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Development of a Reusable Metal 3D-Printed Heat and Moisture Exchanger

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Additive manufacturing's attributes include print customization, low per-unit cost for small- to mid-batch production, seamless interfacing with mainstream medical 3D imaging techniques, and feasibility to create free-form objects in materials that are biocompatible and biodegradable. Consequently, additive manufacturing is apposite for a wide range of biomedical applications including custom biocompatible implants that mimic the mechanical response of bone, biodegradable scaffolds with engineered degradation rate, medical surgical tools, and biomedical instrumentation. This review surveys the materials, 3D printing methods and technologies, and biomedical applications of metal 3D printing, providing a historical perspective while focusing on the state of the art. It then identifies a number of exciting directions of future growth: (a) the improvement of mainstream additive manufacturing methods and associated feedstock; (b) the exploration of mature, less utilized metal 3D printing techniques; (c) the optimization of additively manufactured load-bearing structures via artificial intelligence; and (d) the creation of monolithic, multimaterial, finely featured, multifunctional implants.
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Background Due to the heat and moisture exchanger's (HME) breathing resistance, laryngectomized patients cannot always use an (optimal) HME during physical exercise. We propose a novel HME cassette concept with adjustable “bypass,” to provide adjustment between different breathing resistances within one device. Methods Under standardized conditions, the resistance and humidification performance of a high resistance/high humidification HME (XM) foam in a cassette with and without bypass were compared to a lower resistance/lesser humidification HME (XF) foam in a closed cassette. Results With a bypass in the cassette, the resistance and humidification performance of XM foam were similar to those of XF foam in the closed cassette. Compared to XM foam in the closed cassette, introducing the bypass resulted in a 40% resistance decrease, whereas humidification performance was maintained at 80% of the original value. Conclusions This HME cassette prototype allows adjustment between substantially different resistances while maintaining appropriate humidification performances.
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Breathing through a tracheostoma results in insufficient warming and humidification of the inspired air. This loss of air-conditioning, especially humidification, can be partially restored with the application of a Heat and Moisture Exchanger (HME) over the tracheostoma. For medical professionals it is not easy to judge differences in water exchange performance of various HMEs due to the lack of universal outcome measures. This study has three aims: assessment of the water exchange performance of commercially available HMEs for laryngectomized patients, validation of these results with absolute humidity outcomes, and assessment of the role of hygroscopic salt present in some of the tested HMEs. Measurements of weight and absolute humidity at end-inspiration and end-expiration at different breathing volumes of a healthy volunteer were performed using a microbalance and humidity sensor. Twenty-three HMEs of six different manufacturers were tested. Associations were determined between core weight, weight change, breathing volume, and absolute humidity, using both linear and non-linear mixed effects models. Water exchange of the 23 HMEs at a breathing volume of 0.5 liter varies between 0.5-3.6 mg. Both water exchange and wet core weight correlate strongly with the end-inspiratory absolute humidity values (R(2)=0.89 / 0.87). Hygroscopic salt increases core weight. The 23 tested HMEs for laryngectomized patients show wide variation in water exchange performance. Water exchange correlates well with the end-inspiratory absolute humidity outcome, which validates the ex vivo weight change method. Wet core weight is a predictor of HME performance. Hygroscopic salt increases the weight of the core material. The results of this study can help medical professionals to obtain a more founded opinion about the performance of available HMEs for pulmonary rehabilitation in laryngectomized patients, and uniquely allow them to make an informed decision on which of HME type to use.
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The thermal conductivity (λ) and the specific heat (cp) of seven polyurethane foam formulations and their melts are obtained using a transient plane source technique called the Hot Disk experiment. In the experiment, the Hot Disk sensor is sandwiched by the samples and acts as both a heat source and a temperature sensor. The fundamental assumption is that throughout the experiment, the heat from the sensor does not penetrate beyond the boundaries of the sample. The suitable sample dimensions and sensor radius are determined from the preliminary calculations. Through sensitivity analysis, the appropriate measuring time and output power for the experiments are established. For polyurethane foams, λ ranges from 0.048 to 0.050 W/m K, and cp ranges from 2359 to 2996 J/kg K. For melts, λ ranges from 0.186 to 0.200 W/m K, and cp ranges from 1958 to 2076 J/kg K. When foam decomposes into melts, the changes in thermophysical properties shows λ increases by approximately 300%, whereas cp decreases by approximately 20%. On the basis of these changes, the collapse of the foam structure into melt appears to improve the heat transfer through the material. Copyright © 2013 John Wiley & Sons, Ltd.
