Number 4

Response - Consideration of the numerous etiologies of carbon monoxide exposures 10.22462/07.08.2021.13

Letter: Letter: Consideration of the numerous etiologies of carbon monoxide exposures 10.22462/07.08.2021.12 

Update: originally posted in Vol 48 #2 Exposure to a reduction in ambient pressure such as in high-altitude climbing, flying in aircrafts, and decompression from underwater diving results in circulating vascular gas bubbles (i.e., venous gas emboli [VGE]). Incidence and severity of VGE, in part, can objectively quantify decompression stress and risk of decompression sickness (DCS) which is typically mitigated by adherence to decompression schedules. However, dives conducted at altitude challenge recommendations for decompression schedules which are limited to exposures of 10,000 feet in the U.S. Navy Diving Manual (Rev. 7). Therefore, in an ancillary analysis within a larger study, we assessed the evolution of VGE for two hours post-dive using echocardiography following simulated altitude dives at 12,000 feet. Ten divers completed two dives to 66 fsw (equivalent to 110 fsw at sea level by the cross correction method) for 30 minutes in a hyperbaric chamber. All dives were completed following a 60-minute exposure at 12,000 feet. Following the dive, the chamber was decompressed back to altitude for two hours. Echocardiograph measurements were performed every 20 minutes post-dive. Bubbles were counted and graded using the Germonpré and Eftedal and Brubakk method, respectively. No diver presented with symptoms of DCS following ..

A significant and consistently positive body of evidence from animal and human studies of thermal injury supports the use of hyperbaric oxygen as a means of preventing dermal ischemia, reducing edema, modulating the zone of stasis, preventing partial- to full-thickness conversion, preserving cellular metabolism and promoting healing. The vast majority of clinical reports have shown reduction in mortality, length of hospital stay, number of surgeries and cost of care. Hyperbaric oxygen has been demonstrated to be safe in the hands of those thoroughly trained in rendering this therapy in the critical care setting and with appropriate monitoring precautions. Careful patient selection is mandatory. 10.22462/07.08.2021.10

Inner ear decompression sickness (IEDCS) is a rare diving complication that presents with vestibular dysfunction, cochlear dysfunction, or a combination of both. While scuba diving is a known cause, no cases have been reported in the occupational hyperbaric setting. We present the case of a 55-year-old man who developed IEDCS after working as a hyperbaric multiplace chamber inside tender. The patient was treated with seven sessions of hyperbaric oxygen therapy, resulting in resolution of the majority of his symptoms. This case illustrates a potential occupational hazard of working in a hyperbaric chamber and demonstrates successful treatment with hyperbaric oxygen therapy. 10.22462/07.08.2021.9

Delayed neuropsychological sequelae (DNS) are relatively common complications of acute carbon monoxide (CO)poisoning, and usually develop within several days to weeks after the initial clinical recovery from acute CO poisoning. DNS can consist of various symptoms such as memory loss, confusion, ataxia, seizures, urinary incontinence, fecal incontinence, emotional lability, disorientation, hallucinations, mutism, cortical blindness, psychosis, parkinsonism, gait disturbances, rigidity, bradykinesia, and other motor disturbances. Paroxysmal sympathetic hyperactivity (PSH) is a potentially life-threatening disease secondary to acute acquired brain injury. It is characterized by episodic and simultaneous paroxysmal increases in sympathetic and motor activities, not rare in patients with a severe traumatic brain injury. The term PSH is clinically more accurate than the previously used ones describing such conditions as non-stimulated tachycardia, hypertension, tachypnea, hyperthermia, external posturing, diaphoresis, and paroxysmal autonomic instability with dystonia. Development of PSH typically prolongs the length of hospital stay and potentially leads to a secondary brain injury or even death. To date, the occurrence of PSH in the DNS after acute CO poisoning has not been reported in the literature. Potential mechanisms underlying the development of DNS in the deep white matter of the brain are immune-related inflammation and vasodilatation. Repetitive hyperbaric oxygen therapy, combined ..

