Mixture Of Nitrous Oxide Research Articles

Flame propagation characteristics and gas-phase oxidation of nitrous oxide and propane

Nitrous oxide and fuel blends propellant as one of the substitutes for highly toxic hydrazine are under investigation. This study investigated the flame structure and dynamics of stoichiometric nitrous oxide and propane mixture (N2O/C3H8) by using polymethyl methacrylate (PMMA) tubes of varying inner diameters (5, 10, 15, and 50 mm) and a consistent length (1400 mm). The influence of tube diameter on flame acceleration was analyzed. The results reveal that within the 50-mm diameter tube, the flame propagation speed increased as the flame front moved forward in the tube, achieving a maximum speed of 532 m/s. In the tubes with 5-, 10-, and 15-mm diameters, all three stages—deflagration, transition to detonation, and detonation attenuation—were observed. Notably, the flame acceleration rate and maximum propagation velocity increased with the tube diameter, with the maximum velocities in the 5-, 10-, and 15-mm tubes being 1900, 2060, and 2140 m/s, respectively. The oxidation pathways of C3H8 reacting with N2O were studied using the B3LYP/6–31++G** method based on density functional theory. Thus, the study could determine changes in the configurations of reactants, intermediates, transition states, and products; the characteristics of the potential energy associated with the reaction pathways; and the reaction laws and thermodynamic parameters.

Detonation Cell Size Prediction Using Artificial Neural Networks (ANNs) for Hydrogen/Hydrocarbon/Ammonia/Nitrous Oxide Mixtures

In this work, a previously developed three-feature Artificial Neural Network (ANN) model with dimensional inputs is directly applied to predict the cell size of hydrocarbon/ammonia/nitrous oxide mixtures and compare these to experimental data. This model uses as inputs three ZND parameters (MCJ, ΔI, and σ˙max), which are mainly calculated using Konnov’s and Mével’s mechanisms. A similar prediction is obtained with the two mechanisms for the biogas–O2, H2–O2, H2–N2O, and NH3–O2 mixtures, indicating that the model is not only limited to Konnov’s chemical kinetic mechanism which was used for its training. The overall good agreement between the ANN predictions and the actual experimental values for the aforementioned mixtures, which are not used in the original training of the ANN model, is promising and shows its potential for application and extension to other mixtures and initial conditions, provided that the chemical kinetic parameters describing the ideal reaction zone structure could be computed. The model is then used to compare experimental cell size data from two detonation tube facilities, and also different chemical kinetic mechanisms for NH3-N2O mixtures. In the end, the original ANN model is expanded with the inclusion of additional cell size data, showing a slightly lower mean error for the predicted cell sizes if the data for the mixtures considered in this study are taken into account for the training of the new ANN model.

Short Term Effects of Inhalation Sedation on Child Dental Fear and Anxiety.

Dental procedures profoundly affect a child's dental fear and anxiety, rendering dental treatment difficult. Inhalation sedation with a mixture of nitrous oxide and oxygen (NO2/02) breathed through a nosepiece is a form of light conscious sedation widely used in apprehensive children to help them relax and accept dental treatment. This, however, can have both shortand long-term effects on child dental fear and anxiety. This study aimed to assess the short-term immediate effect of inhalation sedation on child dental fear and anxiety scores. This analytical cross-sectional study was conducted at the Department of Paediatric Dentistry at Rehman College of Dentistry, Peshawar, Pakistan, over a period of 1.9 years (January 2019- October 2020). A total of 171 children aged 6-11 years were selected with moderate to severe dental anxiety using the Child Fear Survey Schedule-Dental Subscale (CFSS-DS), requiring pulp therapy in at least one of their deciduous molars. Baseline anxiety scores were calculated using Venham Clinical Anxiety Score (VCAS) and Venham Picture test (VPT) with a dental check-up and fluoride application. VCAS and VPT scores were then assessed at the end of their scheduled second dental visit involving dental anaesthesia and inhalation sedation. VCAS and VPT scores at the end of treatment were compared with the baseline scores. Out of 171 children, 86 were male and 85 were female, with a mean age of 7.77. Females showed a higher range of VCAS and VPT scores (p ≤0.001) compared to males. The VCAS and VPT scores declined just at the end of the second dental visit following dental anaesthesia with inhalation sedation (mean difference = 1.96 and 3.39, respectively), which was statistically significant (p ≤0.001). Inhalation sedation has a significant role in reducing child dental fear and anxiety in the short term.

