Use Of Heat And Moisture Exchanger Research Articles

Thermal imaging and velocity measurements of the exhaled airflow in total laryngectomized patients during COVID-19 pandemic.

In patients after total laryngectomies, the trachea and the lung can be easily infected by SARS-CoV-2 because the respiration happens through the tracheostoma. The aim of our study was to examine whether patients with LaryTube™ can distribute aerosols to a greater extent than without LaryTube™, and to observe whether the surface of different protective instruments can be examined using the thermal camera in total laryngectomees. An important objective was also to confirm the assumption that the use of HME (heat and moisture exchanger) alone does not provide protection during COVID-19 pandemic. Finally, during our tests, we tried to get an answer to our assumption that the sample taken from the inner surface of the HME can be tested for SARS-CoV-2. A total of 23 patients who underwent total laryngectomies were analyzed by velocity measurements and thermal imaging with and without HMEs and laryngeal tubes, using different types of PPEs. COVID-19 PCR testing was performed on patient tracheas and the inner surfaces of the HMEs. Male patients with laryngeal tubes without HMEs demonstrated an increase in exhaled airflow velocity of more than 43% compared to male patients without laryngeal tubes; in female patients, the same value was more than 39%. Thermal imaging results confirmed that the lowest surface temperature was measured on FFP2 masks. The sent samples can be tested for SARS-CoV-2 using PCR, the presence of the virus was not detected. Laryngectomized patients without laryngeal tubes pose a lower risk for spreading viral aerosols due to the reduced velocity of the exhaled airflow caused by the absence of the tube as the narrowing factor. Patients with laryngeal tubes who undergo total laryngectomies during the COVID-19 pandemic should use HMEs with viral filter, if possible, also changing the laryngeal tubes to dermal adhesives for fitting their HMEs seems to be the best option. The surface of the used protective equipment can also be examined with thermal camera in the case of total laryngectomees. COVID-19 PCR testing of the tracheal secretion from the inner HME surfaces should become a routine in clinical practice if deemed necessary. Orv Hetil. 2023; 164(34): 1327-1336.

New Heat and Moisture Exchangers for Laryngectomized Patients in Germany: Mixed Methods Study on the Expected Effectiveness.

Notwithstanding the benefits of heat and moisture exchangers (HMEs) in both clinical research and practice, a gap exists between the optimal physiological humidification created through the nasal function and the humidification capacity of HMEs for patients after total laryngectomy. In this study, 5 new HMEs (Provox Life) specialized for situational use with improved humidification capacities were evaluated. This study aims to evaluate the effectiveness of the existing HMEs, assess the potential effectiveness of the new HMEs, and elicit expert judgments on the new HMEs' expected effectiveness and impact on health care use. First, a rapid literature review (RLR) was performed to identify evidence on the clinical outcomes, health outcomes, and complications of HMEs in patients who underwent laryngectomy. Second, semistructured interviews with German experts (n=4) were conducted to validate the findings of the RLR and identify reasonable expectations regarding the potential of the new HMEs. Third, a structured expert elicitation among German experts (n=19) was used to generate quantitative evidence on the expected effectiveness of the new HMEs in clinical and health outcomes. The RLR (n=10) demonstrated that HME use by patients has advantages compared with no HME use concerning breathing resistance, tracheal dryness and irritation, mucus production and plugging, frequency of cough and forced expectorations, sleep quality, voice quality, use of physiotherapy, tracheobronchitis or pneumonia episodes, quality of life, and patient satisfaction. From the expert interviews and structured expert elicitation, it was found that, on average, experts expect that compared with the second-generation HMEs, the new HMEs will lead to a decrease in tracheal dryness or irritation (51%, SD 24%, of patients), mucus plug events (33%, SD 32%, of patients), mucus production (53%, SD 22%, of patients), physiotherapy (0.74, SD 0.70, days) and pulmonary infections (34%, SD 32%) and an increase or improvement in speech quality (25%, SD 23%, of patients), social contacts (13%, SD 18%), quality of life (33%, SD 30%), and patient satisfaction (44%, SD 30%). An improvement in breathing (53%, SD 28%, of patients) and shortness of breath (48%, SD 25%, of patients) was expected. The average number of daily cough periods and forced expectorations was expected to be 2.95 (SD 1.61) and 2.46 (SD 1.42), respectively. Experts expect that, on average, less than half of the patients will experience sleeping problems (48%, SD 22%) and psychosocial problems (24%, SD 20%). According to German experts, it is expected that the new HMEs with improved humidification levels will lead to additional (clinical) effectiveness on pulmonary health and an improved overall quality of life of patients compared with the currently available HMEs.

