Preliminary Study of Wound Oxygenation Comparing Skin Substitutes and Dressings

Background

Improving oxygen delivery to challenging wound types has been shown to optimize and accelerate several key contributors to healing. This study aims to compare selective skin substitutes and primary dressings and evaluate their ability to transfer oxygen to the wound.

Methods

Visual and quantitative methods were employed to measure gas and fluid movement across several skin substitutes, including a bilayer nylon and silicone dressing coated with porcine gelatin and aloe vera (CNS), a porous bovine collagen-glycosaminoglycan (GAG) matrix dressing coated with silicone (UBC), and a urethane biodegradable temporizing matrix (PFD).

Results

Fluids did not move across solid silicone membranes or urethane foam while oxygen movement across solid silicone membranes was inversely proportional to the thickness of the membrane. Oxygen moved across the coated nylon and silicone dressing 5.63 times faster than across the bovine-GAG scaffold and 2.0 times faster than the biodegradable temporizing matrix of polyurethane.

Conclusions

The coated nylon and silicone matrix functioned like a membrane oxygenator, potentially augmenting atmospheric oxygen delivery to healing wounds.

Physiological and cognitive responses to hyperoxic exercise in full water submersion

AbstractThe positive effects of combined hyperoxia and physical exercise on physiological parameters and cognitive functioning are established for normobaric laboratory contexts. Still, increased practicability exists in hyperbaric settings like underwater activities and SCUBA diving, where environmental and sport-specific factors might moderate effects. Improved cognition, reduced ventilation (V_E), and lower blood lactate concentrations [Lac^-] are highly relevant, especially during high-stress and rescue scenarios. Fifteen participants performed 3 × 8 min of continuous underwater fin-swimming at 25% (low), 45% (moderate), and 75% (vigorous) heart rate reserve (HRR) in each test. Three separate test days differed solely by the inspiratory oxygen partial pressure (P_IO₂: 29kPa, 56kPa, and 140kPa). V_E was measured continuously, whereas breathing gas analysis, blood sampling, and Eriksen Flanker tasks for inhibitory control (100 stimuli) were performed post-exercise. Two-way ANOVAs with repeated measures on the factors P_IO₂ and exercise intensity investigated physiological outcome variables and reactions times (RT) and accuracy (ACC) of inhibitory control. V_E was significantly reduced for 140kPa during moderate and vigorous and for 56kPa during vigorous compared to 29kPa. 56kPa and 140kPa showed no differences. [Lac^-], post-exercise VCO₂, and velocity were unaffected by P_IO₂. Faster RTs but lower ACC of inhibitory control were observed following exercise at 75% HRR compared to rest, 25%, and 45% HRR, while P_IO₂ produced no effects. Underwater performance in hyperoxia presents reduced V_E, possible by dampened chemoreceptor sensitivity, and effects on cognition that differ from laboratory results and emphasize the moderating role of sport-specific factors.

Hyperbaric polymer microcapsules for tunable oxygen delivery

Over the past decade, there have been many attempts to engineer systems capable of delivering oxygen to overcome the effects of both systemic and local hypoxia that occurs as a result of traumatic injury, cell transplantation, or tumor growth, among many others. Despite progress in this field, which has led to a new class of oxygen-generating biomaterials, most reported techniques lack the tunability necessary for independent control over the oxygen flux (volume per unit time) and the duration of delivery, both of which are key parameters for overcoming tissue hypoxia of varying etiologies. Here, we show that these critical parameters can be effectively manipulated using hyperbarically-loaded polymeric microcapsules (PMC). PMCs are micron-sized particles with hollow cores and polymeric shells. We show that oxygen delivery through PMCs is dependent on its permeability through the polymeric shell, the shell thickness, and the pressure gradient across the shell. We also demonstrate that incorporating an intermediate oil layer between the polymeric shell and the gas core prevents rapid outgassing by effectively lowering the resultant pressure gradient across the polymeric membrane following depressurization.

