Development of a New Method for Evaluating Heat and Moisture Exchanger Performance.

BACKGROUND: A model system described in International Organization for Standardization 9360 is the standard method for estimating the humidifying performance of heat and moisture exchangers (HMEs). However, there are no reliable bedside methods for evaluating the ongoing humidification performance of HMEs. Therefore, this study aimed to develop 2 clinically applicable methods for estimating the ongoing humidifying performance of HMEs and to evaluate their reliability in a model system. METHODS: Physiologically expired gas was simulated using a heated humidifier, and ventilation was delivered using a ventilator with constant flow through 3 different types of HMEs. Relative humidity (RH) was measured using a capacitive-type moisture sensor. Water content lost during expiration was calculated by integrating absolute humidity (AH), instantaneous gas flow measured at the expiratory outlet of the ventilator, and time. We also calculated the water content released and captured by the HMEs during tidal ventilation by integrating the difference in AH across the HMEs, instantaneous gas flow, and time. RESULTS: We found that the RH, temperature, and AH were almost constant on the expiratory outlet of the ventilator but rapidly varied near the HMEs. The water content lost by the 3 HMEs was associated with the manufacturer-reported values and inversely correlated with the calculated values of the water content exchanged by the HMEs. The water content released and captured by HMEs was closely correlated with the difference in HME weight measured at the end of inspiration and expiration; however, the water content captured by HMEs seemed to be overestimated. CONCLUSIONS: Our results demonstrated that our system was able to detect the differences in the performance of 3 models of HMEs and suggest that our method for calculating water loss is reliable for estimating the water retention performance of HMEs during mechanical ventilation, even in the presence of a constant flow.

Impact of Humidification Modality on Incidence of Endotracheal Tube Occlusion in COVID-19 Patients.

Background: Endotracheal tube (ETT) occlusion is reported at a higher frequency among coronavirus disease-2019 (COVID-19) patients. Prior to the COVID-19 pandemic, literature examining patient and ventilator characteristics, including humidification, as etiologies of ETT occlusion yielded mixed results. Our study examines the relationship of humidification modality with ETT occlusion in COVID-19 patients undergoing invasive mechanical ventilation (IMV). Methods: We conducted a retrospective chart review of COVID-19 patients requiring IMV at a tertiary care center in New York from April 2020 to April 2021. Teleflex Neptune heated wire heated humidification (HH) and hygroscopic Intersurgical FiltaTherm and Sunmed Ballard 1500 heat and moisture exchangers (HME) were used. Episodes of ETT occlusion were recorded. Univariate and multivariable logistic regression models were used to investigate the relationship between humidification modality and the occurrence of ETT occlusion. Findings: A total of 201 eligible patients were identified. Teleflex HH was utilized in 50.2% of the population and the others Intersurgical and Sunmed HME devices. Median age was 62 years and 78.6% of patients had at least one medical comorbidity. Precisely, 24% of patients experienced an ETT occlusion after a median of 12 days. The HME group was younger (58.5 vs 64 years), predominantly male (75% vs 59.4%), and experienced more total ventilator days than the HH group (24 vs 12). Those using the studied HME devices had significantly higher odds of ETT occlusion (OR 4.4, 95% CI 1.8-10.6, P = .0011). Three patients (6.1%) experienced cardiac arrest as a consequence of their occlusion. There were no deaths directly attributed to ETT occlusion. Conclusions: The studied HME devices were significantly associated with higher odds of ETT occlusion in COVID-19 patients requiring invasive mechanical ventilation. These events are not without significant clinical consequences. Prolonged use of under-performing HME devices remains suspect in the occurrence of ETT occlusions.

Understanding and predicting the performance of passive heat and moisture exchangers using a numerical model.

