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

Ventilator-associated pneumonia: pathobiological heterogeneity and diagnostic challenges

Ventilator-associated pneumonia (VAP) affects up to 20% of critically ill patients and induces significant antibiotic prescription pressure, accounting for half of all antibiotic use in the ICU. VAP significantly increases hospital length of stay and healthcare costs yet is also associated with long-term morbidity and mortality. The diagnosis of VAP continues to present challenges and pitfalls for the currently available clinical, radiological and microbiological diagnostic armamentarium. Biomarkers and artificial intelligence offer an innovative potential direction for ongoing future research. In this Review, we summarise the pathobiological heterogeneity and diagnostic challenges associated with VAP.

Rebound Inverts the Staphylococcus aureus Bacteremia Prevention Effect of Antibiotic Based Decontamination Interventions in ICU Cohorts with Prolonged Length of Stay

Could rebound explain the paradoxical lack of prevention effect against Staphylococcus aureus blood stream infections (BSIs) with antibiotic-based decontamination intervention (BDI) methods among studies of ICU patients within the literature? Two meta-regression models were applied, each versus the group mean length of stay (LOS). Firstly, the prevention effects against S. aureus BSI [and S. aureus VAP] among 136 studies of antibiotic-BDI versus other interventions were analyzed. Secondly, the S. aureus BSI [and S. aureus VAP] incidence in 268 control and intervention cohorts from studies of antibiotic-BDI versus that among 165 observational cohorts as a benchmark was modelled. In model one, the meta-regression line versus group mean LOS crossed the null, with the antibiotic-BDI prevention effect against S. aureus BSI at mean LOS day 7 (OR 0.45; 0.30 to 0.68) inverted at mean LOS day 20 (OR 1.7; 1.1 to 2.6). In model two, the meta-regression line versus group mean LOS crossed the benchmark line, and the predicted S. aureus BSI incidence for antibiotic-BDI groups was 0.47; 0.09-0.84 percentage points below versus 3.0; 0.12-5.9 above the benchmark in studies with 7 versus 20 days mean LOS, respectively. Rebound within the intervention groups attenuated and inverted the prevention effect of antibiotic-BDI against S. aureus VAP and BSI, respectively. This explains the paradoxical findings.

Association of hypernatremia with outcomes of COVID-19 patients: A protocol for systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis aimed to assess the association of hypernatremia with the outcomes of COVID-19 patients.

METHODS

We performed a systematic literature search on PubMed, Google Scholar, and Science Direct until October 2021 and found a total of 131 papers. With meticulous screening finally, 17 papers met the inclusion criteria. COVID-19 patients with sodium levels greater than the reference level were the study population and the outcome of interest was the poor outcome; such as mortality, mechanical ventilation, intensive care unit (ICU) admission, and prolonged hospital stay. The pooled estimate was calculated as the odds ratio (OR).

RESULTS

There were 19,032 patients with hypernatremia in the 17 studies included. An overall random effect meta-analysis showed that hypernatremia was associated with mortality (OR: 3.18 [1.61, 6.28], P < .0001, I2 = 91.99%), prolong hospitalization (OR: 1.97 [1.37, 2.83], P < .001, I2 = 0.00%) and Ventilation (OR: 5.40 [1.89, 15.42], P < .001, I2 = 77.35%), ICU admission (OR: 3.99 [0.89, 17.78], P = .07, I2 = 86.79%). Meta-regression analysis showed the association of age with the ICU outcome of hypernatremia patients. Whereas, other parameters like male, hypertension, chronic kidney disease, and diabetes mellitus did not significantly influence the odds ratio.

CONCLUSION

Hypernatremia was markedly associated with poor outcomes in patients with COVID-19. Hence, a blood ionogram is warranted and special attention must be given to hypernatremia COVID-19 patients.

Humidicare - an implementation study of a novel HME safety device designed to prevent ventilator circuit occlusion due to inadvertent dual humidification

Mechanical ventilation bypasses the protective mechanisms of the upper respiratory tract which are designed to heat and humidify inspired air to 37 °C and 44 mg H₂O/L respectively. Artificial humidification systems are therefore incorporated into ventilation circuits to condition cold and dry medical gases before they reach the lower respiratory tract and cause patient harm. Commonly either a heat and moisture exchanger (HME) or a heated humidifier (HH) are utilised for this purpose, however the inadvertent simultaneous use of both devices within the same circuit can cause critical airway occlusion within 24 h. The Humidicare HME (Medovate, Cambridge, UK) is a safety engineered temperature-dependent warning system designed to activate when inadvertently placed into a warm circuit containing a HH. This study aimed to determine the efficacy of the Humidicare HME warning system in simulated clinical conditions. The threshold temperature for activation of the device was determined in a digital incubator, and the device was tested for efficacy with a HH present or absent from the breathing circuit. The device performed reliably and activated rapidly when required across all simulations. The Humidicare HME warning system is a simple and unobtrusive device which can effectively alert the operator to the error of dual humidification.

