Anatomy and mechanisms of vocal production in harvest mice.

Characterizing mechanisms of vocal production provides important insight into the ecology of acoustic divergence. In this study, we characterized production mechanisms of two types of vocalizations emitted by western harvest mice (Reithrodontomys megalotis), a species uniquely positioned to inform trait evolution because it is a sister taxon to peromyscines (Peromyscus and Onychomys spp.), which use vocal fold vibrations to produce long-distance calls, but more ecologically and acoustically similar to baiomyines (Baiomys and Scotinomys spp.), which employ a whistle mechanism. We found that long-distance calls (∼10 kHz) were produced by airflow-induced vocal fold vibrations, whereas high-frequency quavers used in close-distance social interactions (∼80 kHz) were generated by a whistle mechanism. Both production mechanisms were facilitated by a characteristic laryngeal morphology. Our findings indicate that the use of vocal fold vibrations for long-distance communication is widespread in reithrodontomyines (Onychomys, Peromyscus, Reithrodontomys spp.) despite overlap in frequency content that characterizes baiomyine whistled vocalizations. The results illustrate how different production mechanisms shape acoustic variation in rodents and contribute to ecologically relevant communication distances.

Breathing a low-density gas reduces respiratory muscle force development and marginally improves exercise performance in master athletes.

INTRODUCTION: We tested the hypothesis that breathing heliox, to attenuate the mechanical constraints accompanying the decline in pulmonary function with aging, improves exercise performance. METHODS: Fourteen endurance-trained older men (67.9 ± 5.9 year, [Formula: see text]O2max: 50.8 ± 5.8 ml/kg/min; 151% predicted) completed two cycling 5-km time trials while breathing room air (i.e., 21% O2-79% N2) or heliox (i.e., 21% O2-79% He). Maximal flow-volume curves (MFVC) were determined pre-exercise to characterize expiratory flow limitation (EFL, % tidal volume intersecting the MFVC). Respiratory muscle force development was indirectly determined as the product of the time integral of inspiratory and expiratory mouth pressure (∫Pmouth) and breathing frequency. Maximal inspiratory and expiratory pressure maneuvers were performed pre-exercise and post-exercise to estimate respiratory muscle fatigue. RESULTS: Exercise performance time improved (527.6 ± 38 vs. 531.3 ± 36.9 s; P = 0.017), and respiratory muscle force development decreased during inspiration (- 22.8 ± 11.6%, P < 0.001) and expiration (- 10.8 ± 11.4%, P = 0.003) with heliox compared with room air. EFL tended to be lower with heliox (22 ± 23 vs. 30 ± 23% tidal volume; P = 0.054). Minute ventilation normalized to CO2 production ([Formula: see text]E/[Formula: see text]CO2) increased with heliox (28.6 ± 2.7 vs. 25.1 ± 1.8; P < 0.001). A reduction in MIP and MEP was observed post-exercise vs. pre-exercise but was not different between conditions. CONCLUSIONS: Breathing heliox has a limited effect on performance during a 5-km time trial in master athletes despite a reduction in respiratory muscle force development.

Heliox Protects SH-SY5Y Cells from Oxygen-Glucose Deprivation/Reperfusion-Induced Ferroptosis.