BACKGROUND: To improve the understanding of the thermodynamics and performance of small passive hygroscopic Heat and Moisture Exchangers (HMEs), a computer model simulating HME function is required. METHODS: We developed a numerical HME model to calculate the HME's water and heat exchange. The model was tuned and verified with experimental data and validated by applying it to HME design variations. RESULTS: Verification of the model's results to the experimental data shows that the tuned model yields reliable results. The mass of the core, which determines the HME's total heat capacity, is the most important parameter influencing the performance of passive HMEs. CONCLUSIONS: Increasing the HME's diameter is an effective way to improve an HME, as it yields higher performance and lowers breathing resistance. HMEs intended for use in warm or dry climates should contain more and those for use in cold humid climates should contain less hygroscopic salt.

Post-laryngectomy pulmonary and related symptom changes following adoption of an optimal day-and-night heat and moisture exchanger (HME) regimen.

BACKGROUND: This study examined post-laryngectomy pulmonary and related symptom changes following establishment of an optimal day/night regimen (all day/night wear of devices with improved humidification) using a new generation range of heat and moisture exchanger (HME) devices. METHODS: In Phase 1 (6 weeks), 42 post-laryngectomy HME users transitioned from their usual HME regime to equivalent new device/s (i.e., "like-for-like"). In Phase 2 (6 weeks) participants used the full range of HMEs to achieve an optimal day/night regimen. Pulmonary symptoms, device use, sleep, skin integrity, quality of life and satisfaction were examined at baseline, and weeks 2 and 6 of each Phase. RESULTS: From baseline to end of Phase 2, cough symptoms and impact significantly improved, as did sputum symptoms, sputum impact, duration and types of HMEs used, reasons for HME replacement, involuntary coughs, and sleep. CONCLUSION: The new HME range supported improved HME use, with pulmonary and related symptom benefits.

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

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: 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.

Impact of Airway Humidification Strategy in Mechanically Ventilated COVID-19 Patients.

BACKGROUND: Humidification of inspiratory gases is mandatory in all mechanically ventilated patients in ICUs, either with heated humidifiers (HHs) or with heat and moisture exchangers (HMEs). In patients with COVID-19, the choice of the humidification device may have relevant impact on patients' management as demonstrated in recent studies. We reported data from 2 ICUs using either HME or HH. METHODS: Data from patients with COVID-19 requiring invasive mechanical ventilation during the first wave in 2 ICUs in Québec City were reviewed. In one ICU, HMEs were used, whereas heated-wire HHs were used in the other ICU. We compared ventilator settings and arterial blood gases at day one after adjustment of ventilator settings. Episodes of endotracheal tube occlusions (ETOs) or subocclusions and a strategy to limit the risk of under-humidification were reported. On a bench test, we measured humidity with psychrometry with HH at different ambient temperature and evaluated the relation with heater plate temperature. RESULTS: We reported data from 20 subjects positive for SARS-Cov-2, including 6 in the ICU using HME and 14 in the ICU using HH. In the HME group, PaCO2 was higher (48 vs 42 mm Hg) despite higher minute ventilation (171 vs 145 mL/kg/min predicted body weight [PBW]). We also reported 3 ETOs occurring in the ICU using HH. The hygrometric bench study reported a strong correlation between heater plate temperatures of the HH and humidity delivered. After implementation of measures to avoid under-humidification, including heater plate temperature monitoring, no more ETOs occurred. CONCLUSIONS: The choice of the humidification device used in subjects with COVID-19 had a relevant impact on ventilation efficiency (increased CO2 removal with lower dead space) and on complications related to low humidity, including ETOs that may be present with heated-wire HHs when used with high ambient temperatures.

Design and application of a new heat-and-moisture exchanger with anti-splash sputum suctioning function / 中华危重病急救医学

In the emergency department, open endotracheal suctioning for mechanically ventilated patients with endotracheal intubation will lead to the spread of respiratory droplets and aerosols, polluting the surrounding environment and medical staff. The traditional heat-and-moisture exchanger has the effect of warming and humidifying, and can block pathogenic microorganisms, but it does not have the function of inserting a sputum suction tube. When the heat-and-moisture exchanger is pulled out for sputum suction, it is easy to cause sputum splash, which pollutes the surrounding environment and medical personnel. The addition of closed sputum suction devices will increase the economic burden on patients. Thus, the medical staff of emergency department of the First People's Hospital of Tongxiang City of Zhejiang Province designed a new type of heat-and-moisture exchanger with anti-splash sputum suctioning function and obtained the National Utility Model Patent of China (ZL 2021 2 0017615.0). The new heat-and-moisture exchanger is mainly composed of a receiving cavity, a connecting tube, a sputum suction tube intubation tube, a sealing valve, etc. The disposable sputum suction tube can be used to insert sputum suction, and at the same time, it can prevent the secretion from splashing to ensure sealing. The patent combines the humidification and pathogen blocking functions of the heat-and-moisture exchanger with the anti-splash sputum suctioning function, which is suitable for use in the emergency and critical care medicine departments and has clinically practical value.

