Moisture Exchange Filter Research Articles

Early Detection of Ventilator-associated Pneumonia From Exhaled Breath in Intensive Care Unit Patients.

Evaluate associations between volatile organic compounds (VOCs) in heat and moisture exchange (HME) filters and the presence of ventilator-associated pneumonia (VAP). Clinical diagnostic criteria for VAP have poor interobserver reliability, and cultures are slow to result. Exhaled breath contains VOCs related to gram-negative bacterial proliferation, the most identified organisms in VAP. We hypothesized that exhaled VOCs on HME filters can predict nascent VAP in mechanically ventilated intensive care unit patients. Gas chromatography-mass spectrometry was used to analyze 111 HME filters from 12 intubated patients who developed VAP. Identities and relative amounts of VOCs were associated with dates of clinical suspicion and culture confirmation of VAP. Matched pairs t tests were performed to compare VOC abundances in HME filters collected within 3 days pre and postclinical suspicion of VAP (pneumonia days), versus outside of these days (non-pneumonia days). A receiver operating characteristic curve was generated to determine the diagnostic potential of VOCs. Carbon disulfide, associated with the proliferation of certain gram-negative bacteria, was found in samples collected during pneumonia days for 11 of 12 patients. Carbon disulfide levels were significantly greater ( P = 0.0163) for filters on pneumonia days. The Area Under the Curve of the Reciever Operating Characteristic curve (AUC ROC) for carbon disulfide was 0.649 (95% CI: 0.419-0.88). Carbon disulfide associated with gram-negative VAP can be identified on HME filters up to 3 days before the initial clinical suspicion, and approximately a week before culture confirmation. This suggests VOC sensors may have potential as an adjunctive method for early detection of VAP.

Compliance to ventilator care bundles and its association with ventilator-associated pneumonia

PurposeVentilator care bundles are effective in the prevention of ventilator-associated pneumonia (VAP). However, the compliance of these bundles in intensive care units (ICUs) remains poorly studied. This study investigates the Medical Information Mart for Intensive Care (MIMIC)-IV cohort’s compliance with the Institute for Healthcare Improvement (IHI) bundle and its resulting association with VAP incidence.MethodsThis is a retrospective cohort study of the MIMIC-IV database. Patients with > 48 h of invasive mechanical ventilation (IMV) were included. Diagnosis of VAP was identified with the International Classification of Diseases (ICD)-9 and ICD-10 codes. Compliance rates to the IHI bundle were extracted. The association of the IHI bundle and its individual interventions with VAP incidence was analyzed with univariate and multivariate analysis.Results8270 patients were included, of which 1328 (16.1%) had VAP. 25 patients (0.3%) had full compliance to the IHI bundle. 137 patients (1.7%) received no interventions from the bundle. Gastroprophylaxis had the lowest (2.1%) while head elevation had the highest (89.3%) compliance rates. In patients receiving the IHI bundle, each additional intervention was associated with lower VAP incidence (OR [odds ratio] = 0.906, 95% CI [confidence interval] 0.847–0.969). Appropriate sedation levels (OR = 0.765, 95% CI 0.661–0.885) and the use of heat and moisture exchanger (HME) filters (OR = 0.862, 95% CI 0.745–0.998) were individually associated with reduced VAP incidence, while active humidification was individually associated with increased VAP incidence (OR = 1.139, 95% CI 1.001–1.296).ConclusionThe use of the IHI bundle was associated with a lower incidence of VAP, but compliance with the bundle was poor. Appropriate sedation and HME filters were individually associated with reduced VAP incidence. Better compliance with the IHI bundle may reduce VAP rates in mechanically ventilated patients.Graphical

Inhaled drug delivery: a randomized study in intubated patients with healthy lungs

BackgroundThe administration technique for inhaled drug delivery during invasive ventilation remains debated. This study aimed to compare in vivo and in vitro the deposition of a radiolabeled aerosol generated through four configurations during invasive ventilation, including setups optimizing drug delivery.MethodsThirty-one intubated postoperative neurosurgery patients with healthy lungs were randomly assigned to four configurations of aerosol delivery using a vibrating-mesh nebulizer and specific ventilator settings: (1) a specific circuit for aerosol therapy (SCAT) with the nebulizer placed at 30 cm of the wye, (2) a heated-humidified circuit switched off 30 min before the nebulization or (3) left on with the nebulizer at the inlet of the heated-humidifier, (4) a conventional circuit with the nebulizer placed between the heat and moisture exchanger filter and the endotracheal tube. Aerosol deposition was analyzed using planar scintigraphy.ResultsA two to three times greater lung delivery was measured in the SCAT group, reaching 19.7% (14.0–24.5) of the nominal dose in comparison to the three other groups (p < 0.01). Around 50 to 60% of lung doses reached the outer region of both lungs in all groups. Drug doses in inner and outer lung regions were significantly increased in the SCAT group (p < 0.01), except for the outer right lung region in the fourth group due to preferential drug trickling from the endotracheal tube and the trachea to the right bronchi. Similar lung delivery was observed whether the heated humidifier was switched off or left on. Inhaled doses measured in vitro correlated with lung doses (R = 0.768, p < 0.001).ConclusionOptimizing the administration technique enables a significant increase in inhaled drug delivery to the lungs, including peripheral airways. Before adapting mechanical ventilation, studies are required to continue this optimization and to assess its impact on drug delivery and patient outcome in comparison to more usual settings.