BACKGROUND: Heliox shows protective effects against acute focal ischemia-reperfusion injury in the brain. However, further research is needed to unveil the intricate molecular mechanisms involved. Determining how heliox affects ferroptosis caused by oxygen-glucose deprivation/reoxygenation (OGD/R) in SH-SY5Y cells as well as the underlying mechanism was the goal of the current work. METHODS: With the use of 2',7'-Dichlorodihydrofluorescein diacetate (DCFH-DA), JC-1, and methyl thiazolyl tetrazolium, we assessed the survival, reactive oxygen species (ROS), and mitochondrial membrane potential in SH-SY5Y cells after they had been exposed to OGD/R and heliox. The expression of molecules associated with ferroptosis and the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway was analyzed using quantitative polymerase chain reaction (PCR) and immunoblotting, while malondialdehyde (MDA), oxidized glutathione disulfide (GSSG), ferrous ion (Fe2+), and reduced glutathione (GSH) levels were evaluated using biochemical kits. RESULTS: OGD/R treatment reduced the GSH to GSSG ratio; the potential of the mitochondrial membrane; the expression of the proteins GSH, SLC7A11, and glutathione peroxidase 4 (GPX4); and the ability of SH-SY5Y cells to survive. In contrast, OGD/R treatment increased the expression of cyclooxygenase-2 (COX2), ACSL4, and ferritin heavy chain 1 (FTH1) proteins, the production of MDA and GSSG, and the levels of ROS and Fe2+. However, heliox effectively mitigated all these OGD/R-induced effects. Furthermore, in OGD/R-treated SH-SY5Y cells, heliox administration stimulated the PI3K/AKT pathway while suppressing the nuclear factor-κB (NF-κB) pathway. When MK-2206, an AKT inhibitor, was applied concurrently to the cells, these outcomes were reversed. CONCLUSIONS: Heliox prevents OGD/R from causing ferroptosis in SH-SY5Y cells by activating the PI3K/AKT pathway. This suggests a promising therapeutic potential for heliox use in the management of ischemia/reperfusion injury.

Mechanisms of sound production in deer mice (Peromyscus spp.).

Rodent diversification is associated with a large diversity of species-specific social vocalizations generated by two distinct laryngeal sound production mechanisms: whistling and airflow-induced vocal fold vibration. Understanding the relative importance of each modality to context-dependent acoustic interactions requires comparative analyses among closely related species. In this study, we used light gas experiments, acoustic analyses and laryngeal morphometrics to identify the distribution of the two mechanisms among six species of deer mice (Peromyscus spp.). We found that high frequency vocalizations (simple and complex sweeps) produced in close-distance contexts were generated by a whistle mechanism. In contrast, lower frequency sustained vocalizations (SVs) used in longer distance communication were produced by airflow-induced vocal fold vibrations. Pup isolation calls, which resemble adult SVs, were also produced by airflow-induced vocal fold vibrations. Nonlinear phenomena (NLP) were common in adult SVs and pup isolation calls, suggesting irregular vocal fold vibration characteristics. Both vocal production mechanisms were facilitated by a characteristic laryngeal morphology, including a two-layered vocal fold lamina propria, small vocal membrane-like extensions on the free edge of the vocal fold, and a singular ventral laryngeal air pocket known as the ventral pouch. The size and composition of vocal folds (rather than total laryngeal size) appears to contribute to species-specific acoustic properties. Our findings suggest that dual modes of sound production are more widespread among rodents than previously appreciated. Additionally, the common occurrence of NLP highlights the nonlinearity of the vocal apparatus, whereby small changes in anatomy or physiology trigger large changes in behavior. Finally, consistency in mechanisms of sound production used by neonates and adults underscores the importance of considering vocal ontogeny in the diversification of species-specific acoustic signals.

Heliox for Pediatric Critical Asthma: A Multicenter, Retrospective, Registry-Based Descriptive Study.