Optimizing Pulmonary Outcomes After Total Laryngectomy: Crossover Study on New Heat and Moisture Exchangers.

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. Prospective crossover study. 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. 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). 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. 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.

Factors Affecting the Lifetime of Third-Generation Voice Prosthesis After Total Laryngectomy.

The study aimed to evaluate the impact of different variables on the longevity of Voice Prosthesis (VP) in patients after total laryngectomy. This retrospective cohort study is based on data about a continuous series of 328 third-generation VP, which were implanted between 2016 and 2020. Data about the VP users' age, sex, place of residence, laryngeal tumor stage, neck irradiation, VP size, and the use of Heat and Moisture Exchanger (HME) were obtained and analyzed. The effect of these variables on VP lifetime was determined. The median lifetime of VPs in patients 65 years old and above was 182 days (95% CI 168-196), versus 146 days (95% CI 130-162) (P=0.033) in patients younger than 65. Neck irradiation was associated with a longer VP median lifetime of 161 days (95% CI 142-180) compared to 126 days (95% CI 100-152) with no prior neck irradiation (P=0.046). HME usage was associated with significantly increased longevity of VPs: 182 days (95% CI 156-208) with HME and 149 days (95% CI 132-166) without HME usage (P=0.039). The results of the present study suggest that neck irradiation, and routine use of use of HME are positively associated with the longevity of VPs.

Gas conditioning during helmet noninvasive ventilation: effect on comfort, gas exchange, inspiratory effort, transpulmonary pressure and patient\u2013ventilator interaction

BackgroundThere is growing interest towards the use of helmet noninvasive ventilation (NIV) for the management of acute hypoxemic respiratory failure. Gas conditioning through heat and moisture exchangers (HME) or heated humidifiers (HHs) is needed during facemask NIV to provide a minimum level of humidity in the inspired gas (15 mg H2O/L). The optimal gas conditioning strategy during helmet NIV remains to be established.MethodsTwenty patients with acute hypoxemic respiratory failure (PaO2/FiO2 < 300 mmHg) underwent consecutive 1-h periods of helmet NIV (PEEP 12 cmH2O, pressure support 12 cmH2O) with four humidification settings, applied in a random order: double-tube circuit with HHs and temperature set at 34 °C (HH34) and 37 °C (HH37); Y-piece circuit with HME; double-tube circuit with no humidification (NoH). Temperature and humidity of inhaled gas were measured through a capacitive hygrometer. Arterial blood gases, discomfort and dyspnea through visual analog scales (VAS), esophageal pressure swings (ΔPES) and simplified pressure–time product (PTPES), dynamic transpulmonary driving pressure (ΔPL) and asynchrony index were measured in each step.ResultsMedian [IqR] absolute humidity, temperature and VAS discomfort were significantly lower during NoH vs. HME, HH34 and HH37: absolute humidity (mgH2O/L) 16 [12–19] vs. 28 [23–31] vs. 28 [24–31] vs. 33 [29–38], p < 0.001; temperature (°C) 29 [28–30] vs. 30 [29–31] vs. 31 [29–32] vs 32. [31–33], p < 0.001; VAS discomfort 4 [2–6] vs. 6 [2–7] vs. 7 [4–8] vs. 8 [4–10], p = 0.03. VAS discomfort increased with higher absolute humidity (p < 0.01) and temperature (p = 0.007). Higher VAS discomfort was associated with increased VAS dyspnea (p = 0.001). Arterial blood gases, respiratory rate, ΔPES, PTPES and ΔPL were similar in all conditions. Overall asynchrony index was similar in all steps, but autotriggering rate was lower during NoH and HME (p = 0.03).ConclusionsDuring 1-h sessions of helmet NIV in patients with hypoxemic respiratory failure, a double-tube circuit with no humidification allowed adequate conditioning of inspired gas, optimized comfort and improved patient–ventilator interaction. Use of HHs or HME in this setting resulted in increased discomfort due to excessive heat and humidity in the interface, which was associated with more intense dyspnea.Trail Registration Registered on clinicaltrials.gov (NCT02875379) on August 23rd, 2016.

