Heat and moisture exchangers (HMEs) and heated humidifiers (HHs) in adult critically ill patients: a systematic review, meta-analysis and meta-regression of randomized controlled trials

Humidification during Invasive and Non-Invasive Ventilation: A Starting Tool Kit for Correct Setting

The humidification process of medical gases plays a crucial role in both invasive and non-invasive ventilation, aiming to mitigate the complications arising from bronchial dryness. While passive humidification systems (HME) and active humidification systems are prevalent in routine clinical practice, there is a pressing need for further evaluation of their significance. Additionally, there is often an incomplete understanding of the operational mechanisms of these devices. The current review explores the historical evolution of gas conditioning in clinical practice, from early prototypes to contemporary active and passive humidification systems. It also discusses the physiological principles underlying humidity regulation and provides practical guidance for optimizing humidification parameters in both invasive and non-invasive ventilation modalities. The aim of this review is to elucidate the intricate interplay between temperature, humidity, and patient comfort, emphasizing the importance of individualized approaches to gas conditioning.

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.

Nursing Practice of Airway Care Interventions and Prone Positioning in ICU Patients with COVID-19-A Dutch National Survey

Background: Airway care interventions and prone positioning are used in critically ill patients with coronavirus disease 2019 (COVID-19) admitted to the intensive care unit (ICU) to improve oxygenation and facilitate mucus removal. At the onset of the COVID-19 pandemic, the decision-making process regarding the practice of airway care interventions and prone positioning was challenging. Objective: To provide an overview of the practice of airway care interventions and prone positioning during the second wave of the pandemic in the Netherlands. Method: Web-based survey design. Seventy ICU nurses, each representing one intensive care in the Netherlands, were contacted for participation. Potential items were generated based on a literature search and formulated by a multidisciplinary team. Questions were pilot tested for face and construct validity by four intensive care nurses from four different hospitals. Results: The response rate was 53/77 (69%). This survey revealed widespread use of airway care interventions in the Netherlands in COVID-19 patients, despite questionable benefits. Additionally, prone positioning was used in invasively and non-invasively ventilated patients. Conclusions: The use of airway care interventions and prone positioning is time consuming and comes with the production of waste. Further research is needed to assess the effectiveness, workload, and environmental impact of airway care interventions and prone positioning.

Effectiveness of nonpharmacological interventions to prevent adverse events in the intensive care unit: A review of systematic reviews

BACKGROUND

Different types of interventions have been assessed for the prevention of adverse events. However, determining which patient-safety practice is most effective can be challenging when there is no systematised evidence synthesis. An overview following the best methodological standards can provide the best reliable integrative evidence.

OBJECTIVES

The objective of this study was to provide an overview of effectiveness nonpharmacological interventions aimed at preventing adverse events in the intensive care unit.

METHODS

A review of systematic reviews (SRs) was conducted according to the Cochrane Handbook and PRISMA recommendations. PubMed, CINAHL, and Cochrane Library were searched for SRs published until March 2022. Two reviewers independently assessed the study's quality, using AMSTAR-2, and extracted data on intervention characteristics and effect on prevention of adverse events.

RESULTS

Thirty-seven SRs were included, and 27 nonpharmacological interventions were identified to prevent 11 adverse events. Most of the reviews had critically low methodological quality. Among all the identified interventions, subglottic secretion drainage, semirecumbent position, and kinetic bed therapy were effective in preventing ventilator-associated pneumonia; the use of earplugs, early mobilisation, family participation, and music in reducing delirium; physical rehabilitation in improving muscle strength; use of respiratory support in preventing reintubation; the use of a computerised physician order entry system in reducing risk of medication errors; and the use of heated water humidifier was effective in reducing artificial airway occlusion.

CONCLUSIONS

Some nonpharmacological interventions reduced adverse events in the intensive care setting. These findings should be interpreted carefully due to the low methodological quality. SRs on preventing adverse events in the intensive care unit should adhere to quality assessment tools so that best evidence can be used in decision-making.

Humidification during mechanical ventilation to prevent endotracheal tube occlusion in critically ill patients: A case control study

BACKGROUND:

Endotracheal tube (ETT) occlusion is a potentially life-threatening event. This study describes a quality improvement project to prevent ETT occlusion in critically ill patients.

METHODS:

After a cluster of clinically significant ETT occlusion incidents at a tertiary-care intensive care unit (ICU), the root cause analysis suggested that the universal use of heat moisture exchangers (HMEs) was a major cause. Then, we prospectively audited new ETT occlusion incidents after changing our practices to evidence-based active and passive humidification during mechanical ventilation (MV). We also compared the outcomes of affected patients with matched controls.

