| 1. |
- Bellippady, Madhura, et al.
(författare)
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Characteristics and performance of suspension plasma sprayed thermal barrier coatings on additively manufactured superalloy substrates
- 2023
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Ingår i: Surface and Coatings Technology. - : Elsevier. - 0257-8972. ; 472
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Tidskriftsartikel (refereegranskat)abstract
- The complex-shaped hot-section parts of new-generation turbine engines demand unique design solutions. Additive Manufacturing (AM) is an emergent production method that can produce metallic parts with complex geometries and minimal material wastage. In this work, the characteristics and performance behavior of Thermal Barrier Coatings (TBCs) deposited on forged and AM-built HAYNES®282® superalloy substrates were studied and compared. The bond coats were produced by High-Velocity Air-Fuel (HVAF) spraying using NiCoCrAlY powder feedstock and TBC top-coats by Suspension Plasma Spraying (SPS) using water- and ethanol-based suspensions of Yttria-Stabilized Zirconia (YSZ). The microstructural features, adhesion, Thermal Cycling Fatigue (TCF) lifetime, and thermal shock lifetimes of the TBCs were comprehensively investigated. The results showed that the deposition of bond coats reduced the roughness and asperities of the AM-built substrates. Depending on the type of suspension used and the spray parameters employed, the TBCs exhibited vertically cracked and columnar microstructures. However, no significant differences in TCF and thermal shock lifetimes of TBCs on AM and forged substrates were observed. It is demonstrated that TBC systems can be produced on AM-built metallic substrates, and the resulting TBCs can have similar microstructures and properties as TBCs deposited on conventional substrates.
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| 2. |
- Bellippady, Madhura, et al.
(författare)
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Performance of Atmospheric Plasma-Sprayed Thermal Barrier Coatings on Additively Manufactured Super Alloy Substrates
- 2024
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Ingår i: Coatings. - : MDPI. - 2079-6412. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- This work represents a preliminary study of atmospheric plasma-sprayed (APS) YttriaStabilized Zirconia (YSZ)-based thermal barrier coatings (TBCs) deposited on forged and additivemanufactured (AM) HAYNES®282® (H282) superalloy substrates. The effect of different feedstockmorphologies and spray gun designs with radial and axial injection on APS-deposited YSZ layercharacteristics such as microstructure, porosity content, roughness, etc., has been investigated. Theperformance of TBCs in terms of thermal cycling fatigue (TCF) lifetime and erosion behaviour werealso comprehensively investigated. In view of the high surface roughness of as-built AM surfacescompared to forged substrates, two different types of NiCoCrAlY bond coats were examined: oneinvolved high-velocity air fuel (HVAF) spraying of a finer powder, and the other involved APSdeposition of a coarser feedstock. Despite the process and feedstock differences, the above two routesyielded comparable bond coat surface roughness on both types of substrates. Variation in porositylevel in the APS topcoat was observed when deposited using different YSZ feedstock powdersemploying axial or radial injection. However, the resultant TBCs on AM-derived substrates wereobserved to possess similar microstructures and functional properties as TBCs deposited on reference(forged) substrates for any given YSZ deposition process and feedstock.
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| 3. |
- Frykholm, Peter, 1961-, et al.
(författare)
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Pre-operative fasting in children : A guideline from the European Society of Anaesthesiology and Intensive Care
- 2022
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Ingår i: European Journal of Anaesthesiology. - : European Society of Anaesthesiology and Intensive Care. - 0265-0215 .- 1365-2346. ; 39:1, s. 4-25
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Tidskriftsartikel (refereegranskat)abstract
- Current paediatric anaesthetic fasting guidelines have recommended conservative fasting regimes for many years and have not altered much in the last decades. Recent publications have employed more liberal fasting regimes with no evidence of increased aspiration or regurgitation rates. In this first solely paediatric European Society of Anaesthesiology and Intensive Care (ESAIC) pre-operative fasting guideline, we aim to present aggregated and evidence-based summary recommendations to assist clinicians, healthcare providers, patients and parents.We identified six main topics for the literature search: studies comparing liberal with conservative regimens; impact of food composition; impact of comorbidity; the use of gastric ultrasound as a clinical tool; validation of gastric ultrasound for gastric content and gastric emptying studies; and early postoperative feeding. The literature search was performed by a professional librarian in collaboration with the ESAIC task force.Recommendations for reducing clear fluid fasting to 1 h, reducing breast milk fasting to 3 h, and allowing early postoperative feeding were the main results, with GRADE 1C or 1B evidence. The available evidence suggests that gastric ultrasound may be useful for clinical decision-making, and that allowing a ‘light breakfast’ may be well tolerated if the intake is well controlled. More research is needed in these areas as well as evaluation of how specific patient or treatment-related factors influence gastric emptying.