Post-operative use of HME filter‑protected open tracheostomy circuit during the COVID-19 pandemic

Introduction In the era of the COVID-19 pandemic, the avoidance of aerosol generating procedures (AGPs) is paramount to reduce the risk of viral transmission to staff and other patients. Perioperative management of a new tracheostomy is challenging as routine care, such as suctioning, frequently involves AGPs. Methods We developed and implemented an apparatus called the heat and moisture exchanger (HME) filter-protected open circuit. This enabled closed suctioning to be performed and allowed spontaneously breathing patients to be managed with an open circuit in a shared environment while reducing the risk of viral aerosolisation. We performed a prospective observational study of 20 cases, recording the incidence of desaturation ( Results There were no incidents of desaturation. There were two circuit disconnections. Apparatus replacement with an alternate circuit was not required for any patient. Most recovery nursing staff agreed or strongly agreed that the apparatus was easy to use and that the apparatus bulk or weight did not interfere with patient care activities. Ninety-five per cent of patients reported that their breathing was comfortable prior to discharge from the Post Anaesthesia Care Unit. Conclusion In conclusion, the HME filter-protected open circuit is a relatively safe, acceptable and practical device to use for spontaneously breathing patients with newly created tracheostomies in the perioperative environment.

Cost-effectiveness analysis of using the heat and moisture exchangers compared with alternative stoma covers in laryngectomy rehabilitation: US perspective.

This study aims to evaluate the cost-effectiveness of using heat and moisture exchangers (HMEs) vs alternative stoma covers (ASCs) following laryngectomy in the United States. A cost-effectiveness and budget impact analysis were conducted including uncertainty analyses using real-world survey data with pulmonary events and productivity loss. HME use was more effective and less costly compared with ASCs. Quality-adjusted life years were slightly higher for HME-users. Total costs per patient (lifetime) were $59 362 (HME) and $102 416 (ASC). Pulmonary events and productivity loss occurred more frequently in the ASC-users. Annual budget savings were up to $40 183 593. Costs per pulmonary event averted were $3770. HME utilization in laryngectomy patients was cost-effective. Reimbursement of HME devices is thus recommended. Utilities may be underestimated due to the generic utility instrument used and sample size. Therefore, we recommend development of a disease-specific utility tool to incorporate in future analyses.

Intervention to reduce carbapenem-resistant Acinetobacter baumannii in a neonatal intensive care unit.

To investigate the effects of environmental cleaning and the installation of heat and moisture exchangers (HMEs) to reduce neonatal carbapenem-resistant Acinetobacter baumannii (CRAB) sepsis and colonization as well as antimicrobial use. We conducted a 7-year, quasi-experimental study. All neonates admitted to a neonatal intensive care unit (NICU). We compared the trends for CRAB sepsis and colonization before (period 1, 2011-2013) and after (period 3, 2015-2017) a 12-month intervention period in 2014 (period 2) to incorporate a combination of HME use and sodium hypochlorite cleaning (5,000 ppm in the NICU and 500 ppm in the neonatal environment) using interrupted time series analysis with segmented regression. During the 7-year study period, 3,367 neonates were admitted to the NICU; the prevalence rates of CRAB sepsis and endotracheal CRAB colonization were 0.5 per 1,000 patient days, and 19.4 per 1,000 ventilator days. A comparison of period 1 to period 3 showed significant decreases in the percentages of both CRAB of A. baumannii sepsis (100% versus 11%) and endotracheal colonization (76% vs 52%) following the introduction of disposable HMEs and sodium hypochlorite cleaning (both P < .001). In period 3, compared with period 1, segmented regression analysis showed significant reductions in endotracheal CRAB colonization per 1,000 ventilator days (ie, change in level) and both carbapenem and colistin use (changes in both level and slope) (P < .001). Interventions featuring environmental cleaning and use of HMEs led to a sustainable reduction of CRAB colonization coupled with a reduction in broad-spectrum antimicrobial use in the NICU.