Salbutamol Delivered by Jet Nebulizer: Closed System Design and Impact of a Model Biofilm.

BACKGROUND: Aerosol therapy is commonly used by intensivists during invasive mechanical ventilation. More information is needed to optimize outcomes. The first aim of this study was to assess the deposition of salbutamol on components of a closed mechanical ventilation system, both in the presence and absence of biofilm generated by Acinetobacter baumannii. The second aim was to evaluate the deposition of salbutamol, using a single dose and a double dose, delivered via a jet nebulizer placed between the flexible tube and the heat and moisture exchanger. METHODS: A mechanical ventilator was connected to a standard system, and a jet nebulizer was placed between the heat and moisture exchanger and the flexible tube. Clinical isolates of A. baumanii were used to generate a biofilm layer on the endotracheal tube. Two amounts of salbutamol were delivered via the jet nebulizer. An analytical liquid chromatography tandem mass spectrometry method was developed to evaluate salbutamol deposition. RESULTS: The presence of a biofilm on the endotracheal tube had no impact on salbutamol deposition (P = .83). There was no difference in surface deposition of salbutamol on component parts of the closed system in a comparison of a single dose and a double dose delivered via a jet nebulizer. CONCLUSIONS: Our findings indicate that an A. baumannii biofilm had no impact on the extent of salbutamol deposition. Salbutamol deposition was comparatively low and could be delivered without removal of the heat and moisture exchanger.

Adjustable breathing resistance for laryngectomized patients: Proof of principle in a novel heat and moisture exchanger cassette.

BACKGROUND: Due to the heat and moisture exchanger's (HME) breathing resistance, laryngectomized patients cannot always use an (optimal) HME during physical exercise. We propose a novel HME cassette concept with adjustable "bypass," to provide adjustment between different breathing resistances within one device. METHODS: Under standardized conditions, the resistance and humidification performance of a high resistance/high humidification HME (XM) foam in a cassette with and without bypass were compared to a lower resistance/lesser humidification HME (XF) foam in a closed cassette. RESULTS: With a bypass in the cassette, the resistance and humidification performance of XM foam were similar to those of XF foam in the closed cassette. Compared to XM foam in the closed cassette, introducing the bypass resulted in a 40% resistance decrease, whereas humidification performance was maintained at 80% of the original value. CONCLUSIONS: This HME cassette prototype allows adjustment between substantially different resistances while maintaining appropriate humidification performances.

Pitfalls in Ventilation Devices.

Adequate ventilation is the greatest concern of all the anaesthesiologists. Any disturbance in the ventilation process could result in serious hazards: hypoxemia or barotrauma. Deficient devices are one of many causes of such derangements. Some of the typical complications of airway/ventilation tools are described extensively in textbooks, but many other uncommon events can still occur. We described two interesting cases of device-related ventilation inadequacy, hoping that acquaintance with such jeopardizes would be helpful in emergency situations for other colleagues.

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

BACKGROUND: 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. METHODS: A cost-effectiveness and budget impact analysis were conducted including uncertainty analyses using real-world survey data with pulmonary events and productivity loss. RESULTS: 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. CONCLUSIONS: 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.

Effect of a heat and moisture exchanger on temperature and humidity of inhaled gas in isoflurane-anesthetized dogs.

