Aerosol spread with use of high-flow nasal cannulae: a computational fluid dynamics analysis.
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ABSTRACT:
SUBMITTER: Kobayashi H
PROVIDER: S-EPMC7292944 | biostudies-literature | 2020 Sep
REPOSITORIES: biostudies-literature
Publications
Aerosol spread with use of high-flow nasal cannulae: a computational fluid dynamics analysis.
Kobayashi H H Takimoto T T Kitaoka H H Kijima T T
The Journal of hospital infection 20200613 1
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Project description: Not available
| S-EPMC6481761 | biostudies-literature
Project description:BackgroundIn obese patients, preoxygenation with non-invasive ventilation (NIV) was reported to improve outcomes compared with facemask. In this setting, high-flow nasal cannulae (HFNC) used before and during intubation has never been studied against NIV.MethodsThe PREOPTIPOP study is a randomised, single-centre, open-labelled, controlled trial including obese patients requiring intubation before scheduled surgery. Patients were randomised to receive preoxygenation by HFNC or NIV. HFNC was maintained throughout intubation whereas NIV was removed when apnea occurred to perform laryngoscopy. The study was designed to assess the superiority of HNFC. The primary outcome was the lowest level of end-tidal oxygen concentration (EtO2) within 2 min after intubation. Secondary outcomes included drop in pulse oximetry and complications related to intubation.Main findingsA total of 100 patients were randomised. The intent-to-treat analysis found median [IQR] lowest EtO2 of 76% [66-82] for HFNC and 88% [82-90] for NIV (mean difference - 12·1 [- 15·1 to - 8·5], p < 0·0001). Mild desaturation below 95% was more frequent with HFNC (30%) than with NIV (12%) (relative risk 2·5, IC 95% [1·1 to 5·9], p = 0·03) and median lowest SpO2 during intubation was 98% [93-99] in HFNC vs. 99% [97-100] in NIV (p = 0·03). Severe and moderate complications were not different but patients reported more discomfort with NIV (28%) vs. HFNC (4%), p = 0·001.InterpretationCompared with NIV, preoxygenation with HFNC in obese patients provided lower EtO2 after intubation and a higher rate of desaturation < 95%.FundingInstitutional funding, additional grant from Fisher & Paykel.Trial registrationClinical trial Submission: April 10, 2017. Registry name: Preoxygenation Optimization in Obese Patients: High-flow Nasal Cannulae Oxygen Versus Non-invasive Ventilation: A Single-centre Randomised Controlled Study. The PREOPTIPOP Study. Clinicaltrials.gov identifier: NCT03106441 N°ID RCB: 2017-A00305-48. Institutional review Board: CPP Nord-Ouest I, registration number 019/2017. URL registry:https://clinicaltrials.gov/ct2/show/NCT03106441.
| S-EPMC6737343 | biostudies-literature
Project description:The objective of this research was to develop an inlet to meet the inhalable sampling criterion at 10 l min(-1) flow using the standard, 37-mm cassette. We designed a porous head for this cassette and evaluated its performance using computational fluid dynamics (CFD) modeling. Particle aspiration efficiency was simulated in a wind tunnel environment at 0.4 m s(-1) freestream velocity for a facing-the-wind orientation, with sampler oriented at both 0 degrees (horizontal) and 30 degrees down angles. The porous high-flow sampler oriented 30 degrees downward showed reasonable agreement with published mannequin wind tunnel studies and humanoid CFD investigations for solid particle aspiration into the mouth, whereas the horizontal orientation resulted in oversampling. Liquid particles were under-aspirated in all cases, however, with 41-84% lower aspiration efficiencies relative to solid particles. A sampler with a single central 15-mm pore at 10 l min(-1) was also investigated and was found to match the porous sampler's aspiration efficiency for solid particles; the single-pore sampler is expected to be more suitable for liquid particle use.
| S-EPMC4780251 | biostudies-literature
Project description:Potential exposure from hazardous dusts may be assessed by evaluating the dustiness of the powders being handled. Dustiness is the tendency of a powder to aerosolize with a given input of energy. We have previously used computational fluid dynamics (CFD) to numerically investigate the flow inside the European Standard (EN15051) Rotating Drum dustiness tester during its operation. The present work extends those CFD studies to the widely used Heubach Rotating Drum. Air flow characteristics are investigated within the Abe-Kondoh-Nagano k-epsilon turbulence model; the aerosol is incorporated via a Euler-Lagrangian multiphase approach. The air flow inside these drums consists of a well-defined axial jet penetrating relatively quiescent air. The spreading of the Heubach jet results in a fraction of the jet recirculating as back-flow along the drum walls; at high rotation rates, the axial jet becomes unstable. This flow behavior qualitatively differs from the stable EN15051 flow pattern. The aerodynamic instability promotes efficient mixing within the Heubach drum, resulting in higher particle capture efficiencies for particle sizes d < 80 μm.