Re-Evaluating Cross-Contamination: Additional Trials on Co-Ventilation

BackgroundMedical equipment can become scarce in disaster scenarios. Prior work has reported that four sheep could be ventilated together on a single ventilator. Others found that this maneuver is possible when needed, but no one has yet investigated whether cross-contamination occurs in co-ventilated individuals. ObjectiveOur goal was to investigate whether an infection could spread between co-ventilated individuals. MethodsFour 2-L anesthesia bags were connected to a sterilized ventilator circuit that used heat and moisture exchange filters and bacterial and viral filters, as would be expected in this dire scenario. Serratia marcescens was inoculated into “lung” no. 1. After running for 24 h, each lung and three additional points in the circuit were cultured to see whether S. marcescens had spread. These cultures were examined at 24 and 48 h to assess for cross-contamination. This entire procedure was performed three times. ResultsS. marcescens was not found in lung no. 2, 3, or 4 or the three additional sites on the expiratory limb at 24 and 48 h in all three trials. ConclusionsCross-contamination does not occur within 24 h using the described ventilator circuit configuration.

Beta-Lactam Antibiotics Can Be Measured in the Exhaled Breath Condensate in Mechanically Ventilated Patients: A Pilot Study.

Different techniques have been proposed to measure antibiotic levels within the lung parenchyma; however, their use is limited because they are invasive and associated with adverse effects. We explore whether beta-lactam antibiotics could be measured in exhaled breath condensate collected from heat and moisture exchange filters (HMEFs) and correlated with the concentration of antibiotics measured from bronchoalveolar lavage (BAL). We designed an observational study in patients undergoing mechanical ventilation, which required a BAL to confirm or discard the diagnosis of pneumonia. We measured and correlated the concentration of beta-lactam antibiotics in plasma, epithelial lining fluid (ELF), and exhaled breath condensate collected from HMEFs. We studied 12 patients, and we detected the presence of antibiotics in plasma, ELF, and HMEFs from every patient studied. The concentrations of antibiotics were very heterogeneous over the population studied. The mean antibiotic concentration was 293.5 (715) ng/mL in plasma, 12.3 (31) ng/mL in ELF, and 0.5 (0.9) ng/mL in HMEF. We found no significant correlation between the concentration of antibiotics in plasma and ELF (R2 = 0.02, p = 0.64), between plasma and HMEF (R2 = 0.02, p = 0.63), or between ELF and HMEF (R2 = 0.02, p = 0.66). We conclude that beta-lactam antibiotics can be detected and measured from the exhaled breath condensate accumulated in the HMEF from mechanically ventilated patients. However, no correlations were observed between the antibiotic concentrations in HMEF with either plasma or ELF.

COVID, Co-Ventilation, and Cross-contamination

Introduction:During the COVID-19 pandemic, consideration was given to co-ventilating multiple patients on a single ventilator. Prior work had shown that this procedure was possible by ventilating four adult-size sheep for twenty-four hours, and other groups had performed this maneuver during dire circumstances. However, no investigation had examined the safety regarding cross-contamination. The purpose of our studies was to investigate if an infection could spread between individuals who were being co-ventilated.Method:Four sterile two-liter anesthesia bags were connected to a sterilized ventilator circuit to simulate the co-ventilated patients’ “lungs.” The circuit utilized Heat and Moisture Exchange filters and bacterial/viral filters, which were strategically inserted to prevent the transmission of infectious droplets. Serratia marcescens was inoculated into “lung” number one. The circuit was then run for 24 hours, after which each “lung” and three additional points in the circuit were cultured to see if S. marcescens had spread. These cultures were examined at 24 and 48 hours to assess for cross-contamination. This entire procedure was performed a total of four times.Results:S. marcescens was not identified in lungs two, three, or four or the three additional sampling sites on the expiratory limb of the tubing at 24 and 48 hours in all four trials.Conclusion:Cross-contamination between co-ventilated patients did not occur within 24 hours utilizing the described ventilator circuit configuration.