Efficacy of inhalation of a nitrous oxide and oxygen mixture for pain management during rigid cystoscopy: a randomized controlled trial

Objective: To evaluate the efficacy of pain management using inhalation of a nitrous oxide and oxygen mixture during rigid cystoscopy. Materials and Methods: A total of 55 patients were prospectively selected and randomized to receive oxygen (27) or Entonox (28). Both groups were given the respective gas for 3 minutes via breath-activated facemask before cystoscopy and continued to breathe the gas until the end of the procedure. The oxygen and Entonox groups received 20 ml 2% lidocaine gel intraurethral 15 minutes before the procedure. Heart rate, and numeric pain rating scales were recorded before, during, and after the cystoscopy. Results: Fifty-five patients were randomized into two groups, 27 were given oxygen and 28 Entonox. There were no statistically significant differences between the groups in terms of baseline patient characteristics. Intraoperative rigid cystoscopy pain scores were significantly lower in the Entonox group than in the oxygen group (2.4 vs 4.2, p = 0.009). There were no significant differences between the two groups as regards postoperative pain, intraoperative and post-operative heart rates, and side effects. Conclusion: Entonox significantly reduces intraoperative cystoscopy-related pain, without significant complications.

Changes in cerebral connectivity and brain tissue pulsations with the antidepressant response to an equimolar mixture of oxygen and nitrous oxide: an MRI and ultrasound study.

Nitrous oxide (N2O) has recently emerged as a potential fast-acting antidepressant but the cerebral mechanisms involved in this effect remain speculative. We hypothesized that the antidepressant response to an Equimolar Mixture of Oxygen and Nitrous Oxide (EMONO) would be associated with changes in cerebral connectivity and brain tissue pulsations (BTP). Thirty participants (20 with a major depressive episode resistant to at least one antidepressant and 10 healthy controls-HC, aged 25-50, only females) were exposed to a 1-h single session of EMONO and followed for 1 week. We defined response as a reduction of at least 50% in the MADRS score 1 week after exposure. Cerebral connectivity of the Anterior Cingulate Cortex (ACC), using ROI-based resting state fMRI, and BTP, using ultrasound Tissue Pulsatility Imaging, were compared before and rapidly after exposure (as well as during exposure for BTP) among HC, non-responders and responders. We conducted analyses to compare group × time, group, and time effects. Nine (45%) depressed participants were considered responders and eleven (55%) non-responders. In responders, we observed a significant reduction in the connectivity of the subgenual ACC with the precuneus. Connectivity of the supracallosal ACC with the mid-cingulate also significantly decreased after exposure in HC and in non-responders. BTP significantly increased in the three groups between baseline and gas exposure, but the increase in BTP within the first 10 min was only significant in responders. We found that a single session of EMONO can rapidly modify the functional connectivity in the subgenual ACC-precuneus, nodes within the default mode network, in depressed participants responders to EMONO. In addition, larger increases in BTP, associated with a significant rise in cerebral blood flow, appear to promote the antidepressant response, possibly by facilitating optimal drug delivery to the brain. Our study identified potential cerebral mechanisms related to the antidepressant response of N2O, as well as potential markers for treatment response with this fast-acting antidepressant.

Experimental Evaluation and Design of Propulsion System For Cubesat: N2o and C2h4 as Green Bipropellant

This work proposes a design of a new propulsion module for a 3U CubeSat that will be used for collision avoidance and for deorbiting the spacecraft. We propose a bi-propellant, a mixture of Ethylene and Nitrous oxide which has no toxicity. The bi-propellant system used does not need an additional pressurizing system and will ignite automatically when the mixture will enter the combustion chamber. Due to these features, our propulsion module uses only 1U space of the CubeSat saving 2U for other systems. In this study, a program such as CEA and RPA were used for chemical equilibrium calculation developed in NASA and German Universities. It contains a thermodynamic data library, the PAC99 program which does regression and estimation of thermodynamics, numerical analysis data and chemical equilibrium analyzed by various stimulations. This propulsion evaluation aims at the calculation of efficiency, feasibility and specific impulse obtained was larger than 300 seconds.

Anesthesia in the Korean War.

