Helium-oxygen Mixture Research Articles

Helium–oxygen mixture for treatment in upper airway obstruction; a mini-review

Abstract In the 1930's Alan Barach introduced helium in combination with oxygen, heliox, to the medical world. He found that helium's physical properties help reduce the work of breathing, reduce airway resistance, and subsequently improve alveolar ventilation in obstructed airways. In the presence of airway narrowing, heliox has the benefits of increasing the tendency to laminar flow (which has lower resistance) and reducing resistance when turbulent flow occurs. Heliox, a helium–oxygen mixture, has since been used sporadically and only scattered reports are found on its use for treatment in patients with upper airway obstruction. The aim of the present review was to search and review the available evidence for its safe and effective clinical use. A total of 20 publications about the use of helium-containing gas mixture for the treatment of upper airway obstruction in adults were found in the search of public domain literature. Most case reports describe short-term beneficial effects, temporarily improving breathing and oxygenation. Authors of the case reports suggest helium–oxygen mixture as an optional bridge, while a more definite treatment takes action. There are, however, no prospective randomized controlled studies and thus there is lack of high-quality proof supporting its safe and efficacious use. In conclusion, the physiochemical properties promoting laminar flow in restricted airways and the sparse but still seemingly positive clinical experience favor the use of helium–oxygen mixture as a symptomatic rescue therapy. The risk for side effects, apart from the reduced oxygen concentration in the inspired gas, seems minor. There is, however, still a lack of evidence to support the general use of oxygen–helium mixture for upper airway compromise due to the sparse information available. Further studies, although not easily designed, are warranted.

Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

Abstract This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions in a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.

Effects of Oxygen Concentration on Pulsed Dielectric Barrier Discharge in Helium-Oxygen Mixture at Atmospheric Pressure**supported by the Fundamental Research Funds of Shandong University, China (No. 2016JC016)

In this work the effects of O2 concentration on the pulsed dielectric barrier discharge in helium-oxygen mixture at atmospheric pressure have been numerically researched by using a one-dimensional fluid model in conjunction with the chosen key species and chemical reactions. The reliability of the used model has been examined by comparing the calculated discharge current with the reported experiments. The present work presents the following significant results. The dominative positive and negative particles are He2+ and O2−, respectively, the densities of the reactive oxygen species (ROS) get their maxima nearly at the central position of the gap, and the density of the ground state O is highest in the ROS. The increase of O2 concentration results in increasingly weak discharge and the time lag of the ignition. For O2 concentrations below 1.1%, the density of O is much higher than other species, the averaged dissipated power density presents an evident increase for small O2 concentration and then the increase becomes weak. In particular, the total density of the reactive oxygen species reaches its maximums at the O2 concentration of about 0.5%. This characteristic further convinces the experimental observation that the O2 concentration of 0.5% is an optimal O2/He ratio in the inactivation of bacteria and biomolecules when radiated by using the plasmas produced in a helium oxygen mixture.

Superhydrophobic Paper by Facile and Fast Atmospheric Pressure Plasma Etching

Superhydrophobic and to some extent oleophobic paper surfaces are prepared using atmospheric pressure plasma etching. A novel dielectric barrier discharge operating in helium–oxygen mixture is used to rapidly etch organic material from paper surface and create hierarchical topography and subsequently a thin fluorocarbon film is deposited to modify the surface energy. The enhancement of surface topography is achieved via the selective removal of organic matter over inorganic calcium carbonate (calcite) fillers that co-exist in paper. The process led to the fabrication of roll-off superhydrophobic paper with water contact angles >150° and hysteresis <10° for all samples treated over 2 min with no deterioration of paper quality. Further treatment over 8 min resulted also in diiodomethane repellent surfaces.

Contemporary treatment of children with critical and near-fatal asthma.