Heat and moisture exchanger use reduces in-hospital complications following total laryngectomy: a case-control study.

BackgroundTotal laryngectomy (TL) is an appropriate oncologic operation for many patients with laryngeal cancer delivering excellent oncologic outcomes, however it remains beset with significant functional consequences. Following TL, the upper and lower airways are permanently disconnected, which causes unfiltered, cold air with reduced humidity to enter the tracheobronchial tree, resulting in mucus overproduction and an increase in the viscosity of the mucus. In response to this, Heat and moisture exchangers were developed to compensate for the lost functions of the upper respiratory tract and their effect on the patients’ respiratory performance in addition to their quality of life.MethodsThe case records of 48 patients undergoing total laryngectomy were reviewed and data concerning demographics, surgical details, post-operative care requirements and adverse events was retrieved. Post hoc analysis of the case patients was undertaken to identify any benefit of using a heat and moisture exchanger (HME) system with particular reference to post-operative respiratory outcomes.ResultsThere was no significant difference between case and control subjects based on demographics, extent of surgery or need for flap repair. 16 patients had used a HME and 32 patients had used external humidification (EH). Of those experiencing mucous plugging, only 3/24 (12.5 %) had used a HME system, in contrast to 21/24 (87.5 %) who used EH (Chi square = 9.375, p = 0.002). The odds ratio of having an adverse event if not using HME was 8.27 (CI = 1.94 – 35.71). Use of HME also significantly reduced the number of days requiring physiotherapy (1.75 days vs. 3.20 days, p = 0.034).ConclusionUse of an HME system can reduce in-hospital complications, in particular episodes of mucus plugging, and post-operative care requirements. Furthermore, there is a cost benefit to using HME systems that warrants more widespread introduction of these devices in head and neck surgery centers.

Cost-effectiveness of heat and moisture exchangers compared to usual care for pulmonary rehabilitation after total laryngectomy in Poland.

The beneficial physical and psychosocial effects of heat and moisture exchangers (HMEs) for pulmonary rehabilitation of laryngectomy patients are well evidenced. However, cost-effectiveness in terms of costs per additional quality-adjusted life years (QALYs) has not yet been investigated. Therefore, a model-based cost-effectiveness analysis of using HMEs versus usual care (UC) (including stoma covers, suction system and/or external humidifier) for patients after laryngectomy was performed. Primary outcomes were costs, QALYs and incremental cost-effectiveness ratio (ICER). Secondary outcomes were pulmonary infections, and sleeping problems. The analysis was performed from a health care perspective of Poland, using a time horizon of 10 years and cycle length of 1 year. Transition probabilities were derived from various sources, amongst others a Polish randomized clinical trial. Quality of life data was derived from an Italian study on similar patients. Data on frequencies and mortality-related tracheobronchitis and/or pneumonia were derived from a Europe-wide survey amongst head and neck cancer experts. Substantial differences in quality-adjusted survival between the use of HMEs (3.63 QALYs) versus UC (2.95 QALYs) were observed. Total health care costs/patient were 39,553 PLN (9465 Euro) for the HME strategy and 4889 PLN (1168 Euro) for the UC strategy. HME use resulted in fewer pulmonary infections, and less sleeping problems. We could conclude that given the Polish threshold of 99,000 PLN/QALY, using HMEs is cost-effective compared to UC, resulting in 51,326 PLN/QALY (12,264 Euro/QALY) gained for patients after total laryngectomy. For the hospital period alone (2 weeks), HMEs were cost-saving: less costly and more effective.

Effects of heat and moisture exchangers on tracheal mucociliary clearance in laryngectomized patients: a multi-center case-control study.