Barotrauma and Arterial Gas Embolism: A Diving Emergencies Simulation Case for Emergency Medicine Residents

Introduction

Arterial gas embolism (AGE) is a rare but severe complication of scuba diving. While AGE is most commonly encountered in coastal areas with high volumes of recreational divers, at-risk populations exist throughout the United States, making basic knowledge of the disease important for all emergency medicine (EM) physicians.

Methods

We used a hypothetical simulation case to train EM residents on diagnosis and management of AGE. A 32-year-old male presented with shortness of breath and unilateral neurologic deficits immediately after scuba diving. Residents were challenged to emergently diagnose and treat tension pneumothorax followed by diagnosis and treatment of AGE. A resident, attending, and simulation technician ran the case for four separate simulation teams in the simulation center with the addition of chest tube supplies to the basic resuscitation bay setup. Teams were allowed to use the internet in real time as a reference tool.

Results

Most teams arrived at the correct diagnosis using real-time internet searches, but none found the Divers Alert Network Emergency Hotline. Learners were debriefed both immediately and in a formal lecture. A follow-up survey showed good retention of knowledge.

Discussion

This case fills a significant knowledge and training gap for many EM physicians. AGE is a rare but highly morbid complication of diving, and EM residents should have knowledge of the disease and available consultation resources. Most EM residents will not have the opportunity to treat a diver during training, and the simulation environment provides a means to teach and practice this skill set.

Improving Sperm Viability After Spinal Cord Injury Using Hyperbaric Therapy

BACKGROUND

Infertility is one of many complications of spinal cord injury (SCI) in male patients, who are often at the peak of their reproductive life. This study evaluated effects of hyperbaric therapy (HT) on quality of sperm of rats with SCI and correlated the findings with histologic analysis of the testicles.

METHODS

This experimental study comprised 18 rats that were submitted to SCI with a MASCIS Impactor and randomly allocated to either a HT or a control group. Testicular biopsies were performed on the first and 28th day of the study; 4 parameters were evaluated: concentration of sperm per mL, number of round cells per field, number of inflammatory cells per field (peroxidase [Endtz] test), and sperm viability (hypo-osmotic swelling test).

RESULTS

There was no difference in sperm concentration between the HT group (P = 0.41) and control group (P = 0.74) during 28 days. From day 1 to day 28, sperm viability decreased twice as much in the control group (P = 0.001) compared with the HT group (P = 0.017). There was no difference between the groups in mean sperm concentration and number of round and inflammatory cells. On the first day, there was no difference in sperm viability between groups. There was a significantly higher (P = 0.001) percentage of viable sperm in the HT group (86.8 ± 5.6) compared with the control group (48.8 ± 21.8) on day 28.

CONCLUSIONS

SCI increased the number of round and inflammatory cells and diminished sperm viability in both groups. HT promoted greater sperm viability in rats with SCI.

Iso-risk air no decompression limits after scoring marginal decompression sickness cases as non-events

Decompression sickness (DCS) in humans is associated with reductions in ambient pressure that occur during diving, aviation, or certain manned spaceflight operations. Its signs and symptoms can include, but are not limited to, joint pain, radiating abdominal pain, paresthesia, dyspnea, general malaise, cognitive dysfunction, cardiopulmonary dysfunction, and death. Probabilistic models of DCS allow the probability of DCS incidence and time of occurrence during or after a given hyperbaric or hypobaric exposure to be predicted based on how the gas contents or gas bubble volumes vary in hypothetical tissue compartments during the exposure. These models are calibrated using data containing the pressure and respired gas histories of actual exposures, some of which resulted in DCS, some of which did not, and others in which the diagnosis of DCS was not clear. The latter are referred to as marginal DCS cases. In earlier works, a marginal DCS event was typically weighted as 0.1, with a full DCS event being weighted as 1.0, and a non-event being weighted as 0.0. Recent work has shown that marginal DCS events should be weighted as 0.0 when calibrating gas content models. We confirm this indication in the present work by showing that such models have improved performance when calibrated to data with marginal DCS events coded as non-events. Further, we investigate the ramifications of derating marginal events on model-prescribed air diving no-stop limits.

