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BACKGROUND: At high ambient temperatures in ICU rooms, the humidification performances of heated-wire humidifiers are significantly reduced, with delivered gas humidity well below 30 mg H2O/L, which leads to an increased risk of endotracheal occlusions, subocclusions, or mucociliary dysfunction. The objective of the study was to evaluate the humidity delivered at the Y-piece with new-generation heated-wire humidifiers with advanced algorithm (FP950 [Fisher & Paykel Healthcare, Auckland, New Zealand] and VHB20 [Vincent Medical, Inspired, Hong Kong]) while varying ambient temperatures. METHODS: We measured, on the bench, the hygrometry of inspiratory gases delivered by a new generation of heated-wire humidifiers (i) FP950, (ii) VHB20 and a previous generation of heated-wire humidifiers, (iii) MR850 (Fisher & Paykel) with the usual settings (37°C at the chamber/40°C at the Y-piece), (iv) MR850 with no temperature gradient (40°C/40°C), and (v) MR850 with the automatic compensation algorithm activated. Hygrometry was measured with the psychrometric method after 1 h of stability while varying the room temperature from 20 to 30°C. RESULTS: Two hundred ninety-four hygrometric bench measurements were performed at steady state for the different tested conditions. With the new heated-wire humidifiers (FP950 and VHB20), gas humidity delivered remained > 30 mg H2O/L in all tested conditions, even at high ambient temperatures (>25°C). With previous generations of heated-wire humidifiers (MR850), at high ambient temperature, humidity delivered was adequate in only 26% (11/42) of the measurements when the usual settings were used (37°C/40°C) and 30% (11/37) with automatic compensation. When no temperature gradient was set (40°C/40°C), humidity delivered was > 30 mg H2O/L in 91% (30/33) of the measurements at a high ambient temperature. With an ambient temperature < 25°C, almost all devices and settings provided adequate humidity. CONCLUSIONS: The new FP950 and VHB20 heated-wire humidifiers by using advanced algorithms demonstrated stable performance while varying the ambient temperature by 20-30°C, better than the previous generation of heated humidifiers when ambient temperatures were high.

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Objective To explore the humidification effects between the humidifiers Venturi high-flow oxygen therapy(HVHF)and the high-flow humidified oxygen therapy in the treatment of patients with tracheotomy after the withdrawal of ventilator,and analyse the humidification performance and effect of airway humidification on the two oxygen therapies hence to provide an objective basis for selection of a humidified oxygen therapy.Methods A total of 146 ICU patients who had tracheotomy and completely withdrawal of ventilator in a general hospital in Shenzhen from July 2020 to December 2021 were randomly divided into trial group(n=73)and control group(n=73).With identical speed of airflow,patients in the trial groups were treated with HVHF and the patients of control group were offered with high-flow humidified oxygen therapy via AIRVOTM2.Data of the two groups were compared at the time points of days 0,2,7 and 14 in terms of absolute humidity(AH),relative humidity(RH),temperature(T)),sputum viscosity,arterial partial pressure of oxygen(PaO2),arterial partial pressure of carbon dioxide(PaCO2),oxygenation index(PaO2/FIO2)and the incidence of pulmonary infection.Results In the study,total of 61 patients in the control group and 72 patients in the trial group completed the high-flow humidified oxygen therapies,due to tubing detachments in 12 and 1 patients in the two groups,respectively.Repeated-Measures ANOVA analysis showed that,in both groups,there was a time effect(P<0.05)between the absolute humidity,relative humidity,temperature of the gas,PaO2,PaCO2,and PaO2/FiO2 at different time points.PaO2 and PaO2/FiO2 in both groups showed interactions at different time points(P<0.05).PaO2 and PaO2/FiO2 in the trial group were better than those in the control group at the time points of days 2,7 and 14(P<0.05).On days 2,7 and 14,the viscosity of sputum in the intervention group was better than that in the control group,and the incidence of pulmonary infection in the trial group was significantly lower than that in the control group(P<0.05).Conclusions HVHF and AIRVOTM2 both exhibit no obvious difference in gas humidification via high-flow humidification oxygen therapy in the patients with tracheotomy after withdrawal of ventilator.However,HVHF is superior to AIRVOTM2 in terms of improving airway humidification and oxygenation as well as reducing lung infection.Therefore,it is suggested that an HVHF is preferable for high-flow humidified oxygen therapy in treating the patients with tracheotomy after the withdrawal of ventilator.