Asthma is the most common chronic illness in childhood. Although the vast majority of children with acute asthma exacerbations do not require critical care, some fail to respond to standard treatment and require escalation of support. Children with critical or near-fatal asthma require close monitoring for deterioration and may require aggressive treatment strategies. This review examines the available evidence supporting therapies for critical and near-fatal asthma and summarizes the contemporary clinical care of these children. Typical treatment includes parenteral corticosteroids and inhaled or intravenous beta-agonist drugs. For children with an inadequate response to standard therapy, inhaled ipratropium bromide, intravenous magnesium sulfate, methylxanthines, helium-oxygen mixtures, and non-invasive mechanical support can be used. Patients with progressive respiratory failure benefit from mechanical ventilation with a strategy that employs large tidal volumes and low ventilator rates to minimize dynamic hyperinflation, barotrauma, and hypotension. Sedatives, analgesics and a neuromuscular blocker are often necessary in the early phase of treatment to facilitate a state of controlled hypoventilation and permissive hypercapnia. Patients who fail to improve with mechanical ventilation may be considered for less common approaches, such as inhaled anesthetics, bronchoscopy, and extracorporeal life support. This contemporary approach has resulted in extremely low mortality rates, even in children requiring mechanical support.

To: Contemporary treatment of children with critical and near-fatal asthma.

Asthma is the most common chronic illness in childhood. Although the vast majority of children with acute asthma exacerbations do not require critical care, some fail to respond to standard treatment and require escalation of support. Children with critical or near-fatal asthma require close monitoring for deterioration and may require aggressive treatment strategies. This review examines the available evidence supporting therapies for critical and near-fatal asthma and summarizes the contemporary clinical care of these children. Typical treatment includes parenteral corticosteroids and inhaled or intravenous beta-agonist drugs. For children with an inadequate response to standard therapy, inhaled ipratropium bromide, intravenous magnesium sulfate, methylxanthines, helium-oxygen mixtures, and non-invasive mechanical support can be used. Patients with progressive respiratory failure benefit from mechanical ventilation with a strategy that employs large tidal volumes and low ventilator rates to minimize dynamic hyperinflation, barotrauma, and hypotension. Sedatives, analgesics and a neuromuscular blocker are often necessary in the early phase of treatment to facilitate a state of controlled hypoventilation and permissive hypercapnia. Patients who fail to improve with mechanical ventilation may be considered for less common approaches, such as inhaled anesthetics, bronchoscopy, and extracorporeal life support. This contemporary approach has resulted in extremely low mortality rates, even in children requiring mechanical support.

Inpatient Treatment after Multi-Dose Racemic Epinephrine for Croup in the Emergency Department

BackgroundEmergency department (ED) discharge is safe when croup-related stridor has resolved after corticosteroids and a single dose of racemic epinephrine (RE). Little evidence supports the traditional practice of hospital admission after ≥ 2 doses of RE. ObjectiveOur aim was to describe the frequency and timing of clinically important inpatient interventions after ≥ 2 ED RE doses. MethodsWe identified patients hospitalized for croup after ED treatment with corticosteroids and ≥2 doses of RE. We compared asymptomatic (admitted solely on the number of RE doses) and symptomatic (admitted due to disease severity) groups with regard to inpatient RE administration, supplemental oxygen, helium-oxygen mixture (heliox) therapy, intubation, or transfer to a higher level of care, time to hospital discharge, and revisit and readmission rates within 48 h of discharge. ResultsOf 200 subjects admitted after ≥ 2 ED RE doses, 72 (36%) received clinically important inpatient interventions: RE (n = 68 [34%]), heliox (n = 9 [5%]), and supplemental oxygen (n = 4 [2%]). Of patients who received inpatient RE, 53% received only 1 dose. No patients underwent intubation or transfer to higher level of care. The 112 asymptomatic patients had fewer interventions (14% vs. 63%; p < 0.001) and shorter hospital durations (14.5 vs. 22 h; p < 0.001). Only 14% of the asymptomatic group received RE, with 75% receiving a single dose. There were no differences in revisit and readmission rates. ConclusionsInpatient interventions after ≥ 2 ED doses of RE for croup were infrequent, most commonly RE administration. Most patients asymptomatic upon admission require 0–1 inpatient RE doses and may be candidates for outpatient management.