Updates in Decompression Illness

Decompression sickness and arterial gas embolism, collectively known as decompression illness (DCI), are rare but serious afflictions that can result from compressed gas diving exposures. Risk is primarily determined by the pressure-time profile but is influenced by several factors. DCI can present idiosyncratically but with a wide range of neurologic symptoms. Examination is critical for assessment in the absence of diagnostic indicators. Many conditions must be considered in the differential diagnosis. High-fraction oxygen breathing provides first aid but definitive treatment of DCI is hyperbaric oxygen.

Sufentanil in combination with low-dose hyperbaric bupivacaine in spinal anesthesia for cesarean section: a randomized clinical trial

A double blind randomized clinical trial of sufentanil as an adjunct in spinal anesthesia for cesarean section and, thereby, be able to reduce the dose of bupivacaine, a local anesthetic, with the same result of an anesthetic block with higher doses but with fewer perioperative side effects, such as hypotension.

Patient Outcomes and Factors Associated with Healing in Calciphylaxis Patients Undergoing Adjunctive Hyperbaric Oxygen Therapy

Calcific uremic arteriolopathy, also known as calciphylaxis, is a rare syndrome of small vessel calcification of unknown etiology causing painful, violaceous skin lesions that progress to form chronic non-healing ulcers and gangrene. Hyperbaric oxygen therapy (HBOT) can be used as adjunctive therapy in the treatment of these ulcers. However, due to paucity of cases, there is limited data on the clinical benefit of HBOT and identifying factors associated with healing. The purpose of this study was to determine patient outcomes and factors associated with healing in patients with calciphylaxis undergoing HBOT. A retrospective chart review was completed on patients who were diagnosed with calciphylaxis and had hyperbaric medicine consultation between May 2012 and January 2016. Clinical outcomes, demographics, risk factors, laboratory values, wound distribution, and HBOT profiles were collected and analyzed. We identified 8 patients. Out of 8 patients consulted for calciphylaxis, five were consented and underwent HBOT (2 males and 3 females). All had coexisting ESRD and Diabetes. All males were able to tolerate being in the chamber and received therapeutic treatments (at least 20 HBOT) with complete resolution of ulcers. HBOT was discontinued in one female due to an inconsistent biopsy report and two others due to death secondary to septic shock or respiratory arrest and severe uremia. Calciphylaxis is a devastating disease with a high mortality rate. Our results demonstrated a positive response to HBOT especially when receiving at least 20 treatments. A majority of calciphylaxis cases are females and indeed female gender has been cited as a risk factor for this disease. However, current literature has not conferred a relationship between gender nor the number of HBOT received and outcomes. Our results showed that males had a more favorable outcome provided they received at least twenty HBOT. Further prospective studies are needed to elucidate these outcomes.

[Sufentanil in combination with low-dose hyperbaric bupivacaine in spinal anesthesia for cesarean section: a randomized clinical trial]

A double blind randomized clinical trial of sufentanil as an adjunct in spinal anesthesia for cesarean section and, thereby, be able to reduce the dose of bupivacaine, a local anesthetic, with the same result of an anesthetic block with higher doses but with fewer perioperative side effects, such as hypotension.

Sublingual microvascular perfusion is altered during normobaric and hyperbaric hyperoxia