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High-flow oxygen therapy (high flow nasal cannula, HFNC), in which an oxygen-air gas mixture is applied at flow rates between 30 and 70 L/min, is a technically simple and highly effective procedure for the treatment of hypoxemic respiratory insufficiency. Furthermore, HFNC can be used during bronchoscopy for oxygenation, before intubation for preoxygenation, and after extubation to avoid reintubation. The high gas flow prevents the patient from inspiring ambient air, allowing precise adjustment of an inspiratory oxygen fraction; furthermore, a positive end-expiratory pressure is built up by a resulting dynamic pressure, mucociliary clearance is improved by humidification and warming of the air breathed and the work of breathing is reduced by flushing the upper airways. Compared with conventional oxygen therapy, aerosol formation is not increased by HFNC; therefore, this procedure can also be used for patients with coronavirus disease 2019 (COVID-19). In hypercapnic respiratory failure the data are inconclusive and in this case noninvasive ventilation should currently be preferred instead of HFNC. It is important to remember that patients treated with HFNC are critically ill and therefore require continuous monitoring. It must be ensured that an escalation of therapy, e.g. to intubation and invasive ventilation, can be performed at any time.

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BACKGROUND: Oxygen (O2) is a drug with specific biochemical and physiological properties, a range of effective doses and may have side effects. In 2015, 14% of over 55,000 hospital patients in the UK were using oxygen. 42% of patients received this supplemental oxygen without a valid prescription. Health care professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed. METHODS: A national S3 guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. A literature search was performed until February 1, 2021, to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for assessing the quality of evidence and for grading guideline recommendation, and a formal consensus-building process was performed. RESULTS: The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O2 therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are based depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort. CONCLUSION: This is the first national guideline on the use of oxygen in acute care. It addresses health care professionals using oxygen in acute out-of-hospital and in-hospital settings.

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OBJECTIVES: We aimed to determine the characteristics of the deceased victims of deaths caused by exposure to humidifier disinfectants, and present the distribution of the victims' data submitted for damage application, demographic characteristics, imaging findings, characteristics of humidifier disinfectant exposure, and distribution of the causes of death. METHODS: An integrated database of victims was established using the medical records data of 1,413 victims submitted during the application for death damage caused by exposure to humidifier disinfectants, and the demographic characteristics, medical records, imaging findings, exposure characteristics, and cause of death were examined. RESULTS: The average numbers of data submissions of each applicant for death damage were 3.0 medical use records. A total of 608 (43.0%) victims had more than one finding of acute, subacute, or chronic interstitial lung diseases. The average daily and cumulative use times of the victims were 14.40 and 24,645.81 hours, respectively, indicating greater exposure in this group than in the survivors. The humidifier disinfectants' components comprised polyhexamethylene guanidine (72.8%), chloromethylisothiazolinone/methylisothiazolinone (10.5%), other components (15.0%), and oligo-[2-(2-ethoxy)-ethoxyethyl] guanidine chloride (1.5%). The components' distribution was 67.8% for single-component use, which was higher than that in the survivors (59.8%). The distribution of the causes of death were: respiratory diseases (54.4%), neoplasms (16.8%), and circulatory diseases (6.3%). Other interstitial lung diseases (65.5%) were the most common cause of death among those who died due to respiratory diseases. CONCLUSIONS: Careful discussions of appropriate remedies should be conducted based on a comprehensive understanding of the characteristics of the deceased victims, considering their specificities and limitations.

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Humidifier disinfectants (HDs) exposure has now been associated with acute lung injury and pulmonary fibrosis; polyhexamethylene guanidine (PHMG) has been confirmed to cause severe lung inflammation and fibrosis in mice. Recent evidence also indicates that HDs exposure increases the asthma risk in children, but the underlying mechanisms remain unclear. We aimed to investigate the effects of PHMG exposure on asthma in mice and the potential underlying mechanisms. BALB/c mice were intranasally administered PHMG (0.1 mg/kg/day; 5 days per week) during 2 episodes of ovalbumin (OVA) sensitization and were then challenged with 1% OVA by inhalation. Bronchial hyperresponsiveness (BHR), inflammatory cell influx into bronchoalveolar lavage (BAL) fluid, serum total and OVA-specific immunoglobulin (Ig) E levels, and histopathological changes in the lung were analyzed. The levels of asthma-related cytokines and chemokines were assayed in the lung tissues to evaluate possible mechanisms. Exposure to PHMG following OVA sensitization and challenge significantly enhanced BHR, inflammatory cell counts in BAL fluid, airway inflammation, and total serum IgE levels in the asthma mouse model. In addition, the levels of chemokine ligand (CCL) 11 and serpine F1/pigment epithelium-derived factor (SERPINF1) were significantly elevated in the lungs of these mice compared to those in the control and OVA-treated only groups. Our findings suggest that PHMG can enhance the development of allergic responses and lung inflammation via CCL11- and SERPINF1-induced signaling in a mouse model of asthma.