After total laryngectomy, inspired air is no longer optimally conditioned by the upper airways. Impaired mucociliary clearance and histological changes of respiratory epithelium, such as loss of ciliated cells, have been described in laryngectomized patients. Heat and moisture exchangers (HMEs) are passive humidifiers that re-condition the inspired air. Aim of this study was to assess the effect of HMEs on tracheal epithelium and tracheal mucus transport velocity (TMV). Tracheal brush biopsies were collected in three groups of TLE patients: 21 long-term HME users, 10 non-HME users, and 16 non-HME users before and after 4-9 months HME use. Tracheal epithelium biopsies were assessed using a digital high-speed camera mounted onto a light microscope. TMV was determined by scintigraphy in the first two patient groups. Significantly more ciliated cells were found in HME users compared to non-HME users (p = 0.05). TMV was higher in HME users (median 2 mm/min; 0-7.9) compared to non-HME users (median 0.8 mm/min; 0-12.3), but this difference was not significant (p = 0.37). One-hour breathing without HME in long-term HME users did not measurably decrease TMV (p = 0.13). The long-term use of an HME restores/prevents the loss of tracheal ciliated cells. A significant improvement in TMV was not found. Short-term (one hour) detachment of an HME has no measurable effect on TMV.

Long-Term Use of Heat and Moisture Exchangers among Laryngectomees: Medical, Social, and Psychological Patterns

After laryngectomy, pulmonary protection is mostly acquired by means of a heat and moisture exchanger (HME) that is placed on an airtight seal around the stoma. The effects of HMEs on the tracheal climate have been well described, and the filtration effect of an HME with an electrostatic filter has been described in vitro. The effects of HME use in patients have been documented in several trials in different countries. The follow-up time of the patients in these trials, however, is limited. Less is known about long-term use of HMEs, and studies describing long-term compliance with HME use are scarce. This study investigated the long-term use of HMEs in laryngectomees. Questionnaires were sent to 195 laryngectomees, and 75 questionnaires were returned. More than 85% of the respondents used an HME, of whom 77% were compliant users (ie, use for more than 20 hours per day). The incidence of pulmonary illnesses (either before or after surgery) was about 25%. More than 90% of the respondents were heavy smokers before laryngectomy. One third of the respondents are regularly exposed to dusty environments. Compliant HME users tend to make less use of external humidifiers and vaporizers, and have better pulmonary status and lower health-care costs. Regarding quality of life, patients who use a FreeHands device tended to have more frequent social contacts (r = 0.251; p = 0.030). The prevalence of depression is high, pointing to an urgent need to recognize and treat psychiatric problems such as depression and suicidal ideation in this patient group. These findings have implications for any postlaryngectomy research that uses pulmonary parameters.

Effect of heat and moisture exchangers on the prevention of ventilator-associated pneumonia in critically ill patients

Ventilator-associated pneumonia (VAP) remains one of the major causes of infection in the intensive care unit (ICU) and is associated with the length of hospital stay, duration of mechanical ventilation, and use of broad-spectrum antibiotics. We compared the frequency of VAP 10 months prior to (pre-intervention group) and 13 months after (post-intervention group) initiation of the use of a heat and moisture exchanger (HME) filter. This is a study with prospective before-and-after design performed in the ICU in a tertiary university hospital. Three hundred and fourteen patients were admitted to the ICU under mechanical ventilation, 168 of whom were included in group HH (heated humidifier) and 146 in group HME. The frequency of VAP per 1000 ventilator-days was similar for both the HH and HME groups (18.7 vs 17.4, respectively; P = 0.97). Duration of mechanical ventilation (11 vs 12 days, respectively; P = 0.48) and length of ICU stay (11 vs 12 days, respectively; P = 0.39) did not differ between the HH and HME groups. The chance of developing VAP was higher in patients with a longer ICU stay and longer duration of mechanical ventilation. This finding was similar when adjusted for the use of HME. The use of HME in intensive care did not reduce the incidence of VAP, the duration of mechanical ventilation, or the length of stay in the ICU in the study population.

