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Humidification Performance of Heat and Moisture Exchangers for Pediatric Use  [PDF]
Yusuke Chikata,Chihiro Sumida,Jun Oto,Hideaki Imanaka,Masaji Nishimura
Critical Care Research and Practice , 2012, DOI: 10.1155/2012/439267
Abstract: Background. While heat and moisture exchangers (HMEs) have been increasingly used for humidification during mechanical ventilation, the efficacy of pediatric HMEs has not yet been fully evaluated. Methods. We tested ten pediatric HMEs when mechanically ventilating a model lung at respiratory rates of 20 and 30?breaths/min and pressure control of 10, 15, and 20?cmH2O. The expiratory gas passed through a heated humidifier. We created two rates of leakage: 3.2?L/min (small) and 5.1?L/min (large) when pressure was 10?cmH2O. We measured absolute humidity (AH) at the Y-piece. Results. Without leakage, eight of ten HMEs maintained AH at more than 30?mg/L. With the small leak, AH decreased below 30?mg/L (26.6 to 29.5?mg/L), decreasing further (19.7 to 27.3?mg/L) with the large leak. Respiratory rate and pressure control level did not affect AH values. Conclusions. Pediatric HMEs provide adequate humidification performance when leakage is absent. 1. Introduction In spontaneous breathing subjects, inspiratory gases are heated and humidified in the nasal cavity and pharynx; by the time, they reach the second bronchial bifurcation, temperature reaches 37°C, and absolute humidity reaches (AH) 44?mg/L [1]. In mechanically ventilated patients, because artificial airways bypass this natural gas conditioning, administered gases require heating and humidification. Inadequate humidification induces inspissations of airway secretions, destruction of airway epithelium, and hypothermia [2]. The incidence of endotracheal tube occlusion was reported between 0.8% and 2.6% in pediatric patients [3, 4]. The American Association for Respiratory Care (AARC) recommends that inspiratory gases should reach a temperature of more than 30°C and AH of more than 30?mg/L [2]. Heat and moisture exchangers (HMEs) and heated humidifiers (active humidification) are commonly employed to warm and humidify medical gases. While HMEs are widely used during the mechanical ventilation of adults [5], their performance varies depending on model [6] and is affected by location, tidal volume, and minute volume [7, 8]. For pediatric patients, because HME adds significant dead space and airway resistance to the circuit, and because there is a high risk of inadequate humidification owing to leakage around the endotracheal tube (ETT), long-term use of HMEs is generally avoided. Few studies, however, have reported how ventilator settings and ETT leakage influence the humidification performance of HMEs used for pediatric patients. Using a pediatric model lung, we carried out a bench study to evaluate the
A new prototype of an electronic jet-ventilator and its humidification system
Paul Kraincuk, Anton Kepka, Gerald Ihra, Christa Schabernig, Alexander Aloy
Critical Care , 1999, DOI: 10.1186/cc351
Abstract: To assess a prototype of an electronic jet-ventilator and its humidification system.Forty patients with respiratory insufficiency were randomly allocated to one of four groups. The criterion for inclusion in this study was respiratory insufficiency exhibiting a Murray score above 2. The four groups of patients were ventilated with three different respirators and four different humidification systems. Patients in groups A and B received superimposed high-frequency jet ventilation (SHFJV) by an electronic jet-ventilator either with (group A) or without (group B) an additional humidification system. Patients in group C received high-frequency percussive ventilation (HFPV) by a pneumatic high-frequency respirator, using a hot water humidifier for warming and moistening the inspiration gas. Patients in group D received conventional mechanical ventilation using a standard intensive care unit respirator with a standard humidification system. SHFJV and HFPV were used for a period of 100 h (4days).A significantly low inspiration gas temperature was noted in patients in group B, initially (27.2 ± 2.5°C) and after 2 days (28.0 ± 1.6°C) (P < 0.05). The percentage of relative humidity of the inspiration gas in patients in group B was also initially significantly low (69.8 ± 4.1%; P < 0.05) but rose to an average of 98 ± 2.8% after 2 h. The average percentage across all four groups amounted to 98 ± 0.4% after 2 h. Inflammation of the tracheal mucosa was found in patients in group B and the mucosal injury score (MIS) was significantly higher than in all the other groups. Patients in groups A, C and D showed no severe evidence of airway damage, exhibiting adequate values of relative humidity and temperature of the inspired gas.The problems of humidification associated with jet ventilation can be fully prevented by using this new jet-ventilator. These data were sustained by nondeteriorating MIS values at the end of the 4-day study period in groups A, C and D.High-frequency jet venti
Humidification for intubated patients  [PDF]
Aphrodite Tsavourelou,Fotoula Babatsikou
To Vima tou Asklipiou , 2008,
Abstract: Artificial airways bypass the physiological mechanism of humidification and filtration of the inspired air, increasing, therefore, the possibilities of copious secretions production. Copious secretions increase the danger for atelektasis and respiratory infections. Moreover, clots can be shaped in the interior of the endotracheal tube or thracheostomy, resulting in increased work of breathing (WOB) and reduced odds of successful extubation. It is also possible to lead progressively to complete obstruction of the endotracheal tube.Thus, the choice of a suitable humidification device during mechanical ventilation is of distinguished importance. There are various types of humidifiers. However, hydroscopic Heat and Moisture Exchangers (HMEs) with filter and Heated Humidifiers (HHs), which provide humidity in form of water vapors, are currently used. When they are used correctly, and not in the cases where they are contraindicated, HMEs’ do not have complications and they decrease the cost of hospitalization as well as the staff workload. HMEs are better choice for short duration of intubation (<96 hours) and during transports. HHs are preferred for patients with persisting hypercapnia, chronic respiratory failure and difficulty in ventilator weaning. HHs should be used for patients with prolonged duration of mechanical ventilation or patients that HMEs are contraindicated for. Neither HMEs nor HHs have been accused for increased incidences of ventilator associated pneumonia (VAP).