Relying on original, primary source documentation from the National Archives, we describe the practice of anesthesia in mobile army surgical hospital (MASH) units and the 171st Evacuation Hospital during the latter part of the Korean War in 1953. Values were scaled and reported as percentages. These Essential Technical Medical Data Sheets reveal a surprising proportion (12.9%) of men received spinal anesthetics, despite official recommendations to the contrary. Still, the majority (69.2%) of the wounded underwent general anesthesia, most commonly through a mixture of thiopental and nitrous oxide. Despite data from World War II demonstrating the advantages of endotracheal intubation in these patients, few patients (20.6%) were intubated. Six percent benefited from the new curare-based drugs. This is the first English-language article that describes the practice of anesthesia during the Korean War. Utilizing primary source documentation, we found that general anesthesia was the most common type utilized. Newer techniques were not as commonly adopted, despite official recommendations and data from the time. The care provided closely resembled that delivered in the Second World War but inspired a series of technological and pedagogical reforms through the 1950s to improve military anesthesia for the next conflict.

The Use of Equimolar Mixtures of Nitrous Oxide and Oxygen in Oral Surgery-A Retrospective Study of Patients in a Swiss University Hospital Setting.

The purpose of the study was to evaluate the success of procedural conscious sedation using inhaled equimolar nitrous oxide-oxygen (NOIS-EMONO) in patients undergoing routine dental and oral surgery procedures in a Swiss university hospital setting. The authors conducted a retrospective cohort study of patients that underwent NOIS-supported procedures between 2018 and 2022 at the oral surgery department of the University Hospital of Geneva (HUG), Switzerland. The primary outcome was the measurement of the procedure's success and efficacy as defined by the European Society of Anesthesiology. Secondary objectives included the analysis of the types of treatments performed, their indications, patient behavior, and the patient-clinician satisfaction score. 55 patients were included in the study; 85% underwent surgical procedures, and the remaining 15% underwent restorative and preventive procedures. The overall treatment success rate was 98.2% and 97.9% for surgically treated patients. Out of the patients, 62% appeared relaxed, calm, and serene, while 16% expressed pain or fear during the procedure. Infiltrative administration of local anesthesia caused stress in 22% of patients. This portion was significantly lower in sub-cohorts who received local topical anesthetics (0%) or a combination of systemic and local topical analgesics (7%). Patients (75%) and clinicians (91%) were satisfied with the procedure. Inhaled equimolar nitrous oxide-oxygen procedural sedation used during dental procedures and oral surgery results in high treatment success and satisfaction rates. The administration of additional topical anesthetics helps to reduce the anxiety and stress related to infiltrative anesthesia. Further dedicated studies and prospective trials are needed to confirm these findings.

Influence of Entonox (mixture of 50% nitrous oxide and 50% oxygen) on physiological labor and neonatal outcome in own material.

The aim of the study was to compare maternal and neonatal outcome of delivery with inhaled anesthesia to delivery without pain control. Authors performed retrospective analysis of 260 term deliveries. In the study group (130 women) a mixture of nitrous oxide and oxygen was used. The control group included 130 patients who used no pain relief during delivery. In nulliparas the pain assessment in 11-points scale was similar in both groups, but the labor was longer (350 ± 152 vs 228 ± 113 minutes; p < 0.001 for the first stage and 46 ± 37 vs 18 ± 18 minutes; p < 0.001 for the second stage), episiotomy incidence was higher (81.4% vs 41.9%; p < 0.001) and perineal laceration lower (2.3% vs 25.7%; p < 0.001) in the study group. In multiparas the pain assessment was lower in the study group (5 vs 7 points; p = 0.006), oxytocin was administered more frequently (45.5% vs 21.4%, p = 0.011), but labor duration was the same in both groups. Episiotomy was more frequent (61.4% vs 37.5%, p = 0.02), but there was no difference in perineal laceration. Apgar score was the same in the study and control group. We found that Entonox prolongs labor significantly and increases frequency of episiotomy in primiparas with no clear analgesic effect. Offering Entonox to the patients giving birth for the first time is thus questionable. In multiparas it has a good analgesic effect but increases probability of episiotomy with no significant influence on perineal tear, what seems not very high cost of decreased pain related to delivery.

Experimental studies on flame propagation and detonation characteristics of premixed nitrous oxide, ammonia, and propane in cylindrical channel

Nitrous oxide fuel blends have been identifiedas a promising propellant to be used as a hydrazine replacement. In this study, the flame propagation and detonation characteristics of nitrous oxide, ammonia, and propane mixtures were investigated experimentally in a cylindrical channel (length, 2000 mm; inner diameter, 15 mm). Tests were performed for five propane mass fractions (0, 2.0, 3.8, 5.7, and 7.4 wt%) to investigate flame behavior and determine the suitablepropellant formulation. The results demonstrated that the flame acceleration rate first increased and then decreased with additional increases of propane. The overpressures and shock velocities exhibited a similar trend and achieved the steady detonation stage except for the mixture with propane fraction of 7.4 wt%. Propane outperformed ammonia as an additive to nitrous oxide, and the addition of 2.0 wt% propane had a positive influence on the flame acceleration process, pressure, and shock buildup for premixed nitrous oxide and ammonia. However, for lower concentrations of nitrous oxide with the addition of excessive propane, a decrease in the aforementioned parameters was observed in the doped flames.