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| 4. |
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| 5. |
- Frykholm, Robert, 1970
(författare)
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Development of Composition Gradients in Cemented Carbides
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the formation of tough surface zones, depleted of cubic carbo-nitrides, in cemented carbides. Several materials with varied phase compositions, binder phase volume fraction, and carbon content have been investigated. The main experimental techniques that have been used are scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and atom probe field ion microscopy (APFIM). Some of the experimental results have been compared to computer simulations based on thermodynamics and diffusion. Good agreement between computer simulations and experimental results of the distribution of elements and phases was found. It was therefore concluded that the formation of surface zones is a process controlled by thermodynamics and diffusion. It was investigated how the gradient surface zone formation depends on cubic phase composition. Addition of Ta to the cubic phase was found to decrease the elemental variations in the gradient profile and to give a thinner surface zone. Addition of Nb gave the opposite effect, with larger elemental variations and a wider surface zone. The effect of the binder phase volume fraction on gradient zone formation was studied. It was found that the zone width is directly proportional to the binder content. It was also found that the diffusivity is reduced with a factor equal to the binder volume fraction due to the presence of dispersed phases, i.e. carbides and carbo-nitrides. Study of materials with varied carbon content showed that with a high C content the driving force for gradient formation becomes stronger, and wider surface zones are formed. The effect of high C content was found to be reduced if Ta or Nb was added to the cubic phase. Methods to prepare APFIM specimens of near surface regions were developed. The methods are based on dimple grinding, electropolishing, and focused ion beam milling (FIB). The methods allow for positioning of APFIM specimens with high accuracy in the material, and to re-sharpen analysed specimens. Analysis was performed of the cubic phase just inside the zone border and the results could be related to the sintering process.
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| 6. |
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| 7. |
- Leiter, Robert, et al.
(författare)
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Comparison of superimposed high-frequency jet ventilation with conventional jet ventilation for laryngeal surgery
- 2012
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Ingår i: British Journal of Anaesthesia. - : Elsevier BV. - 0007-0912 .- 1471-6771. ; 108:4, s. 690-697
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundNew ventilators have simplified the use of supraglottic superimposed high-frequency jet ventilation (SHFJVSG), but it has not been systematically compared with other modes of jet ventilation (JV) in humans. We sought to investigate whether SHFJVSG would provide more effective ventilation compared with single-frequency JV techniques.MethodsA total of 16 patients undergoing minor laryngeal surgery under general anaesthesia were included. In each patient, four different JV techniques were applied in random order for 10-min periods: SHFJVSG, supraglottic normal frequency (NFJVSG), supraglottic high frequency (HFJVSG), and infraglottic high-frequency jet ventilation (HFJVIG).Chest wall volume variations were continuously measured with opto-electronic plethysmography (OEP), intratracheal pressure was recorded and blood gases were measured.ResultsChest wall volumes were normalized to NFJVSG end-expiratory level. The increase in end-expiratory chest wall volume (EEVCW) was 239 (196) ml during SHFJVSG (P<0.05 compared with NFJVSG). EEVCW was 148 (145) and 44 (106) ml during HFJVSG and HFJVIG, respectively (P<0.05 compared with SHFJVSG). Tidal volume (VT) during SHFJVSG was 269 (149) ml. VT was 229 (169) ml (P=1.00 compared with SHFJVSG), 145 (50) ml (P<0.05), and 110 (33) ml (P<0.01) during NFJVSG, HFJVSG, and HFJVIG, respectively.Intratracheal pressures corresponded well to changes in both EEVCW and VT. All JV modes resulted in adequate oxygenation. However, PACO2was lowest during HFJVSG [4.3 (1.3) kPa; P<0.01 compared with SHFJVSG].ConclusionSHFJVSG was associated with increased EEVCW and VT compared with the three other investigated JV modes. All four modes provided adequate ventilation and oxygenation, and thus can be used for uncomplicated laryngeal surgery in healthy patients with limited airway obstruction.
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| 8. |
- Lo Mauro, Antonella, et al.