RESULTS:

During 100 weeks, 18 incidents of clinically significant ETT occlusion occurred on a median of 7 days after intubation (interquartile range, 4.8–9.5): 8 in the 10 weeks before and 10 in the 90 weeks after changing humidification practices (8.1 vs. 1.0 incidents per 1000 ventilator days, respectively). The incidents were not suspected in 94.4%, the peak airway pressure was >30 cm H₂O in only 25%, and 55.6% were being treated for pneumonia when ETT occlusion occurred. Compared with 51 matched controls, ETT occlusion cases had significantly longer MV duration (median of 13.5 vs. 4.0 days; P = 0.002) and ICU stay (median of 26.5 vs. 11.0 days; P = 0.006) and more tracheostomy (55.6% vs. 9.8%; P < 0.001). The hospital mortality was similar in cases and controls.

CONCLUSIONS:

The rate of ETT occlusion decreased after changing humidification practices from universal HME use to evidence-based active and passive humidification. ETT occlusion was associated with more tracheostomy and a longer duration of MV and ICU stay.

Establishment of evidence-based nursing review indicators for airway management of adult critical patients and analysis of obstacle factors

AIM

To select and obtain relevant evidence of airway management in adult critically ill patients at home and abroad, formulate clinical quality review indicators based on evidence and analyse obstacle factors and promoting factors in evidence-based nursing practice. To promote standardized ICU airway management evidence-based nursing practice to provide the basis.

DESIGN

Obstacle factor analysis.

METHODS

Take the Joanna Briggs Institute (JBI) evidence-based healthcare model as theoretical guidance, establish evidence-based problems, form a team, systematically search for literature, evaluate quality and summarize evidence, establish quality review indicators and review methods, analyse obstacles and facilitating factors based on the review results and formulate corresponding action strategies.

RESULTS

According to the 29 best evidences, 21 review indicators were developed. Through the results of clinical quality review, the main barriers to evidence-based practice were analysed: the lack of nurse training and relevant evidence-based knowledge at the practitioner level, the lack of standardized procedures for airway management and the lack of materials at the system level.

CONCLUSION

There is a big gap between airway management evidence and clinical practice in critically ill adult patients. Therefore, improvement measures should be formulated for obstacle factors to promote effective transformation of evidence into clinical practice.

Removal of a catheter mount and heat-and-moisture exchanger improves hypercapnia in patients with acute respiratory distress syndrome: A retrospective observational study

ABSTRACT

To avoid ventilator-associated lung injury in acute respiratory distress syndrome (ARDS) treatment, respiratory management should be performed at a low tidal volume of 6 to 8 mL/kg and plateau pressure of ≤30 cmH2O. However, such lung-protective ventilation often results in hypercapnia, which is a risk factor for poor outcomes. The purpose of this study was to retrospectively evaluate the effectiveness and safety of the removal of a catheter mount (CM) and using heated humidifiers (HH) instead of a heat-and-moisture exchanger (HME) for reducing the mechanical dead space created by the CM and HME, which may improve hypercapnia in patients with ARDS.This retrospective observational study included adult patients with ARDS, who developed hypercapnia (PaCO2 > 45 mm Hg) during mechanical ventilation, with target tidal volumes between 6 and 8 mL/kg and a plateau pressure of ≤30 cmH2O, and underwent stepwise removal of CM and HME (replaced with HH). The PaCO2 values were measured at 3 points: ventilator circuit with CM and HME (CM + HME) use, with HME (HME), and with HH (HH), and the overall number of accidental extubations was evaluated. Ventilator values (tidal volume, respiratory rate, minutes volume) were evaluated at the same points.A total of 21 patients with mild-to-moderate ARDS who were treated under deep sedation were included. The values of PaCO2 at HME (52.7 ± 7.4 mm Hg, P < .0001) and HH (46.3 ± 6.8 mm Hg, P < .0001) were significantly lower than those at CM + HME (55.9 ± 7.9 mm Hg). Measured ventilator values were similar at CM + HME, HME, and HH. There were no cases of reintubation due to accidental extubation after the removal of CM.The removal of CM and HME reduced PaCO2 values without changing the ventilator settings in deeply sedated patients with mild-to-moderate ARDS on lung-protective ventilation. Caution should be exercised, as the removal of a CM may result in circuit disconnection or accidental extubation. Nevertheless, this intervention may improve hypercapnia and promote lung-protective ventilation.