| S-EPMC10193456 | biostudies-literature
Project description:BackgroundWe performed a systematic review and meta-analysis to evaluate the efficacy and safety of high-flow oxygen via nasal cannulae (HFNC) compared to non-invasive ventilation (NIV) and/or standard oxygen in patients with acute, hypoxemic respiratory failure.MethodsWe reviewed randomized controlled trials from CENTRAL, EMBASE, MEDLINE, Scopus and the International Clinical Trials Registry Platform (inception to February 2016), conference proceedings, and relevant article reference lists. Two reviewers independently screened and extracted trial-level data from trials investigating HFNC in patients with acute, hypoxemic respiratory failure. Internal validity was assessed in duplicate using the Cochrane Risk of Bias tool. The strength of evidence was assessed in duplicate using the Grading of Recommendations Assessment, Development and Evaluation framework. Our primary outcome was mortality. Secondary outcomes included dyspnea, PaO2:FiO2 ratio, PaCO2, and pH. Safety outcomes included respiratory arrest, intubation, delirium, and skin breakdown.ResultsFrom 2023 screened citations, we identified seven trials (1771 patients) meeting inclusion criteria. All trials were at high risk of bias due to lack of blinding. There was no evidence for a mortality difference in patients receiving HFNC vs. NIV and/or standard oxygen (RR 1.01, 95% CI 0.69 to 1.48, I 2 = 63%, five trials, 1629 patients). In subgroup analyses of HFNC compared to NIV or standard oxygen individually, mortality differences were not observed. Measures of patient tolerability were heterogeneous. The PaO2:FiO2 ratio at 6-12 h was significantly lower in patients receiving oxygen via HFNC compared to NIV or standard oxygen for hypoxemic respiratory failure (MD - 53.34, 95% CI - 71.95 to - 34.72, I 2 = 61%, 1143 patients). There were no differences in pH, PaCO2, or rates of intubation or cardio-respiratory arrest. Delirium and skin breakdown were infrequently reported in included trials.ConclusionsIn patients with acute hypoxemic respiratory failure HFNC was not associated with a difference in mortality compared to NIV or standard oxygen. Secondary outcomes including dyspnea, tolerance, and safety were not systematically reported. Residual heterogeneity and variable reporting of secondary outcomes limit the conclusions that can be made in this review. Prospective trials designed to evaluate the efficacy and safety of HFNC in patients with acute hypoxemic respiratory failure are required.
| S-EPMC5644261 | biostudies-literature
Project description:A perfusion system was developed to generate well defined flow conditions within a well of a standard multidish. Human vein endothelial cells were cultured under flow conditions and cell response was analyzed by microscopy. Endothelial cells became elongated and spindle shaped. As demonstrated by computational fluid dynamics (CFD), cells were cultured under well defined but time varying shear stress conditions. A damper system was introduced which reduced pulsatile flow when using volumetric pumps. The flow and the wall shear stress distribution were analyzed by CFD for the steady and unsteady flow field. Usage of the volumetric pump caused variations of the wall shear stresses despite the controlled fluid environment and introduction of a damper system. Therefore the use of CFD analysis and experimental validation is critical in developing flow chambers and studying cell response to shear stress. The system presented gives an effortless flow chamber setup within a 6-well standard multidish.
| S-EPMC2289785 | biostudies-other
Project description:Using high-flow nasal cannula (HFNC) as a "vehicle" to administer aerosolized medication has attracted clinicians' interest in recent years. In this paper, we summarize the current evidence to answer the common questions raised by clinicians about this new aerosol delivery route and best practices of administration. Benefits of trans-nasal aerosol delivery include increased comfort, ability to speak, eat, and drink for patients while meeting a range of oxygen requirements, particularly for those who need to inhale aerosolized medication for long periods. Aerosol administration via HFNC has been shown to be well tolerated by children and adults, with comparable or better delivery efficacy than other interfaces, ranging from 2-20%. In vitro and in vivo scintigraphy studies among pediatric and adult populations reported that the inhaled dose delivered via a vibrating mesh nebulizer is 2 to 3 fold greater than that via a jet nebulizer. For adults, placement of nebulizer at the inlet of humidifier increases inhaled dose while reducing rainout obstructing nasal prongs. When HFNC gas flow is set below patient inspiratory flow, aerosol deposition is higher than when the gas flow exceeds patient inspiratory flow; thus, if tolerated, titrating down HFNC gas flow during trans-nasal aerosol delivery, with close monitoring and the use of unit dose with high concentration are recommended. Trans-nasal pulmonary aerosol delivery has not been shown to increase bioaerosols generated by patients, but gas flow may disperse aerosols. Placement of a surgical or procedure mask over HFNC might reduce aerosol dispersion.