Significance of Hypernatremia Due to SARS-CoV-2 Associated ARDS in Critically Ill Patients

Background and Objectives

SARS-CoV-2-induced ARDS is a new entity that should be characterized as it appears to be different from standard ARDS. Hypernatremia is a biological alteration that seems to occur very often in this population without any clear cause. The present study aims to clarify the possible causes of hypernatremia and evaluate its impact on patient outcome.

Patients and Methods

We conducted a retrospective one-day prevalence study in 2 intensive care units, which only treated COVID-19 patients with moderate to severe ARDS. We measured blood and urine electrolytes in all the patients. Patients with chronic renal failure or renal replacement therapy were excluded from the study. Hypernatremia was defined as plasma sodium levels above 145 mmol/L.

Results

Inclusion criteria were met in 17 out of 24 patients. Hypernatremia was present in 52% patients. All had a natriuresis higher than 20 mmol/L and a urine osmolality above 600 mOsm/L. Hypernatremia was acquired in ICU as all the patients had a normal serum sodium level at admission.

Conclusion

The incidence of hypernatremia was elevated and appears to be linked to significant insensible water losses. This should trigger us to optimize the maintenance fluid therapy in critically ill patients with SARS-CoV-2-induced ARDS.

Tracheotomy in the intensive care unit: Guidelines from a French expert panel: The French Intensive Care Society and the French Society of Anaesthesia and Intensive Care Medicine

Tracheotomy is widely used in intensive care units, albeit with great disparities between medical teams in terms of frequency and modality. Indications and techniques are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of tracheotomy in adult critically ill patients developed using the grading of recommendations assessment, development and evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de réanimation de langue française) and the French Society of Anesthesia and Intensive Care Medicine (Société francaise d'anesthésie réanimation) with the participation of the French Emergency Medicine Association (Société française de médecine d'urgence), the French Society of Otorhinolaryngology. Sixteen experts and two coordinators agreed to consider questions concerning tracheotomy and its practical implementation. Five topics were defined: indications and contraindications for tracheotomy in intensive care, tracheotomy techniques in intensive care, modalities of tracheotomy in intensive care, management of patients undergoing tracheotomy in intensive care, and decannulation in intensive care. The summary made by the experts and the application of GRADE methodology led to the drawing up of 8 formal guidelines, 10 recommendations, and 3 treatment protocols. Among the 8 formal guidelines, 2 have a high level of proof (Grade 1±) and 6 a low level of proof (Grade 2±). For the 10 recommendations, GRADE methodology was not applicable and instead 10 expert opinions were produced.

Tracheotomy in the intensive care unit: guidelines from a French expert panel

Tracheotomy is widely used in intensive care units, albeit with great disparities between medical teams in terms of frequency and modality. Indications and techniques are, however, associated with variable levels of evidence based on inhomogeneous or even contradictory literature. Our aim was to conduct a systematic analysis of the published data in order to provide guidelines. We present herein recommendations for the use of tracheotomy in adult critically ill patients developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method. These guidelines were conducted by a group of experts from the French Intensive Care Society (Société de Réanimation de Langue Française) and the French Society of Anesthesia and Intensive Care Medicine (Société Francaise d'Anesthésie Réanimation) with the participation of the French Emergency Medicine Association (Société Française de Médecine d'Urgence), the French Society of Otorhinolaryngology. Sixteen experts and two coordinators agreed to consider questions concerning tracheotomy and its practical implementation. Five topics were defined: indications and contraindications for tracheotomy in intensive care, tracheotomy techniques in intensive care, modalities of tracheotomy in intensive care, management of patients undergoing tracheotomy in intensive care, and decannulation in intensive care. The summary made by the experts and the application of GRADE methodology led to the drawing up of 8 formal guidelines, 10 recommendations, and 3 treatment protocols. Among the 8 formal guidelines, 2 have a high level of proof (Grade 1+/-) and 6 a low level of proof (Grade 2+/-). For the 10 recommendations, GRADE methodology was not applicable and instead 10 expert opinions were produced.