Thermodynamic, Exergoeconomic and Multi-Objective Analyses of Supercritical N2O-He Recompression Brayton Cycle for a Nuclear Spacecraft Application

Detailed thermodynamic, exergoeconomic, and multi-objective analysis are performed for a supercritical recompression Brayton cycle in which the advanced working medium mixture of nitrous oxide and helium (N2O–He) is utilized for power generation. The thermodynamic and exergoeconomic models are propitious based on the standard components’ mass and energy conservation, exergy balance equation, and exergy cost calculation equation. An investigation of the sensitivity parametric is considered for judging the impact of crucial decision variable parameters on the performance of the proposed Brayton cycle. The proposed cycle’s performance is evaluated by systematic analysis of the thermal efficiency (ηth), exergy efficiency (ηex), total cost rate (C.total), levelized cost of electricity (LCOE), and the total heat transfer area (Atotal). Furthermore, multi-objective optimization is adopted from the viewpoint of the first and second laws of exergoeconomics to find the optimum operating parameters and to improve the circular’s exergoeconomic performance. The final results illustrate that the optimization calculation is based on the fact of the exergoeconomics method; the whole system produces electrical power of 0.277 MW with C.total of USD 18.37/h, while the ηth, ηex, Atotal, and LCOE are 49.14%, 67.29%, 165.55 m2 and USD 0.0196/kWh, respectively. It is concluded that the work exergy destruction for the reactor and turbine is higher than that of other components; then, after the multi-objective optimization analysis, the ηth and ηex improved by 2.08% and 5.07%, respectively, and the C.total, Atotal, and LCOE decreased by 13.99%, 0.01%, and 5.13%, respectively.

P39 Virtual reality headset as an alternative to Entonox for intraarticular corticosteroid injection

P39 Virtual reality headset as an alternative to Entonox for intraarticular corticosteroid injection

The Use of a Fixed 50:50 Mixture of Nitrous Oxide and Oxygen to Reduce Lumbar Puncture-Induced Pain in the Emergency Department: A Randomized Controlled Trial.

Lumbar puncture (LP) is stressful and often painful. We evaluated the efficacy of a fixed 50% nitrous oxide–oxygen mixture (50%N2O-O2) versus placebo to reduce immediate procedural pain and anxiety during LP performed in an emergency setting. We conducted a randomized controlled trial involving adults who needed a cerebrospinal fluid analysis in an emergency department. Patients were randomly assigned to inhale either 50%N2O-O2 or medical air. The primary endpoint, assessed using a numerical scale, was the maximum pain felt by the patient during the procedure and the maximum anxiety and satisfaction as secondary outcomes. Eighty-eight patients were randomized and analyzed (ITT). The maximal pain was 5.0 ± 2.9 for patients receiving air and 4.2 ± 3.0 for patients receiving 50%N2O-O2 (effect-size = −0.27 [−0.69; 0.14], p = 0.20). LP-induced anxiety was 4.7 ± 2.8 vs. 3.7 ± 3.7 (p = 0.13), and the proportion of patients with significant anxiety (score ≥ 4/10) was 72.7% vs. 50.0% (p = 0.03). Overall satisfaction was higher among patients receiving 50%N2O-O2 (7.4 ± 2.4 vs. 8.9 ± 1.6, p < 0.001). No serious adverse events were attributable to 50%N2O-O2 inhalation. Although inhalation of 50%N2O-O2 failed to reduce LP-induced pain in an emergency setting, it tended to reduce anxiety and significantly increased patient satisfaction.

