Outcomes after pancreaticoduodenectomy with or without preoperative hyperbaric oxygen therapy.

Background: Hyperbaric oxygen (HBO2) therapy is an alternative method against the deleterious effects of ischemic/reperfusion (I/R) injury and its inflammatory response. This study assessed the effect of preoperative HBO2 on patients undergoing pancreaticoduodenectomy. Study Design: Patients were randomized via a computer-generated algorithm. Patients in the HBO2 cohort received two sessions of HBO2 the evening before and the morning of surgery. Measurements of inflammatory mediators and self-assessed pain scales were determined pre-and postoperatively. In addition, perioperative variables and long-term survival were collected and analyzed. Data are presented as median (mean ± SD). Results: 33 patients were included; 17 received preoperative HBO2, and 16 did not. There were no intraoperative or postoperative statistical differences between patients with or without preoperative HBO2. Erythrocyte sedimentation rate (ESR), IL-6, and IL-10 increased slightly before returning to normal, while TGF-alpha decreased before increasing. However, there were no differences with or without HBO2. At postoperative day 30, the pain level measured with VAS score (Visual Analog Score) was lower after HBO2 (1 ± 1.3 vs. 3 ± 3.0, p=0.05). Eleven (76%) patients in the HBO2 cohort and 12 (75%) patients in the non- HBO2 had malignant pathology. The percentage of positive lymph nodes in the HBO2 was 7% compared to 14% in the non-HBO2 (p<0.001). Overall survival was inferior after HBO2 compared to the non- HBO2 (p=0.03). Conclusions: Preoperative HBO2 did not affect perioperative outcomes or significantly change the inflammatory mediators for patients undergoing robotic pancreaticoduodenectomy. Long-term survival was inferior after preoperative HBO2. Further randomized controlled studies are required to assess the full impact of this treatment on patients' prognosis.

Relative hypoxemia at depth during breath-hold diving investigated through arterial blood gas analysis and lung ultrasound.

Pulmonary gas exchange in breath-hold diving (BHD) consists of a progressive increase in arterial partial pressures of oxygen ([Formula: see text]) and carbon dioxide ([Formula: see text]) during descent. However, recent findings have demonstrated that [Formula: see text] does not consistently rise in all subjects. This study aimed at verifying and explaining [Formula: see text] derangements during BHD analyzing arterial blood gases and searching for pulmonary alterations with lung ultrasound. After ethical approval, 14 fit breath-hold divers were included. Experiments were performed in warm water (temperature: 31°C). We analyzed arterial blood gases immediately before, at depth, and immediately after a breath-hold dive to -15 m of fresh water (mfw) and -42 mfw. Signs of lung interstitial edema and atelectasis were searched simultaneously with a marinized lung ultrasound. In five subjects (-15 mfw) and four subjects (-42 mfw), the [Formula: see text] at depth seems to decrease instead of increasing. [Formula: see text] and lactate showed slight variations. At depth, no lung ultrasound alterations were seen except in one subject (hypoxemia and B-lines at -15 mfw; B-lines at the surface). Lung interstitial edema was detected in 3 and 12 subjects after resurfacing from -15 to -42 mfw, respectively. Two subjects developed hypoxemia at depth and a small lung atelectasis (a focal pleural irregularity of triangular shape, surrounded by thickened B-lines) after resurfacing from -42 mfw. Current experiments confirmed that some BH divers can experience hypoxemia at depth. The hypothesized explanation for such a discrepancy is lung atelectasis, which could not be detected in all subjects probably due to limited time available at depth.NEW & NOTEWORTHY During breath-hold diving, arterial partial pressure of oxygen ([Formula: see text]) and arterial partial pressure of carbon dioxide ([Formula: see text]) are believed to increase progressively during descent, as explained by theory, previous end-tidal alveolar gas measurements, and arterial blood gas analysis in hyperbaric chambers. Recent experiments in real underwater environment found a paradoxical [Formula: see text] drop at depth in some divers. This work confirms that some breath-hold divers can experience hypoxemia at depth. The hypothesized explanation for such a discrepancy is lung atelectasis, as suggested by lung ultrasound findings.