(författare)
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Comparison of different methods for lung immobilization in an animal model
- 2020
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 150, s. 151-158
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Respiratory-induced motion introduces uncertainties in the delivery of dose in radiotherapy treatments. Various methods are used clinically, e.g. breath-holding, while there is limited experience with other methods such as apneic oxygenation and high frequency jet ventilation (HFJV). This study aims to compare the latter approaches for lung immobilization and their clinical impact on gas exchange in an animal model.MATERIALS AND METHODS: Two radiopaque tumor surrogate markers (TSM) were placed in the central (cTSM) and peripheral (dTSM) regions of the lungs in 9 anesthetized and muscle relaxed pigs undergoing 3 ventilatory interventions (1) HFJV at rates of 200 (JV200), 300 (JV300) and 400 (JV400) min-1; (2) apnea at continuous positive airway pressure (CPAP) levels of 0, 8 and 16 cmH2O; (3) conventional mechanical ventilation (CMV) as reference mode. cTSM and dTSM were visualized using fluoroscopy and their coordinates were computed. The ventilatory pattern was registered, and oxygen and carbon dioxide (pCO2) partial pressures were measured.RESULTS: The highest range of TSM motion, and ventilation was found during CMV, the lowest during apnea. During HFJV the amount of motion varied inversely with increasing frequency. The reduction of TSM motion at JV300, JV400 and all CPAP levels came at the cost of increased pCO2, however the relatively low frequency of 200 min-1 for HFJV was the only ventilatory setting that enabled adequate CO2 removal.CONCLUSION: In this model, HFJV at 200 min-1 was the best compromise between immobilization and gas exchange for sessions of 10-min duration.
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| 9. |
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| 10. |
- Sütterlin, Robert, et al.
(författare)
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Efficacy of Superimposed High Frequency Jet Ventilation and High Frequency Jet Ventilation in an Animal Model of Tracheal Obstruction
- 2014
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Ingår i: Anesthesiology. - 0003-3022 .- 1528-1175.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundSuperimposed high frequency jet ventilation (SHFJV) and high-frequency jet ventilation (HJFV) are widely used for airway interventions using rigid bronchoscopy. SHFJV was found to provide higher lung volume and better gas exchange than HFJV in unobstructed airways.We hypothesized that, also in the presence of airway obstruction, SHFJV would provide higher lung volumes, better oxygenation and more effective CO2 removal than HFJV.MethodsIn a porcine model, we used a stent with ID 4 mm to create tracheal obstruction. The anesthetized animals (25-31.5kg) were alternately ventilated with SHFJV (low frequency 16min-1, combined with a high frequency fHF) and HFJV (solely fHF) at a set of different fHF from 50-600min-1. Chest wall volume changes were measured with opto-electronic plethysmography, airway pressures were registered continuously and arterial blood gases were obtained repeatedly.ResultsSHFJV provided higher ∆EEVCW than HFJV with a difference between both modes of 129 ml (fHF=50min-1) to 62 ml (fHF=400min-1). Tidal volume (VT) was always greater than 213 ml with SHFJV, but with HFJV, increasing fHF reduced VT from 112 (97-130) ml at fHF=50 min-1 to negligible values at fHF>150 min-1.In analogy, SHFJV provided paO2 of >30 kPa and acceptable CO2 removal for all fHF, whereas fHF>150 min-1 resulted in severe hypoxia and hypercarbia during HFJV.ConclusionSHFJV effectively increased lung volumes and maintained gas exchange compared with HFJV. SHFJV may be a safer option than HFJV in laser surgery, where low FiO2 is required. HFJV with frequencies >100-150 min-1 should not be used in severe airway obstruction.
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| 11. |
- Sütterlin, Robert, et al.