Unusually High Incidences of Staphylococcus aureus Infection within Studies of Ventilator Associated Pneumonia Prevention Using Topical Antibiotics: Benchmarking the Evidence Base

Selective digestive decontamination (SDD, topical antibiotic regimens applied to the respiratory tract) appears effective for preventing ventilator associated pneumonia (VAP) in intensive care unit (ICU) patients. However, potential contextual effects of SDD on Staphylococcus aureus infections in the ICU remain unclear. The S. aureus ventilator associated pneumonia (S. aureus VAP), VAP overall and S. aureus bacteremia incidences within component (control and intervention) groups within 27 SDD studies were benchmarked against 115 observational groups. Component groups from 66 studies of various interventions other than SDD provided additional points of reference. In 27 SDD study control groups, the mean S. aureus VAP incidence is 9.6% (95% CI; 6.9–13.2) versus a benchmark derived from 115 observational groups being 4.8% (95% CI; 4.2–5.6). In nine SDD study control groups the mean S. aureus bacteremia incidence is 3.8% (95% CI; 2.1–5.7) versus a benchmark derived from 10 observational groups being 2.1% (95% CI; 1.1–4.1). The incidences of S. aureus VAP and S. aureus bacteremia within the control groups of SDD studies are each higher than literature derived benchmarks. Paradoxically, within the SDD intervention groups, the incidences of both S. aureus VAP and VAP overall are more similar to the benchmarks.

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.

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

BACKGROUND

The aims of this systematic review and meta-analysis of randomized controlled trials are to evaluate the effects of active heated humidifiers (HHs) and moisture exchangers (HMEs) in preventing artificial airway occlusion and pneumonia, and on mortality in adult critically ill patients. In addition, we planned to perform a meta-regression analysis to evaluate the relationship between the incidence of artificial airway occlusion, pneumonia and mortality and clinical features of adult critically ill patients.

METHODS

Computerized databases were searched for randomized controlled trials (RCTs) comparing HHs and HMEs and reporting artificial airway occlusion, pneumonia and mortality as predefined outcomes. Relative risk (RR), 95% confidence interval for each outcome and I ² were estimated for each outcome. Furthermore, weighted random-effect meta-regression analysis was performed to test the relationship between the effect size on each considered outcome and covariates.

RESULTS

Eighteen RCTs and 2442 adult critically ill patients were included in the analysis. The incidence of artificial airway occlusion (RR = 1.853; 95% CI 0.792-4.338), pneumonia (RR = 932; 95% CI 0.730-1.190) and mortality (RR = 1.023; 95% CI 0.878-1.192) were not different in patients treated with HMEs and HHs. However, in the subgroup analyses the incidence of airway occlusion was higher in HMEs compared with HHs with non-heated wire (RR = 3.776; 95% CI 1.560-9.143). According to the meta-regression, the effect size in the treatment group on artificial airway occlusion was influenced by the percentage of patients with pneumonia (β = -0.058; p = 0.027; favors HMEs in studies with high prevalence of pneumonia), and a trend was observed for an effect of the duration of mechanical ventilation (MV) (β = -0.108; p = 0.054; favors HMEs in studies with longer MV time).

CONCLUSIONS

In this meta-analysis we found no superiority of HMEs and HHs, in terms of artificial airway occlusion, pneumonia and mortality. A trend favoring HMEs was observed in studies including a high percentage of patients with pneumonia diagnosis at admission and those with prolonged MV. However, the choice of humidifiers should be made according to the clinical context, trying to avoid possible complications and reaching the appropriate performance at lower costs.

Cost-Effectiveness Analysis of Heat and Moisture Exchangers in Mechanically Ventilated Critically Ill Patients

Background

Moisturizing, heating and filtering gases inspired via the mechanical ventilation (MV) circuits help to reduce the adverse effects of MV. However, there is still no consensus regarding whether these measures improve patient prognosis, shorten MV duration, decrease airway secretion and lower the incidence of ventilator associated pneumonia (VAP) and other complications.

Objectives

The aim of this study was to study the incremental cost-effectiveness ratio associated with the use of heat and moisture exchangers (HME) filter to prevent VAP compared with the heated humidifiers (HH) presently adopted by intensive care unit (ICU) services within the Brazilian Healthcare Unified System.

Patients and Methods

This study was a cost-effectiveness analysis (CEA) comparing HME and HH in preventing VAP (outcome) in mechanically ventilated adult patients admitted to an ICU of a public university hospital.