BACKGROUND: In cases of critical asthma (CA), heliox may be applied as an adjunctive rescue therapy to avoid invasive mechanical ventilation (MV), improve deposition of aerosolized medications, and enhance laminar airflow through obstructed airways. Using the Pediatric Health Information System (PHIS) registry, we evaluate heliox prescribing and explored for differences in MV rates and hospital length of stay (LOS) among children with and without heliox exposure. METHODS: We performed a retrospective cohort study using PHIS data from 42 pediatric intensive care units among children 5-17 years of age admitted for CA from 2010 through 2019. Primary outcomes were heliox prescribing rates and trends. Secondary outcomes were invasive MV rates and LOS assessed in a subgroup of children receiving ≥ 1 adjunctive intervention(s). RESULTS: Of the 19,780 studied, heliox was prescribed in 12.5% and linearly declined from 16.1% in 2010 to 5.6% in 2019. The overall MV rate was 12.8% and was lower in subjects receiving heliox alone (4.9%) compared to heliox plus alternative adjunctive therapies [31.2%] or children receiving non-heliox adjunctive therapies [22.1%], P < .01). Accounting for MV, no difference in LOS was observed. In exploratory adjusted models, MV free hospitalization was associated with heliox-only exposure (OR: 0.33, 95% CI: 0.17-0.63, P < .01) and exposure to multiple adjunctive therapies was associated with MV (OR: 2.48, 95% CI: 1.56-3.94, P < .01). CONCLUSIONS: In this multicenter retrospective study from 42 children's hospitals, heliox prescribing for CA declined over the last decade. Subjects receiving multiple adjunctive therapies more commonly required invasive MV perhaps indicating a greater severity of illness. At this time, prospective trials needed to identify the role of heliox for pediatric CA.

[Chronic respiratory failure correction in cicatricial laryngeal and tracheal stenosis using helium-oxygen mixture]. / Korrektsiya khronicheskoi dykhatel'noi nedostatochnosti pri rubtsovykh stenozakh gortani i sheinogo otdela trakhei s ispol'zovaniem gelii-kislorodnoi smesi.

The article provides a review of the literature on the development of chronic respiratory failure in patients with chronic cicatricial stenosis of the larynx and cervical trachea. The authors provide data on the etiology, pathogenetic features of the course of cicatricial stenosis of the larynx and trachea, the reasons for the development of chronic respiratory failure, the effect of hypoxemia on general metabolic processes in the body and on regeneration processes, as well as on methods of their correction and improvement of the postoperative period. The methods of respiratory impact on chronic respiratory failure in these patients are considered, based on the experience of a number of researchers and technical advances in recent years.

The effects of heliox non-saturation diving on the cardiovascular system and cognitive functions.

The purpose of this study was to investigate the effects of a single bout of heliox non-saturation diving on the cardiovascular system and cognitive function. Ten recreational scuba divers (10 males, ∼35 years old) participated in this study. These subjects made two pool dives within a one-week interval, alternating gases with compressed air (21% O2, 79% N2) and with heliox (21% O2 and 79% He). The depth was to 26 meters over a 20-minute duration. The results showed that heliox diving significantly increased blood O2 saturation by 1.15% and significantly decreased blood lactate levels by ∼57% when compared with air diving (P ≺ 0.05). However, there were no significant differences in resting heart rate, systolic or diastolic pressure, core body blood pressure, and pulse wave velocity between the heliox and air dives. The Stroop test showed that the heliox dive significantly increased cognitive function compared with the air dive in both the simple test (Offtime) and interference test (Ontime) (P ≺ 0.05). It was concluded that the heliox dive increases blood O2 saturation and decreases blood lactate concentration when compared with air dives. These conditions are likely to help divers reduce hypoxia in the water, reduce the risk of loss of consciousness, reduce fatigue and allow them to dive for longer. Heliox diving may also help judgment and risk coping skills in the water due to the improvement of cognitive ability as compared to air breathing dives.

Manipulation of mechanical ventilatory constraint during moderate intensity exercise does not influence dyspnoea in healthy older men and women.