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BACKGROUND: Continuous nebulization of prostacyclins and albuterol by infusion pump during mechanical ventilation evolved as a popular off-label treatment for severe hypoxemic respiratory failure and asthma. Most institutions use a vibrating mesh nebulizer. A new breath-enhanced jet nebulizer is a potential alternative. This study was designed to compare these devices to better define factors influencing continuous infusion aerosol delivery. Device function, ventilator settings, and infusion pump flow were studied in vitro. METHODS: Using a bench model of adult mechanical ventilation, radiolabeled saline was infused at 6 flows (1.5-12 mL/h) into test nebulizers; 4 examples of each were used in rotation to test device reproducibility. Four breathing patterns with duty cycles (percentage of inspiratory time) ranging from 0.13 to 0.34 were tested. The vibrating mesh nebulizer was installed on the "dry" side of the heated humidifier (37°C). The breath-enhanced jet nebulizer, installed on the "wet" side, was powered by air at 3.5 L/min and 50 psi. Infusion time was 1 h. Inhaled mass of aerosol was collected on a filter at the airway opening. Inhaled mass was expressed as the percentage of the initial syringe radioactivity delivered per hour. Radioactivity deposited in the circuit was measured with a gamma camera. Data were analyzed with multiple linear regression. RESULTS: Variation in inhaled mass was significantly explained by pump flow and duty cycle (R2 0.92) and not by nebulizer technology. Duty cycle effects were more apparent at higher pump flow. Vibrating mesh nebulizers failed to nebulize completely in 20% of the test runs. Mass balance indicated that vibrating mesh nebulizers deposited 15.3% in the humidifier versus 0.2% for breath-enhanced jet nebulizer. CONCLUSIONS: Aerosol delivery was determined by infusion pump flow and ventilator settings with comparable aerosol delivery between devices. The breath-enhanced jet nebulizer was more reliable than the vibrating mesh nebulizer; 10-12 mL/h was the maximum infusion flow for both nebulizer technologies.

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BACKGROUND: Aerosol transport during noninvasive ventilation follows the flow of pressurized gas through the noninvasive ventilation circuit, vented via leak port and face mask, and inhaled by the patient. Recommendations for nebulizer placement are based on in vitro models that have focused primarily on aerosol losses via the leak port; face mask leaks have been avoided. This study tested aerosol delivery in the setting of controlled face mask leak. METHODS: Three nebulizer technologies were studied on a bench model using a lung simulator with a face mask placed onto a manikin head. Radiolabeled aerosol delivery (ie, inhaled mass) was determined by mass balance using filters and a gamma camera that tested the effects of nebulizer location and face mask leak. Low (15-20 L/min) and high (55-60 L/min) mask leaks were used to mimic realistic clinical conditions. RESULTS: Inhaled mass (% nebulizer charge) was a function of nebulizer technology (with the nebulizer at ventilator outlet position: Aerogen 22.8%, InspiRx 11.1%, and Hudson 8.1%; P = .001). The location of the nebulizer before or after the leak port was not important (P = 0.13 at low leak and P = 0.38 at high leak). Aerosol delivery was minimal with high mask leak (inhaled mass 1.5-7.0%). Aerosol losses at the leak port at low mask leak were 28-36% versus 9-24% at high mask leak. Aerosol losses via the mask leak were 16-20% at low mask leak versus 46-72% at high mask leak. Furthermore, high face mask leak led to significant deposition on the mask and face (eg, up to 50% of the nebulizer charge with the Aerogen mask). CONCLUSIONS: During noninvasive ventilation, nebulizer placement at the ventilator outlet, which is a more practical position, is effective and minimizes deposition on face and mask. Aerosol therapy should be avoided when there is high face mask leak.