Results

The analysis considered a period of 12 months; MV duration of 11 and 12 days for patients in HH and HME groups, respectively and a daily cost of R$ 16.46 and R$ 13.42 for HH and HME, respectively. HME was more attractive; costs ranged from R$ 21,000.00 to R$ 22,000.00 and effectiveness was close to 0.71, compared with a cost of R$ 30,000.00 and effectiveness between 0.69 and 0.70 for HH. HME and HH differed significantly for incremental effectiveness. Even after an effectiveness gain of 1.5% in favor of HH, and despite the wide variation in the VAP rate, the HME effectiveness remained stable. The mean HME cost-effectiveness was lower than the mean HH cost-effectiveness, being the HME value close to R$ 44,000.00.

Conclusions

Our findings revealed that HH and HME differ very little regarding effectiveness, which makes interpretation of the results in the context of clinical practice difficult. Nonetheless, there is no doubt that HME is advantageous. This technology incurs lower direct cost.

Impact of selective digestive decontamination on respiratory tract Candida among patients with suspected ventilator-associated pneumonia. A meta-analysis

The purpose here is to establish the incidence of respiratory tract colonization with Candida (RT Candida) among ICU patients receiving mechanical ventilation within studies in the literature. Also of interest is its relationship with candidemia and the relative importance of topical antibiotic (TA) use as within studies of selective digestive decontamination (SDD) versus other candidate risk factors towards it. The incidence of RT Candida was extracted from component (control and intervention) groups decanted from studies of various TA and non-TA ICU infection prevention methods with summary estimates derived using random effects. A benchmark RT Candida incidence to provide overarching calibration was derived using (observational) groups from studies without any prevention method under study. A multi-level regression model of group level data was undertaken using generalized estimating equation (GEE) methods. RT Candida data were sourced from 113 studies. The benchmark RT Candida incidence is 1.3; 0.9-1.8 % (mean and 95 % confidence intervals). Membership of a concurrent control group of a study of SDD (p = 0.02), the group-wide presence of candidemia risk factors (p < 0.001), and proportion of trauma admissions (p = 0.004), but neither the year of study publication, nor membership of any other component group, nor the mode of respiratory sampling are predictive of the RT Candida incidence. RT Candida and candidemia incidences are correlated. RT Candida incidence can serve as a basis for benchmarking. Several relationships have been identified. The increased incidence among concurrent control groups of SDD studies cannot be appreciated in any single study examined in isolation.

Characterization and Use of a Fiber Optic Sensor Based on PAH/SiO2 Film for Humidity Sensing in Ventilator Care Equipment

OBJECTIVE

To develop a compact probe that can be used to monitor humidity in ventilator care equipment. A mesoporous film of alternate layers of Poly(allylamine hydrochloride) (PAH) and silica (SiO2) nanoparticles (bilayers), deposited onto an optical fibre was used. The sensing film behaves as a Fabry-Perot cavity of low-finesse where the absorption of water vapour changes the optical thickness and produces a change in reflection proportional to humidity.

METHODS

The mesoporous film was deposited upon the cleaved tip of an optical fibre using the layer-by-layer method. The sensor was calibrated in a bench model against a commercially available capacitive sensor. The sensitivity and response time were assessed in the range from 5 % relative humidity (RH) to 95%RH for different numbers of bilayers up to a maximum of nine.

RESULTS

The sensitivity increases with the number of bilayers deposited; sensitivity of 2.28 mV/%RH was obtained for nine bilayers. The time constant of the response was 1.13 s ± 0.30 s which is faster than the commercial device (measured as 158 s). After calibration, the optical fibre humidity sensor was utilised in a bench top study employing a mechanical ventilator. The fast response time enabled changes in humidity in individual breaths to be resolved.

CONCLUSION

Optical fibre sensors have the potential to be used to monitor breath to breath humidity during ventilator care.

SIGNIFICANCE

Control of humidity is an essential part of critical respiratory care and the developed sensor provides a sensitive, compact and fast method of humidity monitoring.

Humidification on Ventilated Patients: Heated Humidifications or Heat and Moisture Exchangers?

The normal physiology of conditioning of inspired gases is altered when the patient requires an artificial airway access and an invasive mechanical ventilation (IMV). The endotracheal tube (ETT) removes the natural mechanisms of filtration, humidification and warming of inspired air. Despite the noninvasive ventilation (NIMV) in the upper airways, humidification of inspired gas may not be optimal mainly due to the high flow that is being created by the leakage compensation, among other aspects. Any moisture and heating deficit is compensated by the large airways of the tracheobronchial tree, these are poorly suited for this task, which alters mucociliary function, quality of secretions, and homeostasis gas exchange system. To avoid the occurrence of these events, external devices that provide humidification, heating and filtration have been developed, with different degrees of evidence that support their use.