Alveolar target ventilation and dead space in children under anaesthesia: The proventiped cohort study.

Ventilator settings in children under anaesthesia remain difficult because of the changes in the physiology and the high dead space. To determine the alveolar minute-volume to sustain normocapnia in children under mechanical ventilation. A prospective observational study. This study was performed between May and October 2019 in a tertiary care children's hospital. Children between 2 months and 12 years, weighing between 5 and 40 kg, admitted for general anaesthesia. Volumetric capnography was used to estimate the alveolar and dead space volume (Vd). Total and alveolar minute ventilation in (ml kg-1 min-1) over 100 breaths. Sixty patients were included comprising 20 per group: 5 to 10 kg (group 1), 10 to 20 kg (group 2), 20 to 40 kg (group 3). Seven patients were excluded for aberrant capnographic curves. After normalisation to weight, the median [IQR] tidal volume per kilogram was similar between the three groups: 6.5 ml kg-1 [6.0 to 7.5 ml kg-1], 6.4 ml kg-1 [5.7 to 7.3 ml kg-1], 6.4 ml kg-1 [5.3 to 6.8 ml kg-1]; P = 0.3. Total Vd (in ml kg-1) was negatively correlated to weight (r = -0.62, 95% confidence interval -0.41 to -0.76, P < 0.001). The total normalised minute ventilation (ml kg-1 min-1) to obtain normocapnia was higher in group 1 than in group 2 and in group 3; 203 ml kg-1 min-1 [175 to 219 ml kg-1 min-1], 150 ml kg-1 min-1 [139 to 181 ml kg-1 min-1] and 128 ml kg-1 min-1 [107 to 157 ml kg-1 min-1]; P < 0.001 (mean ± SD), but (mean ± SD) alveolar minute ventilation was similar between the three groups; 68 ± 21 ml kg-1 min-1. Total dead space volume (including apparatus dead space) represents a major component of tidal volume in children less than 30 kg, when using large heat and moisture exchanger filters. The total minute ventilation necessary to achieve normocapnia decreased with increasing weight, while the alveolar minute ventilation remained constant. ClinicalTrials.gov, identifier: NCT03901599.

The role of the alveolar epithelial glycocalyx in acute respiratory distress syndrome.

The alveolar epithelial glycocalyx is a dense anionic layer of glycosaminoglycans (GAGs) and proteoglycans that lines the apical surface of the alveolar epithelium. In contrast to the pulmonary endothelial glycocalyx, which has well-established roles in vascular homeostasis and septic organ dysfunction, the alveolar epithelial glycocalyx is less understood. Recent preclinical studies demonstrated that the epithelial glycocalyx is degraded in multiple murine models of acute respiratory distress syndrome (ARDS), particularly those that result from inhaled insults (so-called "direct" lung injury), leading to shedding of GAGs into the alveolar airspaces. Epithelial glycocalyx degradation also occurs in humans with respiratory failure, as quantified by analysis of airspace fluid obtained from ventilator heat moisture exchange (HME) filters. In patients with ARDS, GAG shedding correlates with the severity of hypoxemia and is predictive of the duration of respiratory failure. These effects may be mediated by surfactant dysfunction, as targeted degradation of the epithelial glycocalyx in mice was sufficient to cause increased alveolar surface tension, diffuse microatelectasis, and impaired lung compliance. In this review, we describe the structure of the alveolar epithelial glycocalyx and the mechanisms underlying its degradation during ARDS. We additionally review the current state of knowledge regarding the attributable effect of epithelial glycocalyx degradation in lung injury pathogenesis. Finally, we address glycocalyx degradation as a potential mediator of ARDS heterogeneity, and the subsequent value of point-of-care quantification of GAG shedding to potentially identify patients who are most likely to respond to pharmacological agents aimed at attenuating glycocalyx degradation.

Heat and moisture exchanger filter as a substitute for T-piece device - A novel approach

Letter to Editor

HME filters: a boon or bane?