Effect of heat and moisture exchanger (HME) positioning on inspiratory gas humidification
Daisuke Inui, Jun Oto, Masaji Nishimura
BMC Pulmonary Medicine , 2006, DOI: 10.1186/1471-2466-6-19
Abstract: Absolute humidity (AH) and temperature (TEMP) at the proximal end of endotracheal tube (ETT) were measured in ten mechanically ventilated patients. The HME was connected either directly proximal to the ETT (Site 1) or at before the circuit Y-piece (Site 2: distance from proximal end of ETT and Site 2 was about 19 cm) (Figure. 1). Two devices, Hygrobac S (Mallinckrodt Dar, Mirandola, Italy) and Thermovent HEPA (Smiths Medical International Ltd., Kent, UK) were tested. AH and TEMP were measured with a hygrometer (Moiscope, MERA Co., Ltd., Tokyo, Japan).Hygrobac S provided significantly higher AH and TEMP at both sites than Thermovent HEPA. Both Hygrobac S and with Thermovent HEPA provided significantly higher AH and TEMP when placed proximally to the ETT.Although placement proximal to the ETT improved both AH and TEMP in both HMEs tested, one HME performed better in the distal position than the other HME in the proximal position. We conclude the both the type and placement of HME can make a significant difference in maintaining AH and TEMP during adult ventilation.During normal breathing, the upper airway effectively deliver inspired air to the lower respiratory tract (at the carina) condition to approximately 32°C with a relative humidity (RH) of more than 90% (absolute humidity (AH) 30.4 mg/L)[1]. As this inspired air enters the alveoli, it is warmed to body temperature (about 37°C) and reaches 100% humidification [2,3]. When the upper airways are circumvented, delivery of dry gas to the lungs has been associated with damage to the tracheobronchial mucosa [4-7]. Consequently, when the natural humidification of the upper airways is bypassed by an endotracheal or tracheostomy tube, artificial humidification of inspiratory gas is essential for mechanically ventilated patients. As an alternative to heated humidifiers, heat and moisture exchangers (HME) have been widely adopted in intensive care units (ICU) [8]. HME performance is influenced by many factors, including mo
Evaluating humidity recovery efficiency of currently available heat and moisture exchangers: a respiratory system model study
Lucato, Jeanette Janaina Jaber;Adams, Alexander Bernard;Souza, Rogério;Torquato, Jamili Anbar;Carvalho, Carlos Roberto Ribeiro;Marini, John J;
Clinics , 2009, DOI: 10.1590/S1807-59322009000600015
Abstract: objectives: to evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. introduction: inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat and water content similar to that provided normally by the nose and upper airways. the absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers' humidifying performance. methods: eight different heat and moisture exchangers were studied using a respiratory system analog. the system included a heated chamber (acrylic glass, maintained at 37°c), a preserved swine lung, a hygrometer, circuitry and a ventilator. humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. recovery of absolute humidity (%rah) was calculated for each setting. results: increasing tidal volumes led to a reduction in %rah for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. conclusions: our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. the roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers.
Umidifica o dos gases inspirados na ventila o mecanica em crian as =Humidification of inspired gases in mechanical ventilation in children  [cached]
Gatiboni, Silvia,Piva, Jefferson Pedro,Garcia, Pedro Celiny Ramos
Scientia Medica , 2008,
Abstract: Objetivos: apresentar os tipos de umidificadores mais utilizados em circuitos de ventila o mecanica, principalmente em pacientes pediátricos, e analisar suas vantagens e desvantagens. Fonte de dados: revis o da literatura científica através de artigos pertinentes incluídos na base de dados PubMed/Medline, enfatizando as palavras umidifica o, ventila o mecanica, crian as, umidificadores aquecidos e trocadores de calor e umidade. Também foram incluídos capítulos de livros sobre o assunto. Síntese dos dados: durante a ventila o mecanica, a umidifica o e o aquecimento dos gases inspirados s o necessários para prevenir os efeitos do frio e dos gases secos no epitélio traqueobr nquico. Os dispositivos mais utilizados s o os Umidificadores Aquecidos e os Filtros Trocadores de Calor e Umidade. Conclus es: n o existe consenso quanto ao melhor dispositivo para aquecimento e umidifica o dos gases inspirados, principalmente em pediatria, porém observamos a tendência ao uso de filtros trocadores de calor e umidade, pela facilidade e menor custo. Novas pesquisas s o necessárias para otimizar os filtros trocadores de calor e umidade, diminuindo a resistência e o espa o morto e aumentando a eficácia dos mesmos. Aims: To present the more utilized types of humidifiers in mechanical ventilation circuits, mainly in pediatric patients, and to analyze their advantages and disadvantages. Source of data: Review of the scientific literature through a PubMed/Medline search, emphasizing the words humidification, mechanical ventilation, children, heated humidifiers and heat and moisture exchangers. Also included were book chapters about the subject. Summary of the findings: During mechanical ventilation, humidification and warming of inspired gases are required to prevent the effects of cool and dry gases on the tracheobronquial epithelium. The most used devices are heated humidifiers and heat and moisture exchangers. Conclusions: There are no consensus about the better device to humidification and warming of gases, mainly in pediatrics, but we observed the trend to use the heat and moisture exchangers, because of simplicity and low expense. New research is needed to optimize the heat and moisture exchangers, reducing the resistance and dead-space and increasing their efficacy.