Hyperoxia and hyperbaric oxygen therapy can restore oxygen tensions in tissues distressed by ischemic injury and poor vascularization and is believed to also yield angiogenesis and regulate tissue perfusion. The aim of this study was to develop a model in which hyperoxia-driven microvascular changes could be quantified and to test the hypothesis that microcirculatory responses to both normobaric (NB) and hyperbaric (HB) hyperoxic maneuvers are reversible. Sublingual mucosa microcirculation vessel density, proportion of perfused vessels, vessel diameters, microvascular flow index, macrohemodynamic, and blood gas parameters were examined in male rabbits breathing sequential O2/air mixtures of 21%, 55%, 100%, and return to 21% during NB (1.0 bar) and HB (2.5 bar) conditions. The results indicate that NB hyperoxia (55% and 100%) produced significant decreases in microvascular density and vascular diameters (p<0.01 and p<0.05, respectively) accompanied by significant increases in systolic and mean arterial blood pressure (p<0.05, respectively) with no changes in blood flow indices when compared to NB normoxia. HB normoxia/hyperoxia resulted in significant decreases in microvascular density (p<0.05), a transient rise in systolic blood pressure at 55% (p<0.01), and no changes in blood vessel diameter and blood flow indices when compared to NB hyperoxia. All microcirculation parameters reverted back to normal values upon return to NB normoxia. We conclude that NB/HB hyperoxia-driven changes elicit reversible physiological control of sublingual mucosa blood perfusion in the presence of steady cardiovascular function and that the absence of microvascular vasoconstriction during HB conditions suggests a beneficial mechanism associated with maintaining peak tissue perfusion states.

Hyperbaric oxygen in chronic traumatic brain injury: oxygen, pressure, and gene therapy

Hyperbaric oxygen therapy is a treatment for wounds in any location and of any duration that has been misunderstood for 353 years. Since 2008 it has been applied to the persistent post-concussion syndrome of mild traumatic brain injury by civilian and later military researchers with apparent conflicting results. The civilian studies are positive and the military-funded studies are a mixture of misinterpreted positive data, indeterminate data, and negative data. This has confused the medical, academic, and lay communities. The source of the confusion is a fundamental misunderstanding of the definition, principles, and mechanisms of action of hyperbaric oxygen therapy. This article argues that the traditional definition of hyperbaric oxygen therapy is arbitrary. The article establishes a scientific definition of hyperbaric oxygen therapy as a wound-healing therapy of combined increased atmospheric pressure and pressure of oxygen over ambient atmospheric pressure and pressure of oxygen whose main mechanisms of action are gene-mediated. Hyperbaric oxygen therapy exerts its wound-healing effects by expression and suppression of thousands of genes. The dominant gene actions are upregulation of trophic and anti-inflammatory genes and down-regulation of pro-inflammatory and apoptotic genes. The combination of genes affected depends on the different combinations of total pressure and pressure of oxygen. Understanding that hyperbaric oxygen therapy is a pressure and oxygen dose-dependent gene therapy allows for reconciliation of the conflicting TBI study results as outcomes of different doses of pressure and oxygen.

Effects of elevated core temperature and normoxic 30% nitrous oxide on human ventilation during short duration, high intensity exercise

It was hypothesized that normoxic 30% nitrous oxide (N2O) would suppress and hyperthermia would increase exercise ventilation during short duration, high intensity exercise. Thirteen males (24.2±0.8y; mean±SE), of normal physique (BMI, 23.8±1.0kgm(-2)), performed 4 separate 30s Wingate tests on a cycle ergometer. Exercise ventilation and its components, as well as mean skin and esophageal temperature (TES), were assessed in 2 way experimental design with factors of Thermal State (Normothermia or Hyperthermia) and Gas Type (Air or 30% Normomoxic N2O). In the 2 hyperthermic tests TES was elevated to ∼38.5°C in a 40°C bath. The main results indicated a significant interaction (F=7.14, P=0.02) between Gas Type and Thermal state for the exercise-induced increase in ventilation (ΔV˙E). During both the normothermia and hyperthermia conditions with AIR breathing, the exercise ΔV˙E was ∼80Lmin(-1) and it was significantly decreased to 73.1±24.1Lmin(-1) in the normothermia condition with N2O breathing relative to that of 92.0±25.0Lmin(-1) in the hyperthermia condition with N2O breathing. In conclusion, normoxic N2O breathing suppressed high intensity exercise ventilation during normothermia relative to that during hyperthermia on account of decreases in the tidal volume and this led CO2 retention.