Airway Care Interventions for Invasively Ventilated Critically Ill Adults-A Dutch National Survey

Airway care interventions may prevent accumulation of airway secretions and promote their evacuation, but evidence is scarce. Interventions include heated humidification, nebulization of mucolytics and/or bronchodilators, manual hyperinflation and use of mechanical insufflation-exsufflation (MI-E). Our aim is to identify current airway care practices for invasively ventilated patients in intensive care units (ICU) in the Netherlands. A self–administered web-based survey was sent to a single pre–appointed representative of all ICUs in the Netherlands. Response rate was 85% (72 ICUs). We found substantial heterogeneity in the intensity and combinations of airway care interventions used. Most (81%) ICUs reported using heated humidification as a routine prophylactic intervention. All (100%) responding ICUs used nebulized mucolytics and/or bronchodilators; however, only 43% ICUs reported nebulization as a routine prophylactic intervention. Most (81%) ICUs used manual hyperinflation, although only initiated with a clinical indication like difficult oxygenation. Few (22%) ICUs used MI-E for invasively ventilated patients. Use was always based on the indication of insufficient cough strength or as a continuation of home use. In the Netherlands, use of routine prophylactic airway care interventions is common despite evidence of no benefit. There is an urgent need for evidence of the benefit of these interventions to inform evidence-based guidelines.

The Shikani HME: A New Tracheostomy Heat and Moisture Exchanger

Purpose Tracheostomy patients face many adversities including loss of phonation and essential airway functions including air filtering, warming, and humidification. Heat and moisture exchangers (HMEs) facilitate humidification and filtering of inspired air. The Shikani HME (S-HME) is a novel turbulent airflow HME that may be used in-line with the Shikani Speaking Valve (SSV), allowing for uniquely preserved phonation during humidification. The aims of this study were to (a) compare the airflow resistance (R _airflow) and humidification efficiency of the S-HME and the Mallinckrodt Tracheolife II tracheostomy HME (M-HME) when dry (time zero) and wet (after 24 hr) and (b) determine if in-line application of the S-HME with a tracheostomy speaking valve significantly increases R _airflow over a tracheostomy speaking valve alone (whether SSV or Passy Muir Valve [PMV]). Method A prospective observational ex vivo study was conducted using a pneumotachometer lung simulation unit to measure airflow (Q) amplitude and R _airflow, as indicated by a pressure drop (P _Drop) across the device (S-HME, M-HME, SSV + S-HME, and PMV). Additionally, P _Drop was studied for the S-HME and M-HME when dry at time zero (T₀) and after 24 hr of moisture testing (T₂₄) at Q of 0.5, 1, and 1.5 L/s. Results R _airflow was significantly less for the S-HME than M-HME (T₀ and T₂₄). R _airflow of the SSV + S-HME in series did not significant increase R _airflow over the SSV or PMV alone. Moisture loss efficiency trended toward greater efficiency for the S-HME; however, the difference was not statistically significant. Conclusions The turbulent flow S-HME provides heat and moisture exchange with similar or greater efficacy than the widely used laminar airflow M-HME, but with significantly lower resistance. The S-HME also allows the innovative advantage of in-line use with the SSV, hence allowing concurrent humidification and phonation during application, without having to manipulate either device.

Tracheostomy care and decannulation during the COVID-19 pandemic. A multidisciplinary clinical practice guideline

Purpose

Traditional critical care dogma regarding the benefits of early tracheostomy during invasive ventilation has had to be revisited due to the risk of COVID-19 to patients and healthcare staff. Standard practises that have evolved to minimise the risks associated with tracheostomy must be comprehensively reviewed in light of the numerous potential episodes for aerosol generating procedures. We meet the urgent need for safe practise standards by presenting the experience of two major London teaching hospitals, and synthesise our findings into an evidence-based guideline for multidisciplinary care of the tracheostomy patient.

Methods

This is a narrative review presenting the extensive experience of over 120 patients with tracheostomy, with a pragmatic analysis of currently available evidence for safe tracheostomy care in COVID-19 patients.

Results

Tracheostomy care involves many potentially aerosol generating procedures which may pose a risk of viral transmission to staff and patients. We make a series of recommendations to ameliorate this risk through infection control strategies, equipment modification, and individualised decannulation protocols. In addition, we discuss the multidisciplinary collaboration that is absolutely fundamental to safe and effective practise.

Conclusion

COVID-19 requires a radical rethink of many tenets of tracheostomy care, and controversy continues to exist regarding the optimal techniques to minimise risk to patients and healthcare workers. Safe practise requires a coordinated multidisciplinary team approach to infection control, weaning and decannulation, with integrated processes for continuous prospective data collection and audit.

