Technical Freediving: An Emerging Breath-Hold Diving Technique

Technical freediving can be defined as freediving augmented by the use of oxygen-enriched gases or oxygen before, during, or after a freedive. As a result of these techniques, breath-hold divers can visit and enjoy underwater wrecks, reefs, and other diving locations previously located at depths unreachable to apnea divers. By pre-breathing oxygen-enriched gases in conjunction with hyperventilation—which decreases the partial pressure of carbon dioxide (PCO2)—the technical freediver now has additional oxygen to facilitate aerobic respiration during the dive. In addition, pre-breathing oxygen decreases tissue nitrogen tensions, which limits inert gas loading and decreases the risk of decompression sickness (DCS). Finally, this technique decreases PCO2, which diminishes the urge to breathe. Consequently, a diver may be able to dive longer before critical hypoxia or hypercarbia forces an ascent. Technical freediving can also be complemented by the use of a diver propulsion vehicle to increase the speed of descent and ascent and minimize exertion. The techniques of technical freediving may be associated with increased risks in central nervous system oxygen toxicity, DCS, and arterial gas embolism. As the boundaries of apnea diving continue to expand, there will be considerable opportunities to investigate the physiological limits of the human body and to determine the safest methodologies to practice this evolving discipline

Silyl trifluoromethanesulfonate-activated para-methoxybenzyl methyl ether as an alkylating agent for thiols and aryl ketones

para-Methoxybenzyl methyl ether acts as an alkylating agent for thiols in the presence of trimethylsilyl trifluoromethanesulfonate and trialkylamine base in good yields (58-96%). Aryl ketones are alkylated under similar conditions, probably through an enol silane intermediate, also in high yields (67-95%). The active alkylating species is likely a p-methoxybenzyl cation

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Characteristics of ocular pain complaints in patients with idiopathic dry eye symptoms

OBJECTIVE: The purpose of this study was to examine the severity and quality of ocular pain complaints in patients with dry eye symptoms. METHODS: Subjects with clinically-relevant dry eye symptoms (dryness, discomfort, tearing) of unknown origin seen in the Miami Veterans Affairs eye clinic were administered questionnaires for dry eye symptoms and ocular pain and underwent a standardized ocular examination. Qualities and severity ratings of ocular pain in subjects with idiopathic dry eye were compared to similar measures from published data in other chronic pain populations. RESULTS: The study sample consisted of 154 subjects, of which 91% were male and ranged in age from 27 to 89 (mean age = 61). Fifty-three percent of participants reported an average ocular pain of at least moderate intensity (numerical rating scale (NRS) ≥ 4), with specific characteristics (i.e., “burning” spontaneous pain) reported at frequencies comparable to prevalent chronic neuropathic pain syndromes as reported in the literature. Significant correlations were found between ocular pain metrics and dry eye symptom severity scores (r=0.57 to 0.66). Dry eye signs, however, did not generally correlate with ocular pain severity. CONCLUSIONS: A significant proportion of subjects with idiopathic dry eye symptoms reported moderate or greater ocular pain intensity, with the majority endorsing descriptors commonly used by patients with non-ocular neuropathic pain conditions. Identifying sub-groups of dry eye patients based on the presence and characteristics of ocular pain complaints may improve dry eye sub classification and better individualize treatment strategies

Deep Brain Stimulation Utilizing Dexmedetomidine: A Clinical Report from the University of Miami Miller School of Medicine

Background: Deep brain stimulation (DBS) is an increasingly utilized technique to treat symptoms of neurological movement disorders, most commonly, Parkinson’s Disease. Patients and surgeons alike appreciate the minimally invasive nature of this procedure, as well as its reversibility. As these surgeries are being performed more often, it is becoming increasingly important to optimize our anesthetic management during these cases. Methods: We conducted a retrospective review of the DBS procedures that have been performed at our institution utilizing monitored anaesthesia care (MAC) via dexmedetomidine infusion to report on the frequency and type of perioperative complications as well as to assess the effectiveness of this technique. Results: A total of 150 patients and 174 lead placements were included in this study. Dexmedetomidine was the sole anaesthetic used in 85.6% of cases. The remaining cases used a combination of dexmedetomidine and adjuvant agents. A total of one perioperative complication was found in our series, resulting in a total complication rate percentage per patient of 0.6%.Conclusions: We found very few perioperative complications associated with the use of dexmedetomidine during these challenging cases. With its anxiolytic, sedative, and analgesic properties coupled with preservation of respiration and a short half-life, dexmedetomidine has ideal properties for DBS procedures

Deep Brain Stimulation Utilizing Dexmedetomidine: A Clinical Report from the University of Miami Miller School of Medicine

Abstract Background: Deep brain stimulation (DBS) is an increasingly utilized technique to treat symptoms of neurological movement disorders, most commonly, Parkinson’s Disease. Patients and surgeons alike appreciate the minimally invasive nature of this procedure, as well as its reversibility. As these surgeries are being performed more often, it is becoming increasingly important to optimize our anesthetic management during these cases. Methods: We conducted a retrospective review of the DBS procedures that have been performed at our institution utilizing monitored anaesthesia care (MAC) via dexmedetomidine infusion to report on the frequency and type of perioperative complications as well as to assess the effectiveness of this technique. Results: A total of 150 patients and 174 lead placements were included in this study. Dexmedetomidine was the sole anaesthetic used in 85.6% of cases. The remaining cases used a combination of dexmedetomidine and adjuvant agents. A total of one perioperative complication was found in our series, resulting in a total complication rate percentage per patient of 0.6%. Conclusions: We found very few perioperative complications associated with the use of dexmedetomidine during these challenging cases. With its anxiolytic, sedative, and analgesic properties coupled with preservation of respiration and a short half-life, dexmedetomidine has ideal properties for DBS procedures