Volume 50: The UHM Journal celebrates a milestone with the publication of this issue.

As the UHMS observes the distinguished anniversary of the publication of 50 volumes of the Undersea and Hyperbaric Medicine Journal, two of our past editors take a look at the evolution of our flagship publications.

Dopamine/BDNF loss underscores narcosis cognitive impairment in divers: a proof of concept in a dry condition.

PURPOSE: Divers can experience cognitive impairment due to inert gas narcosis (IGN) at depth. Brain-derived neurotrophic factor (BDNF) rules neuronal connectivity/metabolism to maintain cognitive function and protect tissues against oxidative stress (OxS). Dopamine and glutamate enhance BDNF bioavailability. Thus, we hypothesized that lower circulating BDNF levels (via lessened dopamine and/or glutamate release) underpin IGN in divers, while testing if BDNF loss is associated with increased OxS. METHODS: To mimic IGN, we administered a deep narcosis test via a dry dive test (DDT) at 48 msw in a multiplace hyperbaric chamber to six well-trained divers. We collected: (1) saliva samples before DDT (T0), 25 msw (descending, T1), 48 msw (depth, T2), 25 msw (ascending, T3), 10 min after decompression (T4) to dopamine and/or reactive oxygen species (ROS) levels; (2) blood and urine samples at T0 and T4 for OxS too. We administered cognitive tests at T0, T2, and re-evaluated the divers at T4. RESULTS: At 48 msw, all subjects experienced IGN, as revealed by the cognitive test failure. Dopamine and total antioxidant capacity (TAC) reached a nadir at T2 when ROS emission was maximal. At decompression (T4), a marked drop of BDNF/glutamate content was evidenced, coinciding with a persisting decline in dopamine and cognitive capacity. CONCLUSIONS: Divers encounter IGN at - 48 msw, exhibiting a marked loss in circulating dopamine levels, likely accounting for BDNF-dependent impairment of mental capacity and heightened OxS. The decline in dopamine and BDNF appears to persist at decompression; thus, boosting dopamine/BDNF signaling via pharmacological or other intervention types might attenuate IGN in deep dives.

Blood gas analyses in hyperbaric and underwater environments: a systematic review.

Pulmonary gas exchange during diving or in a dry hyperbaric environment is affected by increased breathing gas density and possibly water immersion. During free diving, there is also the effect of apnea. Few studies have published blood gas data in underwater or hyperbaric environments: this review summarizes the available literature and was used to test the hypothesis that arterial Po2 under hyperbaric conditions can be predicted from blood gas measurement at 1 atmosphere assuming a constant arterial/alveolar Po2 ratio (a:A). A systematic search was performed on traditional sources including arterial blood gases obtained on humans in hyperbaric or underwater environments. The a:A was calculated at 1 atmosphere absolute (ATA). For each condition, predicted arterial partial pressure of oxygen ([Formula: see text]) at pressure was calculated using the 1 ATA a:A, and the measured [Formula: see text] was plotted against the predicted value with Spearman correlation coefficients. Of 3,640 records reviewed, 30 studies were included: 25 were reports describing values obtained in hyperbaric chambers, and the remaining were collected while underwater. Increased inspired O2 at pressure resulted in increased [Formula: see text], although underlying lung disease in patients treated with hyperbaric oxygen attenuated the rise. [Formula: see text] generally increased only slightly. In breath-hold divers, hyperoxemia generally occurred at maximum depth, with hypoxemia after surfacing. The a:A adequately predicted the [Formula: see text] under various conditions: dry (r = 0.993, P < 0.0001), rest versus exercise (r = 0.999, P < 0.0001), and breathing mixtures (r = 0.995, P < 0.0001). In conclusion, pulmonary oxygenation under hyperbaric conditions can be reliably and accurately predicted from 1 ATA a:A measurements.