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ABSTRACT Objective Humidity and temperature are fundamental for the balance in the life cycle of living beings and, consequently, for maintaining the well-being of the human population and reducing the prevalence of infectious diseases. Thus, in order to mitigate the impact of climate change, especially in the period when humidity is not the ideal, it is necessary to adopt some assistance measures. The present experimental study aims to elucidate what would be the recommended option to improve the quality of life of the human being and to clarify which resources (air humidifier, bucket of water or wet towel) will be effective to improve the humidity of the air in times of drought and low moisture. Methods The experimental study was carried out with INKBIRD hygrometers allowing the analysis of the variation of air humidity throughout the day. Three forms of treatment were established: humidifier, wet towel and bucket of water. In each room, two hygrometers were placed equidistant from the occupant of the room and their respective treatment that varied between 1m and 2m away from the headboard indoor each room. In addition, two environments were used as controls, one being an external environment and the other an internal closed environment, totaling five rooms for the study. The rooms were monitored between the end of July and the end of August 2019 in Goiania (GO). Results Although assistance measures are used to significantly improve air pollution in times of extreme drought, there was a significant difference between them. The humidifier and a wet towel had 7.50% and 5.71% more humidity in the external relation (external control), respectively, more efficient. The volume of water, however, did not show significant difference (p>0.05) and, therefore, there was no variation. Conclusion The humidifier and the towel are treatments considered more efficient, and that there was a significant effect of distance on humidity. Therefore, 1m of distance is more efficient in increasing and/or maintaining air humidity, inducing improvements in the populations' health.

RESUMO Objetivo A umidade e a temperatura são fundamentais para o equilíbrio no ciclo da vida dos seres vivos e, consequentemente, para manter o bem-estar da população humana e diminuir a prevalência de doenças infecciosas. Visando mitigar o impacto das alterações climáticas, principalmente no período em que a umidade não é a ideal, é preciso adotar algumas medidas assistencialistas. O presente estudo visa elucidar qual seria a opção mais indicada para melhorar a qualidade de vida do ser humano e esclarecer qual melhor recurso (umidificador de ar, balde com água ou toalha molhada) é eficaz para melhorar a umidade do ar em épocas de seca e baixa umidade. Métodos Estudo experimental realizado com higrômetros INKBIRD que permitiram a análise da variação da umidade do ar ao longo do dia. Foram estabelecidas três formas de tratamento: umidificador, toalha molhada e balde com água. Em cada quarto, foram colocados dois higrômetros equidistantes do ocupante do quarto e seu respectivo tratamento, que variava entre 1m e 2m de distância da cabeceira da cama dentro de cada cômodo. Além disso, dois ambientes foram utilizados como controle, sendo um externo e outro fechado interno, totalizando cinco cômodos para o estudo. Os cômodos foram monitorados entre o final do mês de julho até final do mês de agosto de 2019 em Goiânia (GO). Resultados Apesar de as medidas assistencialistas serem utilizadas para melhora significativa da umidade do ar em épocas de extrema seca, há uma diferença significativa entre elas. O umidificador e a toalha molhada possuíram 7,50% e 5,71% a mais de umidade em relação à área externa (controle externo), respectivamente, sendo considerados mais eficientes. Já o balde de água não se diferenciou significativamente (p>0,05), não havendo variação. Conclusão O umidificador e a toalha foram os tratamentos considerados mais eficientes, com efeito significativo da distância sobre a umidade. Portanto, 1m de distância é mais eficiente no aumento e/ou na manutenção da umidade do ar, induzindo melhorias na saúde da população.

