Natural Polymers as Heat and Moisture Exchange Devices for Medical Applications

In recent decades, Heat and Moisture Exchange (HME) devices have been employed increasingly for short-term use in anaesthesia and long-term use in intensive care units. These devices work as heat exchangers, accumulating the patient’s expired heat and moisture and returning them to the patient during the inhalation phase. Porous matrices obtained from freeze-drying of blends of natural polymers exhibit high open and interconnected porosity and water vapour intake characteristics which make them possible candidates for HME devices. Preliminary tests were conducted on specimens made of gelatine blended with chitosan and treated with a non-toxic cross-linking agent. The tests were carried out in cyclic flow conditions with saturated and dried air. Results show water vapour retention comparable with accepted standards for HME devices.

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A Reappraisal of the Multiple Gauze Heat and Moisture Exchanger

Anaesthesia and Intensive Care ◽

10.1177/0310057x7300100511 ◽

1973 ◽

Vol 1 (5) ◽

pp. 428-432 ◽

Cited By ~ 1

Author(s):

C. A. Shanks ◽

C., A. Sara

Keyword(s):

Water Vapour ◽

Considerable Increase ◽

High Water ◽

Heat And Moisture Exchanger ◽

Water Vapour Content ◽

Moisture Exchanger ◽

Moisture Exchange ◽

Controlled Ventilation ◽

Heat And Moisture

The multiple gauze heat and moisture exchanger was assessed under standardized conditions, at five levels of predetermined fresh gas humidity. As predicted theoretically, the unit functioned best when presented with fresh gases with high water vapour content. The ordinary unit moistened arid gases during inspiration to a level unacceptable for prolonged use. Unheated simple humidification systems dampen anhydrous stored gases and combined with the standard condenser-humidifier produce a microclimate suitable for entry into the trachea during spontaneous or controlled ventilation. Quadrupling the number of gauzes improved heat and moisture exchange with all but the saturated fresh gases. However, there was a considerable increase in weight.

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In vitro evaluation of disposable transport ventilators with combination aerosol therapy

BMJ Open Respiratory Research ◽

10.1136/bmjresp-2020-000739 ◽

2021 ◽

Vol 8 (1) ◽

pp. e000739

Author(s):

Marc Mac Giolla Eain ◽

Andrew O'Sullivan ◽

Mary Joyce ◽

Ronan MacLoughlin

Keyword(s):

Drug Delivery ◽

Ventilatory Support ◽

Aerosol Therapy ◽

Lung Dose ◽

Short Term ◽

Moisture Exchange ◽

Paediatric Patients ◽

Generator Type ◽

Heat And Moisture

BackgroundThe COVID-19 pandemic has highlighted the need for alternative short-term, reliable means to aid in the treatment of patients requiring ventilatory support. Concurrent aerosol drug delivery is often prescribed to such patients. As such, this study examines one such short-term option, the disposable gas-powered transport ventilator to effectively deliver aerosol therapy. Factors such as aerosol generator type, patient breathing pattern, humidification and nebuliser position within the respiratory circuit were also examined.MethodsAerosol drug delivery characterisation was undertaken using two different disposable transport ventilators (DTVs). Two different nebuliser types, a closed circuit vibrating mesh nebuliser (VMN) and an open circuit jet nebuliser (JN), at different locations in a respiratory circuit, proximal and distal to an endotracheal tube (ETT), with and without passive humidification, were evaluated in simulated adult and paediatric patients.ResultsPlacement of a nebuliser proximal to the ETT (VMN: 25.19%–34.15% and JN: 3.14%–8.92%), and the addition of a heat and moisture exchange filter (VMN: 32.37%–40.43% and JN: 5.60%–9.91%) resulted in the largest potential lung dose in the adult patient model. Irrespective of nebuliser position and humidification in the respiratory circuit, use of the VMN resulted in the largest potential lung dose (%). A similar trend was recorded in the paediatric model data, where the largest potential lung dose was recorded with both nebuliser types placed proximal to the ETT (VMN: 8.12%–10.89% and JN: 2.15%–3.82%). However, the addition of a heat and moisture exchange filter had no statistically significant effect on the potential lung dose (%) a paediatric patient would receive (p>>0.05).ConclusionsThis study demonstrates that transport ventilators, such as DTVs, can be used concurrently with aerosol generators to effectively deliver aerosolised medication in both adult and paediatric patients.