Effectiveness of heat and moisture exchangers in preventing ventilator-associated pneumonia in critically ill patients: a meta-analysis

BACKGROUND

Patients may acquire ventilator-associated pneumonia (VAP) by aspirating the condensate that originates in the ventilator circuit upon use of a conventional humidifier. The bacteria that colonize the patients themselves can proliferate in the condensate and then return to the airways and lungs when the patient aspirates this contaminated material. Therefore, the use of HME might contribute to preventing pneumonia and lowering the VAP incidence. The aim of this study was to evaluate how the use of HME impacts the probability of VAP occurrence in critically ill patients.

METHODS

On the basis of the acronym "PICO" (Patient, Intervention, Comparison, Outcome), the question that guided this review was "Do critically ill patients under invasive mechanical ventilation present lower VAP incidence when they use HME as compared with HH?". Two of the authors of this review searched the databases PUBMED/Medline, The Cochrane Library, and Latin-American and Caribbean Literature in Health Sciences, LILACS independently; they used the following keywords: "heat and moisture exchanger", AND "heated humidifier", AND "ventilator-associated pneumonia prevention". This review included papers in the English language published from January 1990 to December 2012.

RESULTS

This review included ten studies. Comparison between the use of HME and HH did not reveal any differences in terms of VAP occurrence (OR = 0.998; 95% CI: 0.778-1.281). Together, the ten studies corresponded to a total sample of 1077 and 953 patients in the HME and HH groups, respectively; heterogeneity among the investigations was low (I(2) < 50%). Information about the outcome mortality was available in only eight of the ten studies. The use of HME and HH did not afford different results in terms of mortality (OR = 1.09; 95% CI: 0.864-1.376). The total sample size was 884 and 762 patients, respectively. Heterogeneity among the studies was low (I(2) = 0.0%).

CONCLUSION

Current meta-analysis was not sufficient to definitely exclude an associate between heat and moisture exchangers and VAP. Despite the methodological limitations found in selected clinical trials, the current meta-analysis suggests that HME does not decrease VAP incidence or mortality in critically ill patients.

Continuous endotracheal tube cuff pressure control system protects against ventilator-associated pneumonia

INTRODUCTION

The use of a system for continuous control of endotracheal tube cuff pressure reduced the incidence of ventilator-associated pneumonia (VAP) in one randomized controlled trial (RCT) with 112 patients but not in another RCT with 142 patients. In several guidelines on the prevention of VAP, the use of a system for continuous or intermittent control of endotracheal cuff pressure is not reviewed. The objective of this study was to compare the incidence of VAP in a large sample of patients (n = 284) treated with either continuous or intermittent control of endotracheal tube cuff pressure.

METHODS

We performed a prospective observational study of patients undergoing mechanical ventilation during more than 48 hours in an intensive care unit (ICU) using either continuous or intermittent endotracheal tube cuff pressure control. Multivariate logistic regression analysis (MLRA) and Cox proportional hazard regression analysis were used to predict VAP. The magnitude of the effect was expressed as odds ratio (OR) or hazard ratio (HR), respectively, and 95% confidence interval (CI).

RESULTS

We found a lower incidence of VAP with the continuous (n = 150) than with the intermittent (n = 134) pressure control system (22.0% versus 11.2%; p = 0.02). MLRA showed that the continuous pressure control system (OR = 0.45; 95% CI = 0.22-0.89; p = 0.02) and the use of an endotracheal tube incorporating a lumen for subglottic secretion drainage (SSD) (OR = 0.39; 95% CI = 0.19-0.84; p = 0.02) were protective factors against VAP. Cox regression analysis showed that the continuous pressure control system (HR = 0.45; 95% CI = 0.24-0.84; p = 0.01) and the use of an endotracheal tube incorporating a lumen for SSD (HR = 0.29; 95% CI = 0.15-0.56; p < 0.001) were protective factors against VAP. However, the interaction between type of endotracheal cuff pressure control system (continuous or intermittent) and endotracheal tube (with or without SSD) was not statistically significant in MLRA (OR = 0.41; 95% CI = 0.07-2.37; p = 0.32) or in Cox analysis (HR = 0.35; 95% CI = 0.06-1.84; p = 0.21).

CONCLUSIONS

The use of a continuous endotracheal cuff pressure control system and/or an endotracheal tube with a lumen for SSD could help to prevent VAP in patients requiring more than 48 hours of mechanical ventilation.