Sugammadex Reduces PACU Recovery Time after Abdominal Surgery Compared with Neostigmine.

OBJECTIVE: This study blindly evaluated sugammadex compared with neostigmine on length of stay in the postanesthesia care unit (PACU). METHODS: Fifty patients undergoing elective laparoscopic cholecystectomy or abdominal wall hernia repair consented to receive either sugammadex (2 mg/kg) or neostigmine (0.07 mg/kg) for the reversal of rocuronium neuromuscular blockade. Reversal agents were administered during surgical closing, and the train of four was measured until a twitch ratio of T4:T1 ≥ 0.9 was obtained to signify a robust reversal. Postreversal outcomes also were measured during PACU stay. Aldrete scores, pain visual analog scale score, and nausea were measured during the PACU stay. RESULTS: Patients receiving sugammadex experienced a shorter PACU stay at the time of discharge than patients receiving neostigmine, by an average of 12 minutes (P < 0.05). CONCLUSIONS: Sugammadex patients had a significantly shorter PACU stay.

Emergency Medicine Cases in Underwater and Hyperbaric Environments: The Use of in situ Simulation as a Learning Technique.

INTRODUCTION: Hyperbaric chambers and underwater environments are challenging and at risk of serious accidents. Personnel aiming to assist patients and subjects should be appropriately trained, and several courses have been established all over the world. In healthcare, simulation is an effective learning technique. However, there have been few peer-reviewed articles published in the medical literature describing its use in diving and hyperbaric medicine. METHODS: We implemented the curriculum of the Master's degree in hyperbaric and diving medicine held at the University of Padova with emergency medicine seminars created by the faculty and validated by external experts. These seminars integrated traditional lectures and eight in situ simulation scenarios. RESULTS: For the hyperbaric medicine seminar, simulations were carried out inside a real hyperbaric chamber at the ATIP Hyperbaric Treatment Centre, only using air and reproducing compression noise without pressurization to avoid damages to the manikins. The four scenarios consisted of hyperoxic seizures, pneumothorax, hypoglycemia, and sudden cardiac arrest. Furthermore, we added a hands-on session to instruct participants to prepare an intubated patient undergoing hyperbaric oxygen treatment with a checklist and simulating the patient transfer inside and outside the hyperbaric chamber. The diving medicine seminar was held at the Y-40 The Deep Joy pool in Montegrotto Terme (Italy), also involving SCUBA/breath-hold diving (BHD) instructors to rescue subjects from the water. These diving medicine scenarios consisted of neurologic syndrome ("taravana/samba") in BHD, drowning of a breath-hold diver, pulmonary barotrauma in BHD, and decompression illness in a SCUBA diver. CONCLUSION: With this experience, we report the integration of simulation in the curriculum of a teaching course in diving and hyperbaric medicine. Future studies should be performed to investigate learning advantages, concept retention, and satisfaction of participants.

Evidence-Supported HBO Therapy in Femoral Head Necrosis: A Systematic Review and Meta-Analysis.

Although many studies have shown that hyperbaric oxygen (HBO) therapy can significantly improve symptoms and quality of life of patients affected by femoral head necrosis, this therapy is not worldwide approved yet. This meta-analysis was performed to evaluate its clinical effect. Relevant studies published before May 2020 were systematically searched using terms related to HBO and femoral head necrosis. Fixed and random-effects models were used to estimate the odds ratio (OR) with 95% confidence intervals (CI). Subgroup analyses and publication bias tests were carried out to explore potential study heterogeneity and bias. Ten studies involving 353 controls and 368 HBO-treated cases were included, most of which were conducted on Asian population. The clinical effect in the HBO therapy group was 3.84 times higher than in the control group (OR = 3.84, 95% CI (2.10, 7.02), p < 0.00001). Subgroup analyses showed that the clinical effect of HBO therapy was statistically significant in the Asian subpopulation which represented most of the subjects (OR = 3.53, 95% CI (1.87, 6.64), p < 0.00001), but not in the non-Asian subpopulation, probably because of insufficient numerosity (OR = 7.41, 95% CI (0.73, 75.71), p = 0.09). The results of this meta-analysis suggest that patients with femoral head necrosis treated with HBO therapy can achieve a significant clinical improvement.