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THE EFFECTS OF INSPIRATION OF GASES SATURATED WITH WATER VAPOUR ON HEAT AND MOISTURE EXCHANGE DURING ENDOTRACHEAL INTUBATION

British Journal of Anaesthesia ◽

10.1093/bja/45.8.887 ◽

1973 ◽

Vol 45 (8) ◽

pp. 887-890 ◽

Cited By ~ 5

Author(s):

C.A. SHANKS

Keyword(s):

Water Vapour ◽

Endotracheal Intubation ◽

Moisture Exchange ◽

Heat And Moisture

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Performance of a new recuperative Heat and Moisture Exchange Mask

Health Promotion & Physical Activity ◽

10.5604/01.3001.0014.7869 ◽

2021 ◽

Vol 14 (1) ◽

pp. 9-16

Author(s):

Mario P. Wehrle ◽

Thomas Küpper ◽

Claus-M. Muth

Keyword(s):

Dead Space ◽

Room Temperature ◽

Airway Resistance ◽

Face Mask ◽

Relative Difference ◽

Cold Weather ◽

Moisture Exchange ◽

Clinical Conditions ◽

Heat And Moisture

Aim of the study: The purpose of this work is to show the possibility to use a recuperative design of a heat and moisture exchange face mask (HME). Such HME are used as cold weather face masks for Arctic expeditions and conditioning of air for long-term intubated patients. Common regenerative HME have the disadvantage of increasing airway resistance and airway volume (dead space). In recuperative devices, the separation of inspired and expired airflow could reduce dead space and resistance. Materials and methods: Prototype HMEs were built using two concentric ducts of aluminium or cotton. A valve ensures that expired and inspired air are led through either the inner or the outer tube. The inner tube’s wall transmits heat and water. The HMEs were tested in a simulated Arctic environment using a breathing simulator and characterized in terms of heat and moisture exchange efficiency. The new design was also tested at room temperature in order to simulate the conditions of long-term intubation. To compare the results, the relative difference in temperature (Performance Coefficient PC) between the expired and the inspired air was calculated. Results: During the experiments, the ambient temperature was −37°C and therefore the absolute water content was about zero. The recuperative HME conditioned the air to 21°C and 10.7 mg/l water (61% relative humidity), giving a PC of 82%. At room temperature the recuperative mask showed a PC of 62%. Conclusion: The recuperative HME shows great potential. It might be of use in clinical conditions and Arctic expeditions.

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Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

Behavioral and Brain Sciences ◽

10.1017/s0140525x15000928 ◽

2016 ◽

Vol 39 ◽

Author(s):

Mary C. Potter

Keyword(s):

Working Memory ◽

Rapid Serial Visual Presentation ◽

Language Comprehension ◽

Short Term Memory ◽

Visual Presentation ◽

Long Term Memory ◽

Short Term ◽

Term Memory ◽

Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

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Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159412 ◽

1990 ◽

Vol 48 (3) ◽

pp. 374-375

Author(s):

D.E. Loudy ◽

J. Sprinkle-Cavallo ◽

J.T. Yarrington ◽

F.Y. Thompson ◽

J.P. Gibson

Keyword(s):

Antidepressant Drug ◽

Beagle Dogs ◽

Long Term Effects ◽

Short Term ◽

Platelet Counts ◽

Toxicological Studies ◽

Induced Aggregation ◽

Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

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Comparison of Auditory, Language, Memory, and Attention Abilities in Children With and Without Listening Difficulties

American Journal of Audiology ◽

10.1044/2020_aja-20-00018 ◽

2020 ◽

Vol 29 (4) ◽

pp. 710-727

Author(s):

Beula M. Magimairaj ◽

Naveen K. Nagaraj ◽

Alexander V. Sergeev ◽

Natalie J. Benafield

Keyword(s):

Auditory Processing ◽

Short Term Memory ◽

Group Differences ◽

Long Term Memory ◽

Short Term ◽

Significant Group ◽

Term Memory ◽

Memory And Attention ◽

Speed And Accuracy

Objectives School-age children with and without parent-reported listening difficulties (LiD) were compared on auditory processing, language, memory, and attention abilities. The objective was to extend what is known so far in the literature about children with LiD by using multiple measures and selective novel measures across the above areas. Design Twenty-six children who were reported by their parents as having LiD and 26 age-matched typically developing children completed clinical tests of auditory processing and multiple measures of language, attention, and memory. All children had normal-range pure-tone hearing thresholds bilaterally. Group differences were examined. Results In addition to significantly poorer speech-perception-in-noise scores, children with LiD had reduced speed and accuracy of word retrieval from long-term memory, poorer short-term memory, sentence recall, and inferencing ability. Statistically significant group differences were of moderate effect size; however, standard test scores of children with LiD were not clinically poor. No statistically significant group differences were observed in attention, working memory capacity, vocabulary, and nonverbal IQ. Conclusions Mild signal-to-noise ratio loss, as reflected by the group mean of children with LiD, supported the children's functional listening problems. In addition, children's relative weakness in select areas of language performance, short-term memory, and long-term memory lexical retrieval speed and accuracy added to previous research on evidence-based areas that need to be evaluated in children with LiD who almost always have heterogenous profiles. Importantly, the functional difficulties faced by children with LiD in relation to their test results indicated, to some extent, that commonly used assessments may not be adequately capturing the children's listening challenges. Supplemental Material https://doi.org/10.23641/asha.12808607

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