(författare)
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Frequency dependence of lung volume changes during superimposed high-frequency jet ventilation and high-frequency jet ventilation
- 2014
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Ingår i: British Journal of Anaesthesia. - : Elsevier BV. - 0007-0912 .- 1471-6771. ; 112:1, s. 141-149
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Tidskriftsartikel (refereegranskat)abstract
- Background. Superimposed high-frequency jet ventilation (SHFJV) has proved to be safe and effective in clinical practice. However, it is unclear which frequency range optimizes ventilation and gas exchange. The aim of this study was to systematically compare high-frequency jet ventilation (HFJV) with HFJV by assessing chest wall volume variations (Delta EEVCW) and gas exchange in relation to variable high frequency. Methods. SHFJV or HFJV were used alternatively to ventilate the lungs of 10 anaesthetized pigs (21-25 kg). The low-frequency component was kept at 16 min(-1) in SHFJV. In both modes, high frequencies ranging from 100 to 1000 min(-1) were applied in random order and ventilation was maintained for 5 min in all modalities. Chest wall volume variations were obtained using opto-electronic plethysmography. Airway pressures and arterial blood gases were measured repeatedly. Results. SHFJV increased Delta EEVCW compared with HFJV; the difference ranged from 43 to 68 ml. Tidal volume (V-T) was always >240 ml during SHFJV whereas during HFJV ranged from 92 ml at theventilation frequency of 100 min(-1) to negligible values at frequencies >300 min(-1). We observed similar patterns for Pa-O2 and Pa-CO2. SHFJV provided generally higher, frequency-independent oxygenation (Pa-O2 at least 32.0 kPa) and CO2 removal (Pa-CO2 similar to 5.5 kPa), whereas HFJV led to hypoxia and hypercarbia at higher rates (Pa-O2 < 10 kPa and Pa-CO2 > 10 kPa at f(HF) > 300 min(-1)). Conclusions. In a porcine model, SHFJV was more effective in increasing end-expiratory volume than single-frequency HFJV, but both modes may provide adequate ventilation in the absence of airway obstruction and respiratory disease, except for HFJV at frequencies >= 300 min(-1).
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| 12. |
- Sütterlin, Robert, et al.
(författare)
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Influence of Tracheal Obstruction on the Efficacy of Superimposed High-frequency Jet Ventilation and Single-frequency Jet Ventilation
- 2015
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Ingår i: Anesthesiology. - 0003-3022 .- 1528-1175. ; 123:4, s. 799-809
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Tidskriftsartikel (refereegranskat)abstract
- Background: Both superimposed high-frequency jet ventilation (SHFJV) and single-frequency (high-frequency) jet ventilation (HFJV) have been used with success for airway surgery, but SHFJV has been found to provide higher lung volumes and better gas exchange than HFJV in unobstructed airways. The authors systematically compared the ventilation efficacy of SHFJV and HFJV at different ventilation frequencies in a model of tracheal obstruction and describe the frequency and obstruction dependence of SHFJV efficacy. Methods: Ten anesthetized animals (weight 25 to 31.5 kg) were alternately ventilated with SHFJV and HFJV at a set of different f(HF) from 50 to 600 min(-1). Obstruction was created by insertion of interchangeable stents with ID 2 to 8 mm into the trachea. Chest wall volume was measured using optoelectronic plethysmography, airway pressures were recorded, and blood gases were analyzed repeatedly. Results: SHFJV provided greater than 1.6 times higher end-expiratory chest wall volume than HFJV, and tidal volume (V-T) was always greater than 200 ml with SHFJV. Increase of f(HF) from 50 to 600 min(-1) during HFJV resulted in a more than 30-fold V-T decrease from 112 ml (97 to 130 ml) to negligible values and resulted in severe hypoxia and hypercapnia. During SHFJV, stent ID reduction from 8 to 2 mm increased end-expiratory chest wall volume by up to 3 times from approximately 100 to 300 ml and decreased V-T by up to 4.2 times from approximately 470 to 110 ml. Oxygenation and ventilation were acceptable for 4 mm ID or more, but hypercapnia occurred with the 2 mm stent. Conclusion: In this in vivo porcine model of variable severe tracheal stenosis, SHFJV effectively increased lung volumes and maintained gas exchange and may be advantageous in severe airway obstruction.
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| 13. |
- Sütterlin, Robert, et al.