KEY POINTS: The perceived intensity of exertional breathlessness (i.e. dyspnoea) is higher in older women than in older men, possibly as a result of sex-differences in respiratory system morphology. During exercise at a given absolute intensity or minute ventilation, older women have a greater degree of mechanical ventilatory constraint (i.e. work of breathing and expiratory flow limitation) than their male counterparts, which may lead to a greater perceived intensity of dyspnoea. Using a single-blind randomized study design, we experimentally manipulated the magnitude of mechanical ventilatory constraint during moderate-intensity exercise at ventilatory threshold in healthy older men and women. We found that changes in the magnitude of mechanical ventilatory constraint within the physiological range had no effect on dyspnoea in healthy older adults. When older men and women perform moderate intensity exercise, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea. ABSTRACT: We aimed to determine the effect of manipulating mechanical ventilatory constraint during submaximal exercise on dyspnoea in older men and women. Eighteen healthy subjects (aged 60-80 years; nine men and nine women) completed two days of testing. On day 1, subjects were assessed for pulmonary function and performed a maximal incremental cycle exercise test. On day 2, subjects performed three 6-min bouts of cycling at ventilatory threshold, in a single-blind randomized manner, while breathing: (i) normoxic helium-oxygen (HEL) to reduce the work of breathing (Wb ) and alleviate expiratory flow limitation (EFL); (ii) through an inspiratory resistance (RES) of ∼5 cmH2 O L-1  s-1 to increase Wb ; and (iii) ambient air as a control (CON). Oesophageal pressure, diaphragm electromyography, and sensory responses (category-ratio 10 Borg scale) were monitored throughout exercise. During the HEL condition, there was a significant decrease in Wb (men: -21 ± 6%, women: -17 ± 10%) relative to CON (both P < 0.01). Moreover, if EFL was present during CON (four men and five women), it was alleviated during HEL. Conversely, during the RES condition, Wb (men: 42 ± 19%, women: 50 ± 16%) significantly increased relative to CON (both P < 0.01). There was no main effect of sex on Wb (P = 0.59). Across conditions, women reported significantly higher dyspnoea intensity than men (2.9 ± 0.9 vs. 1.9 ± 0.8 Borg scale units, P < 0.05). Despite significant differences in the degree of mechanical ventilatory constraint between conditions, the intensity of dyspnoea was unaffected, independent of sex (P = 0.46). When older men and women perform moderate intensity exercise, mechanical ventilatory constraint does not contribute significantly to the sensation of dyspnoea.

A proof-of-concept trial of HELIOX with different fractions of helium in a human study modeling upper airway obstruction.

BACKGROUND: Helium in oxygen (HELIOX) can relieve airway obstruction and lower the work of breathing because it increases the threshold at which turbulent gas flow is induced. Less turbulent and more laminar flow lowers the work of breathing. According to guidelines, the fraction of Helium in HELIOX should be maximized (e.g. to 79%). Here, we investigate whether HELIOX with less than 60% of Helium is able to relieve the sensation of dyspnea in healthy volunteers. METHODS: 44 volunteers underwent resistive loading breathing different gases (medical air and HELIOX with a fraction of 25%, 50% or 75% helium in oxygen) in a double-blinded crossover design. Subjects rated their degree of dyspnea (primary outcome parameter) and the variability of noninvasively measured systolic blood pressure was assessed. RESULTS: Dyspnea was significantly reduced by HELIOX-containing mixtures with a fraction of helium of 25% or more. Similarly, blood pressure variability was reduced significantly even with helium 25% during respiratory loading with the higher load, whereas with the smaller load an effect could only be obtained with the highest helium fraction of 75%. CONCLUSION: In this clinical trial, HELIOX with less than 60% of helium in oxygen decreased the sensation of dyspnea and blood pressure variability, a surrogate parameter for airway obstruction. Therefore, higher oxygen fractions might be applied without losing the helium-related benefits for the treatment of upper airway obstruction. TRIAL REGISTRATION: Registration with clinical trials (NCT00788788) and EMA (EudraCT number: 2006-005289-37).

Respiration of thermogenic inflorescences of skunk cabbage Symplocarpus renifolius in heliox.