A capnography and transcutaneous CO2 profile of bariatric patients during early postoperative period after opioid-sparing anesthesia.

BACKGROUND: Noninvasive monitoring of partial pressure of carbon dioxide can be accomplished indirectly with capnography (PETCO2) or with transcutaneous carbon dioxide monitoring (PTCCO2). The use of capnography has been shown to offer an advantage over pulse oximetry alone in the early detection of adverse respiratory events when supplemental oxygen is administered. Furthermore, capnography allows for the monitoring of various respiratory measures, including end-tidal carbon dioxide, respiratory rate, tidal volume, and changes in breathing patterns. Transcutaneous CO2 also closely approximates arterial CO2 values, but is not as easy to monitor for prolonged periods. The purpose of this study was to examine the usefulness of capnography and of transcutaneous carbon dioxide monitoring in patients recovering from obesity surgery at high risk of developing postoperative obstructive sleep apnea. METHODS: In a prospective observational study, 64 bariatric surgery patients at risk of developing obstructive sleep apnea were monitored in the postanesthesia care unit (PACU) with either capnography alone (31 patients) or capnography plus transcutaneous carbon dioxide monitoring (33 additional patients) every 3-5 minutes for the duration of their recovery. Primary endpoints included end-tidal and transcutaneous carbon dioxide, peripheral oxygen saturation, respiratory rate, pain scores, and incidence of adverse respiratory events. RESULTS: Although no adverse pulmonary events were observed, capnography detected several patients who experienced short periods of respiratory apnea while maintaining pulse oximetry readings within normal limits. Transcutaneous values were slow to change and averaged 4.5 ± 5.5 mm Hg (P < .05) higher than corresponding end-tidal measurements. CONCLUSIONS: These results indicate the capabilities of both these noninvasive techniques for postoperative monitoring. Capnography acutely monitors changes in respiration, whereas transcutaneous monitoring more accurately reflects arterial CO2 levels.

Hyperbaric Oxygen Therapy and A-PRF Pre-Treated Implants in Severe Periodontitis: A Case Report.

Implantation is currently the best option for tooth replacement in periodontitis. Some major contraindications for the immediate implant are acute periodontitis and active infection. We present the case of a 51-year-old female patient with the highest grade and stage periodontitis treated with advanced platelet-rich fibrin-enriched zirconia implants and with hyperbaric oxygen therapy (HBOT). In particular, HBOT before and after implantation promoted bone regeneration and implant integration, also providing an antiseptic effect. After six months, the implants were well established and fully healed from periodontal disease within 14 months. Further research could confirm a new indication for HBOT in treating periodontitis and dental implantation.

Critical Review and Meta-Analysis of Postoperative Sedation after Adult Cardiac Surgery: Dexmedetomidine Versus Propofol.