Decompression sickness in naval divers

Introduction: Diving is a n operational commitment of navy. Diving operations are conducted with I without the presence of a MM spl. Study of MM done along with phases of attachments at different diving operational units as practical orientation. Classes of Divers: (a) Ship Diver (SD). Trained to dive up to 35 MSW (b) Clearance Diver (CD): They are trained to dive up to 55 MSW. (c) CD (DD): They are Deep divers, also trained in saturation diving using Helium Oxygen mixture, (d) Chariot Diver: They are combat divers of the Navy. (e)Air crew diver: Specially trained SD & CD. (f) Combat Diver: from Army. Diving Establishments: Diving School - shore estt, kochi. INS Nireekshak - floating platform. INS Satavahana - submarine training estt - shore estt, vizag. INS Abhimanyu - chariot diving with pure Oxygen breather for clandestine operations. CCDH! - one per command, CDU at A & N. INS Matanga, INS Gaj - floating platforms. Recompression Chamber Complex, INHS Asvini Decompression Sickness: Due to metabolically inert gases and due to fast ascent rate. It is never with pure oxygen diving. Never occur while at bottom. As per grading, Type I - not serious type, generally known as bends and Type II - serious type Treatment: Treatment for DCS is followed as per guidelines promulgated in INBR 2806. Mainstay of treatment remains with Oxygen Table 61 & 62 of INBR 2806 which is same as RNBR 2806 as table 5&60fUS navy D i v i n g Manual. Incidences: Incidences of DCS are found at Diving School and Nireekshak. At ETS other diving related injuries like Mask injury, hypoxia, CAGE are documented. At CCDTk no DCS documented in last five years. Conclusion: DCS in Navy is rather very less due to stringent training, fitness of divers and proper follow of procedures.

Transpulmonary hypothermia: A novel method of rapid brain cooling through augmented heat extraction from the lungs

AimDelay in instituting neuroprotective measures after cardiac arrest increases death and decreases neuronal recovery. Current hypothermia methods are slow, ineffective, unreliable, or highly invasive. We report the feasibility of rapid hypothermia induction in swine through augmented heat extraction from the lungs. MethodsTwenty-four domestic crossbred pigs (weight, 50–55kg) were ventilated with room air. Intraparenchymal brain temperature and core temperatures from pulmonary artery, lower esophagus, bladder, rectum, nasopharynx, and tympanum were recorded. In eight animals, ventilation was switched to cooled helium–oxygen mixture (heliox) and perfluorocarbon (PFC) aerosol and continued for 90min or until target brain temperature of 32°C was reached. Eight animals received body-surface cooling with water-circulating blankets; eight control animals continued to be ventilated with room air. ResultsBrain and core temperatures declined rapidly with cooled heliox–PFC ventilation. The brain reached target temperature within the study period (mean [SD], 66 [7.6]min) in only the transpulmonary cooling group. Cardiopulmonary functions and poststudy histopathological examination of the lungs were normal. ConclusionTranspulmonary cooling is novel, rapid, minimally invasive, and an effective technique to induce therapeutic hypothermia. High thermal conductivity of helium and vaporization of PFC produces rapid cooling of alveolar gases. The thinness and large surface area of alveolar membrane facilitate rapid cooling of the pulmonary circulation. Because of differences in thermogenesis, blood flow, insulation, and exposure to the external environment, the brain cools at a different rate than other organs. Transpulmonary hypothermia was significantly faster than body surface cooling in reaching target brain temperature.

Limiting explosible concentration of hydrogen–oxygen–helium mixtures related to the practical operational case

This paper presents data on the limiting (minimum) concentrations of hydrogen in oxygen, in the presence of added helium, at elevated temperature and pressure related to the practical operational case. A 5 L explosion vessel, an ignition sub-system and a transient pressure measurement sub-system were used. Through a series of experiments carried out using this system, the limiting concentrations of hydrogen in oxygen and helium at different initial pressures and temperatures for the practical operational case were studied, and the influence of ignition energy and initial temperature on the limiting concentration of hydrogen in oxygen and helium was analyzed and discussed. The variation of ignition energy within the studied range is found to have a significant effect on the limiting concentration of hydrogen in oxygen and helium at lower initial temperature. However, when the ignition energy is higher than 32 mJ, the limiting hydrogen concentration remains almost changeless as the initial temperature increases from 21 °C to 90 °C. The limiting explosible concentration of hydrogen–oxygen–helium mixture decreases as the ignition energy increases when the initial temperature is lower. When the initial temperature is higher, the ignition energy has little effect on the limiting hydrogen concentration of hydrogen–oxygen–helium mixtures. When the initial temperature reaches 90 °C, the limiting hydrogen concentration remains almost changeless with an increase in ignition energy. The limiting explosible concentration of hydrogen in the mixtures, at the initial temperature of 21 °C and the ignition energy of 0.5 mJ, is 8.5% and that of oxygen is 11.25%.