Properties of Nitrous Oxide and Helium mixtures for space nuclear recompression Brayton cycle

Space nuclear reactors are the research foundation of space nuclear power and nuclear propulsion. Thermoelectric conversion efficiency and mass of high-power nuclear reactors have always been essential factors that restrict aerospace design. Supercritical nitrous oxide (S-N2O) Brayton cycle is becoming hot research due to its high-power conversion efficiency, low energy loss, compact and simple system structure, making it widely used in space nuclear reactor application. The recompression cycle is proposed to improve the thermal efficiency of the S-N2O cycle and effectively weaken the “pinch point” phenomenon that may occur in the regenerators. The thermodynamic of the S-N2O Brayton cycle has been studied but has little research on the nitrous oxide (N2O) and helium (He) mixtures as the working medium for the Brayton cycle. In this paper, physical properties were studied on the mixture of supercritical nitrous oxide and helium (S-N2O+He) as the working medium of the space power system based on a recompression Brayton cycle. Consider the thermodynamic properties of the mixture at seven different temperature nodes, analyze the variation trend of compressibility factor, specific heat, specific heat ratio, thermal conductivity, and dynamic viscosity with temperature, respectively. Finally, determined the mixing ratio of the working medium at the maximum thermoelectric conversion efficiency of the cycle and estimated the mass and specific mass of the Brayton rotating unit.

Optimization of a recompression supercritical nitrous oxide and helium Brayton cycle for space nuclear system

Long life, high energy density, high efficiency, and compact power system is necessary for space exploration to achieve a future goal. Recompression supercritical Brayton cycle has excellent potential for application of space nuclear power generation systems. However, it faces the choice of cycle working fluid which limits the cycle thermal efficiency and quality. In order to improve the thermal efficiency of the nuclear power system, a new composition of the working fluid, nitrous oxide and helium (N2O–He) mixture is used in the system. Comprehensive studies and optimization are performed for the significant parameters, including the split ratio, pressure ratio, minimum operating temperature, maximum operating temperature, and minimum operating pressure. Optimum values have been obtained at which the maximum thermal efficiency and minimum Brayton rotating unit (BRU) mass of the cycle occur. Results show that the thermal efficiency improves with an increase in the split ratio, main compressor pressure ratio, and maximum operating temperature, and decreasing minimum operating temperature and minimum operating pressure. The proposed novel working fluid cycle has superior performance compared with N2O (deviation of 5.1%) and CO2 (deviation of 6.5%). The optimized thermal efficiency and BRU mass are calculated as 42.67% and 3584.80 kg at optimum conditions.

Hybrid rocket propulsion technology for space transportation revisited - propellant solutions and challenges

This paper presents the status of developments worldwide regarding use of hybrid rocket motors for space transportation. Historical roots are presented and reasons for revisiting hybrid technology after a few decades of limited interest are examined. Modern developments in sounding rockets, reusable suborbital systems and launch vehicles are discussed with particular focus on propellant technology. Various propellant combinations include use of liquid oxygen, hydrogen peroxide, nitrous oxide and nitrous oxide-oxygen mixtures as oxidizers. Different fuels are considered, taking into account performance, as well as inter alia obtainable regression rates. Results of preliminary calculations for vehicles using different propellant combinations are presented and analysed. This is compared with proposed configurations of hybrid rockets worldwide. Unresolved problems and several unknowns are pointed out, including hybrid rocket motor scalability issues, large motor combustion instabilities, combustion efficiency of metalized fuels, propellant volumetric performance and mass of fuel residuals in case of wagon wheel grain geometry. It is discussed whether new-space hybrid launch vehicles, while typically with limited stage reusability, may be cost-competitive in regard to other chemical rocket propulsion system developments. The paper is summarized with a list of potential future advances and technical opportunities. The main purpose of the conducted research is to provide a comparison between different hybrid propulsion technologies available, or currently under development, worldwide.

Use of Hypnosis in Paediatric Gastrointestinal Endoscopy: A Pilot Study.