Heat and moisture exchange filters (HMEFs) have been a controversial yet widely used adjunct to breathing circuit. Here we discuss a case scenario where clogging of HMEF with moisture presented as elevated peak airway pressures. Apart from stressing the importance of monitoring airway pressure, we discuss about the judicious use of HMEFs, problems associated with their use and measures to overcome the same. Being a ubiquitous adjunct, a thorough knowledge of its functioning and constant vigilance during its use is of paramount importance

Evaluation of deadspace effects created by heat and moisture exchange filter during artificial lung ventilation in newborns

Heat and moisture exchange filters create additional dead space, comparable in volume to physiological, in premature newborns. It makes carbon dioxide remove difficultу. Reducing the dead space volume by increasing the flow in the ventilator circuit can lead to the hypocapnia. Aim of the study was to determine the safety and efficiency of gas flow boost in the ventilator circuit to hypercapnia compensation created by the additional dead space. Material and methods. The effect of the additional dead space created by a heat and moisture exchange filter on hemoglobin saturation and partial pressure of carbon dioxide at the end of expiration in premature newborns at flows of 5 and 6 l/min was studied. Results and discussion. It has been demonstrated that flows of 5–6 l/min satisfactorily compensate for the effect of additional deadspace without hypocapnia. Conclusions. It is possible to recommend the widespread use of heat and moisture exchange filters in newborn weighing at least 1.0 kg during long-term transportation.

Development and characterization of triclosan coated heat and moisture exchange filter for ventilation therapy

An indigenous heat and moisture exchange filter has been developed using an open cell reticulated hygroscopic impregnated polyurethane foam and polypropylene nonwoven to maintain heat and moisture exchange and bacterial filtration efficiency respectively. Also, the spun bond polypropylene nonwoven is treated with an optimized concentration of biocide (triclosan-5gpl) mainly on the 1 st contact layer of ventilator gas using padding mangle in 2 dips/2 nips method for better antibacterial efficiency. Three different polypropylene made nonwoven materials [spunbond (SB), meltblown (MB) and needle-punched (NP)] are stacked in different layer arrangement and evaluated for their efficiency in filtering bacteria. The five- layered composite filter (SB-MB-NP-MB-SB biocide treated) with double layers of meltblown and spunbond treated with biocide, in addition to the needle-punched middle layer, shows a bacterial filtration of 99.9% along with excellent antimicrobial properties and acceptable pressure drop. The developed biocide-coated multilayer composite filter provides comfortable and ideal humidification to the users besides delivering excellent antimicrobial activity. This developed filter will be an alternative to existing commercial filters, without any compromise, and having all the inherent properties.

High efficiency particulate air filters and heat & moisture exchanger filters increase positive end-expiratory pressure in helmet continuous positive airway pressure: A bench-top study

BackgroundHelmet continuous positive airway pressure (CPAP) has been widely used during the COVID-19 pandemic. Specific filters (i.e. High Efficiency Particulate Air filter: HEPA; Heat & Moisture Exchanger Filter: HMEF) were used to prevent Sars-CoV2 environmental dispersion and were connected to the CPAP helmet. However, HEPA and HMEF filters may act as resistors to expiratory gas flow and increase the levels of pressure within the hood. MethodsIn a bench-top study, we investigated the levels of airway pressure generated by different HEPA and HMEF filters connected to the CPAP helmet in the absence of a Positive End Expiratory Pressure (PEEP) valve and with two levels of PEEP (5 and 10 cmH2O). All steps were performed using 3 increasing levels of gas flow (60, 80, 100 L/min). ResultsThe use of 8 different commercially available filters significantly increased the pressure within the hood of the CPAP helmet with or without the use of PEEP valves. On average, the increase of pressure above the set PEEP ranged from 3 cmH2O to 10 cmH2O across gas flow rates of 60 to 100 L/min. The measure of airway pressure was highly correlated between the laboratory pressure transducer and the Helmet manometer. Bias with 95% Confidence Interval of Bias between the devices was 0.7 (-2.06; 0.66) cmH2O. ConclusionsThe use of HEPA and HMEF filters placed before the PEEP valve at the expiratory port of the CPAP helmet significantly increase the levels of airway pressure compared to the set level of PEEP. The manometer can detect accurately the airway pressure in the presence of HEPA and HMEF filters in the helmet CPAP and its use should considered.

Sensitivity and specificity of heat and moisture exchange filters sampling for SARS-CoV-2 detection in mechanically ventilated COVID-19 patients.

We assessed the sensitivity and specificity of SARS-CoV-2 detection by polymerase chain reaction in heat and moisture exchange filters (HMEF) in mechanically ventilated COVID-19 patients. We showed that testing HMEF might obviate the need for a tracheal sample to affirm that a patient is not ready to end isolation.

The Effect of Filters on CPAP Delivery by Helmet.