The respiration rate of the thermogenic inflorescences of Japanese skunk cabbage Symplocarpus renifolius can reach 300 nmol s-1 g-1 , which is sufficient to raise spadix temperature (Ts ) up to 15 °C above ambient air temperature (Ta ). Respiration rate is inversely related to Ta , such that the Ts achieves a degree of independence from Ta , an effect known as temperature regulation. Here, we measure oxygen consumption rate (Mo2 ) in air (21% O2 in mainly N2 ) and in heliox (21% O2 in He) to investigate the diffusive conductance of the network of gas-filled spaces and the thermoregulatory response. When Ts was clamped at 15 °C, the temperature that produces maximal Mo2 in this species, exposure to high diffusivity heliox increased mean Mo2 significantly from 137 ± 17 to 202 ± 43 nmol s-1 g-1 FW, indicating that respiration in air is normally limited by diffusion in the gas phase and some mitochondria are unsaturated. When Ta was clamped at 15 °C and Ts was allowed to vary, exposure to heliox reduced Ts 1 °C and increased Mo2 significantly from 116 ± 10 to 137 ± 19 nmol s-1 g-1 , indicating that enhanced heat loss by conduction and convection can elicit the thermoregulatory response.

Acute management of croup in the emergency department.

Croup is one of the most common causes of upper airway obstruction in young children. It is characterized by sudden onset of barky cough, hoarse voice, inspiratory stridor and respiratory distress caused by upper airway inflammation secondary to a viral infection. Published guidelines for the diagnosis and treatment of croup advise using steroids as the mainstay treatment for all children who present to emergency department (ED) with croup symptoms. Dexamethasone, given orally as a single dose at 0.6 mg/kg, is highly efficacious in treating croup symptoms. Despite the evidence supporting the use of steroids as the cornerstone of croup treatment, there is significant practice variation among physicians treating croup in the ED. This practice point discusses evidence-based management of typical croup in the ED.

Total and regional deposition of inhaled aerosols in supine healthy subjects and subjects with mild-to-moderate COPD.

Despite substantial development of sophisticated subject-specific computational models of aerosol transport and deposition in human lungs, experimental validation of predictions from these new models is sparse. We collected aerosol retention and exhalation profiles in seven healthy volunteers and six subjects with mild-to-moderate COPD (FEV1 = 50-80%predicted) in the supine posture. Total deposition was measured during continuous breathing of 1 and 2.9 µm-diameter particles (tidal volume of 1 L, flow rate of 0.3 L/s and 0.75 L/s). Bolus inhalations of 1 µm particles were performed to penetration volumes of 200, 500 and 800 mL (flow rate of 0.5 L/s). Aerosol bolus dispersion (H), deposition, and mode shift (MS) were calculated from these data. There was no significant difference in total deposition between healthy subjects and those with COPD. Total deposition increased with increasing particle size and also with increasing flow rate. Similarly, there was no significant difference in aerosol bolus deposition between subject groups. Yet, the rate of increase in dispersion and of decrease in MS with increasing penetration volume was higher in subjects with COPD than in healthy volunteers (H: 0.798 ± 0.205 vs. 0.527 ± 0.122 mL/mL, p=0.01; MS: -0.271±0.129 vs. -0.145 ± 0.076 mL/mL, p=0.05) indicating larger ventilation inhomogeneities (based on H) and increased flow sequencing (based on MS) in the COPD than in the healthy group. In conclusion, in the supine posture, deposition appears to lack sensitivity for assessing the effect of lung morphology and/or ventilation distribution alteration induced by mild-to-moderate lung disease on the fate of inhaled aerosols. However, other parameters such as aerosol bolus dispersion and mode shift may be more sensitive parameters for evaluating models of lungs with moderate disease.

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions.

