diving injuries sustained by divers treated by the Diving Medical Centre of the Royal Netherlands Navy. Methods: This retrospective cohort study was performed on diving injuries treated by the Diving Medical Centre between 1966 and 2023. Baseline characteristics and information pertinent to all four steps of the reduced CEA model were extracted and recorded in a database. Results: A total of 288 cases met the inclusion criteria. In 111 cases, all four steps of the CEA model could be applied. Predisposing factors were identified in 261 (90%) cases, triggers in 142 (49%), disabling agents in 195 (68%), and 228 (79%) contained a (possible-) disabling condition. The sustained diving injury led to a fatality in seven cases (2%). The most frequent predisposing factor was health conditions (58%). Exertion (19%), primary diver errors (18%), and faulty equipment (17%) were the most frequently identified triggers. The ascent was the most frequent disabling agent (52%). Conclusions: The CEA framework was found to be a valuable tool in this analysis. Health factors present before diving were identified as the most frequent predisposing factors. Arterial gas emboli were the most lethal injury mechanism.

Volatile Organic Compounds in Cellular Headspace after Hyperbaric Oxygen Exposure: An In Vitro Pilot Study.

Volatile organic compounds (VOCs) might be associated with pulmonary oxygen toxicity (POT). This pilot study aims to identify VOCs linked to oxidative stress employing an in vitro model of alveolar basal epithelial cells exposed to hyperbaric and hyperoxic conditions. In addition, the feasibility of this in vitro model for POT biomarker research was evaluated. The hyperbaric exposure protocol, similar to the U.S. Navy Treatment Table 6, was conducted on human alveolar basal epithelial cells, and the headspace VOCs were analyzed using gas chromatography-mass spectrometry. Three compounds (nonane [p = 0.005], octanal [p = 0.009], and decane [p = 0.018]), of which nonane and decane were also identified in a previous in vivo study with similar hyperbaric exposure, varied significantly between the intervention group which was exposed to 100% oxygen and the control group which was exposed to compressed air. VOC signal intensities were lower in the intervention group, but cellular stress markers (IL8 and LDH) confirmed increased stress and injury in the intervention group. Despite the observed reductions in compound expression, the model holds promise for POT biomarker exploration, emphasizing the need for further investigation into the complex relationship between VOCs and oxidative stress.

[Cerebral arterial air embolism: the effect of hyperbaric oxygen therapy]. / Cerebrale arteriële luchtembolie.

BACKGROUND: Iatrogenic gas embolism is the presence of gas in vascular structures. Feared are those in coronary or cerebral arteries. These can result in cerebral or myocardial infarction. CASE DESCRIPTION: A 79-year-old female underwent CT-guided biopsy of the lung. Minutes later she developed neurological symptoms. After administration of oxygen her symptoms initially improved, but later worsened. Based on her symptoms air embolism was suspected. She recovered fully after treatment with hyperbaric oxygen. CONCLUSION: Air embolism is a potentially life-threatening complication of surgical, radiological or vascular interventions. Early recognition can lead to prompt treatment and better prognosis. If air embolism is suspected the patient should be treated according to ABCDE principles and oxygen should be administered. In case of neurological or circulatory symptoms a hospital that could provide hyperbaric oxygen therapy should be contacted as soon as possible.

Analysis of Volatile Organic Compounds in Exhaled Breath Following a COMEX-30 Treatment Table.