| S-EPMC8105792 | biostudies-literature
Project description:Many intensive care unit patients who undergo endotracheal extubation experience extubation failure and require reintubation. Because of the high mortality rate associated with reintubation, postextubation respiratory management is crucial, especially for high-risk populations. We conducted the present study to compare the effectiveness of oxygen therapy administered using high-flow nasal cannulae (HFNC) and noninvasive positive pressure ventilation (NIPPV) in preventing reintubation among patients receiving prolonged mechanical ventilation (PMV). This single-center, prospective, unblinded randomized controlled trial was at the respiratory care center (RCC). Participants were randomized to an HFNC group or an NIPPV group (20 patients in each) and received noninvasive respiratory support (NRS) administered using their assigned method. The primary outcome was reintubation within7 days after extubation. None of the patients in the NIPPV group required reintubation, whereas 5 (25%) of the patients in the HFNC group required reintubation (P = 0.047). The 90-day mortality rates of the NIPPV and HFNC groups (four patients [20%] vs. two patients [10%], respectively) did not differ significantly. No significant differences in length of RCC stay, length of hospital stay, time to liberation from NRS, and ventilator-free days at 28-day were identified. The time to event outcome analysis also revealed that the risk of reintubation in the HFNC group was higher than that in the NIPPV group (P = 0.018). Although HFNC is becoming increasingly common as a form of postextubation NRS, HFNC may not be as effective as NIPPV in preventing reintubation among patients who have been receiving PMV for at least 2 weeks. Additional studies evaluating HFNC as an alternative to NIPPV for patients receiving PMV are warranted.ClinicalTrial.gov ID: NCT04564859; IRB number: 20160901R.Trial registration: ClinicalTrial.gov ( https://clinicaltrials.gov/ct2/show/NCT04564859 ).
| S-EPMC10033681 | biostudies-literature
Project description:Grocery stores provide essential services to communities all over the world. The COVID-19 pandemic has necessitated better understanding of the transport and dynamics of aerosolized viruses, particularly for the assessment of infection transmission risk within grocery stores and for other providers of essential services. In this study, a 3D computational fluid dynamics model was developed for a medium-sized grocery store in the United States using Ansys Fluent software. Different cases were simulated of a single infected person releasing viral aerosols with and without wearing a face mask. Results showed characteristic airflow and temperature distribution patterns inside the store that can drive the indoor dispersal of viral aerosols. Unsteady spatial distribution of mean age of air was used as a metric to indirectly quantify areas of higher risk of infection. Several factors affected the localization of suspended viral aerosols. Major recirculation patterns in certain locations of the store caused by persistent eddies were primarily attributed to increased mean age of air. The maximum mean age of air in the grocery store was found to be less than 30 min. Simulation results indicate that, without wearing a face mask, the aerosol particles released from a coughing infected person can be spread throughout nearly one-quarter of the grocery store in less than 6 min. The source-control strategy with a face mask showed significant reduction of viral aerosols being dispersed indoors.
| S-EPMC8656192 | biostudies-literature
Project description:BackgroundNasal High Flow (NHF) therapy delivers flows of heated humidified gases up to 60 LPM (litres per minute) via a nasal cannula. Particles of oral/nasal fluid released by patients undergoing NHF therapy may pose a cross-infection risk, which is a potential concern for treating COVID-19 patients.MethodsLiquid particles within the exhaled breath of healthy participants were measured with two protocols: (1) high speed camera imaging and counting exhaled particles under high magnification (6 participants) and (2) measuring the deposition of a chemical marker (riboflavin-5-monophosphate) at a distance of 100 and 500 mm on filter papers through which air was drawn (10 participants). The filter papers were assayed with HPLC. Breathing conditions tested included quiet (resting) breathing and vigorous breathing (which here means nasal snorting, voluntary coughing and voluntary sneezing). Unsupported (natural) breathing and NHF at 30 and 60 LPM were compared.ResultsImaging: During quiet breathing, no particles were recorded with unsupported breathing or 30 LPM NHF (detection limit for single particles 33 μm). Particles were detected from 2 of 6 participants at 60 LPM quiet breathing at approximately 10% of the rate caused by unsupported vigorous breathing. Unsupported vigorous breathing released the greatest numbers of particles. Vigorous breathing with NHF at 60 LPM, released half the number of particles compared to vigorous breathing without NHF.Chemical marker tests: No oral/nasal fluid was detected in quiet breathing without NHF (detection limit 0.28 μL/m3). In quiet breathing with NHF at 60 LPM, small quantities were detected in 4 out of 29 quiet breathing tests, not exceeding 17 μL/m3. Vigorous breathing released 200-1000 times more fluid than the quiet breathing with NHF. The quantities detected in vigorous breathing were similar whether using NHF or not.ConclusionDuring quiet breathing, 60 LPM NHF therapy may cause oral/nasal fluid to be released as particles, at levels of tens of μL per cubic metre of air. Vigorous breathing (snort, cough or sneeze) releases 200 to 1000 times more oral/nasal fluid than quiet breathing (p < 0.001 with both imaging and chemical marker methods). During vigorous breathing, 60 LPM NHF therapy caused no statistically significant difference in the quantity of oral/nasal fluid released compared to unsupported breathing. NHF use does not increase the risk of dispersing infectious aerosols above the risk of unsupported vigorous breathing. Standard infection prevention and control measures should apply when dealing with a patient who has an acute respiratory infection, independent of which, if any, respiratory support is being used.Clinical trial registrationACTRN12614000924651.
| S-EPMC7880466 | biostudies-literature