Total evaporative water loss of endotherms is assumed to be determined essentially by biophysics, at least at temperatures below thermoneutrality, with evaporative water loss determined by the water vapor deficit between the animal and the ambient air. We present here evidence, based on the first measurements of evaporative water loss for a small mammal in heliox, that mammals may have a previously unappreciated ability to maintain acute constancy of total evaporative water loss under perturbing environmental conditions. Thermoregulatory responses of ash-grey mice (Pseudomys albocinereus) to heliox were as expected, with changes in metabolic rate, conductance, and respiratory ventilation consistent with maintaining constancy of body temperature under conditions of enhanced heat loss. However, evaporative water loss did not increase in heliox. This is despite our confirmation of the physical effect that heliox augments evaporation from nonliving surfaces, which should increase cutaneous water loss, and increases minute volume of live ash-grey mice in heliox to accommodate their elevated metabolic rate, which should increase respiratory water loss. Therefore, mice had not only a thermoregulatory but also a hygroregulatory response to heliox. We interpret these results as evidence that ash-grey mice can acutely control their evaporative water loss under perturbing environmental conditions and suggest that hygroregulation at and below thermoneutrality is an important aspect of the physiology of at least some small mammals.

A Pediatric Bench Model of Continuous Albuterol Delivery Using Heliox.

BACKGROUND: The optimal setup for continuously administering albuterol with heliox remains unclear, especially for pediatric patients. This study aimed to evaluate the efficiency of continuous albuterol delivery with heliox using different nebulizer setups in a pediatric model. METHODS: A pediatric manikin with simulated spontaneous breathing was used to receive continuous albuterol (20 mg/h) with heliox (80/20) in 3 setups: (1) The MiniHEART nebulizer, driven by oxygen at 3 L/min, was attached to a Y-piece, linking to a non-rebreather mask and a valved reservoir with 11 L/min heliox; (2) a vibrating mesh nebulizer (VMN) placed at the humidifier inlet of high-flow nasal cannula (HFNC) with 11 L/min heliox and the manikin's mouth sealed; and (3) a VMN placed between a valved reservoir with 11 L/min heliox and a non-rebreather mask. Both tight-fitting and loose-fitting mask configurations were tested in the setup with vibrating mesh nebulizer and mask. Heliox of 70/30 was tested with a VMN and a loose-fitting mask. Albuterol was delivered continuously to the nebulizer via an infusion pump at 8 mL (20 mg)/h for each 20-min run and each experiment was repeated five times. A collecting filter placed between the manikin's trachea and lung model was removed after each run, and the drug was eluted and assayed via ultraviolet spectrophotometry (276 nm). RESULTS: During continuous albuterol nebulization using heliox, the VMN either in line with HFNC or with a tight-fitting mask achieved the highest and similar inhaled dose (8.5 ± 0.4 vs 8.8 ± 0.7%, P = .35), while the MiniHEART nebulizer yielded the lowest aerosol deposition (1.5 ± 0.2%). The inhaled dose was lower with the loose-fitting mask than with the tight-fitting mask (5.9 ± 0.9 vs 8.8 ± 0.7%, P=.009), and heliox of 80/20 delivered a higher inhaled dose than heliox of 70/30 (5.9 ± 0.9 vs 3.9 ± 0.4%, P=.009). CONCLUSIONS: When administering continuous albuterol with heliox in a pediatric model, utilizing a VMN in line with HFNC during closed-mouth breathing yielded a higher inhaled dose compared to both the MiniHEART nebulizer and VMN with a loose-fitting mask.

Heliox ventilation in elderly, hypertensive ICU patients improves microcirculation: A randomized controlled study.