OBJECTIVE: To evaluate reports from the published literature of all randomized clinical trials (RCT) comparing postoperative sedation with dexmedetomidine versus propofol in adult patients, after open cardiac surgery. DESIGN: A computerized search on Medline, EMBASE, Web of Science, and Agency for Healthcare Research and Quality databases was completed through June 2020. Meta-analysis of all published RCT comparing dexmedetomidine versus propofol utilization in the postoperative phase, using the standard Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. SETTING: Assemblage and critical discussion of 11 RCTs comparing postoperative sedation from standard published reports from 2003 to 2019. PARTICIPANTS: The study comprised 1,184 patients and analyzed critical discussion of time-based parameters (time to extubation, intensive care unit length of stay, and hospital length of stay) and nontime-dependent factors (delirium, bradycardia, and hypotension). MEASUREMENTS AND MAIN RESULTS: Time to extubation was significantly reduced in the dexmedetomidine group (standardized mean difference [SMD] = -0.70, 95% confidence interval [CI] -0.98 to -0.42, p < 0.001); however, no difference in mechanical ventilation time was observed (SMD = -0.72, 95% CI -1.60 to 0.15, N.S.). Dexmedetomidine significantly reduced the intensive care unit length of stay (SMD = 0.23, 95% CI -1.06 to -0.16, p = 0.008), but this did not translate into a reduced hospital length of stay (SMD = -1.13, 95% CI -2.43 to 0.16, N.S). For nontime-dependent factors, incidence of delirium was unaffected between groups (odds ratio [OR]: 0.68, 95% CI 0.43-1.06, N.S), and higher rates of bradycardia (OR: 3.39, 95% CI: 1.20-9.55, p = 0.020) and hypotension (OR: 1.68, 95% CI 1.09-2.58, p = 0.017) were reported with propofol. CONCLUSIONS: Despite the ICU time advantages afforded by dexmedetomidine over propofol, the former did not seem to contribute to an overall reduction in hospital length of stay or improvement in postoperative outcomes of heart valve surgery and CABG patients.

The Role of Hyperbaric Oxygen Treatment for COVID-19: A Review.

The recent coronavirus disease 2019 (COVID-19) pandemic produced high and excessive demands for hospitalizations and equipment with depletion of critical care resources. The results of these extreme therapeutic efforts have been sobering. Further, we are months away from a robust vaccination effort, and current therapies provide limited clinical relief. Therefore, several empirical oxygenation support initiatives have been initiated with intermittent hyperbaric oxygen (HBO) therapy to overcome the unrelenting and progressive hypoxemia during maximum ventilator support in intubated patients, despite high FiO2. Overall, few patients have been successfully treated in different locations across the globe. More recently, less severe patients at the edge of impending hypoxemia were exposed to HBO preventing intubation and obtaining the rapid resolution of symptoms. The few case descriptions indicate large variability in protocols and exposure frequency. This summary illustrates the biological mechanisms of action of increased O2 pressure, hoping to clarify more appropriate protocols and more useful application of HBO in COVID-19 treatment.

Hyperbaric Oxygen Treatment for Carbon Monoxide Poisoning in Italy: Retrospective Validation of a Data Collection Tool for the Italian Registry of Carbon Monoxide Poisonings (IRCOP).

Background: Carbon Monoxide (CO) poisoning is a frequent cause of intoxication. However, CO poisoning incidence is globally underreported, as well as its features, especially in Italy. The aim of this study was to investigate such characteristics of CO intoxication and foster the creation of the Italian Registry of Carbon Monoxide Poisonings. Methods: A data collection tool was developed and organized in five sections: Patient's characteristics; CO intoxication modality; emergency medical service and emergency department; hyperbaric facility; outcomes. The tool was validated through a retrospective analysis, including CO intoxicated patients treated in 14 Italian hyperbaric facilities between 2015 and 2016. Results: A total of 1383 patients were included. The high completion ratio (85%) of the collection tool suggests its feasibility in practical terms. CO intoxications were mostly accidental (93.64%) and caused by solid fuel (48.59%). There was not a uniform application of hyperbaric oxygen treatment protocols, but most of the patients were adequately treated at least at 2.5 ATA for more than 60 min (44.97%). Conclusion: This analysis provided new information that was previously unavailable in this country. Furthermore, this tool proved to be a valid base for future registry aiming to consolidate the body of knowledge about CO intoxications in Italy.

Association of Serum Albumin and Severity of Pulmonary Embolism.