Humidification in intensive care
T Williams
Southern African Journal of Critical Care , 2005,
Abstract: Humidification of inspired gases is an essential part of modern intensive care practice, but there is wide international variation in the application of humidification devices.1 This review aims to briefly cover the reasons why humidification is important and the main methods of humidification used, outlining their different strengths and weaknesses. SAJCC Vol. 21 (1) 2005: pp. 26-31
Advantages of a new humidification technique
G Via, M Olivei, A Palo, S Neri, G Ragni, M Bertolini, N Fusilli, F Capra-Marzani, G Rodi, G lotti, A Braschi
Critical Care , 2000, DOI: 10.1186/cc389
Abstract: The study included seven mechanically ventilated patients. In each patient, the AHME was used for 24 h and then substituted with a conventional active humidifier (F&P) (MR730, Fisher & Paykel) with a heated wire in the inspiratory limb, for the next 24 h. AHME was preset to keep the temperature of inspired gases at 37°C. The F&P was set to 37°C in the humidifier-chamber, and to 37°C at the Y piece. The AHME and the F&P were compared in terms of: humidity and temperature output, water consumption and condensate in the water traps. The humidity output was evaluated on the basis of the condensate in the flex tube, which was scored from 0 (absent) to 3 (excessive).Minute ventilation did not differ during application of AHME and of F&P. Both devices kept the set temperatures, and provided adequate humidification, as assessed by the condensate in the flex tube. However, when the F&P was used, there was formation of condensate in the ventilator tubings, and the water traps needed to be emptied on average eight times (range: 6–9) per day. No condensation of water was found in the ventilator tubings with AHME. Compared with F&P, the AHME remarkably reduced the water usage.Compared to a conventional active humidifier, the AHME provides equivalent humidification, with the advantages of both reducing the time-expenditure for handling, and of eliminating the risk caused by water condensation in the ventilator tubings.
Optimal hjordsammans ttning - ett systemanalytisk problem
?je Danell
Rangifer , 1984,
Abstract: Optimal hjordsammans ttning - ett systemanalytisk problem.
A new device for 100 per cent humidification of inspired air
Anders Larsson, Ann Gustafsson, Lennart Svanborg
Critical Care , 2000, DOI: 10.1186/cc651
Abstract: To test the performance of the new humidifier at different ventilator settings in a lung model, and to compare this new humidifier with a conventional active humidifier in ventilator-treated critically ill patients.The humidifier (Humid-Heat; Louis Gibeck AB, Upplands V?sby, Sweden) consists of a supply unit with a microprocessor and a water pump, and a humidification device, which is placed between the Y-piece and the endotracheal tube. The humidification device is based on a hygroscopic heat-moisture exchanger (HME), which absorbs the expired heat and moisture and releases it into the inspired gas. External heat and water are then added to the patient side of the HME, so the inspired gas should reach 100% humidity at 37°C (44 mg H2O/l air). The external water is delivered to the humidification device via a pump onto a wick and then evaporated into the inspired air by an electrical heater. The microprocessor controls the water pump and the heater by an algorithm using the minute ventilation (which is fed into the microprocessor) and the airway temperature measured by a sensor mounted in the flex-tube on the patient side of the humidification device.The performance characteristics were tested in a lung model ventilated with a constant flow (inspiratory:expiratory ratio 1:2, rate 12–20 breaths/min and a minute ventilation of 3–25 l/min) or with a decelerating flow (inspiratory:expiratory ratio 1:2, rate 12–15 breaths/min and a minute ventilation of 4.7–16.4 l/min). The device was also tested prospectively and in a randomized order compared with a conventional active humidifier (Fisher & Paykel MR730, Auckland, New Zealand) in eight mechanically ventilated, endotracheally intubated patients in the intensive care unit. The test period with each device was 24 h. The amount of fluid consumed and the amount of water in the water traps were measured. The number of times that the water traps were emptied, changes of machine filters, the suctions and quality of secretions, n
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