BACKGROUND: Conventional mechanical ventilation has adverse impacts on the hemodynamics of elderly, hypertensive ICU patients. Limited studies have addressed ways to ameliorate these negative effects. This study aimed to determine whether heliox ventilation could improve the hemodynamics, especially microcirculation, of elderly, hypertensive patients undergoing mechanical ventilation. METHODS: Thirty-eight patients, over the age of 65 with essential hypertension who underwent invasive mechanical ventilation treatment, were divided into two groups: a control group of nitrogen­oxygen ventilation (n = 19) and an experimental group of heliox ventilation (n = 19). The control group received conventional room air ventilation and the experimental group adopted the innovative, closed heliox ventilation technique. Changes in blood pressure, heart rate (HR), peripheral oxygen saturation (SpO2), central venous oxygen saturation (ScvO2), regional cerebral oxygen saturation (rSO2), lactic acid (Lac) and airway pressure were measured at 0,1,2,3 h under volume-controlled ventilation (VCV) mode throughout the study. Sublingual microcirculation parameters were additionally measured at 0 h and 3 h of ventilation treatment. RESULTS: SpO2 in both groups increased after 1 h of ventilation compared with 0 h (p < 0.001), subsequently remaining stable. Compared with the control group, the experimental group showed a decrease in airway pressure and Lac, while blood pressure, ScvO2, and rSO2 increased (p < 0.05). Moreover, the sublingual microcirculation indexes in the experimental group improved compared with the control group (p < 0.05). CONCLUSIONS: Heliox ventilation improves blood pressure and microcirculation in elderly hypertensive patients and may resolve the limitations of traditional nitrogen­oxygen ventilation. TRIAL REGISTRATION: This trial was registered. The Chinese trial registration number is ChiCTR2100043945. The date of registration is 6-3-2021.

Effect of a helium and oxygen mixture on physiological parameters of rats with cerebral arterial air embolism.

Introduction: Cerebral arterial air embolism (CAE) is a serious and potentially dangerous condition that can interrupt the blood supply to the brain and cause stroke. One of the promising gas mixtures for emergency treatment of air embolism is an oxygen-helium mixture. Methods: We modeled CAE in awake rats by injecting air into the common carotid artery. Immediately after CAE, animals were either untreated or underwent hyperbaria, oxygen inhalation, heated air inhalation, or helium-oxygen mixture inhalation. Body temperature, locomotor activity, respiratory and cardiovascular parameters were monitored in the animals before CAE modeling, and 3 and 24 h after CAE modeling. Results: After 3 hours of CAE modeling in awake rats, depression of the nervous, cardiovascular and respiratory systems, as well as decreased body temperature were observed. 24 h after CAE modeling multifocal cerebral ischemia was observed. Normobaric helium-oxygen mixture inhalation, on par with hyperbaric treatment, restored body temperature, locomotor activity, respiratory volume, respiratory rate, and blood pressure 3 hours after CAE, and prevented the formation of ischemic brain damage lesions 24 h after CAE. Discussion: Thus, inhalation of a heated oxygen-helium gas mixture (O2 30% and He 70%) immediately after CAE improves the physiological condition of the animals and prevents the foci of ischemic brain damage formation.

Heliox Preconditioning Exerts Neuroprotective Effects on Neonatal Ischemia/Hypoxia Injury by Inhibiting Necroptosis Induced by Ca2+ Elevation.

Our previous studies have indicated that heliox preconditioning (HePC) may exert neuroprotective effects on neonatal hypoxic-ischemic encephalopathy (HIE). The present study was to investigate whether HePC alleviates neonatal HIE by inhibiting necroptosis and explore the potential mechanism. Seven-day-old rat pups were randomly divided into Sham group, HIE group, HIE + HePC group, HIE + Dantrolene (DAN) group, and HIE + Necrostatin-1 (Nec-1) group. HIE was induced by common carotid artery ligation and subsequent hypoxia exposure. The neurological function, brain injury, and molecular mechanism were evaluated by histological staining, neurobehavioral test, Western blotting, Ca2+, immunofluorescence staining, co-immunoprecipitation (Co-IP), and transmission electron microscopy (TEM). Results supported that the expression of necroptosis markers and p-RyR2 in the brain increased significantly after HIE. HePC, DAN, or Nec-1 was found to improve the neurological deficits after H/I and inhibit neuronal necroptosis. Interestingly, both HePC and DAN inhibited the increases in cytoplasmic Ca2+ and CaMK-II phosphorylation in the brain secondary to HIE, but Nec-1 failed to affect Ca2+. In conclusion, our results suggest HePC may alleviate cytoplasmic Ca2+ overload by regulating p-RyR2, which inhibits the necroptosis in the brain, exerting neuroprotective effects on HIE.