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BACKGROUND: This study compared 3 nebulizer technologies for inter- and intradevice reproducibility, humidification, and fill volume sensitivity during mechanical ventilation: a breath-enhanced jet nebulizer, a vibrating mesh nebulizer, and a jet nebulizer. The breath-enhanced jet nebulizer featured a new design located on the wet side of the humidifier to reduce aerosol loss and potential humidifier contamination. The vibrating mesh nebulizer and the jet nebulizer were placed on the dry side. METHODS: Aerosol delivery was measured using multiple ventilator settings (inspiratory time = 0.45-1.01 s). Using radiolabeled saline and a gamma camera, bench studies were performed using a ventilator to test 4 breathing patterns. Four scenarios were assessed during testing: 3 mL and 6 mL fill volumes with and without heated wire humidification. Measurements included inhaled mass (as a percentage of the nebulizer charge), nebulizer residual, mass balance, and aerosol particle size distribution. Statistics were determined using Mann-Whitney and linear regression. RESULTS: The inhaled mass for the breath-enhanced jet nebulizer was 10.5-29.2% and was affected by fill volume (P = .004) but not by humidity. The inhaled mass for the vibrating mesh nebulizer was 0.9-33% and was unaffected by fill volume and humidity. The inhaled mass for the jet nebulizer was 2.5-25.9% and was affected by both fill volume (P = .009) and humidity (3 mL, P = .002). The inhaled mass for the vibrating mesh nebulizer was more variable due to random failures to achieve complete nebulization, and inhaled mass correlated closely with residual mass: IM% = -0.233(Residual%) + 24.3, r2 = 0.67, P < .001. For all devices, large particles were lost in the ventilator tubing; large particles were also lost in the humidifier for the vibrating mesh nebulizer (17% nebulizer charge), resulting in similar particle distributions (mass median aerodynamic diameter 1.33-1.95 µm) for all devices. CONCLUSIONS: Nebulization with the breath-enhanced jet nebulizer was less sensitive to humidification than the jet nebulizer. Delivery via the vibrating mesh nebulizer was not predictable, with random failure to empty (55% experimental runs). All devices delivered similar particle distributions. Wet-side aerosol delivery avoids humidifier contamination, and breath-enhanced technology can ensure better control of drug delivery.

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BACKGROUND: The present study tested a novel nebulizer and circuit that use breath enhancement and breath actuation to minimize ventilator influences. The unique circuit design incorporates "wet-side" jet nebulization (the nebulizer connected to the humidifier outlet port) to prevent unpredictable aerosol losses with active humidification. The system was studied using several ventilator brands over a wide range of settings, with and without humidification. METHODS: During treatment, a 2-position valve directed all ventilator flow to the nebulizer, providing breath enhancement during inspiration. Aerosol was generated by air 50 psi 3.5 L/m triggered during inspiration by a pressure-sensitive circuit. Particles were captured on an inhaled mass filter. Testing was performed by using active humidification or bypassable valved heat and moisture exchanger (HME) over a range of breathing patterns, ventilator modes, and bias flows (0.5-5.0 L/m). The nebulizer was charged with 6 mL of radiolabeled saline solution. Mass balance was performed by using a gamma camera. Tidal volume was monitored by ventilator volume (exhaled VT) and test lung volume. The Mann-Whitney test was used. RESULTS: A total of 6 mL was nebulized within 1 h. Inhaled mass (% neb charge): mean ± SD (all data) 31.1% ± 6.45; no. = 83. Small significant differences were seen with humidification for all modes (humidified 36.1% ± 5.60, no. = 26; bypassable valved HME 28.8% ± 5.51, no. = 57 [P < .001]), continuous mandatory ventilation modes [P < .001], and pressure support airway pressure release ventilation modes [P < .001]. Mass median aerodynamic diameter ranged from 1.04 to 1.34 µm. The VT was unaffected (exhaled VT -5.0 ± 12.9 mL; P = .75) and test lung (test lung volume 25 ± 14.5 mL; P = .13). Bias flow and PEEP had no effect. CONCLUSIONS: Breath enhancement with breath actuation provided a predictable dose at any ventilator setting or type of humidification. Preservation of drug delivery during active humidification is a new finding, compared with previous studies. The use of wall gases and stand alone breath actuation standardizes conditions that drive the nebulizer independent of ventilator design. Wet-side nebulizer placement at the humidifier outlet allows delivery without introducing aerosol into the humidification chamber.

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BACKGROUND: The objective of this study was to evaluate the effects of three single-limb heated wired circuits (SLHWC) for NIV, on ventilatory parameters and humidification performance in a simulation lung model. METHODS: Three SLHWC compatible with the MR-850 Heated Humidifier (HH) (Fisher & Paykel, Auckland, New Zealand) were tested: RT-319 (FP) (Fisher & Paykel, Auckland, New Zealand), Respironics 1045770 (RP) (DEAS, Castel Bolognese, Italy) and Intersurgical B/SYS 5809001 (IT) (Intersurgical, Wokingham, UK). A Bipap Vision ventilator (Philips Respironics, Murrysville, PA, USA) in pressure control ventilation (PCV) connected to a test lung was used for simulation. Each SHWC performance was evaluated in four ventilatory conditions: IPAP of 15cmH2O with FiO2 0.3 and 1, respectively; and, IPAP of 25cmH2O with FiO2 0.3 and 1, respectively. EPAP was set at 5cmH2O. Hygrometric and ventilatory measurements including: relative humidity (RH), temperature (T), Pplat, PIP, PEEP, peak inspiratory flow (PIF), and tidal volume (Vt) were measured. RESULTS: In each FiO2 group absolute humidity (AH) was similar with FP regardless of the IPAP level employed compared to IT and RP (P<.001). Except for RP at FiO2 0.3, AH increased significantly in IT and RP groups as IPAP increased (P<.001). PIP, Pplat, PEEP, PIF, and Vt values were significantly higher with FP and RP in each FiO2 group compared to IT (P<.001). CONCLUSIONS: Humidification performance varied significantly among the three circuits, being FP the only one able to maintain stable AH values during the study with no influence on ventilatory parameters.