Active humidification in mechanical ventilation is not associated to an increase in respiratory infectious complications in a quasi-experimental pre-post intervention study

OBJECTIVE

There is controversy regarding the influence of humidification systems upon the incidence of respiratory infections associated to invasive mechanical ventilation (IMV). An evaluation was made of the differences in the incidence of pneumonia and tracheobronchitis associated to mechanical ventilation (VAP and VAT, respectively) with passive and active humidification.

DESIGN

A retrospective pre-post quasi-experimental study was carried out.

SETTING

A polyvalent ICU with 14 beds.

PATIENTS

All patients connected to IMV for >48h during 2014 and 2016 were included.

INTERVENTIONS

During 2014, passive humidification with an hygroscopic heat and moisture exchanger (HME) was used, while during 2016 active humidification with a heated humidifier (HH) and an inspiratory heated wire was used. Identical measures for the prevention of VAP were established (Zero Pneumonia Project).

MAIN OUTCOME MEASURES

The incidence of VAP and VAT was estimated for 1000 days of IMV in both groups, and statistically significant differences were assessed using Poisson regression analysis.

RESULTS

A total of 287 patients were included (116 with HME and 171 with HH). The incidence density of VAP per 1000 days of IMV was 5.68 in the HME group and 5.80 in the HH group (p=ns). The incidence density of VAT was 3.41 and 3.26 cases per 1000 days of VMI with HME and HH respectively (p=ns). The duration of IMV was identified as a risk factor for VAP.

CONCLUSIONS

In our population, active humidification in patients ventilated for >48h was not associated to an increase in respiratory infectious complications.

Tidal Volume Lowering by Instrumental Dead Space Reduction in Brain-Injured ARDS Patients: Effects on Respiratory Mechanics, Gas Exchange, and Cerebral Hemodynamics

Background

Limiting tidal volume (V_T), plateau pressure, and driving pressure is essential during the acute respiratory distress syndrome (ARDS), but may be challenging when brain injury coexists due to the risk of hypercapnia. Because lowering dead space enhances CO₂ clearance, we conducted a study to determine whether and to what extent replacing heat and moisture exchangers (HME) with heated humidifiers (HH) facilitate safe V_T lowering in brain-injured patients with ARDS.

Methods

Brain-injured patients (head trauma or spontaneous cerebral hemorrhage with Glasgow Coma Scale at admission < 9) with mild and moderate ARDS received three ventilatory strategies in a sequential order during continuous paralysis: (1) HME with V_T to obtain a PaCO₂ within 30–35 mmHg (HME1); (2) HH with V_T titrated to obtain the same PaCO₂ (HH); and (3) HME1 settings resumed (HME2). Arterial blood gases, static and quasi-static respiratory mechanics, alveolar recruitment by multiple pressure–volume curves, intracranial pressure, cerebral perfusion pressure, mean arterial pressure, and mean flow velocity in the middle cerebral artery by transcranial Doppler were recorded. Dead space was measured and partitioned by volumetric capnography.

Results

Eighteen brain-injured patients were studied: 7 (39%) had mild and 11 (61%) had moderate ARDS. At inclusion, median [interquartile range] PaO₂/FiO₂ was 173 [146–213] and median PEEP was 8 cmH₂O [5–9]. HH allowed to reduce V_T by 120 ml [95% CI: 98–144], V_T/kg predicted body weight by 1.8 ml/kg [95% CI: 1.5–2.1], plateau pressure and driving pressure by 3.7 cmH₂O [2.9–4.3], without affecting PaCO₂, alveolar recruitment, and oxygenation. This was permitted by lower airway (− 84 ml [95% CI: − 79 to − 89]) and total dead space (− 86 ml [95% CI: − 73 to − 98]). Sixteen patients (89%) showed driving pressure equal or lower than 14 cmH₂O while on HH, as compared to 7 (39%) and 8 (44%) during HME1 and HME2 (p < 0.001). No changes in mean arterial pressure, cerebral perfusion pressure, intracranial pressure, and middle cerebral artery mean flow velocity were documented during HH.

Conclusion

The dead space reduction provided by HH allows to safely reduce V_T without modifying PaCO₂ nor cerebral perfusion. This permits to provide a wider proportion of brain-injured ARDS patients with less injurious ventilation.

Active humidification in mechanical ventilation is not associated to an increase in respiratory infectious complications in a quasi-experimental pre-post intervention study

OBJECTIVE

There is controversy regarding the influence of humidification systems upon the incidence of respiratory infections associated to invasive mechanical ventilation (IMV). An evaluation was made of the differences in the incidence of pneumonia and tracheobronchitis associated to mechanical ventilation (VAP and VAT, respectively) with passive and active humidification.

DESIGN

A retrospective pre-post quasi-experimental study was carried out.