Background and Objectives: Inflammation is considered a risk factor for venous thromboembolism. The association between inflammatory markers and the severity of acute pulmonary embolism (APE) has not been explored. Methods: We studied the association between two crude markers of inflammation, serum albumin, and red cell distribution width (RDW) and massive versus non-massive APE. Results: Among 552 consecutive cases of CT-angiogram-confirmed APE, a total of 46 cases (8.3%) had massive APE. Despite similar demographics and comorbidities, patients with massive APE had higher frequency of acute kidney injury (P = 0.005), higher lactic acid (P = 0.011), higher troponin (P = 0.001), higher BNP (P < 0.001), higher frequency of RV dilation (P = 0.017) and hypokinesis (P = 0.003), and higher in-hospital mortality (15.2% vs. 2%, P < 0.001). Patients with massive APE had significantly lower albumin level (median (IQR): 2.8 (2.2, 3.0) vs. 3.2 (2.8, 3.6) gm/dL, P < 0.001) and higher RDW (median (IQR): 14.7 (13.8, 17.1) vs. 14.2 (13.3, 15.6), P = 0.006) compared with non-massive APE. ROC curves showed that albumin and RDW had an AUC of 0.750 (P < 0.001) and 0.621 (P = 0.006) in predicting a massive APE, respectively. The optimal cutoff values for albumin and RDW that had the highest combined sensitivity and specificity for predicting APE was ≤3 gm/dL and >14, for albumin and RDW, respectively. Restricted cubic splines showed a significant association between albumin (P = 0.0002) and RDW (P = 0.0446) and the occurrence of massive APE. After adjustment for patients' age, body mass index, white blood cell count, the requirement of antibiotics during hospitalization, diabetes, RDW, and peak creatinine, serum albumin was independently associated with massive APE (OR 0.234, 95% CI 0.129-0.4242, P < 0.001). Conclusion: low serum albumin is associated with massive APE. This association is likely a proxy for higher inflammatory state in massive compared with non-massive APE.

Arterial blood gases in divers at surface after prolonged breath-hold.

PURPOSE: Adaptations during voluntary breath-hold diving have been increasingly investigated since these athletes are exposed to critical hypoxia during the ascent. However, only a limited amount of literature explored the pathophysiological mechanisms underlying this phenomenon. This is the first study to measure arterial blood gases immediately before the end of a breath-hold in real conditions. METHODS: Six well-trained breath-hold divers were enrolled for the experiment held at the "Y-40 THE DEEP JOY" pool (Montegrotto Terme, Padova, Italy). Before the experiment, an arterial cannula was inserted in the radial artery of the non-dominant limb. All divers performed: a breath-hold while moving at the surface using a sea-bob; a sled-assisted breath-hold dive to 42 m; and a breath-hold dive to 42 m with fins. Arterial blood samples were obtained in four conditions: one at rest before submersion and one at the end of each breath-hold. RESULTS: No diving-related complications were observed. The arterial partial pressure of oxygen (96.2 ± 7.0 mmHg at rest, mean ± SD) decreased, particularly after the sled-assisted dive (39.8 ± 8.7 mmHg), and especially after the dive with fins (31.6 ± 17.0 mmHg). The arterial partial pressure of CO2 varied somewhat but after each study was close to normal (38.2 ± 3.0 mmHg at rest; 31.4 ± 3.7 mmHg after the sled-assisted dive; 36.1 ± 5.3 after the dive with fins). CONCLUSION: We confirmed that the arterial partial pressure of oxygen reaches hazardously low values at the end of breath-hold, especially after the dive performed with voluntary effort. Critical hypoxia can occur in breath-hold divers even without symptoms.

A Collaborative Initiative for Reducing Operating Room Waste of Unused Refrigerated Medication.

BACKGROUND: Inappropriate management of anesthetic medications requiring refrigeration creates waste and increases costs of intraoperative care. At Tampa General Hospital, pharmacy personnel refill medications in cardiovascular operating rooms (CVOR) nightly and noticed large amounts of unattended medications at room temperature for unknown periods of time. Per protocol, these medications were disposed. OBJECTIVE: To effectively decrease pharmaceutical waste in the CVOR. METHODS: A pharmacy-led anesthesia committee identified the most used intraoperative medications requiring refrigeration and implemented changes to decrease waste. As a result, norepinephrine intravenous piggyback (IVPB), norepinephrine vials, nitroglycerin vials, and epinephrine IVPB were physically relocated into preexisting mini-refrigerators inside each CVOR. Vasopressin vials and phenylephrine syringes/vials were relocated into automated anesthesia cabinets. Amounts and cost of wasted medication were analyzed before and after protocol implementation. RESULTS: Average weekly cost of wasted medication was significantly reduced (preintervention: US$1188.59 vs postintervention: US$322.96; P < .001), despite a consistent caseload. CONCLUSION: Recorded weekly savings of US$865.63 (∼annual savings of >US$45 000) reflect only the explicit cost of waste. True savings are higher when including opportunity costs such as salary of pharmacy personnel and supplies needed to replace wasted medications. We demonstrate the benefits of a collaborative approach to improving inefficiencies in health care.