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INTRODUCTION AND OBJECTIVES: Humidification and non-invasive ventilation are frequently used together, despite the lack of precise recommendations regarding this practice. We aimed to analyse the impact of active external and built-in humidifiers on the performance of home ventilators, focusing on their pressurization efficacy and their behaviour under different inspiratory efforts. METHODS: We designed a bench study of a lung simulator programmed to emulate mechanical conditions similar to those experienced by real respiratory patients and to simulate three different levels of inspiratory effort: five different commonly used home NIV devices and active humidifiers attached to the latter (internal or "built-in") or to the circuit (external). To test ventilator pressurization under different humidification and effort settings, pressure-time products in the first 300ms and 500ms of the respiratory cycle were calculated in the 45 situations simulated. Inferential statistical analysis was performed. RESULTS: A significant reduction of PTP 300 and PTP 500 was observed with the external humidifier in three of the devices. The same pattern was noted for another device with an internal humidifier, and only one device showed no significant changes. This impact on pressurization was commonly higher under high inspiratory effort. CONCLUSIONS: These results indicate the need to monitor pressure changes in the use of external humidification devices in some home NIV ventilators.

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Ultrasonic humidifier use is a potential source of human exposure to inhalable particulates. This research evaluated the behavior of insoluble iron oxide and aluminum oxide particles in water used to fill room-sized ultrasonic humidifiers. Solutions of 10 mg/L Fe, as iron oxide particles, or 5 mg/L Al, as aluminum oxide suspension, were added into tap water used to fill ultrasonic humidifiers. The humidifiers were operated for 14 h; samples were obtained over time and monitored for soluble and particulate Fe and Al, as well as particle sizes in the humidifier reservoir and emitted in aerosols. Denser, settleable particles of approximately 1.5 µm diameter of iron or aluminum oxides accumulated at the bottom of the humidifier reservoir. Smaller, suspended metal oxide particles of 0.22-0.57 µm diameter were emitted as aerosols from the humidifier. Soluble anions and cations in tap water were also present in the aerosols emitted from humidifiers. The results indicate that a typical 1.6 MHz ultrasonic humidifier can emit 0.22-0.57 µm particles and dissolved minerals from fill water into breathable air.

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BACKGROUND: Humidification is a standard of care during invasive mechanical ventilation. Two types of devices are used for this purpose: heated humidifiers and heat-and-moisture exchangers (HME). AIM: To compare the short-term physiologic effects of an active HME, with those of heated humidifiers and HMEs in terms of respiratory effort, ventilatory pattern, and arterial blood gases during invasive mechanical ventilation. METHODS: We conducted a randomized crossover study with 3 different devices in 15 stable subjects who had a tracheostomy and were ventilator-dependent. Transdiaphragmatic pressure, ventilatory pattern, arterial blood gases, and dyspnea scale were recorded at baseline and at the end of a 20-min period with each device. RESULTS: Compared with heated humidifiers, the active HME was associated with higher diaphragmatic pressure-time product per minute (117.10 [interquartile range {IQR} 34.58-298.60]) versus 80.86 (IQR, 25.46-110.55) cm H2O×s/min, P = .01), higher PaCO2 (48.50 [IQR, 40.65-53.70] vs 39.60 [IQR, 37.50-49.95]) mm Hg, P = .02) and lower pH (7.41 [IQR, 7.36-7.49] vs 7.45 [IQR, 7.40-7.51], P = .030) without any significant difference in ventilatory pattern. A significantly worse dyspnea scale score (active HME, 3 (2-4) vs heated humidifiers: 4 (3-5); P = .009) was also observed. No significant differences were seen between active HME and HME. CONCLUSIONS: This study indicated that, compared with the heated humidifiers, the use of the active HME or the HME increased inspiratory effort, PaCO2 , pH, and dyspnea in stable subjects who were tracheostomized and ventilator-dependent. (ClinicalTrials.gov registration NCT02499796.).