The COMEX-30 hyperbaric treatment table is used to manage decompression sickness in divers but may result in pulmonary oxygen toxicity (POT). Volatile organic compounds (VOCs) in exhaled breath are early markers of hyperoxic stress that may be linked to POT. The present study assessed whether VOCs following COMEX-30 treatment are early markers of hyperoxic stress and/or POT in ten healthy, nonsmoking volunteers. Because more oxygen is inhaled during COMEX-30 treatment than with other treatment tables, this study hypothesized that VOCs exhaled following COMEX-30 treatment are indicators of POT. Breath samples were collected before and 0.5, 2, and 4 h after COMEX-30 treatment. All subjects were followed-up for signs of POT or other symptoms. Nine compounds were identified, with four (nonanal, decanal, ethyl acetate, and tridecane) increasing 33-500% in intensity from before to after COMEX-30 treatment. Seven subjects reported pulmonary symptoms, five reported out-of-proportion tiredness and transient ear fullness, and four had signs of mild dehydration. All VOCs identified following COMEX-30 treatment have been associated with inflammatory responses or pulmonary diseases, such as asthma or lung cancer. Because most subjects reported transient pulmonary symptoms reflecting early-stage POT, the identified VOCs are likely markers of POT, not just hyperbaric hyperoxic exposure.

Hyperbaric oxygen treatment for late radiation-induced tissue toxicity in treated gynaecological cancer patients: a systematic review.

PURPOSE: The aim of this study was to investigate the result of hyperbaric oxygen therapy (HBOT) in women with treated gynaecological malignancies who suffer from late radiation-induced tissue toxicity (LRITT). Moreover, which symptoms of LRITT benefit most from HBOT was evaluated as well. MATERIAL AND METHODS: An online literature search was conducted using PubMed; Embase and the Cochrane Library. Studies were included if the study examined gynaecological cancer patients who had been treated with radiotherapy, who suffered from LRITT and who subsequently received HBOT. In addition, the outcome measures were based on examining the effects of HBOT. RESULTS: Twenty-one articles were included. The study investigating proctitis reported an improvement and three out of four studies investigating cystitis reported decreased complaints in women treated for gynaecological malignancies. In addition, all studies reported improvement in patients with wound complications and fifty percent of the studies reported better Patient Reported Outcome Measurements (PROMS) in women with gynaecological malignancies. Finally, all studies, except one related to pelvic malignancies reported reduced prevalence of symptoms for cystitis and proctitis and all studies reported better PROMS. However, only eleven studies reported p-values, nine of which were significant. CONCLUSION: This study demonstrated that HBOT has a positive effect in women with gynaecological LRITT. Within the included patient group, gynaecological cancer patients with wound complications seem to benefit most from this treatment compared to other late side effects of LRITT.

Volatile Organic Compounds Frequently Identified after Hyperbaric Hyperoxic Exposure: The VAPOR Library.

Diving or hyperbaric oxygen therapy with increased partial pressures of oxygen (pO2) can have adverse effects such as central nervous system oxygen toxicity or pulmonary oxygen toxicity (POT). Prevention of POT has been a topic of interest for several decades. One of the most promising techniques to determine early signs of POT is the analysis of volatile organic compounds (VOCs) in exhaled breath. We reanalyzed the data of five studies to compose a library of potential exhaled markers for the early detection of POT. GC-MS data from five hyperbaric hyperoxic studies were collected. Wilcoxon signed-rank tests were used to compare baseline- and postexposure measurements; all ion fragments that significantly varied were compared by similarity using the National Institute of Standards and Technology (NIST) library. All identified molecules were cross-referenced with open-source databases and other scientific publications on VOCs to exclude compounds that occurred as a result of contamination, and to identify the compounds most likely to occur due to hyperbaric hyperoxic exposure. After identification and removal of contaminants, 29 compounds were included in the library. This library of hyperbaric hyperoxic-related VOCs can help to advance the development of an early noninvasive marker of POT. It enables validation by others who use more targeted MS-related techniques, instead of full-scale GC-MS, for their exhaled VOC research.

Pulmonary Oxygen Toxicity Through Exhaled Breath Markers After Hyperbaric Oxygen Treatment Table 6.