The effect of a pediatric heat and moisture exchanger on dead space in healthy pediatric anesthesia

BackgroundHeat and moisture exchangers (HME) are often used to maintain humidity of breathing circuits during anesthesia. It is also known to increase dead space ventilation in respiratory distress syndromes. However, the effect of a pediatric HME in healthy pediatric patients has not yet been clarified. The purpose of this study was to evaluate the effect of a pediatric HME on dead space in healthy pediatric patients during anesthesia.Methods20 ASA physical class I pediatric patients, without respiratory impairment, who underwent elective surgery for inguinal hernia or hydrocele with general anesthesia were enrolled. Fifteen minutes after ventilation with and without pediatric HME (internal volume of 22 ml), hemodynamic variables, end tidal CO2, minute volume and airway pressure were measured, and arterial blood sampling was conducted simultaneously.ResultsThe removal of pediatric HME decreased PaCO2 significantly from 46.1 ± 6.9 mmHg to 37.9 ± 4.3 mmHg (P < 0.001) and increased the pH from 7.32 to 7.37 (P < 0.001). The differences between PaCO2 with and without HME (Δ PaCO2) were significantly correlated with weight (P < 0.001, β1 = -0.749) and age (P = 0.002, β1 = -0.623).ConclusionsThe use of a pediatric HME significantly increased PaCO2 in healthy pediatric patients that was inversely proportional to weight and age. The use of pediatric HME should be carefully considered in small pediatric patients.

Heat and Moisture Exchangers and Humidification Efficacy in Pediatrics: Effects of Ventilator Settings and ETT Leakage

Heat and moisture exchangers (HMEs) have been increasingly used for humidification during mechanical ventilation in pediatric patients [1]. However, efficacy of HMEs in the pediatric population has not yet been fully evaluated and there is limited information in the literature regarding the effects of ventilator settings and endotracheal tube (ETT) leakage on the humidification performance of HMEs. Chikata et al. [2] tested ten pediatric HMEs in a model lung, measuring performance under different respiratory rates, tidal volumes TVs (achieved with different pressure control levels), and leakage conditions. They found that eight of the ten HMEs maintained absolute humidity (AH) at more than 30 mg/L, the minimum level recommended by the American Association for Respiratory Care (AARC). With a 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 a larger leak. Pressure control (tidal volume) level did not statistically significantly affect AH values, although there was a trend to decreased AH at higher tidal volumes. In three of the HMEs, increased respiratory rate resulted in a significantly higher AH. In six of the other seven HMEs, there was a nonstatistically significant trend to higher AH with increased respiratory rate, with one HME showing a nonsignificant trend to lower AH. We think this is a well-designed and conducted study and provides valuable information regarding the use of HMEs in pediatric patients under different conditions. The effect of ETT leakage on AH is nicely demonstrated and is consistent with previously published data on mechanically ventilated adults. However, we had some questions regarding the study's other findings and their possible explanation as follows the study found that 8 out of 10 pediatric HMEs maintained AH at more than 30 mg/L, while they quote the Luchetti et al. [3] study they reference as showing “AH of less than 28 mg/L in all HMEs used with pediatric patients” despite using similar one-way valve methodology in their circuit to prevent mixing of inspired and expired gases? This finding is even more puzzling given that one of the two HMEs used in the Luchetti study, the Hygroboy (Covidien [formerly Tyco Healthcare], Mirandola, Italy), in the present study was found to produce the highest AH (32.4 mg/L) of the ten HMEs tested. How is this difference in findings between the 2 studies of the same HME explained? the finding that increased respiratory rates resulted in a trend to higher AH that reached significance in 3 of the tested humidifiers is interesting. Previous studies of HMEs in adults and children have found lower AH associated with higher tidal volumes [4, 5] and minute volumes (MVs) [1, 6, 7]. It would seem more logical that an increasing respiratory rate presumably would result in a higher MV, with resultant lower AH, but Chikata et al. found the opposite. The authors did not comment on this in their paper, and we wonder if they have a plausible explanation for this; finally, the authors speculate that the finding of a linear relationship between increasing dead space and increasing AH might possibly be related to improved humidification in those HMEs with larger internal volume and dead space. Since it is generally recommended to minimize dead space with HMEs, in particular in pediatric use, would the authors care to comment on striking a balance between maximizing humidification capacity and minimizing dead space?