Assessment of Somatosensory Function in Patients With Idiopathic Dry Eye Symptoms

Somatosensory dysfunction likely underlies dry eye (DE) symptoms in many individuals yet remains an understudied component of the disease. Its presence has important diagnostic and therapeutic implications. To assess the integrity of nociceptive system processes in persons with DE and ocular pain using quantitative sensory testing (QST) techniques applied at a site remote from the eye. A cross-sectional study conducted at Miami Veterans Affairs Hospital included 118 individuals with a wide variety of DE symptoms and signs. The study was conducted from October 31, 2013, to January 28, 2016. Individuals completed questionnaires regarding ocular symptoms (5-Item Dry Eye Questionnaire [DEQ5], Ocular Surface Disease Index [OSDI], and Neuropathic Pain Symptom Inventory modified for the eye [NPSI-E]), psychological status, and medication use and underwent an ocular surface examination. The QST metrics included measures of vibratory and thermal thresholds and cold and hot pain temporal summation (surrogate measures of central sensitization) on the forearm. Correlations among DE and ocular pain symptom severity with QST metrics measured on the forearm. The OSDI score ranges from 0 to 100, with 100 indicating the most severe DE symptoms. The DEQ5 score ranges from 0 to 22, with the highest score indicating the most severe symptoms, and the NPSI-E score ranges from 0 to 100, with the highest score indicating the most severe symptoms. Psychological state was measured with the 9-item Patient Health Questionnaire, the PTSD Checklist-Military Version for PTSD, and the Symptom Checklist-90 for anxiety. Of the 118 patients who participated in the study, 105 (88.9%) were men (mean [SD] age, 60 [10] years), and a mean of 41% had PTSD, 10% depression, and 0.93% anxiety. Using stepwise linear regression analyses, significant associations were identified between overall DE symptom severity and posttraumatic stress disorder scores and tear breakup time (DEQ5 model: R = 0.54; OSDI model: R = 0.61, P < .001). All other variables (ie, demographics, comorbidities, medications, tear film factors, and QST metrics) dropped out of these models. When specifically considering neuropathic-like qualities of DE pain, however, anxiety and hot pain temporal summation at the forearm explained 17% of the variability in ocular burning (R = 0.41; P < .001), and PTSD score, tear breakup time, and hot pain temporal summation at the forearm explained 25% of the variability in sensitivity to wind (R = 0.50; P < .001) and 30% of the variability in total NPSI-E scores (R = 0.55; P < .001). Our findings demonstrate that neuropathic-like DE pain symptom severity correlates with quantitative measures of pain sensitivity at a site remote from the eye. This result provides additional evidence that DE symptoms are not only manifestations of a local disorder but also involve somatosensory dysfunction beyond the trigeminal system

Future methane emissions from the heavy-duty natural gas transportation sector for stasis, high, medium, and low scenarios in 2035

<p>Today’s heavy-duty natural gas–fueled fleet is estimated to represent less than 2% of the total fleet. However, over the next couple of decades, predictions are that the percentage could grow to represent as much as 50%. Although fueling switching to natural gas could provide a climate benefit relative to diesel fuel, the potential for emissions of methane (a potent greenhouse gas) from natural gas–fueled vehicles has been identified as a concern. Since today’s heavy-duty natural gas–fueled fleet penetration is low, today’s total fleet-wide emissions will be also be low regardless of per vehicle emissions. However, predicted growth could result in a significant quantity of methane emissions. To evaluate this potential and identify effective options for minimizing emissions, future growth scenarios of heavy-duty natural gas–fueled vehicles, and compressed natural gas and liquefied natural gas fueling stations that serve them, have been developed for 2035, when the populations could be significant. The scenarios rely on the most recent measurement campaign of the latest manufactured technology, equipment, and vehicles reported in a companion paper as well as projections of technology and practice advances. These “pump-to-wheels”(PTW) projections do not include methane emissions outside of the bounds of the vehicles and fuel stations themselves and should not be confused with a complete wells-to-wheels analysis. Stasis, high, medium, and low scenario PTW emissions projections for 2035 were 1.32%, 0.67%, 0.33%, and 0.15% of the fuel used. The scenarios highlight that a large emissions reductions could be realized with closed crankcase operation, improved best practices, and implementation of vent mitigation technologies. Recognition of the potential pathways for emissions reductions could further enhance the heavy-duty transportation sectors ability to reduce carbon emissions.</p> <p><i>Implications</i>: Newly collected pump-to-wheels methane emissions data for current natural gas technologies were combined with future market growth scenarios, estimated technology advancements, and best practices to examine the climate benefit of future fuel switching. The analysis indicates the necessary targets of efficiency, methane emissions, market penetration, and best practices necessary to enable a pathway for natural gas to reduce the carbon intensity of the heavy-duty transportation sector.</p