Ventilator Settings Research Articles

How low should we go? Outcomes of ECMO in neonates with low gestational age or birth weight.

Initial recommendations for ECMO had relative contraindications for low birth weight (BW) or low gestational age (GA) babies. However, more recent literature has demonstrated improved and acceptable outcomes of ECMO in smaller neonates. The purpose of this study was to understand both utilization and survival in patients with lower GA and BW. All neonates captured in the Extracorporeal Life Support Organization (ELSO) registry who underwent a single ECMO run from 2009 to 2019 were included. The primary outcome measure was mortality and the secondary outcome measure was major adverse outcomes, defined as a composite outcome variable any severe ECMO complications. Univariate and multivariable statistical tests were performed to estimate the association between GA and BW with both outcome variables. A total of 14,167 cases met inclusion criteria. Univariate analysis noted that birth weight, gestational age, ECMO mode, pulmonary support type, pH and ventilator settings were highly significant predictors of survival. Multivariable assessment noted significant linear relationship of mortality rates with increasing GA and BW (p < 0.001, OR = 0.82 GA, 0.51 BW). The highest ECMO-related mortality was observed in neonates with GA 30-31weeks and BW 1.5-2.0kg, with a 70-75% in-hospital mortality rate. Decreasing GA and BW were strongly correlated with increasing odds of mortality and/or ECMO-related complications. However, even in low GA or BW neonates, survival may be possible in up to a quarter of patients put on ECMO.

Assessing fluid responsiveness by using functional hemodynamic tests in critically ill patients: a narrative review and a profile-based clinical guide.

Fluids are given with the purpose of increasing cardiac output (CO), but approximately only 50% of critically ill patients are fluid responders. Since the effect of a fluid bolus is time-sensitive, it diminuish within few hours, following the initial fluid resuscitation. Several functional hemodynamic tests (FHTs), consisting of maneuvers affecting heart-lung interactions, have been conceived to discriminate fluid responders from non-responders. Three main variables affect the reliability of FHTs in predicting fluid responsiveness: (1) tidal volume; (2) spontaneous breathing activity; (3) cardiac arrythmias. Most FTHs have been validated in sedated or even paralyzed ICU patients, since, historically, controlled mechanical ventilation with high tidal volumes was the preferred mode of ventilatory support. The transition to contemporary methods of invasive mechanical ventilation with spontaneous breathing activity impacts heart-lung interactions by modifying intrathoracic pressure, tidal volumes and transvascular pressure in lung capillaries. These alterations and the heterogeneity in respiratory mechanics (that is present both in healthy and injured lungs) subsequently influence venous return and cardiac output. Cardiac arrythmias are frequently present in critically ill patients, especially atrial fibrillation, and intuitively impact on FHTs. This is due to the random CO fluctuations. Finally, the presence of continuous CO monitoring in ICU patients is not standard and the assessment of fluid responsiveness with surrogate methods is clinically useful, but also challenging. In this review we provide an algorithm for the use of FHTs in different subgroups of ICU patients, according to ventilatory setting, cardiac rhythm and the availability of continuous hemodynamic monitoring.

A novel breath pattern model and analysis to minimize patient discomfort in medical ventilators

Typical waveforms used for the simulation of pressure and volume-controlled ventilation in medical ventilators have been extensively studied in the literature. The majority of simulation studies reported employ the step pattern or ramp pattern to model the pressure and flow variations in pressure/volume-controlled ventilation. It was observed that the above waveforms tend to add to the discomfort level of patients due to the presence of jerks in derivatives of pressure/flow variations; the pressure/flow variation of air and oxygen mixture should be smooth so that the patient discomfort is kept at a minimal level. To overcome the above-mentioned drawback, a careful study of the flow/pressure simulation using a cycloidal pattern during the inhalation and exhalation phases of the breath cycle was proposed and investigated in this work. Based on transient analysis of the pressure variation simulation, it was observed that the air and oxygen mixture delivered to the patient was relatively jerk-free due to the finite values of first and second-order derivatives of pressure/flow curves. Mathematical models of the proposed simulation study of the cycloidal pattern of flow variation in both pressure/volume-controlled ventilation, are formulated and presented for use by ventilator designers. A comparative study of the simulation of step, ramp and cycloidal profiles applied to the breath cycle in a typical pressure-controlled ventilation is carried out and a marginal decrease in tidal volumes was observed in the case of cycloidal profiles for a given set of ventilator settings and the results are discussed. A typical natural breath pattern of a healthy adult was experimentally measured using a CITRIX breath analyser and the above mathematical model for the volume-controlled ventilation was found to closely describe the natural breathing process, using statistical parameters. Thus, the proposed cycloidal profile of pressure/flow variations in medical ventilators will be a better alternative, when compared to the step/ramp profiles investigated in this work; further, the proposed cycloidal profile matches closely with the natural breath pattern, based on typical experimental studies.