OBJECTIVE: To investigate the effects of a heat and moisture exchanger (HME) on the temperature and humidity of inhaled gas in isoflurane-anesthetized dogs. STUDY DESIGN: Prospective, interventional study. ANIMALS: A total of four experimental dogs and four client-owned dogs weighing 13.9 ± 7.4 kg (mean ± standard deviation). METHODS: The four experimental dogs were anesthetized on two occasions with and without an intact HME at least 1 week apart. The four client-owned dogs were anesthetized once only for a surgical procedure and assigned to the HME group or no-HME group in alternate order, resulting in six dogs for each group. All dogs were premedicated, anesthetized with propofol and intubated. The HME was connected to the endotracheal tube. Anesthesia was maintained with isoflurane. A digital thermo-hygrometer was placed between the endotracheal tube and HME. The temperature and relative humidity of the inhaled gas were measured every 5 minutes for 60 minutes and the absolute humidity was calculated at each time point. RESULTS: The temperature and absolute humidity of the inhaled gas was significantly higher at 5-60 minutes after intubation in the HME group than in the no-HME group. Absolute humidity was maintained above 29 mg H2O L-1 in the HME group. No significant time-dependent effects on temperature, relative humidity or absolute humidity of the inhaled gas were observed. CONCLUSIONS AND CLINICAL RELEVANCE: The temperature and absolute humidity of the inhaled gas were higher when an HME was used during isoflurane anesthesia in dogs. The use of an HME may reduce the risk of dehydration and dysfunction of the airway mucosal epithelium.

Multicenter randomized crossover trial evaluating the provox luna in laryngectomized subjects.

OBJECTIVES: The aim of this study was to compare the relative compliance and the dermatological and pulmonary outcomes when the Provox Luna system (Atos Medical, Malmö, Sweden) is added during the night to the usual tracheastoma care of laryngectomized subjects. METHODS: This was a multicenter randomized crossover trial conducted in the Netherlands Cancer Institute, Erasmus Medical Center, and Maastricht University Medical Center in The Netherlands. The study included 46 laryngectomized subjects with prior heat and moisture exchanger (HME) and adhesive experience. RESULTS: A significant improvement in the number of compliant individuals was found: Luna: n = 43 of 45 (96%); usual care: n = 35 of 46 (76%), P = 0.02. The Luna period was associated with longer intervals of daily HME use (Luna 23.2 hours [range: 15.6-24.0 hours], usual care [UC]: 21.5 hours [range: 6.0-24.0 hours], P = 0.003) and an increased frequency of skin improvement overnight (Luna 3.9 days [standard deviation (SD)]: 7.0 days), Usual Care: 8.1 days ([SD: 10.8 days], P = 0.008). Fifty-six percent (n = 26) of participants wanted to continue using the Provox Luna system at the conclusion of the study. CONCLUSION: An improvement in compliance and skin recovery overnight was observed when the Provox Luna was added to the usual adhesive and HME use. Therefore, there is utility in supplementing the usual post-total laryngectomy care with the Provox Luna system at night, particularly in the setting of compliance concerns and in subjects who desire dermatological relief overnight. LEVEL OF EVIDENCE: 1b Laryngoscope, 129:2354-2360, 2019.

Humidification Performance of Passive and Active Humidification Devices Within a Spontaneously Breathing Tracheostomized Cohort.