When helmet CPAP is performed using a Venturi system, filters are frequently interposed in the respiratory circuit to reduce noise within the helmet. The effect of the interposition of these filters on delivered fresh gas flow and the resulting FIO2 is currently unknown. In a bench study, 2 different Venturi systems (WhisperFlow and Harol) were used to generate 3 different gas flow/FIO2 combinations (80 L/min-FIO2 0.6, 100 L/min-FIO2 0.5, 120 L/min-FIO2 0.4). Different combinations of filters were applied at the flow generator input line and/or at the helmet inlet port. Two types of filters were used for this purpose: a heat and moisture exchanger filter and an electrostatic filter. The setup without filters was used as baseline. Gas flow and FIO2 were measured for each setup. Compared to baseline, the interposition of filters reduced the gas flow between 1-13% (P < .001). The application of a filter at the Venturi system or at the helmet generated a comparable flow reduction (-3 ± 2% vs -4 ± 2%, P = .12), whereas a greater flow reduction (-7 ± 4%) was observed when filters were applied at both sites (P < .001). An increase in FIO2 up to 5% was observed with filters applied. A strong inverse linear relationship (P < .001) was observed between the resulting gas flow and FIO2 . The use of filters during helmet CPAP reduced the flow delivered to the helmet and, consequently, modified FIO2 . If filters are applied, an adequate gas flow should be administered to guarantee a constant CPAP during the entire respiratory cycle and avoid rebreathing. Moreover, it might be important to measure the effective FIO2 delivered to the patient to guarantee a precise assessment of oxygenation.

Delayed recognition of breathing system contamination with blood containing hepatitis C virus following failure of a heat and moisture exchange filter.

Delayed recognition of breathing system contamination with blood containing hepatitis C virus following failure of a heat and moisture exchange filter.

Intubation of COVID-19 patients with catheter mount and heat and moisture exchanger filter preconnected to endotracheal tube

Intubation of COVID-19 patients with catheter mount and heat and moisture exchanger filter preconnected to endotracheal tube

Airway Obstruction Caused by Sputa in Heat and Moisture Exchange Filter During Ventilation Using Supra-Laryngeal Mask Airway: A Case Report

Introduction: Supra-laryngeal mask airway (LMA) is widely accepted as an alternative to the tracheal tube. However, compared to the use of a tracheal tube, it may take longer to identify the many different causes of sudden respiratory distress. In particular, heat and moisture exchange filters are one of the most overlooked causes. Case presentation: The case was that of a 76-year-old male Japanese patient (161.9 cm, 66.5 kg) who underwent an open renal biopsy. He presented with chronic obstructive pulmonary disease, with a Hugh–Jones dyspnea score of 2. The patient did not discontinue smoking prior to the operation. Anesthesia was induced using propofol (100 mg), fentanyl (100 ?g), and remifentanil (0.3 ?g/kg/min). I-gel™ #4 was inserted following neuromuscular blockade with rocuronium (40 mg). Anesthesia was maintained with 3–6% desflurane under positive pressure ventilation. After induction in the left lateral and jackknife positions, the following ventilator settings were used: volume-controlled ventilation with tidal volumes of 450 mL, respiratory rate of 12 breaths per minute, an inspiratory: expiratory ratio of 1:2, and a positive end expiratory pressure of 5 cmH2O. With these settings, the peak inspiratory pressure was 16 cmH2O. Five minutes after initiating the operation, the peak inspiratory pressure steadily increased to 30 cmH2O. Although we administered rocuronium, the peak inspiratory pressure and end-tidal carbon dioxide concentration increased over time. When we disconnected the heat and moisture exchange filter and LMA, we noticed a large quantity of sputa. A suction catheter was passed down the LMA and the sputa was removed, but the LMA was not obstructed. The peak inspiratory pressure continued to increase with tidal volumes of only 20–30 mL. Despite a normal external appearance of the heat and moisture exchange filter, we replaced it with a new one. The ability to ventilate improved immediately and the SpO2 recovered from 92% to 100%. Conclusions

Effect of Heat and Moisture Exchange Filter on the Dead Space Ventilation in a Pediatric Patient

AbstractThe use of heat and moisture exchange filter (HMEF) has become a routine standard of care in general anesthesia (GA), more so, during the current COVID-19 pandemic times. However its routine use, especially in pediatric patients, has several issues. We report a case of increased dead space ventilation in a pediatric patient due to the presence of HMEF. Hypercapnia and its cause was instantly diagnosed with two capnography sampling lines placed at two ends of the HMEF.

Perioperative management of post-COVID-19 surgical patients: Indian Society of Anaesthesiologists (ISA National) Advisory and Position Statement.

Perioperative management of post-COVID-19 surgical patients: Indian Society of Anaesthesiologists (ISA National) Advisory and Position Statement.