SETTING

A polyvalent ICU with 14 beds.

PATIENTS

All patients connected to IMV for>48hours during 2014 and 2016 were included.

INTERVENTIONS

During 2014, passive humidification with an hygroscopic heat and moisture exchanger (HME) was used, while during 2016 active humidification with a heated humidifier (HH) and an inspiratory heated wire was used. Identical measures for the prevention of VAP were established (Zero Pneumonia Project).

MAIN OUTCOME MEASURES

The incidence of VAP and VAT was estimated for 1000 days of IMV in both groups, and statistically significant differences were assessed using Poisson regression analysis.

RESULTS

A total of 287 patients were included (116 with HME and 171 with HH). The incidence density of VAP per 1000 days of IMV was 5.68 in the HME group and 5.80 in the HH group (p=ns). The incidence density of VAT was 3.41 and 3.26 cases per 1000 days of VMI with HME and HH respectively (p=ns). The duration of IMV was identified as a risk factor for VAP.

CONCLUSIONS

In our population, active humidification in patients ventilated for>48hours was not associated to an increase in respiratory infectious complications.

Heat and moisture exchangers versus heated humidifiers for mechanically ventilated adults and children

BACKGROUND

Invasive ventilation is used to assist or replace breathing when a person is unable to breathe adequately on their own. Because the upper airway is bypassed during mechanical ventilation, the respiratory system is no longer able to warm and moisten inhaled gases, potentially causing additional breathing problems in people who already require assisted breathing. To prevent these problems, gases are artificially warmed and humidified. There are two main forms of humidification, heat and moisture exchangers (HME) or heated humidifiers (HH). Both are associated with potential benefits and advantages but it is unclear whether HME or HH are more effective in preventing some of the negative outcomes associated with mechanical ventilation. This review was originally published in 2010 and updated in 2017.

OBJECTIVES

To assess whether heat and moisture exchangers or heated humidifiers are more effective in preventing complications in people receiving invasive mechanical ventilation and to identify whether the age group of participants, length of humidification, type of HME, and ventilation delivered through a tracheostomy had an effect on these findings.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase and CINAHL up to May 2017 to identify randomized controlled trials (RCTs) and reference lists of included studies and relevant reviews. There were no language limitations.

SELECTION CRITERIA

We included RCTs comparing HMEs to HHs in adults and children receiving invasive ventilation. We included randomized cross-over studies.

DATA COLLECTION AND ANALYSIS

We assessed the quality of each study and extracted the relevant data. Where possible, we analysed data through meta-analysis. For dichotomous outcomes, we calculated the risk ratio (RR) and 95% confidence interval (95% CI). For continuous outcomes, we calculated the mean difference (MD) and 95% CI or standardized mean difference (SMD) and 95% CI for parallel studies. For cross-over trials, we calculated the MD and 95% CI using correlation estimates to correct for paired analyses. We aimed to conduct subgroup analyses based on the age group of participants, how long they received humidification, type of HME and whether ventilation was delivered through a tracheostomy. We also conducted sensitivity analysis to identify whether the quality of trials had an effect on meta-analytic findings.

MAIN RESULTS

We included 34 trials with 2848 participants; 26 studies were parallel-group design (2725 participants) and eight used a cross-over design (123 participants). Only three included studies reported data for infants or children. Two further studies (76 participants) are awaiting classification.There was no overall statistical difference in artificial airway occlusion (RR 1.59, 95% CI 0.60 to 4.19; participants = 2171; studies = 15; I2 = 54%), mortality (RR 1.03, 95% CI 0.89 to 1.20; participants = 1951; studies = 12; I2 = 0%) or pneumonia (RR 0.93, 95% CI 0.73 to 1.19; participants = 2251; studies = 13; I2 = 27%). There was some evidence that hydrophobic HMEs may reduce the risk of pneumonia compared to HHs (RR 0.48, 95% CI 0.28 to 0.82; participants = 469; studies = 3; I2 = 0%)..The overall GRADE quality of evidence was low. Although the overall methodological risk of bias was generally unclear for selection and detection bias and low risk for follow-up, the selection of study participants who were considered suitable for HME and in some studies removing participants from the HME group made the findings of this review difficult to generalize.

AUTHORS' CONCLUSIONS

The available evidence suggests no difference between HMEs and HHs on the primary outcomes of airway blockages, pneumonia and mortality. However, the overall low quality of this evidence makes it difficult to be confident about these findings. Further research is needed to compare HMEs to HHs, particularly in paediatric and neonatal populations, but research is also needed to more effectively compare different types of HME to each other as well as different types of HH.