BACKGROUND: Most heat-and-moisture exchangers (HMEs) for patients with tracheostomy and spontaneously breathing are small and have suction ports that allow some expiratory gas to escape, which loses water vapor held in the expired gas. Recently, a heated-and-humidified high-flow system for spontaneously breathing patients with tracheostomy was developed. Little is known, however, about the humidifying performance of HMEs or heated-and-humidified high-flow systems for spontaneous breathing patients with a tracheostomy. OBJECTIVE: To investigate the humidifying performance of the HMEs and heated-and-humidified high-flow systems for spontaneously breathing patients with tracheostomy. METHODS: Adult spontaneously breathing subjects with tracheostomy and were enrolled when their respiratory parameters and SpO2 were stable. We measured absolute humidity, relative humidity, and temperature by using a capacitance-type moisture sensor at the outlet of the tracheostomy tube. Heated-and-humidified high flow was delivered via the a humidifier and tracheostomy interface, and a selected HME. The subjects received heated-and-humidified high flow, after which an HME was used for humidification before switching back to a heated-and-humidified high-flow system. RESULTS: Ten subjects (5 men, 5 women; mean ± SD age, 72 ± 12 y) were enrolled. The admission diagnoses were neurologic (5 subjects), respiratory failure (3), and cardiac arrest (2). The APACHE (Acute Physiology and Chronic Health Evaluation) II score was 24 (interquartile range, 20-27). Tracheostomy was performed on day 7 (interquartile range, 5-11 d) after endotracheal intubation, and the duration of mechanical ventilation was 10 d (interquartile range, 6-11 d). The temperature with the HME was 29.9 ± 1.0°C and, during heated-and-humidified high-flow use was 35.3 ± 0.8°C (P < .001). With both the HME and the heated-and-humidified high-flow system, the relative humidity reached 100%; the absolute humidity with HME was 30.2 ± 1.8 mg/L, and, with the heated-and-humidified high-flow system, was 40.3 ± 1.8 mg/L (P < .001). CONCLUSIONS: In spontaneously breathing subjects with tracheostomy, an heated-and-humidified high-flow system achieved higher absolute humidity than did an HME.

Accidental dual humidification in intensive care units: Repeated alerts and system changes are not enough.

PURPOSE: The inadvertent, simultaneous use of heat and moisture exchangers (HMEs) and heated humidifiers (HHs) can result in waterlogging of the filter and sudden ventilation tube occlusion, with potentially fatal consequences. Following an NHS England Safety Alert, a near miss and educational reminders in our institution, we introduced new guidelines to solely use HHs in the intensive care unit and HMEs only for patient transfers. No further incidents have occurred, however this solution is potentially fallible. Two years later, we sought to assess staff knowledge and likelihood of recognising this error should it occur. MATERIALS AND METHODS: In a simulation study, a tracheally intubated and ventilated mannequin had a breathing circuit containing both a HME and a HH. Participants were asked to assess the circuit, identify errors and undertake corrective measures. RESULTS: Only 30% (6/20) recognised and undertook corrective measures. CONCLUSIONS: Despite educational efforts and system changes, recognition of this error remained poor. System changes may reduce the likelihood of the error occurring, but when it does, recognition may not occur. Substantial reductions or elimination of this error may be achieved through a safety-engineered fail-safe within the equipment, which alerts staff to improve recognition and prevent the mistake.

Do heat and moisture exchangers in the anaesthesia breathing circuit preserve body temperature in dogs undergoing anaesthesia for magnetic resonance imaging?

OBJECTIVE: To investigate whether the use of a heat and moisture exchanger (HME) preserves body temperature in dogs weighing <10 kg anaesthetised for magnetic resonance imaging (MRI). STUDY DESIGN: Prospective, randomised, clinical trial. ANIMALS: Thirty-one client-owned dogs. METHODS: Dogs were assigned randomly to a treatment group [HME (n = 16) or no HME (n = 15)]. Dogs were pseudorandomised according to the premedication they were administered, either dexmedetomidine or no dexmedetomidine. Induction agents were not standardised. General anaesthesia was maintained with isoflurane vaporised in 100% oxygen delivered using a T-piece and a fresh gas flow of 600 mL kg-1 minute-1. Rectal temperature was measured before premedication (T1), after induction (T2), before moving to the MRI unit (T3) and at the end of the MRI scan (T4). Ambient temperatures were measured in the induction room, outside and inside the MRI unit. Data were analysed using a general linear model with T4 as the outcome variable. Linear correlations were performed between T1, T2, T3 and T4, and variables that predicted T4 were investigated. RESULTS: Sex, age and body mass were not significantly different between groups. There were no significant differences in rectal temperature between groups at any time point (group with HME at the end of MRI = 36.3 ± 1.1 °C; group with no HME at the end of MRI = 36.2 ± 1.4 °C) but at the end of the MRI, dogs administered dexmedetomidine (36.6 ± 0.7 °C) had a higher rectal temperature compared with dogs not administered dexmedetomidine (35.9 ± 1.6 °C) for premedication. Rectal temperature varied directly with ambient temperature in MRI scanning room and inversely with anaesthetic duration. CONCLUSIONS AND CLINICAL RELEVANCE: Using an HME did not alter body temperature in dogs weighing <10 kg undergoing an MRI, but including dexmedetomidine in the premedication regimen seemed to preserve the body temperature during anaesthesia.