Objectives: Experience of hypnosis in gastrointestinal (GI) endoscopy is scarce in children. Our aims were to assess the rate of successful GI endoscopy performed using hypnosis alone or in combination with midazolam, with or without additional equimolar mixture of oxygen and nitrous oxide (EMONO), and to identify predictive factors of successful endoscopy in children.Methods: This prospective single-centre study included children older than 6 years requiring a diagnostic esophagogastroduodenoscopy (EGD) or rectosigmoidoscopy. Ericksonian hypnosis was performed alone or in combination with midazolam, with or without additional EMONO. Successful endoscopy was defined by a complete and well-tolerated procedure. Levels of satisfaction of the endoscopist, nurse, and patient were assessed.Results: One hundred forty children [70 boys, median age: 12 years (Q1–Q3: 9–14)] were included over a 14-month period. They underwent EGD in 51.4% (n = 72) and rectosigmoidoscopy in 48.6% (n = 68) of cases. EMONO and midazolam were combined with hypnosis in 136 cases (97.1%). Successful endoscopy rate reached 82.9%. The procedure was interrupted due to poor tolerance and was rescheduled under general anaesthesia in 11 patients (7.9%). Predictive factors for successful endoscopy were older age (13 vs. 8 years, OR: 1.34, CI 95% [1.10–1.62], p = 0.003) and type of endoscopy (EGD vs. rectosigmoidoscopy, OR: 16.34 [2.14–124.68], p = 0.007). A good cooperation of the patient was reported by the endoscopist and the nurse in 88.4 and 86.9% of cases, respectively. Ninety-two per cent of patients mentioned that the procedure went well.Conclusions: Our study suggests that hypnosis combined with EMONO and/or midazolam is of additional value to perform diagnostic EGD or rectosigmoidoscopy in children older than 6 years without systematic need for general anaesthesia.

Ignition temperature of combustible liquids in mixtures of air with nitrous oxide

SummaryWhile ignition temperatures in the air are well known for a large number of flammable substances and to a lesser extent in pure oxygen too, no such values exist for ignition temperatures in nitrous oxide in spite of the fact that nitrous oxide is used as oxidizer in combustion processes or aerosol propellant in industry. The ignition temperatures of some pure compounds have now been investigated in oxidizer mixtures of nitrous oxide and air with varying concentration of nitrous oxide up to 80 vol% using a slightly modified standardized apparatus. The ignition temperature increases with increasing nitrous oxide concentration. Up to 580°C, none of the investigated substances ignited in pure nitrous oxide.

\u201cGreen propellants\u201d as a hydrazine substitute: experimental investigations of ethane/ethene-nitrous oxide mixtures and validation of detailed reaction mechanism

Mixtures of hydrocarbons and nitrous oxide are known as green propellants and could replace the highly toxic hydrazine and hydrazine derivatives as rocket fuel, since they are non-toxic and easier to handle, but still have a high specific impulse. Possible hydrocarbon candidates are ethane or ethene. To check the applicability of the two reaction systems, C2H6/N2O and C2H4/N2O, experiments are a prerequisite for accurate predictions under various conditions that are of great importance for the design of safe and reliable thrusters. Therefore, experimental literature data obtained from ignition delay times and laminar burning velocities were used to validate and optimize a new reaction mechanism, which is designed for C0–C3 and nitrogen oxides formation. To achieve a better predictive power of the detailed mechanism, the Arrhenius parameters of three reactions were adjusted: N2O + H ⇌ N2 + OH, N2O (+ M) ⇌ N2 + O (+ M), and NH + NO ⇌ N2O + H. A good agreement was achieved between simulation and experiment for ignition delay times at various pressures and equivalence ratios in a broad temperature range before and after the mechanism optimization. However, the laminar burning velocities in the whole measured range of the equivalence ratio for all pressures and dilutions showed a significant improvement after the optimization.

Safety and efficacy of an equimolar mixture of oxygen and nitrous oxide: a randomized controlled trial in patients with peripheral neuropathic pain

Nitrous oxide (N2O) is an odorless and colorless gas routinely used as an adjuvant of anesthesia and for short-duration analgesia in various clinical settings mostly in the form of an N2O/O2 50%-50% equimolar mixture (EMONO). Experimental studies have suggested that EMONO could also induce long-lasting analgesic effects related to the blockade of N-methyl-D-aspartate receptors. We designed the first international multicenter proof of concept randomized, placebo-controlled study to assess the efficacy and safety of a 1-hour administration of EMONO or placebo (medical air) on 3 consecutive days up to 1 month after the last administration in patients with chronic peripheral neuropathic pain. A total of 240 patients were recruited in 22 centers in France and Germany and randomly assigned to 1 study group (120 per group). Average pain intensity (primary outcome), neuropathic pain characteristics (Neuropathic Pain Symptom Inventory), Patient Global Impression of Change, anxiety, depression, and quality of life were systematically assessed before and after treatment. The changes in average pain intensity between baseline and 7 days after the last administration were not significantly different between the 2 groups. However, evoked pain intensity (predefined secondary endpoint) and Patient Global Impression of Change (exploratory endpoint) were significantly improved in the EMONO group, and these effects were maintained up to 4 weeks after the last treatment administration. Mostly transient side effects were reported during the treatment administration. These encouraging results provide a basis for further investigation of the long-term analgesic effects of EMONO in patients with neuropathic pain.