Impact of ion cyclotron wall conditioning on fuel removal from plasma-facing components at TEXTOR

Ion cyclotron wall conditioning (ICWC) is based on low temperature and low density plasmas produced and sustained by ion cyclotron resonance (ICR) pulses in reactive or noble gases. The technique is being developed for ITER. It is tested in tokamaks in the presence of toroidal magnetic field (0.2–3.8 T) and heating power of the order of 105 W. ICWC with hydrogen, deuterium and oxygen–helium mixture was studied in the TEXTOR tokamak. The exposed samples were pre-characterized limiter tiles mounted on specially designed probes. The objectives were to assess the reduction of deuterium content, the uniformity of the reduction and the retention of seeded oxygen. For the last objective oxygen-18 was used as a marker. ICWC in hydrogen caused a drop of deuterium content in the tile by a factor of more than 2: from 4.5 × 1018 to 1.9 × 1018 D cm−2. A decrease of the fuel content by approximately 25% was achieved by the ICWC in oxygen, while no reduction of the fuel content was measured after exposure to discharges in deuterium. These are the first data ever obtained showing quantitatively the local decrease of deuterium in wall components treated by ICWC in a tokamak. The oxygen retention in the tiles exposed to ICWC with oxygen–helium was analyzed for different orientations and radial positions with respect to plasma. An average retention of 1.38 × 1016 18O cm−2 was measured. A maximum of the retention, 4.4 × 1016 18O cm−2, was identified on a sample surface near the plasma edge. The correlation with the gas inlet and antennae location has been studied.

High flow nasal cannula (HFNC) with Heliox decreases diaphragmatic injury in a newborn porcine lung injury model

High flow nasal cannula (HFNC) improves ventilation by washing out nasopharyngeal dead space while delivering oxygen. Heliox (helium-oxygen gas mixture), a low-density gas mixture, decreases resistance to airflow, reduces the work of breathing, and facilitates distribution of inspired gas. Excessive lung work and potential injury increases the workload on the immature diaphragm predisposing the muscle to fatigue, and can lead to inflammatory and oxidative stress, thereby contributing to impaired diaphragmatic function. We tested the hypothesis that HFNC with Heliox will decrease the work of breathing thereby unloading the neonatal diaphragm, and potentially reducing diaphragmatic injury. Spontaneously breathing neonatal pigs were randomized to Nitrox (nitrogen-oxygen gas mixture) or Heliox, and studied over 4 hr following oleic acid injury. Gas exchange, pulmonary mechanics indices, and systemic markers of inflammation were measured serially. Diaphragm inflammation biomarkers and histology for muscle injury were assessed at termination. Heliox breathing animals demonstrated decreased respiratory load and work of breathing with lower pressure-rate product, lower labored breathing index, and lower levels of diaphragmatic inflammatory markers, and muscle injury score as compared to Nitrox. These results suggest that HFNC with Heliox is a useful adjunct to attenuate diaphragmatic fatigue in the presence of lung injury by unloading the diaphragm, resulting in a more efficient breathing pattern, and decreased diaphragm injury.

Heliox augmented mechanical ventilation in the treatment of premature infants with respiratory distress syndrome

The aim of the study was to assess the influence of mechanical ventilation with helium-oxygen mixture (heliox) on basic vital signs, oxygenation, acid-base balance and respiratory mechanics in newborns with respiratory distress syndrome (RDS), previously treated with surfactant. The study was carried out in preterm newborns with respiratory failure requiring mechanical ventilation due to RDS, requiring Fi02>0.4 after a single dose of surfactant. Patients were ventilated using PC-SIMV Parameters of mechanical ventilation, respiratory function, oxygenation, acid-base balance and vital signs were recorded at baseline, one hour during and one hour after heliox ventilation. Ten newborns with RDS were enrolled in the study Mechanical ventilation with heliox did not affect vital signs and patient general condition remained stable during and after ventilation with heliox. Mechanical ventilation with heliox was associated with a statistically significant increase in tidal volume (mean 5.48 vs. 6.55 ml/kg). There were no significant changes in minute ventilation and peak expiratory flow rate. Mechanical ventilation with heliox allowed the use of significantly lower fractions of inspired oxygen (mean 0.55 vs. 0.35), with a significant decrease in the oxygenation index (mean 8.77 vs. 5.02) and alveolar-arterial oxygen tension difference (mean 263.81 vs. 113.28 mm Hg). After ventilation with this gas mixture was stopped, the patients required higher Fi02, 01 and AaD02 levels increased. Mechanical ventilation with heliox was safe, improved oxygenation and caused an increase in tidai, volume in newborns with RDS previously treated with surfactant.