Introduction: The hyperbaric oxygen treatment table 6 (TT6) is widely used to manage dysbaric illnesses in divers and iatrogenic gas emboli in patients after surgery and other interventional procedures. These treatment tables can have adverse effects, such as pulmonary oxygen toxicity (POT). It is caused by reactive oxygen species' damaging effect in lung tissue and is often experienced after multiple days of therapy. The subclinical pulmonary effects have not been determined. The primary aim of this study was to measure volatile organic compounds (VOCs) in breath, indicative of subclinical POT after a TT6. Since the exposure would be limited, the secondary aim of this study was to determine whether these VOCs decreased to baseline levels within a few hours. Methods: Fourteen healthy, non-smoking volunteers from the Royal Netherlands Navy underwent a TT6 at the Amsterdam University Medical Center-location AMC. Breath samples for GC-MS analysis were collected before the TT6 and 30 min, 2 and 4 h after finishing. The concentrations of ions before and after exposure were compared by Wilcoxon signed-rank tests. The VOCs were identified by comparing the chromatograms with the NIST library. Compound intensities over time were tested using Friedman tests, with Wilcoxon signed-rank tests and Bonferroni corrections used for post hoc analyses. Results: Univariate analyses identified 11 compounds. Five compounds, isoprene, decane, nonane, nonanal and dodecane, showed significant changes after the Friedman test. Isoprene demonstrated a significant increase at 30 min after exposure and a subsequent decrease at 2 h. Other compounds remained constant, but declined significantly 4 h after exposure. Discussion and Conclusion: The identified VOCs consisted mainly of (methyl) alkanes, which may be generated by peroxidation of cell membranes. Other compounds may be linked to inflammatory processes, oxidative stress responses or cellular metabolism. The hypothesis, that exhaled VOCs would increase after hyperbaric exposure as an indicator of subclinical POT, was not fulfilled, except for isoprene. Hence, no evident signs of POT or subclinical pulmonary damage were detected after a TT6. Further studies on individuals recently exposed to pulmonary irritants, such as divers and individuals exposed to other hyperbaric treatment regimens, are needed.

Hyperbaric oxygen therapy for the treatment of perianal fistulas in 20 patients with Crohn's disease: Results of the HOT-TOPIC trial after 1-year follow-up.

BACKGROUND: Previously published short-term results (week 16) of this trial showed a significant improvement in clinical, radiologic and biochemical outcomes in Crohn's disease patients with therapy-refractory perianal fistulas after treatment with hyperbaric oxygen therapy. OBJECTIVE: To assess the long-term (week 60) efficacy, safety and feasibility of hyperbaric oxygen therapy in perianal fistula in Crohn's disease. METHODS: Crohn's disease patients with high perianal fistula(s) failing conventional treatment >6 months were included. Exclusion criteria were presence of a stoma, rectovaginal fistula(s) and recent changes in treatment regimens. Patients received 40 hyperbaric oxygen sessions and outcomes were assessed at week 16 and week 60. RESULTS: Twenty patients were included (median age 34 years). At week 16, median scores of the perianal disease activity index and modified Van Assche index (co-primary outcomes) decreased from 7.5 (95% CI 6-9) to 4 (95% CI 3-6, p < 0.001) and 9.2 (95% CI 7.3-11.2) to 7.3 (95% CI 6.9-9.7, p = 0.004), respectively. At week 60, the respective scores remained significantly lower than baseline: 4 (95% CI 3-7, p < 0.001) and 7.7 (95% CI 5.2-10.2, p = 0.003). Perianal disease activity index score of 4 or less (representing inactive perianal disease) was observed in 13 patients at week 16 and 12 patients at week 60. Using fistula drainage assessment, 12 and 13 patients showed a clinical response at week 16 and 60, respectively, and clinical remission was achieved in four patients for both time points. At week 16, a statistically significant biochemical improvement (C-reactive protein and faecal calprotectin levels) was found, but this effect was no longer significant at week 60. CONCLUSIONS: The clinical and radiologic improvement of perianal fistula in Crohn's disease, that was found at week 16 after treatment with hyperbaric oxygen therapy, is maintained at 1-year follow-up.