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Mechanical ventilation of the anesthetized infant requires careful attention to equipment and ventilator settings to assure optimal gas exchange and minimize the potential for lung injury. Apparatus dead space, defined as dead space resulting from devices placed between the endotracheal tube and the Y-piece of the breathing circuit, is the primary source of dead space controlled by the clinician. Due to the small tidal volumes required by infants and neonates, it is easy to create excessive apparatus dead space resulting in unintended hypercarbia or increased minute ventilation in an effort to achieve a desirable PCO2 . The goal of this review was to evaluate the apparatus that are commonly added to the breathing circuit during anesthesia care, and develop recommendations to guide the clinician in selecting apparatus that are best matched to the clinical goals and the patient's size. We include specific recommendations for apparatus that are best suited for different size pediatric patients, with a particular focus on patients <5 kg.

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In 2011, a cluster of peripartum patients were admitted to the intensive care unit of a tertiary hospital in Seoul with signs and symptoms of severe respiratory distress of unknown etiology. Subsequent epidemiological and animal studies suggested that humidifier disinfectant (HD) might represent the source of this pathology. Epidemiological studies, animal studies, and dose-response analysis demonstrated a strong association between HD use and lung injuries. The diagnostic criteria for HD-associated lung injury (HDALI) was defined on the basis of the clinical, pathological, and radiological attributes of the patients. The clinical spectrum of HDALI appears to range from asymptomatic to full-blown acute respiratory failure, and some patients have required actual lung transplantation for survival. The overall mortality of the exposed population was not significant, although peripartum patients and children who were admitted to the intensive care unit did show high mortality rates. Persistent clinical findings such as diffuse ill-defined centrilobular nodules and restrictive lung dysfunction were observed in some of the survivors. The findings of this review emphasize the importance of assessment of the level of toxicity of chemical inhalants utilized in a home setting, as well as the need to identify and monitor afflicted individuals after inhalational injury.

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INTRODUCTION: Nosocomial pneumonia accounts for the vast majority of healthcare-associated infections (HAI). Although numerous medical devices have been discussed as potential vehicles for microorganisms, very little is known about the role played by oxygen humidifiers as potential sources of nosocomial pathogens. The purpose of this research was to evaluate the safety of the reuse of humidifiers by analysing the rate of microbial contamination in reusable and disposable oxygen humidifiers used during therapy, and then discuss their potential role in the transmission of respiratory pathogens. METHODS: Water samples from reusable and disposable oxygen humidifiers were collected from different wards of the University Hospital of Messina, Italy, where nosocomial pneumonia has a higher incidence rate due to the "critical" clinical conditions of inpatients. In particular, we monitored the Internal Medicine and Pulmonology wards for the medical area; the General Surgery and Thoracic and Cardiovascular Surgery wards for the surgical area and the Intensive Care Unit and Neonatal Intensive Care Unit for the emergency area. The samples were always collected after a period of 5 days from initial use for both types of humidifiers. Samples were processed using standard bacteriological techniques and microbial colonies were identified using manual and automated methods. RESULTS: High rates of microbial contamination were observed in samples from reusable oxygen humidifiers employed in medical (83%), surgical (77%) and emergency (50%) areas. The most relevant pathogens were Pseudomonas aeruginosa, amongst the Gram-negative bacteria, and Staphylococcus aureus, amongst the Gram-positive bacteria. Other pathogens were detected in lower percentage. The disposable oxygen humidifier samples showed no contamination. CONCLUSIONS: This research presents evidence of the high rate and type of microbial contamination of reusable humidifiers employed for oxygen therapy. These devices may thus be involved in the transmission of potential pathogens. It could be important, for the prevention of nosocomial pneumonia, to replace them with singleuse humidifiers for which the absence of microbial contamination has been confirmed.