The use of heliox in critical care.

This paper reviews the medical use of helium oxygen mixture in obstructive airway disease in patients with croup, narrow endotracheal tubes (ETTs), respiratory distress syndrome, asthma, bronchiolitis, as well as patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) and acute lung injury. In addition, some other indications of heliox use and some innovative methods of ventilation applied in pediatrics and adults are presented through review of the literature of current decade. Yet, to recommend heliox use seems to require more research based on clinical practice and observation through vaster and more robust investigations.

Divers’ neurobehavioral performance under 4.7 MPa: A real-time monitoring

Patients with COPD exhibit increased inspiratory work and dyspnea due to dynamic hyperinflation caused by expiratory flow limitation. Helium-oxygen mixtures (ie, heliox) have been used in treating these patients on the assumption that, by lowering airway resistance, they might be beneficial.In 22 patients with COPD, the presence of expiratory flow limitation was assessed with patients in the sitting and supine positions using the negative expiratory pressure technique, and the effects of heliox (80% He, 20% O2) on breathing pattern, expiratory flow limitation, and dynamic hyperinflation, evaluated from the change in inspiratory capacity (IC), were measured at rest and were compared with those due to inhaled salbutamol.During air breathing, 13 patients experienced flow limitation while in the sitting position and 18 experienced flow limitation while in the supine position. Neither heliox nor salbutamol therapy changed the breathing pattern in any of the patients, regardless of posture and the presence or absence of expiratory flow limitation. However, in both positions IC increased significantly in most flow-limited patients after bronchodilator administration, but not after heliox administration.Since heliox had no effect on dynamic hyperinflation, the use of this gas mixture, which is costly and cumbersome, does not appear to be beneficial in stable patients with COPD breathing at rest.

Heliox-driven β2-agonists nebulization for children and adults with acute asthma: a systematic review with meta-analysis

BackgroundThe effect of heliox as a nebulizer β2-agonist driving gas in acute asthma remains controversial. ObjectiveTo perform a systematic review with a meta-analysis of randomized trials designed to evaluate the efficacy of heliox versus oxygen in driving β2-agonist nebulization in patients with acute asthma. MethodsA search was conducted of all randomized controlled trials published before August 2013. Primary outcomes were change in spirometric measurements and severity composite score (pediatric studies); secondary outcomes were hospitalizations and serious adverse effects. ResultsEleven trials from 10 studies (697 participants) met the inclusion criteria (7 included adults and 3 included children). The mean duration of heliox therapy was 120 minutes and the most common helium–oxygen mixture used was 70:30. Patients receiving heliox presented a statistically significant difference for mean percentage of change in peak expiratory flow (17.2%; 95% confidence interval 5.2–29.2, P = .005). Post hoc subgroup analysis showed that patients with severe and very severe asthma showed a significant improvement in peak expiratory flow compared with those with mild to moderate acute asthma. Heliox-driven nebulization also produced significant decreases in the risk of hospitalizations (odds ratio 0.49, 95% confidence interval 0.31–0.79, P = .003) and severity of exacerbations (pediatric studies; standard mean difference −0.74, 95%% confidence interval −1.45 to −0.03, P = .04). There were no group differences for serious adverse effects. ConclusionThis review suggests that heliox benefits in airflow limitation and hospital admissions could be considered clinically significant. Data support the use of heliox as a nebulizing β2-agonist driving gas in the routine care of patients with acute asthma.