The effects of respiratory muscle training on respiratory mechanics and energy cost

Resistance respiratory muscle training (RRMT) increases respiratory muscle strength and can increase swimming endurance time by as much as 85%. The purpose of this study was to examine potential mechanisms by which RRMT improves exercise endurance. Eight healthy adult male scuba divers underwent experiments in a hyperbaric chamber at sea level (1 atmosphere absolute (ATA)), 2.7 ATA and 4.6 ATA, both dry and fully submersed. Subjects rested, exercised, and rested while mimicking their own exercise breathing (ISEV). Airway resistance (R(aw)), exhaled nitric oxide output (V˙(NO)), and respiratory duty cycle (T(I)/T(Tot)) were determined before and after four weeks of RRMT. RRMT decreased T(I)/T(Tot) (-10% at rest at 1 ATA), V˙(O2) (-17% at 2.7 ATA during submersed exercise), V˙(E) (-6% at 2.7 ATA during submersed exercise), and R(aw) (-34% inspiratory at 4.6 ATA submersed, -38% expiratory at 2.7 ATA dry), independent of changes in V˙(NO). Most importantly, respiratory muscle efficiency increased (+83% at 2.7 ATA submersed).

The Use of Hyperbaric Oxygen Therapy in the Treatment of Non-healing Ulcers Secondary to Graft-versus-host Disease

We present the case of a 69 year-old gentleman with non-healing ulcers of the bilateral medial malleoli as a result of graft-versus-host disease (GvHD). The patient discussed was diagnosed with stage IV mantle cell lymphoma. Over the course of 4 years the patient was treated with autologous stem cell transplant, later reduced-intensity allogeneic stem cell transplant, and finally donor lymphocyte infusion due to recurrence. Following these therapies, the patient developed extensive GvHD that resulted in bilateral non-healing ulcers of the medial malleoli. The patient was seen in the wound care center, and his ulcers were treated with standard care that included off-loading, minor outpatient debridement, macrovascular assessment, and local moist wound healing. Despite this care, the ulcers failed to heal over a 6 month period. The patient underwent adjunctive hyperbaric oxygen therapy (HBO). He healed both ulcers within a month of completing HBO. It is our goal to discuss the pathophysiologic mechanism of non-healing wounds in the setting of GvHD and discuss the potential role of HBO in their treatment.

The effects of hyperbaric or isobaric bupivacaine on bispectral index in spinal anesthesia for cesarean section

BACKGROUND

Hyperbaric and isobaric bupivacaine has been shown to reduce bispectral index (BIS) during spinal anesthesia. The aim of this study was to compare the effect of isobaric bupivacaine and hyperbaric bupivacaine on the BIS during cesarean section with spinal anesthesia.

MATERIALS AND METHODS

In this double-blind randomized controlled clinical trial, 84 pregnant women with ASA (American Society of Anesthesiologists) class I or II were randomly assigned to receive isobaric or hyperbaric bupivacaine. BIS was measured using electro encephalography (EEG) and recorded at the baseline and 5th, 10th, 15th, 30th, 45th, 60th, 90th and 120th minutes after spinal injection. The heart rate (HR), mean arterial pressure (MAP), signal quality index (SQI), electromyography (EMG) and the temperature were also recorded during surgery.

RESULTS

From recruited subjects, 41 completed the study in each group and their data were analyzed. The BIS score began to reduce until 30(th) minute for isobaric bupivacaine and 45(th) minute for hyperbaric bupivacaine after spinal injection. The recorded BIS was not significantly different between two groups at all the time points. Difference of BIS from baseline was not significant between two groups at most time points except for the 45(th) minute after injection that it was 5.9 ± 9 vs. 2.7 ± 4.6 for hyperbaric and isobaric bupivacaine, respectively (p = 0.047). The changing trend was not significantly different between groups with hyperbaric and isobaric bupivacaine.

CONCLUSION

According to the present study, the BIS score during surgery began to decrease when the patients were injected spinally by both of these drugs. The greatest decrease from baseline BIS values occurred at 30 and 45 minutes after induction of spinal anesthesia. However, hyperbaric or isobaric bupivacaine did not have different effects on the BIS during spinal anesthesia.