Heated Humidification Versus Heat and Moisture Exchangers for Ventilated Adults and Children

Humidification by artificial means must be provided when the upper airway is bypassed during mechanical ventilation. Heated humidification (HH) and heat and moisture exchangers (HMEs) are the most commonly used types of artificial humidification in this situation. To determine whether HHs or HMES are more effective in preventing mortality and other complications in people who are mechanically ventilated. We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2010, Issue 4) and MEDLINE, EMBASE and CINAHL (January, 2010) to identify relevant randomized controlled trials. We included randomized controlled trials comparing HMEs to HHs in mechanically ventilated adults and children. We included randomized crossover studies. We assessed the quality of each study and extracted the relevant data. Where appropriate, results from relevant studies were meta-analyzed for individual outcomes. We included 33 trials with 2833 participants; 25 studies were parallel group design (n = 2710) and 8 crossover design (n = 123). Only 3 included studies reported data for infants or children. There was no overall effect on artificial airway occlusion, mortality, pneumonia, or respiratory complications; however, the PaCO(2) and minute ventilation were increased when HMEs were compared to HHs and body temperature was lower. The cost of HMEs was lower in all studies that reported this outcome. There was some evidence that hydrophobic HMEs may reduce the risk of pneumonia and that blockages of artificial airways may be increased with the use of HMEs in certain subgroups of patients. There is little evidence of an overall difference between HMEs and HHs. However, hydrophobic HMEs may reduce the risk of pneumonia and the use of an HMEs may increase artificial airway occlusion in certain subgroups of patients. Therefore, HMEs may not be suitable for patients with limited respiratory reserve or prone to airway blockage. Further research is needed relating to hydrophobic versus hygroscopic HMEs and the use of HMEs in the pediatric and neonatal populations. As the design of HMEs evolves, evaluation of new generation HMEs will also need to be undertaken.

Airway humidification with a heat and moisture exchanger in mechanically ventilated neonates

We set out to evaluate the efficacy of passive inspiratory gas conditioning in mechanically ventilated neonates and compared it with that of a heated humidifier (HH). Prospective, randomized, controlled study. Neonatal and pediatric intensive care unit. Fourteen mechanically ventilated neonates nursed in incubators. The HH was set to deliver a temperature of 37 degrees C and an absolute humidity of 40 mgH(2)O/l at the incubator entrance. Inspired temperature (T degrees ) and absolute humidity (AH) were measured by the psychometric method, transpulmonary pressure (Tpres) by means of a differential pressure transducer. Measurements were performed at 5, 10, and 15 min. The values of T degrees were significantly higher using the HH (34.6+/-1.6 degrees C) than the heat and moisture exchanger (HME) (33.8+/2.3, p<0.001). The values of AH were significantly higher using the HH (36.6+/-2.5 mgH(2)O/l) than the HME (32.4+/-2.8 mgH(2)O/l, p<0.001). No significant changes were observed in transpulmonary pressure. A significant positive correlation was observed between incubator temperature and the temperature delivered by the HH (R(2)=0.61, p<0.001). The use of HMEs in neonates made it possible to achieve an absolute humidity of 28 mgH(2)O/l or more and a temperature of 30 degrees C or more. Higher values are obtained using a HH.

Ventilator-associated pneumonia using a heated humidifier or a heat and moisture exchanger: a randomized controlled trial [ISRCTN88724583