Ventilator-associated pneumonia in patients using HME filters and heated humidifiers

BACKGROUND

Ventilator-associated pneumonia (VAP) is a clinical form of hospital-associated pneumonia, which may develop within 48 h in patients on mechanical ventilation who had no pre-existing pneumonia at the time of intubation.

OBJECTIVE

The objective of this study was to compare the incidence of VAP among patients who started receiving treatment with heat and moisture exchanger (HME) filters and heated humidifiers (HHs) for mechanical ventilation.

METHODS

Patients who were on the first day of intubation, did not have pre-intubation pneumonia, presented to the healthcare centre with no infections at the time of presentation, were not on antibiotic treatment for pulmonary infections and did not have evidence of infiltration with chest radiography were included in the study. Data were evaluated using Fischer's exact, Mann-Whitney's U and t tests.

RESULTS

The patients in the HME filter and HHs groups had a mean age of 47.9 ± 2.2 and 44.5 ± 2.1 years, respectively. Infiltration on chest radiography was identified on day 6.33 for the patients in the HME filter group and on day 5.8 in the HHs group. Patients using HME filters and HHs did not differ significantly with regard to the day of mechanical ventilation and number of days hospitalized (p > 0.5). Comparison of the two groups with regard to presence of fever during the first 24 h, however, demonstrated higher than expected values for the patients using HHs, with a significant difference (p = 0.001).

CONCLUSION

There were no significant differences between the groups on HME filters and heated humidifiers in terms of infection development; although pulmonary radiography showed delayed average days to infiltration development for subjects using HME filters.

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.

Ventilator-associated pneumonia with or without toothbrushing: a randomized controlled trial

Certain guidelines for the prevention of ventilator-associated pneumonia (VAP) recommend oral care with chlorhexidine, but none refer to the use of a toothbrush for oral hygiene. The role of toothbrush use has received scant attention. Thus, the objective of this study was to compare the incidence of VAP in critical care patients receiving oral care with and without manual brushing of the teeth. This was a randomized clinical trial developed in a 24-bed medical-surgical intensive care unit (ICU). Patients undergoing invasive mechanical ventilation for than 24 h were included. Patients were randomly assigned to receive oral care with or without toothbrushing. All patients received oral care with 0.12 % chlorhexidine digluconate. Tracheal aspirate samples were obtained during endotracheal intubation, then twice a week, and, finally, on extubation. There were no significant differences between the two groups of patients in the baseline characteristics. We found no statistically significant differences between the groups regarding the incidence of VAP (21 of 217 [9.7 %] with toothbrushing vs. 24 of 219 [11.0 %] without toothbrushing; odds ratio [OR] = 0.87, 95 % confidence interval [CI] = 0.469-1.615; p = 0.75). Adding manual toothbrushing to chlorhexidine oral care does not help to prevent VAP in critical care patients on mechanical ventilation.

Trocador de calor e umidade: proteção contra infecções pulmonares? Estudo piloto

O objetivo deste trabalho foi realizar um estudo bacteriológico comparativo entre os sistemas de umidificação aquoso aquecido (UAA) e filtro trocador de calor e umidade (FTCU) quanto à colonização bacteriana e a incidência de infecção respiratória em pacientes submetidos à ventilação mecânica (VM). Trata-se de uma pesquisa prospectiva, controlada e randomizada, na qual 15 pacientes internados na Unidade de Terapia Intensiva (UTI) foram distribuídos em dois grupos. O primeiro fez uso de UAA (n=7) e o outro de FTCU (n=8). Foram coletadas amostras da secreção traqueal, condensado do circuito e FTCU na admissão do paciente, no quarto e oitavo dias, e realizada análise bacteriológica dos mesmos. Quanto às características antropométricas, não observou-se diferenças entre os grupos estudados. A prevalência de pneumonia associada à ventilação (PAV) foi de 57,1% no UAA e 62,5% no FTCU. Ao realizar a análise bacteriológica quantitativa entre eles, não foram observadas variações, sugerindo não haver diferença na prevenção de PAV entre os sistemas de umidificação; porém a presença das mesmas bactérias na secreção traqueal e no condensado e ausência destas na membrana do FTCU podem indicar que a principal fonte de contaminação é o próprio paciente.

Infection prevention in the intensive care unit: review of the recent literature on the management of invasive devices

Over the last 5 y, clinical trials investigating products, procedures, and treatments aimed at preventing infections in the intensive care unit have been described. The findings of these studies appear to confirm the effectiveness of certain preventive procedures. With regard to ventilator-associated pneumonia, the efficacies of decontamination of the oral cavity, continuous suction of subglottic secretions, positioning of the patient, selective decontamination of the digestive tract, and (for higher-risk patients) endotracheal tubes coated with silver, have been demonstrated. Medicated catheters and chlorhexidine-based dressings have been found useful for catheter-related bloodstream infections, and medical catheters have also been shown to be efficacious against urinary tract infections. All these procedures can be incorporated into departmental protocols for the prevention of nosocomial infections in the intensive care unit.