Central retinal artery occlusion (CRAO) is a condition that causes sudden vision loss due to obstruction of the retinal artery, typically from a thrombotic or embolic source. It is often associated with atherosclerotic risk factors, including cardiovascular disease, diabetes, hyperlipidemia, and a history of cerebrovascular disease. CRAO often leads to a poor visual outcome as well as neovascularization of the iris, retina, and optic disc, which can exacerbate vision loss and cause pain. While there are several treatment modalities for CRAO, few have been proven to be effective in decreasing the effects of neovascularization. The use of hyperbaric oxygen (HBO2) therapy is often used in the treatment of CRAO due to its ease of use and relatively benign side effect profile. This study aims to assess the degree of improvement in visual acuity (VA) and neovascularization following HBO2. Our data ultimately shows that 20% of patients developed neovascularization after HBO2 compared to 29.8% of those who did not undergo HBO2 (p<.05). Our findings suggest that HBO2 has a statistically significant protective effect against neovascularization and may improve long-term visual acuity. 10.22462/07.08.2021.7

This study aimed to compare the efficacy of two commonly used therapeutic pressures, 2.0 atmospheres absolute (ATA) versus 2.2 ATA, applied in hyperbaric oxygen (HBO2) therapy for sudden sensorineural hearing loss (SSNHL). We retrospectively reviewed the clinical records of 160 SSNHL patients treated by typical therapy or additional HBO2 therapy with pressure 2.0 or 2.2 ATA at Yijishan Hospital, the First Affiliated Hospital of Wannan Medical College, from February 2018 to May 2020. The pure-tone threshold audiometry results pre- and post-treatment were compared across three groups. In the range of frequencies 250-500 Hz, P2.0 (20.92±26.11 dB, p=0.047) and P2.2 group (20.47±21.54 dB, p=0.012) both acquired higher hearing gain compared to the control group (11.94±23.32 dB). While in the range of frequencies 1,000-2,000 Hz, only the P2.2 group showed significant improvement of the hearing gain compared to the control group (19.70±21.13 dB vs.10.56±25.24 dB, p=0.015). In the range of frequencies 4,000-8,000, both the P2.0 and P2.2 groups failed to reach the desired effect. Our results suggest that the therapeutic effect is associated with HBO2 therapeutic pressure when applying HBO2 treatment combined with standard medical therapy. Within the range of appropriate pressure, the higher pressure, which means higher partial pressure of ..

Critically ill patients needing mechanical ventilation may require hyperbaric oxygen therapy. Some institutions still use ventilators that were available prior to the advent of hyperbaric-specific units, such as the Uni-Vent Eagle™ model 754. Here we examine the performance of the Uni-Vent model 754 under hyperbaric conditions and investigate concerns of an oxygen leak in the ventilator housing, which poses a fire risk. We studied the ventilator at 1.0, 2.4 and 2.8 ATA in assist control mode using a Michigan test lung and a variety of tidal volumes and respiratory rates. We recorded the delivered volumes, peak pressures, and oxygen percentages within the hyperbaric chamber at 2.4 and 2.8 ATA and within the ventilator housing. At those pressures the ventilator delivered approximately 25% less volume than at 1.0 ATA. We observed breath stacking at high respiratory rates, but this was blunted at both 2.4 and 2.8 ATA. Oxygen levels did not rise in the housing during our investigation. In addition, we fit a linear regression to the data comparing set tidal volumes and delivered tidal volumes in order to model the changes observed. Hyperbaric conditions caused decreased delivered tidal volumes in a depth-dependent fashion, and oxygen levels within the housing ..

Introduction: Inner ear decompression sickness (IEDCS) is a condition from which only a minority of patients recover completely, the majority ending up with mild to moderate residual symptoms. IEDCS has been reported after deep technical dives using mixed breathing gases, and moderate recreational dives with compressed air as the breathing gas. Considering this and the high proportion of technical diving in Finland, a comparison between IEDCS cases resulting from technical and recreational dives is warranted. Methods: This is a retrospective examination of IEDCS patients treated at Hyperbaric Center Medioxygen or National Hyperbaric Centre of Turku University Hospital from 1999 to 2018. Patients were included if presenting with hearing loss, tinnitus, or vertigo and excluded if presenting only with symptoms of middle ear or cerebellar involvement. Patients were divided into technical and recreational divers, based on incident dive. Results: A total of 89 (15.6%) of all DCS patients presented with IEDCS, two-thirds treated during the latter decade. The most common predisposing factors were consecutive days of diving (47.2%), multiple dives per day (53.9%), and factors related to an increase in intrathoracic pressure (27.0%). The symptoms were cochlear in 19.1% and vestibular in 93.3% of cases, symptoms being more common and severe in ..