Generation of Reactive Oxygen Species in Helium–Oxygen Radio-Frequency Discharges at Atmospheric Pressure

Reactive oxygen species (ROS) generated in atmospheric plasmas are believed to play an important role in plasma medicine and related areas. In this paper, we explored a fluid model to investigate the production and destruction of ROS in atmospheric radio-frequency (RF) discharges with helium-oxygen mixture as working gas; to speed up the computation, only 17 species and 48 reactions are considered in plasmas. At a given applied voltage, the variations of ROS depending on the oxygen admixture are discussed and the key reactions related to the generation of ROS are further confirmed. Through increasing the applied voltage, the evolution of ROS based on the simulation results are also given. The simulation data agree well with the experimental measurements.

Microbial decontamination of red pepper powder by cold plasma

Effects of the microwave-powered cold plasma treatments (CPTs) on the inhibition of microorganisms in red pepper powder, including Aspergillus flavus and Bacillus cereus spores, were investigated. Combinations of heat treatment with CPT were investigated for the inhibition of B. cereus spores on the powder. The number of A. flavus was reduced by 2.5 ± 0.3 log spores/g by the CPT with nitrogen at 900 W and 667 Pa for 20 min. CPT at 900 W and 667 Pa for 20 min inhibited naturally occurring total aerobic bacteria in the red pepper powder by approximately 1 log CFU/g. B. cereus spores were inhibited (3.4 ± 0.7 log spores/g reduction) only when heat treatment at 90 °C for 30 min was integrated with the CPT using a helium-oxygen gas mixture at 900 W. Fermi's model and Weibull model adequately described the inhibition of A. flavus on the red pepper powder by the CPT. The changes in treatment temperature and water activity were less than 5.0 °C (initial temperature: 23.8 °C) and 0.22, respectively, and were affected by both treatment power and time (P < 0.05). The CPTs have demonstrated the potential to reduce the microbial counts of red pepper powder and other powder products.

Interacting kinetics of neutral and ionic species in an atmospheric-pressure helium–oxygen plasma with humid air impurities

We unravel the complex chemistry in both the neutral and ionic systems of a radio-frequency-driven atmospheric-pressure plasma in a helium–oxygen mixture (He–0.5% O2) with air impurity levels from 0 to 500 ppm of relative humidity from 0% to 100% using a zero-dimensional, time-dependent global model. Effects of humid air impurity on absolute densities and the dominant production and destruction pathways of biologically relevant reactive neutral species are clarified. A few hundred ppm of air impurity crucially changes the plasma from a simple oxygen-dependent plasma to a complex oxygen–nitrogen–hydrogen plasma. The density of reactive oxygen species decreases from 1016 to 1015 cm−3, which in turn results in a decrease in the overall chemical reactivity. Reactive nitrogen species (1013 cm−3), atomic hydrogen and hydroxyl radicals (1011–1014 cm−3) are generated in the plasma. With 500 ppm of humid air impurity, the densities of positively charged ions and negatively charged ions slightly increase and the electron density slightly decreases (to the order of 1011 cm−3). The electronegativity increases up to 2.3 compared with 1.5 without air admixture. Atomic hydrogen, hydroxyl radicals and oxygen ions significantly contribute to the production and destruction of reactive oxygen and reactive nitrogen species.

Extremely low flow tracheal gas insufflation of helium-oxygen mixture improves gas exchange in a rabbit model of piston-type high-frequency oscillatory ventilation

ObjectiveThe purpose of this study was to show the effects of the tracheal gas insufflation (TGI) technique on gas exchange using helium-oxygen mixtures during high-frequency oscillatory ventilation (HFOV). We hypothesized that a helium-oxygen mixture delivered into the trachea using the TGI technique (0.3 L/min) would enhance gas exchange during HFOV.MethodsThree rabbits were prepared and ventilated by HFOV with carrier 70% helium/oxygen or 70% nitrogen/oxygen gas mixture with TGI in a crossover study. Changing the gas mixture from nitrogen70% to helium70% and back was performed three times per animal with constant ventilation parameters.ResultsCompared with the nitrogen-oxygen mixture, the helium-oxygen mixture of TGI reduced PaCO2 by 7.6 mmHg (p < 0.01) and improved PaO2 by 14 mmHg (p < 0.01). Amplitude during TGI was significantly lower with the helium-oxygen mixture than with the nitrogen-oxygen mixture (p < 0.01) and did not significantly affect mean airway pressure.ConclusionsThis study demonstrated that a helium-oxygen mixture delivered into the trachea using the TGI technique would enhance CO2 elimination and improve oxygenation during HFOV.