Effects of Heat and Moisture Exchangers and Exhaled Humidity on Aerosol Deposition in a Simulated Ventilator-Dependent Adult Lung Model.

BACKGROUND: Many in vitro models report higher inhaled dose with dry versus heated humidity. Heat-and-moisture exchangers (HMEs) provide passive humidity in ventilator-dependent patients but act as a barrier to aerosol. The HMEs designed to allow aerosol delivery (HME-ADs) have not been well described. The purpose of this study is to determine the impact on aerosol deposition of HME-ADs with and without active exhaled humidity in a simulated ventilator-dependent adult model. METHODS: We used an in vitro lung model consisting of an intubated teaching mannequin with an endotracheal tube of 8.0 mm inner diameter with bronchi directly attached to a collecting filter and passive rubber test lung to provide testing without active exhaled humidity. To simulate exhaled humidity, a Cascade humidifier (37°C and 100% relative humidity) was placed between the collecting filter and test lung, simulating body temperature and pressure saturated exhaled humidity at the bronchi. Albuterol sulfate (2.5 mg/3 mL) was administered with a mesh nebulizer (Aerogen Solo) placed in the inspiratory limb of the ventilator circuit at the Y-piece, with no HME in place (control) and with 3 HME-AD devices, including the CircuVent, Humid-Flo, and AirLife, with and without exhaled humidity. Drug was eluted from the collecting filter and analyzed with spectrophotometry. Student t tests and analysis of variance were used for data analysis (P < .05). RESULTS: The percentage of drug dose delivered (mean ± SD) distal to the bronchi in the control experiments was greater than all of the HME-ADs without exhaled humidity 18 ± 0.7 and with active exhaled humidity 10.8 ± 0.2% (P < .005). Without exhaled humidity, aerosol delivery with the CircuVent (12.6 ± 0.8), Humid-Flo (15.3 ± 0.8), and AirLife (12.0 ± 0.5) was less than control (P < .001, P = .01 and P < .001, respectively). In contrast, with exhaled humidity, no difference was found between control and HME-ADs (P = .89). Also, a greater variation between control and the 3 HME-ADs was observed without exhaled humidity. Drug delivery without exhaled humidity exceeded aerosol deposition obtained with exhaled humidity in all conditions tested in this study. CONCLUSIONS: In this model simulating active exhaled humidity, aerosol drug delivery was lower and more consistent with both control and the HME-ADs than with the standard nonhumidified model. Further studies are needed to determine whether greater deposition in a dry model is an artifact of the model that does not simulate exhaled humidity.

Ex vivo humidifying capacity and patient acceptability of stoma cloths in laryngectomized individuals.

BACKGROUND: Heat and moisture exchangers (HMEs) improve respiratory function after laryngectomy, but there is virtually no information on the benefit of traditional stoma cloths or other covers. METHODS: Two sequential studies were performed: (1) an ex vivo test was used to compare the humidifying capacity of stoma cloths to other coverings; and (2) a 4-week randomized trial was then performed to assess patient acceptability of cloths both alone and with an HME (N = 18). RESULTS: The humidifying capacity of the coverings tested varied widely. For stoma cloths, a humidifying capacity of 13.7 mg/L was found to decrease to 8.5 mg/L if air-leaks around the cloth occurred. Patients who used HMEs disliked stoma cloths because they interfered with voicing, they became soiled more easily, and were less effective at reducing coughing and mucus production. CONCLUSION: Although less acceptable to patients who use an HME, stoma cloths do provide significant humidifying capacity and should be encouraged when HMEs are unavailable or inappropriate. © 2017 Wiley Periodicals, Inc. Head Neck 39: 921-931, 2017.