Background: Changes in barometric pressure conditions that occur during flying and diving under hyperbaric oxygen conditions were found to influence the retention of dental restorations. Aim: This experimental laboratory study aimed to evaluate the bond strength of glass fiber posts after being cemented with self-adhesive resin cement (RelyX™ Unicem, 3M ESPE) and self-etch adhesive resin cement (RelyX™ Ultimate, 3M ESPE) under normal atmospheric pressure and hyperbaric pressure cycles that simulate diving conditions. Methods: A total of 40 extracted, single-rooted mandibular premolars were treated endodontically and randomly divided into two groups according to the cements used for fiber post cementation. Each group was further randomly divided into two equal subgroups that were subjected to normal atmospheric pressure conditions and a simulated hyperbaric condition in a hyperbaric chamber. The pull-out bond strength of fiber posts was tested using a universal testing machine. Data were analyzed using one-way analysis of variance with the Tukey post-hoc test (p<0.05). Results: At normal atmospheric pressure the mean value of the pull-out bond strength of RelyX Ultimate cement was significantly higher than that of RelyX Unicem cement. At hyperbaric pressure condition no significant difference was found between the mean values of the pull-out bond strength of RelyX Ultimate and ..

Introduction: Global evidence on the epidemiology of prevalent diving-related injuries (DRI) different from decompression sickness (DCS) and other fatalities is lacking. This study aimed to perform a comprehensive review of DRIs in the year-period between 2010-2020 in a non-hyperbaric tertiary hospital in the Spanish Mediterranean coast, in addition to identifying patient risk factors for severe middle ear barotrauma.  Methods: The study was conducted via a retrospective review of medical records during a 10-year period (2010- 2020) at the University and Polytechnic Hospital La Fe (UPHLF) of Valencia. We performed a case-control study recruiting controls through an online survey to identify independent predictors for severe middle ear barotrauma. Results: A total of 68 patients with DRI attended the emergency department of our tertiary referral hospital. Barotrauma accounted for more than 80% of DRI, followed by unrecognized DCS and animal-related injuries. Most patients required neither hospital admission nor surgery; appropriate treatment could be carried out largely on an outpatient basis. The presence of subsequent sequelae was minimal. Previous presence of significant ear, nose and throat (ENT) comorbidities (OR 3.05 – CI 95% 1.11 – 8.35), and older age (OR of younger age 0.94 – CI 95% 0.91 – 0.98) were identified as independent risk factors ..

Swimming requires frequent lifting and rotating of the head to inhale. A snorkeler saves energy by avoiding this maneuver, but the snorkel adds breathing work due to air flow resistance. The needed power of these head movements has never been examined, although the extra power of breathing through a snorkel was studied recently. This study aimed: 1) to model the work of vertically lifting and rotating in comparison with the breathing work added by a snorkel; 2) to compare heart rate (HR) and velocity (v) while swimming under both conditions; 3) to evaluate the results for surface-swimming divers. Presumably the power when using a snorkel is less, and the difference in power predicts the difference in swimming velocity. Kinematics of head lifting and rotation, and the difference between the hydrodynamics were modeled. A swim test lasting 12 minutes at maximum speed (Cooper swim test) was performed in a pool by nine recreational divers in the front crawl style, with face mask but without fins. All subjects performed the test both with and without snorkel. The average velocity with a snorkel, 0.72±0.09 m∙s-1, was 4.4±3.9% higher than without (p=0.008), but HR (144±16 bpm) showed no difference (0.8±3.4%). The model based ..