Undersea and Hyperbaric Medicine最新文献

Introduction: Since the U.S. Navy transitioned from the MK10 to the MK11 submarine escape and immersion equipment (SEIE), there has been an increase in the incident rate of pulmonary barotrauma during submarine escape training. This study compares the ascent rate profiles of the MK10 and MK11 SEIE to determine if ascent rate differences between the escape suits are associated with increased pulmonary barotraumas.

Methods: Buoyant ascent rates of the MK10 and MK11 SEIE were compared using weighted manikins equivalent to the 1st, 50th, and 99th percentile body weight of a submariner. Human ascents using the MK11 (n=126) were compared to human ascents in the same trainer wearing the MK10 (n=124).

Results: Manikin mean ascent times were faster for the MK10 than the MK11 (5.19 seconds vs 5.28 seconds, p ≺ 0.05). Terminal velocity (Vt) was affected by manikin weight (p ≺ 0.001). Human trials confirmed the manikin results. The average mean ascent velocity for the MK10 group was 0.155 meters/ second faster than the MK11 group's mean ascent velocity (p ≺ 0.001). Mean ascent velocity was inversely correlated with all anthropometrics for the MK10 group (p ≺ 0.01). Neither height nor body mass index showed a significant association with mean ascent velocity for the MK11 group.

Conclusions: The Vt of buoyant ascents is significantly affected by body weight. As the mean ascent rate of the MK11 is slower than that of the MK10, ascent rate profile differences between the suits do not appear to explain the recent increase in pulmonary barotrauma incident rates during escape training.

Background: The pathophysiology of traumatic brain injury (TBI) is caused by the initial physical damage and by the subsequent biochemical damage (secondary brain injury). Oxidative stress is deeply involved in secondary brain injury, so molecular hydrogen therapy may be effective for TBI. Hydrogen gas shows the optimal effect at concentrations of 2% or higher, but can only be used up to 1.3% in the form of a gas cylinder mixed with oxygen gas, which may not be sufficiently effective. The partial pressure of hydrogen increases in proportion to the pressure, so hyperbaric hydrogen therapy (HBH2) is more effective than that at atmospheric pressure.

Methods: A total of 120 mice were divided into three groups: TBI + non-treatment group (TBI group; n = 40), TBI + HBH2 group (n = 40), and non-TBI + non-treatment group (sham group; n = 40). The TBI and TBI + HBH2 groups were subjected to moderate cerebral contusion induced by controlled cortical impact. The TBI + HBH2 group received hyperbaric hydrogen therapy at 2 atmospheres for 90 minutes, at 30 minutes after TBI. Brain edema, neuronal cell loss in the injured hippocampus, neurological function, and cognitive function were evaluated.

Results: The TBI + HBH2 group showed significantly less cerebral edema (p ≺ 0.05). Residual hippocampal neurons were significantly more numerous in the TBI + HBH2 group on day 28 (p ≺ 0.05). Neurological score and behavioral tests showed that the TBI + HBH2 group had significantly reduced hyperactivity on day 14 (p ≺ 0.01).

Conclusion: Hyperbaric hydrogen therapy may be effective for posttraumatic secondary brain injury.

Objective: The presentation of a novel prospective treatment for scenarios where bubble presence in the bloodstream poses a clinical risk. The method relies on generating resonant acoustic standing waves within a limb to non-invasively accelerate the dissolution of bubbles present in the bloodstream via bubble rupture. Additionally, a preliminary assessment of the effects of the resonant acoustic waves and bubble rupture events on red blood cell viability is provided.

Methods: Two semicircular piezoelectric (PZT) transducers electrically connected to each other were assembled around a small-girth segment of a rear thigh removed from a swine specimen. When driven at the frequency of electric resonance, this swine thigh and PZT transducer arrangement generates resonant acoustic standing waves within the swine thigh. Consequently, mechanical resonance of the system was non-invasively established by monitoring the electric response of the PZT to the applied frequency. The resonant acoustic field generated was used for the detection and rupture of bubbles that travel through a simulated blood vessel installed across the swine thigh. Two sets of experiments were carried out using this methodology, one with the artificial blood vessel filled with saline solution and one with defibrinated sheep blood. For the latter case, a preliminary hematologic assessment was done with red blood cell counts.