Femoral condylar necrosis: treatment with hyperbaric oxygen therapy.

BACKGROUND: Osteonecrosis of the knee (ONK) is a form of aseptic necrosis resulting from ischemia to subchondral bone tissue. Typically, treatment is invasive. Hyperbaric oxygen therapy (HBOT) may provide a noninvasive alternative by improving oxygenation and reperfusion of ischemic areas. This study evaluates the efficacy of HBOT in a series of ONK patients. METHODS: This retrospective study evaluates 37 ONK patients (29 male, 8 female; mean age ± 1 standard deviation: 54 ± 14); 83.7% of patients presented with Aglietti stage I-II; 16.3% presented with Aglietti stage III. Patients were treated with HBOT once a day, 5 days a week, at 2.5 atmosphere absolute with 100% inspired oxygen by mask for an average of 67.9 ± 15 sessions. Magnetic resonance imaging was performed before HBOT, within 1 year after completion of HBOT, and in 14 patients, 7 years after treatment. Oxford Knee Scores (OKSs) were recorded before HBOT and at the end of each HBOT treatment cycle. RESULTS: After the 30 sessions of HBOT, 86% of patients experienced improvement in their OKS, 11% worsened, and 3% did not change. All patients improved in OKS after 50 sessions. Magnetic resonance imaging evaluation 1 year after HBOT completion showed that edema at the femoral condyle had resolved in all but 1 patient. CONCLUSIONS: HBOT is beneficial for treating ONK. Patients experienced improvements in pain and mobility as demonstrated by improvement in OKS. Radiographic improvements were also seen upon post-treatment follow-up. Aglietti staging for the entire sample saw an aggregate decrease (P < .01) from 1.7 ± 0.7 to 0.3 ± 0.6.

Arterial Blood Gas Analysis in Breath-Hold Divers at Depth.

The present study aimed to evaluate the partial pressure of arterial blood gases in breath-hold divers performing a submersion at 40 m. Eight breath-hold divers were enrolled for the trials held at "Y-40 THE DEEP JOY" pool (Montegrotto Terme, Padova, Italy). Prior to submersion, an arterial cannula in the radial artery of the non-dominant limb was positioned. All divers performed a sled-assisted breath-hold dive to 40 m. Three blood samplings occurred: at 10 min prior to submersion, at 40 m depth, and within 2 min after diver's surfacing and after resuming normal ventilation. Blood samples were analyzed immediately on site. Six subjects completed the experiment, without diving-related problems. The theoretically predicted hyperoxia at the bottom was observed in 4 divers out of 6, while the other 2 experienced a reduction in the partial pressure of oxygen (paO2) at the bottom. There were no significant increases in arterial partial pressure of carbon dioxide (paCO2) at the end of descent in 4 of 6 divers, while in 2 divers paCO2 decreased. Arterial mean pH and mean bicarbonate ( HCO 3 - ) levels exhibited minor changes. There was a statistically significant increase in mean arterial lactate level after the exercise. Ours was the first attempt to verify real changes in blood gases at a depth of 40 m during a breath-hold descent in free-divers. We demonstrated that, at depth, relative hypoxemia can occur, presumably caused by lung compression. Also, hypercapnia exists at depth, to a lesser degree than would be expected from calculations, presumably because of pre-dive hyperventilation and carbon dioxide distribution in blood and tissues.