IntroductionSome guidelines to prevent ventilator-associated pneumonia (VAP) do not establish a recommendation for the preferential use of either heat and moisture exchangers (HMEs) or heated humidifiers (HHs), while other guidelines clearly advocate the use of HMEs. The aim of this study was to determine the incidence of VAP associated with HHs or HMEs.MethodsA randomized study was conducted in the intensive care unit of a university hospital involving patients expected to require mechanical ventilation for >5 days. Patients were assigned to two groups; one group received HH and the other group received HME. Tracheal aspirate samples were obtained on endotracheal intubation, then twice a week, and finally on extubation, in order to diagnose VAP. Throat swabs were taken on admission to the intensive care unit, then twice a week, and finally at discharge from the intensive care unit in order to classify VAP as primary endogenous, secondary endogenous, or exogenous.ResultsA total of 120 patients were assigned to HMEs (60 patients) and HHs (60 patients); 16 patients received mechanical ventilation for less than five days and were excluded from the analysis. Data analysis of the remaining 104 patients (53 HMEs and 51 HHs) showed no significant differences between groups regarding sex, age, Acute Physiology and Chronic Health Evaluation II score, pre-VAP use of antibiotics, days on mechanical ventilation, and diagnosis group. VAP was found in eight of 51 (15.69%) patients in the HH group and in 21 of 53 (39.62%) patients in the HME group (P = 0.006). The median time free of VAP was 20 days (95% confidence interval, 13.34–26.66) for the HH group and was 42 days (95% confidence interval, 35.62–48.37) for the HME group (P <0.001). Cox regression analysis showed the HME as a risk factor for VAP (hazard rate, 16.2; 95% confidence interval, 4.54–58.04; P < 0.001).ConclusionThe patients mechanically ventilated for more than five days developed a lower incidence of VAP with a HH than with a HME.

Tracheal Climate in Laryngectomees after Use of a Heat and Moisture Exchanger

Heat and moisture exchangers (HME) are frequently used in the treatment and prevention of tracheobronchial dryness and infections. In this study, the short-term influence of the HME Prim-Air System (Heimomed, Kerpen, Germany) in laryngectomized patients was tested. Prospective study. After adaptation to the laboratory environment, tracheal humidity and temperature were measured before HME application, 1 minute after HME application, 10 minutes after HME application, 1 minute after removal of the HME, and 10 minutes after removal of the HME. When the HME was placed on the tracheal stoma, the end-inspiratory humidity and temperature increased significantly. Ten minutes after commencement of use of the HME, tracheal humidity further increased significantly. Ten minutes after removal of the HME, tracheal humidity and temperature decreased to values as before start of use of HME. The results indicate that short-term use of the HME Prim-Air system rapidly changes the tracheal climate. The significant increase in tracheal temperature and humidity may have beneficial effects on tracheal dryness in laryngectomized patients.

Randomized clinical trial of extended use of a hydrophobic condenser humidifier: 1 vs. 7 days

To determine whether extended use (7 days) would affect the efficiency on heat and water preservation of a hydrophobic condenser humidifier as well as the rate of ventilation-acquired pneumonia, compared with 1 day of use. Prospective, controlled, randomized, not blinded, clinical study. Twelve-bed intensive care unit of a university hospital. One hundred and fifty-five consecutive patients undergoing mechanical ventilation for > or = 48 hrs. After randomization, patients were allocated to one of the two following groups: a) heat and moisture exchangers (HMEs) changed every 24 hrs; b) HMEs changed only once a week. Devices in both groups could be changed at the discretion of the staff when signs of occlusion or increased resistance were identified. Efficient airway humidification and heating were assessed by clinical variables (numbers of tracheal suctionings and instillations required, peak and mean airway pressures). The frequency rates of bronchial colonization and ventilation-acquired pneumonia were evaluated by using clinical and microbiological criteria. Endotracheal tube occlusion, ventilatory support variables, duration of mechanical ventilation, length of intensive care, acquired multiorgan dysfunction, and mortality rates also were recorded. The two groups were similar at the time of randomization. Endotracheal tube occlusion never occurred. In the targeted population (patients ventilated for > or = 7 days), the frequency rate of ventilation-acquired pneumonia was 24% in the HME 1-day group and 17% in the HME 7-day group (p > .05, not significant). Ventilation-acquired pneumonia rates per 1000 ventilatory support days were 16.4/1000 in the HME 1-day group and 12.4/1000 in the HME 7-day group (p > .05, not significant). No statistically significant differences were found between the two groups for duration of mechanical ventilation, intensive care unit length of stay, acquired organ system derangements, and mortality rate. There was indirect evidence of very little, if any, change in HME resistance. Changing the studied hydrophobic HME after 7 days did not affect efficiency, increase resistance, or altered bacterial colonization. The frequency rate of ventilation-acquired pneumonia was also unchanged. Use of HMEs for > 24 hrs and up to 7 days is safe.