Conclusion: Resonant acoustic standing waves effectively rupture bubbles of 300μm to 900μm within a simplified swine thigh model. The average dissolved gas content was 44% due to resonant acoustic waves at powers above 20W. No significant effect on red blood cell counts was observed.

Parosmia is a qualitative olfactory dysfunction characterized by distortion of odor perception. Traditional treatments for parosmia include olfactory training and steroids. Some patients infected with COVID-19 have developed chronic parosmia as a result of their infection. Here, we present the case of a patient who developed parosmia after a COVID-19 infection that was not improved by traditional treatments but found significant improvement after hyperbaric oxygen therapy[A1].

Introduction: The United States Navy (USN) developed and refined standardized oxygen treatment tables for diving injuries, but USN tables may not address all situations of spinal decompression sickness (DCS). We describe a detailed recompression treatment regimen that deviated from standard USN protocol for an active-duty USN diver with a severe, delayed presentation of spinal cord DCS.

Case report: A USN diver surfaced from his second of three dives on a standard Navy 'no-Decompression' Air SCUBA dive (Max depth 101 fsw utilizing a Navy Dive Computer) and developed mid-thoracic back pain, intense nausea, paresthesias of bilateral feet, and penile erection. Either not recognizing the con- stellation of symptoms as DCS and after resolution of the aforementioned symptoms, he completed the third planned dive (essentially an in-water recompression). Several hours later, he developed paresthesias and numbness of bilateral feet and legs and bowel incontinence. He presented for hyperbaric treatment twenty hours after surfacing from the final dive and was diagnosed with severe spinal DCS. Based on the severity of clinical presentation and delay to treatment, the initial and follow-on treatments were modified from standard USN protocol. MRI of the spine four days after initial presentation demonstrated a 2.2 cm lesion at the T4 vertebral level extending caudally. Follow-up examinations over two years demonstrated almost complete return of motor and sensory function; however, the patient continued to suffer fecal incontinence and demonstrated an abnormal post-void residual urinary volume. An atypical presenting symptom, a discussion of MRI findings, and clinical correlations to the syndrome of spinal DCS are discussed throughout treatment and long-term recovery of the patient.

Introduction: Growing evidence demonstrates that hyperbaric oxygen therapy (HBO2) induces neuroplasticity and can benefit individuals with post-traumatic stress disorder (PTSD). The aim of the current study was to evaluate the rate and pattern of memory surfacing during the course of HBO2 among veterans with combat-related PTSD.

Methods: In a post-hoc analysis of a prospective study of the effect of HBO2 on PTSD symptoms in veterans, we evaluated the rate and character of memory surfacing during the course of HBO2 treatment. The treatment consisted of 60 daily 90-minute sessions, at 2 atmospheres absolute (ATA) pressure and 100% oxygen.

Results: For 10 (35.7%) of the 28 participants, surfacing of new memories was reported during the HBO2 treatment course. Memories surfaced mainly during the second month of the treatment, at the mean session of 30.5±13.2. For 9 of these 10 participants, prodromal symptoms such as distress, anxiety, or worsening depression were documented; and in four, somatic pain was reported prior to memory surfacing. The pain and distress of memory surfacing resolved over the course of one to 10 days.

Discussion: Among individuals with PTSD, the surfacing of new memories, accompanied by emotional distress and somatic pain, is common during HBO2. The surfacing of memories sheds light on the biological effect of HBO2 on the brain sequela of PTSD. It is highly important that in treating patients for any indication, HBO2 medical teams be aware and capable of addressing memory surfacing, particularly in those with a history of trauma.

Closed-circuit rebreather diving is becoming more common. Rebreathers are complicated, adding to the stress of diving. Also adding to this complexity in the presented case is diving at a high-altitude, cold-water reservoir in Colorado. One diver experienced an oxygen-induced seizure at depth. The other diver had a rapid ascent with loss of consciousness. In this case, two experienced divers recovered from a possible devastating dive. Fortunately, they both returned to their pre-dive baseline health. Dive plan- ning is important, but as in this case, dive execution is paramount. This is a clinical case for an uncommon event presenting to an emergency department.