Diagnosis, management and prevention of ventilator-associated pneumonia: an update

Ventilator-associated pneumonia (VAP) affects 10-20% of mechanically ventilated patients and is associated with increased morbidity and mortality and high costs. Early diagnosis is crucial for rapid appropriate antimicrobial therapy to be instituted, but debate remains as to the optimal diagnostic strategy. Noninvasive clinical-based diagnosis is rapid but may not be as accurate as invasive techniques. Increased use of biomarkers and advances in genomics and proteomics may help speed up diagnosis. Management of VAP relies principally on appropriate antimicrobial therapy, which should be selected according to individual patient factors, such as previous antibacterial therapy and length of hospitalization or mechanical ventilation, and local infection and resistance patterns. In addition, once bacterial culture and sensitivity results are available, broad-spectrum therapy should be de-escalated to provide a more specific, narrower-spectrum cover. Optimum duration of antibacterial therapy is difficult to define and should be tailored to clinical response. Biomarker levels may be useful to monitor response to therapy. With the high morbidity and mortality, prevention of VAP is important and several strategies have been shown to reduce the rates of VAP in mechanically ventilated patients, including using noninvasive ventilation where possible, and semi-recumbent positioning. Other potentially beneficial preventive techniques include subglottal suctioning, oral decontamination strategies and antimicrobial-coated endotracheal tubes, although further study is needed to confirm the cost effectiveness of these strategies.

Paradoxical ventilator associated pneumonia incidences among selective digestive decontamination studies versus other studies of mechanically ventilated patients: benchmarking the evidence base

Introduction

Selective digestive decontamination (SDD) appears to have a more compelling evidence base than non-antimicrobial methods for the prevention of ventilator associated pneumonia (VAP). However, the striking variability in ventilator associated pneumonia-incidence proportion (VAP-IP) among the SDD studies remains unexplained and a postulated contextual effect remains untested for.

Methods

Nine reviews were used to source 45 observational (benchmark) groups and 137 component (control and intervention) groups of studies of SDD and studies of three non-antimicrobial methods of VAP prevention. The logit VAP-IP data were summarized by meta-analysis using random effects methods and the associated heterogeneity (tau²) was measured. As group level predictors of logit VAP-IP, the mode of VAP diagnosis, proportion of trauma admissions, the proportion receiving prolonged ventilation and the intervention method under study were examined in meta-regression models containing the benchmark groups together with either the control (models 1 to 3) or intervention (models 4 to 6) groups of the prevention studies.

Results

The VAP-IP benchmark derived here is 22.1% (95% confidence interval; 95% CI; 19.2 to 25.5; tau² 0.34) whereas the mean VAP-IP of control groups from studies of SDD and of non-antimicrobial methods, is 35.7 (29.7 to 41.8; tau² 0.63) versus 20.4 (17.2 to 24.0; tau² 0.41), respectively (P < 0.001). The disparity between the benchmark groups and the control groups of the SDD studies, which was most apparent for the highest quality studies, could not be explained in the meta-regression models after adjusting for various group level factors. The mean VAP-IP (95% CI) of intervention groups is 16.0 (12.6 to 20.3; tau² 0.59) and 17.1 (14.2 to 20.3; tau² 0.35) for SDD studies versus studies of non-antimicrobial methods, respectively.

Conclusions

The VAP-IP among the intervention groups within the SDD evidence base is less variable and more similar to the benchmark than among the control groups. These paradoxical observations cannot readily be explained. The interpretation of the SDD evidence base cannot proceed without further consideration of this contextual effect.

Heat and moisture exchangers and breathing system filters: their use in anaesthesia and intensive care. Part 2 - practical use, including problems, and their use with paediatric patients

Heat and moisture exchangers and breathing system filters are intended to replace the normal warming, humidifying and filtering functions of the upper airways. The first part of this review considered the history, principles of operation and efficiency of these devices. The aim of this part of the review is to summarise recent guidelines on the use of these devices and outline the problems that can occur. In particular, the effect of these devices on gas analysis, dead space, resistance to gas flow and blockage of the breathing system is considered. In children, it is important to consider the addition of dead space and resistance to gas flow. A body weight of 2.5 kg is probably the lower weight limit for use with heat and moisture exchangers, and 3 kg for filters. The resistance to gas flow of a heat- and moisture-exchanging filter added to a Mapleson F breathing system can cause a delay in the induction of anaesthesia.