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Evaluate the effects of the improvement of filtration, heating and humidification of inspired air with Cyranose heat and moisture exchanger (HME) on voice quality, breathing, and secretion handling in laryngectomized patients. Prospective study. Fifteen laryngectomized patients, mean age 68, ages ranging from 50 to 91 years. Information was given to patients through video and brochures. Patients were selected if they had minimal understanding, permanent decanulization, no tumour progression or bronchopulmonary infections, and received no recent radiation therapy treatment. They were given the prosthesis and a starter kit. They were then evaluated by a speech pathologist with a structured questionnaire after one week, one month, and three months. The outcomes measured were comfort, breathing, secretions, and ease of use of the prosthesis as well as its effect on voice. Impressions of patients on humidification, filtration, and heating of inspired air were also recorded. At conclusion of trial, 75% of patients wore the prosthesis on a daily basis and they all found it easy to use. All patients who completed the trial found breathing and handling of secretions easier as they thought humidification and filtration of air had improved. Quality of voice improved for 50% while remaining unchanged for 37%. The positive effect of the prosthesis progressed throughout the trial. Seven patients dropped out of the trial, mainly because of adhesive-related issues. Laryngectomized patients from the Montreal area could benefit from Cyranose artificial nose following an adaptation period during our cold winter.
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Objective To evaluate the effects of new devices—heat and moisture exchangers (HMEs) and adhesives—on pulmonary symptoms, subject adherence, quality of life, dermatologic symptoms, and patient satisfaction after laryngectomy. Study Design Prospective crossover study. Setting Between December 2020 and April 2021, 40 patients were enrolled who had undergone laryngectomy, routinely used HMEs and adhesive, and were followed in our Department of Otolaryngology–Head and Neck Surgery. Methods Patients were allocated into group A (new products) or group B (usual care) for 6 weeks. Then the 2 groups reversed, and each patient acted as his or her own control. Patients kept a diary and cough tally sheet. At baseline and after each 6-week period, 2 questionnaires were administered: EQ-5D (European Quality of Life–5 Dimensions) and CASA-Q (Cough and Sputum Assessment Questionnaire). Results Six weeks of using new products resulted in the following effects for both groups: (1) a significant reduction in daily forced expectoration and dry coughs, (2) a significant improvement in all domains of the CASA-Q, (3) an increase in adherence to HME use, (4) a significant reduction in shortness of breath and skin irritation, and (5) significantly better scores in the anxiety/depression domain of the EQ-5D. Conclusion Achieving this reduction in patients who were already highly adherent to HME use is clinically relevant and underscores the importance of using better-performing HMEs that can compensate for the humidification deficit. Improving pulmonary symptomatology could reduce patient restrictions in daily life and avoidance of social activity, with a consequent positive effect on quality of life.
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After total laryngectomy, patients suffer from pulmonary complaints due to the shortcut of the upper airways that results in decreased warming and humidification of inspired air. Laryngectomized patients are advised to use a heat and moisture exchanger (HME) to optimize the inspired air. According to manufacturers' guidelines, these medical devices should be replaced every 24 hours. The aim of this study is to determine whether HMEs still function after 24-hour tracheostoma application. Assessment of residual water uptake capacity of used HMEs by measuring the difference between wet and dry core weight. Tertiary comprehensive cancer center. Three hygroscopic HME types were tested after use by laryngectomized patients in long-term follow-up. Water uptake of 41 used devices (including 10 prematurely replaced devices) was compared with that of control (unused) devices of the same type and with a control device with a relatively low performance. After 24 hours, the mean water uptake of the 3 device types had decreased compared with that of the control devices. For only one type was this difference significant. None of the used HMEs had a water uptake lower than that of the low-performing control device. The water uptake capacity of hygroscopic HEMs is clinically acceptable although no longer optimal after 24-hour tracheostoma application. From a functional point of view, the guideline for daily device replacement is therefore justified.
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Degreasing with solvents, chemical etching, polishing, oxygen and argon plasma treatment and heating and drying produce stainless-steel surfaces with different amounts of organic contamination and ‘bonded water’. The hydroxide/oxide layer of the passive film formed on stainless-steel foils is also affected by surface pretreatment. Electron spectroscopy for chemical analysis (ESCA) has been used to analyze the composition of the surface film formed after different cleaning procedures. Organic contamination on 304 stainless-steel foils can be reduced by a factor of five using various cleaning treatments. Wettability or surface energy measurements have been performed on the treated surfaces and it was found that the surface energy of the metal decays with the inverse of the contamination layer thickness. As these cleaning treatments lead to different oxide layers, it is concluded that the nature of the oxide layer is not the main parameter that determines the surface free energy of metals.
Anaesthetic and respiratory equipment -Heat and moisture exchangers (HMEs) for humidifying respired gases in humans -Part 2: HMEs for use with tracheostomized patients having minimum tidal volumes of 250 mL. ISO 9360-2: International Standards Organization
ISO 9360-2:2001 -Anaesthetic and respiratory equipment -Heat and moisture exchangers (HMEs) for humidifying respired gases in humans -Part 2: HMEs for use with tracheostomized patients having minimum tidal volumes of 250 mL. ISO 9360-2: International Standards Organization, Geneva; 2001. pp. 9360-9362.
An in-situ study of the nucleation process of polyurethane rigid foam formation
  • Minoguee
Minogue E. An in-situ study of the nucleation process of polyurethane rigid foam formation [PhD thesis]. Department of Chemical Sciences Dublin City University; 2000.