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RESUMO Objetivo: Avaliar as possíveis alterações do volume corrente, volume-minuto e frequência respiratória causadas pela utilização de trocadores de calor e umidade em pacientes submetidos à ventilação mecânica na modalidade pressão de suporte, e quantificar a variação da pressão de suporte necessária para compensar o efeito causado pelo trocador de calor e umidade. Métodos: Os pacientes sob ventilação mecânica invasiva na modalidade pressão de suporte foram avaliados utilizando umidificadores aquecidos e trocadores de calor e umidade. Caso o volume encontrado com uso de trocadores de calor e umidade fosse menor que o achado com o umidificador aquecido, iniciava-se o aumento da pressão de suporte, perante o uso de trocadores de calor e umidade, até ser encontrado um valor de pressão de suporte que possibilitasse ao paciente gerar um valor próximo do volume corrente inicial com umidificador aquecido. A análise foi realizada por meio do teste t pareado, e os valores de incremento foram expressos em porcentagem de aumento necessário. Resultados: Foram avaliados 26 pacientes. O uso de trocadores de calor e umidade aumentou a frequência respiratória, e reduziu o volume corrente e o volume-minuto, quando comparados com o uso do umidificador aquecido. Com o uso de trocadores de calor e umidade, os pacientes precisaram de um incremento de 38,13% na pressão de suporte para manter os volumes prévios. Conclusão: O trocador de calor e umidade alterou os parâmetros de volume corrente, volume-minuto e frequência respiratória, sendo necessário um aumento da pressão de suporte para compensar estas alterações.

ABSTRACT Objective: To evaluate the possible changes in tidal volume, minute volume and respiratory rate caused by the use of a heat and moisture exchanger in patients receiving pressure support mechanical ventilation and to quantify the variation in pressure support required to compensate for the effect caused by the heat and moisture exchanger. Methods: Patients under invasive mechanical ventilation in pressure support mode were evaluated using heated humidifiers and heat and moisture exchangers. If the volume found using the heat and moisture exchangers was lower than that found with the heated humidifier, an increase in pressure support was initiated during the use of the heat and moisture exchanger until a pressure support value was obtained that enabled the patient to generate a value close to the initial tidal volume obtained with the heated humidifier. The analysis was performed by means of the paired t test, and incremental values were expressed as percentages of increase required. Results: A total of 26 patients were evaluated. The use of heat and moisture exchangers increased the respiratory rate and reduced the tidal and minute volumes compared with the use of the heated humidifier. Patients required a 38.13% increase in pressure support to maintain previous volumes when using the heat and moisture exchanger. Conclusion: The heat and moisture exchanger changed the tidal and minute volumes and respiratory rate parameters. Pressure support was increased to compensate for these changes.

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BACKGROUND: The aims of this systematic review and meta-analysis of randomized controlled trials are to evaluate the effects of active heated humidifiers (HHs) and moisture exchangers (HMEs) in preventing artificial airway occlusion and pneumonia, and on mortality in adult critically ill patients. In addition, we planned to perform a meta-regression analysis to evaluate the relationship between the incidence of artificial airway occlusion, pneumonia and mortality and clinical features of adult critically ill patients. METHODS: Computerized databases were searched for randomized controlled trials (RCTs) comparing HHs and HMEs and reporting artificial airway occlusion, pneumonia and mortality as predefined outcomes. Relative risk (RR), 95% confidence interval for each outcome and I 2 were estimated for each outcome. Furthermore, weighted random-effect meta-regression analysis was performed to test the relationship between the effect size on each considered outcome and covariates. RESULTS: Eighteen RCTs and 2442 adult critically ill patients were included in the analysis. The incidence of artificial airway occlusion (RR = 1.853; 95% CI 0.792-4.338), pneumonia (RR = 932; 95% CI 0.730-1.190) and mortality (RR = 1.023; 95% CI 0.878-1.192) were not different in patients treated with HMEs and HHs. However, in the subgroup analyses the incidence of airway occlusion was higher in HMEs compared with HHs with non-heated wire (RR = 3.776; 95% CI 1.560-9.143). According to the meta-regression, the effect size in the treatment group on artificial airway occlusion was influenced by the percentage of patients with pneumonia (ß = -0.058; p = 0.027; favors HMEs in studies with high prevalence of pneumonia), and a trend was observed for an effect of the duration of mechanical ventilation (MV) (ß = -0.108; p = 0.054; favors HMEs in studies with longer MV time). CONCLUSIONS: In this meta-analysis we found no superiority of HMEs and HHs, in terms of artificial airway occlusion, pneumonia and mortality. A trend favoring HMEs was observed in studies including a high percentage of patients with pneumonia diagnosis at admission and those with prolonged MV. However, the choice of humidifiers should be made according to the clinical context, trying to avoid possible complications and reaching the appropriate performance at lower costs.

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