Heliox simulations for initial management of congenital laryngotracheal stenosis.

OBJECTIVES: Congenital laryngotracheal stenosis is rare, potentially severe, and difficult to manage. Heliox is a medical gas effective in obstructive airway pathologies, given its physical properties. This study aims to model the interest of Heliox in reducing the respiratory work in congenital laryngotracheal stenosis, using numerical fluid flow simulations, before considering its clinical use. DESIGN: This is a retrospective study, performing Computational Fluid Dynamics numerical simulations of the resistances to airflow and three types of Heliox, on 3D reconstructions from CT scans of children presenting with laryngotracheal stenosis. PATIENTS: Infants and children who were managed in the Pediatric ENT department of a tertiary-care center and underwent CT scanning for laryngotracheal stenosis between 2008 and 2018 were included. RESULTS: Fourteen models of congenital laryngotracheal stenosis were performed in children aged from 16 days to 5 years, and one model of the normal trachea in a 5-year-old child. Tightest stenosis obtained the highest airway resistances, ranging from 40 to 10 kPa/L/s (up to 800 times higher than in the normal case). Heliox enabled a decrease in pressure drops and airway resistances in all stenosis cases, correlated to increasing Helium concentration. CONCLUSIONS: Heliox appears to reduce pressure drops and airway resistances in 3D models of laryngotracheal stenosis. It may represent a supportive treatment for laryngotracheal stenosis, while waiting for specialized care, thanks to the reduction of respiratory work.

Evaluation of the Efficiency of Oxygen-Helium Therapy for Patients with Covid-19-Associated Pneumonia.

This article summarizes the experience of managing patients with COVID-19-associated pneumonia treated in one of the intensive care units of a multidisciplinary hospital with and without a heated oxygen-helium mixture. It has been shown that the use of a heated oxygen-helium mixture in the complex therapy of pneumonia caused by SARS-CoV-2 is effective. A comparative analysis of the clinical manifestations of the disease and the results of laboratory tests in the main and control groups of patients confirm with a high degree of reliability the improvement of blood oxygenation, the normalization of the acid-base balance and the positive dynamics of the main parameters, which ultimately increases the efficacy and reduces the time of treatment.

Lung function changes in divers after a single deep helium-oxygen dive.

INTRODUCTION: This study measured pulmonary function in divers after a single helium-oxygen (heliox) dive to 80, 100, or 120 metres of sea water (msw). METHODS: A total of 26 divers participated, of whom 15, five, and six performed a 80, 100, or 120 msw dive, respectively. While immersed, the divers breathed heliox and air, then oxygen during surface decompression in a hyperbaric chamber. Pulmonary function was measured twice before diving, 30 min after diving, and 24 h after diving. RESULTS: At 30 min after the 80 msw dive the forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio and the maximum expiratory flow at 25% of vital capacity (MEF25) values decreased (89.2% to 87.1% and 2.57 L·s⁻¹ to 2.35 L·s⁻¹, P = 0.04, P = 0.048 respectively) but FEV1/FVC returned to the baseline values by 24 h post-dive. Other pulmonary indicators exhibited downward trends at 30 min after the dive, but statistical significance was lacking. Interestingly, though several parameters decreased after the 100 msw dive, statistical significance was not reached. After the 120 msw dive, the FEV1/FVC and MEF75 decreased (90.4% to 85.6% and 8.05 L·s⁻¹ to 7.46 L·s⁻¹, P = 0.01, P = 0.007). The relatively small numbers of subjects who dived to 100 and 120 msw depths may explain the inconsistent results. The subjects diving to 100 and 120 msw were more trained / skilled, but this would not explain the inconsistencies in results between these depths. CONCLUSIONS: We conclude that single deep heliox dives cause a temporary decrease in FEV1/FEV and MEF25 or MEF75, but these changes can recover at 24 h after the dive.