[Applications of noninvasive mechanical ventilation in anesthesiology and postanesthesia recovery care]

Noninvasive ventilation (NIV) can be useful to anesthesiologists working in critical care units, postanesthesia recovery units, operating theaters, or other settings. NIV can help in situations of acute respiratory failure or serve as a preventive measure in patients undergoing interventions under local-regional anesthesia or diagnostic or therapeutic procedures requiring sedation. Successful NIV depends on adequately trained health personnel and the proper choice of material (interfaces, respirators, etc.) for each setting where this modality is used.

Heated humidification versus heat and moisture exchangers for ventilated adults and children

BACKGROUND

Humidification by artificial means must be provided when the upper airway is bypassed during mechanical ventilation. Heated humidification (HH) and heat and moisture exchangers (HME) are the most commonly used types of artificial humidification in this situation.

OBJECTIVES

To determine whether HHs or HMEs are more effective in preventing mortality and other complications in people who are mechanically ventilated.

SEARCH STRATEGY

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 (RCTs).

SELECTION CRITERIA

We included RCTs comparing heat and moisture exchangers (HMEs) to heated humidifiers (HHs) in mechanically ventilated adults and children. We included randomized crossover studies.

DATA COLLECTION AND ANALYSIS

We assessed the quality of each study and extracted the relevant data. Where appropriate, results from relevant studies were meta-analysed for individual outcomes.

MAIN RESULTS

We included 33 trials with 2833 participants, 25 studies were parallel group design (n = 2710) and eight crossover design (n = 123). Only three 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.

AUTHORS' CONCLUSIONS

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 HME 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 paediatric and neonatal populations. As the design of HMEs evolves, evaluation of new generation HMEs will also need to be undertaken.

Prevention of ventilator-associated pneumonia: analysis of studies published since 2004

As the most recent guidelines for the prevention of ventilator-associated pneumonia (VAP) were published four years ago, we have conducted a systematic review to discover whether the recently published articles should further influence existing guidelines. Articles published since 2004 dealing with infection control measures for prevention of VAP were gathered and evaluated in order to identify evidence for the possible modification of routine practice. Special emphasis was placed on randomized controlled trials (RCTs), meta-analyses or systematic reviews and studies applying multi-module interventions. A total of 15 RCTs and seven meta-analyses or systematic reviews were found. In addition to these, five cohort studies were identified where multi-module programmes were introduced for reducing VAP rates. The data lead to the conclusion that topical use of chlorhexidine for oral care is beneficial and subglottic secretion drainage may lead to delayed onset of VAP. The remaining studies had only a minor influence on existing guidelines for the prevention of VAP and confirmed the earlier recommendations in several points. However, the studies investigating multi-module programmes led to a substantial reduction of VAP of between 31 and 57%. The data show that many VAP cases are preventable and that there is room for improvement in many institutions. Often simple interventions are useful for the reduction of VAP rates, for which the best chances appeared to be the application of multi-module programmes. On average a reduction of more than 40% seems to be possible.

Patterns and dynamics of airway colonisation in mechanically-ventilated patients

The aim of this study was to investigate the patterns and dynamics of the microbiota in the airways of ventilated patients. Seventy-four mechanically-ventilated patients were recruited consecutively, and oropharyngeal, tracheal and bronchoalveolar (BAL) fluid specimens were collected 48 h after intubation, and every 72 h thereafter until the patient was extubated or a total of five sample sets had been collected. Ventilator-associated pneumonia (VAP) pathogens were identified, quantified and genotyped. Microbial findings were highly correlated both between airway locations and over time when samples were taken no more than 72 h apart. If no VAP pathogen was present in the oral flora, it was unlikely to be found in a lower airway sample; i.e., the positive predictive value of the oropharyngeal sample was 0.73 (95% CI 0.67-0.80), and the negative predictive value was 0.95 (95% CI 0.92-0.99). Colonisation with Enterobacteriacae, non-fermentative bacteria and Staphylococcus aureus was monoclonal in the airways and over time, whereas colonisation with microbes normally found in the oropharynx, i.e., Haemophilus influenzae, Haemophilus parainfluenzae and Streptococcus pneumoniae, was polyclonal. When antibiotics were used, the chance of recovering VAP pathogens from all sampling sites was reduced three-fold. No correlation was observed between a bacterial count of > or =10(4) CFU/mL in BAL fluid and chest X-rays compatible with VAP.