(författare)
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Influence of Tracheal Obstruction on the Efficacy of Superimposed High-frequency Jet Ventilation and Single-frequency Jet Ventilation
- 2015
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Ingår i: Anesthesiology. - 0003-3022 .- 1528-1175. ; 123:10, s. 799-809
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundSuperimposed high frequency jet ventilation (SHFJV) has been used successfully in selected patients with severe central airway obstruction undergoing airway interventions.We sought to systematically describe the efficacy of SHFJV in relation to obstruction and the high frequency component (fHF) in a model of tracheal stenosis.MethodsTen anesthetized animals (25-31.5kg) were alternately ventilated with SHFJV (low frequency 16min-1, random fHF) at a set of different fHF from 50-600min-1. Tracheal obstruction was created using exchangeable stents with different inner diameter (2, 4, 6, 8mm) that were inserted into the trachea. Chest wall volume was measured using optoelectronic plethysmography, airway pressures were recorded and blood gases were analyzed repeatedly.ResultsStent ID reduction from 8 to 2mm resulted in an increase of ∆EEVCW by up to 3x (e.g. 323 [255 - 410] ml vs 106 [81 - 138] ml at fHF=100 min-1). At the same time, VT decreased by up to 4.2x (e.g. 477 [434 – 524] ml vs 114 [79 – 165] ml). PaO2 and paCO2 remained at acceptable levels for 4-8 mm stent ID but CO2 removal became suddenly impaired at 2mm stent ID (paCO2>12 kPa). Pre-stenotic airway pressure monitoring was accurate at 8mm stent ID, but overestimation of peak inspiratory pressure (PIP) up to 2x and underestimation of PEEP up to 19x was observed at 2mm stent ID.ConclusionSHFJV was able to maintain oxygenation and carbon dioxide removal over a wide range of obstructions, despite decreasing VT and successive air trapping. At 2 mm stent ID, only carbon dioxide removal became insufficient.
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| 14. |
- Sütterlin, Robert, 1981-
(författare)
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Jet Ventilation for Airway Surgery : The Influence of Mode and Frequency on Ventilation Efficacy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In surgery for airway obstruction, the anesthetist and the ear-nose-throat surgeon share the approach to the airway and jet ventilation (JV) is a mutually convenient ventilation technique for both parties. As a consequence of the open system jet ventilation is applied in, bedside measurements of lung volumes are cumbersome to perform and thus, there is a lack of studies comparing different modes of JV or investigating the influence of ventilator settings on lung volumes and gas exchange. In this thesis, single frequency jet ventilation and superimposed high frequency jet ventilation (SHFJV) at different frequencies are systematically compared with respect to lung volume changes, underlying airway pressure variations and the resulting gas exchange.We compared three single-frequency JV modalities with SHFJV in patients. Moreover, we performed a systematic investigation of single frequency JV and SHFJV in a porcine model. Single frequency JV and SHFJV were compared frequency-wise in intact airways and in a newly developed model of tracheal obstruction. This model was also used to assess the influence of variable airway diameter on ventilation effectiveness during SHFJV. We measured chest wall volume variations with opto-electronic plethysmography and obtained airway pressures as well as gas exchange parameters.In unobstructed airways, both single-frequency JV and SHFJV provided adequate oxygenation, despite differences in lung volumes. Carbon dioxide removal was most effective using single frequency JV at a frequency of 150 min-1. During SHFJV, for both intact and obstructed airways, the choice of frequency for the high frequency component had little influence on lung volumes, airway pressures and gas exchange. With decreasing airway diameter and SHFJV, we observed air trapping and lower tidal volumes and acceptable oxygenation. Carbon dioxide removal, however, was insufficient at the narrowest airway diameter. In single frequency JV, very high frequencies resulted in negligible tidal volume and inacceptable gas exchange. Airway obstruction potentiated this frequency dependence.In conclusion, in intact airways, single frequency JV at sufficiently low frequencies provided adequate oxygenation and better CO2 removal than SHFJV. With decreasing airway diameter, SHFJV provided better oxygenation and CO2 removal and may therefore be the mode of choice in more complicated cases.
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| 15. |
- Taavo, Micael, et al.
(författare)
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Role of Renal Sympathetic Nerve Activity in Volatile Anesthesia's Effect on Renal Excretory Function
- 2021
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Ingår i: Function. - : Oxford University Press. - 2633-8823. ; 2:6
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Tidskriftsartikel (refereegranskat)abstract
- Regulation of fluid balance is pivotal during surgery and anesthesia and affects patient morbidity, mortality, and hospital length of stay. Retention of sodium and water is known to occur during surgery but the mechanisms are poorly defined. In this study, we explore how the volatile anesthetic sevoflurane influences renal function by affecting renal sympathetic nerve activity (RSNA). Our results demonstrate that sevoflurane induces renal sodium and water retention during pediatric anesthesia in association with elevated plasma concentration of renin but not arginine–vasopressin. The mechanisms are further explored in conscious and anesthetized ewes where we show that RSNA is increased by sevoflurane compared with when conscious. This is accompanied by renal sodium and water retention and decreased renal blood flow (RBF). Finally, we demonstrate that renal denervation normalizes renal excretory function and improves RBF during sevoflurane anesthesia in sheep. Taken together, this study describes a novel role of the renal sympathetic nerves in regulating renal function and blood flow during sevoflurane anesthesia.
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