Longitudinal Ventilation for Smoke Control and Evacuation in High-Temperature Tunnel Fires

When high-temperature geothermal conditions occur within road tunnels, the safety of emergency exits becomes more challenging, especially in cases of fire. The high background temperature increases the speed of the smoke stratification process, and therefore, is unfavorable for people rescue and safety evacuation. In China, longitudinal ventilation systems are widely used to control the smoke within road tunnels during emergency fire events and help ensure safety evacuation. This paper aims to evaluate the performance of the longitudinal ventilation system when applied to a high-temperature road tunnel. The results show that the high-temperature geothermal in the tunnel will result in an accelerated stratification of the smoke layer, and the ventilation speed must be reasonably adjusted to meet the demands of smoke control. Under an optimal ventilation setting, the smoke density in the passage was reduced and the visibility was dramatically improved, which tremendously increased the evacuation efficiency. Overall, this study provides some practical suggestions for tunnels exposed to high geothermal temperatures, including the potential for variable-speed ventilation systems and localized smoke extraction strategies.

Association of ventilation volumes, pressures and rates with the mechanical power of ventilation in patients without acute respiratory distress syndrome: exploring the impact of rate reduction

SummaryIntroductionHigh mechanical power is associated with mortality in patients who are critically ill and require invasive ventilation. It remains uncertain which components of mechanical power – volume, pressure or rate – increase mechanical power the most.MethodsWe conducted a post hoc analysis of a database containing individual patient data from three randomised clinical trials of ventilation in patients without acute respiratory distress syndrome. The primary endpoint was mechanical power. We used linear regression; double stratification to create subgroups of participants; and mediation analysis to assess the impact of changes in volumes, pressures and rates on mechanical power.ResultsA total of 1732 patients were included and analysed. The median (IQR [range]) mechanical power was 12.3 (9.3–17.1 [3.7–50.1]) J.min‐1. In linear regression, respiratory rate (36%) and peak pressure (51%) explained most of the increase in mechanical power. Increasing quintiles of peak pressure stratified on constant levels of respiratory rate resulted in higher risks of high mechanical power (relative risk 2.2 (95%CI 1.8–2.6), p &lt; 0.01), while decreasing quintiles of respiratory rate stratified on constant levels of peak pressure resulted in lower risks of high mechanical power (relative risk 0.2 (95%CI 0.2–0.3), p &lt; 0.01). Mediation analysis showed that a reduction in respiratory rate, with the increase in tidal volume, partially mediates an effect of reduction in mechanical power (average causal mediation effect ‐0.10, 95%CI ‐0.12 to ‐0.09, p &lt; 0.01), but still with a direct effect of tidal volume on mechanical power (average direct effect 0.15, 95%CI 0.11–0.19, p &lt; 0.01).DiscussionIn this cohort of patients without acute respiratory distress syndrome, pressure and respiratory rate were the most important determinants of mechanical power. The respiratory rate may be the most attractive ventilator setting to adjust when targeting a lower mechanical power.

Impact of Country Income Level on Outcomes in Patients with Acute Brain Injury Requiring Invasive Mechanical Ventilation: A Secondary Analysis of the ENIO Study.

Invasive mechanical ventilation can present complex challenges for patients with acute brain injury (ABI) in middle-income countries (MICs). We characterized the impact of country income level on weaning strategies and outcomes in patients with ABI. A secondary analysis was performed on a registry of critically ill patients with ABI admitted to 73 intensive care units (ICUs) in 18 countries from 2018 to 2020. Patients were classified as high-income country (HIC) or MIC. The primary outcome was ICU mortality. Secondary outcomes were days to first extubation, tracheostomy, extubation failure, ICU length of stay, and hospital mortality. Multivariable analyses were adjusted for clinically preselected covariates such as age, sex, body mass index, neurological severity, comorbidities, and ICU management. Extubation and tracheostomy outcomes were also adjusted for arterial blood gas values and ventilatory settings. Of 1512 patients (median age = 54years, 66% male), 1170 (77%) were from HICs, and 342 (23%) were from MICs. Median age was significantly lower in MICs [35 (range 26-52) vs. 58 (range 45-68) years in HICs]. Neurosurgical procedures (47.7% vs. 38.2%) and decompressive craniectomy (30.7% vs. 15.9%) were more common in MICs, whereas intracranial pressure monitoring (12.0% vs. 51.5%) and external ventricular drain (7.6% vs. 35.6%) were less common. Compared with HICs, patients from MICs had 2.27 times the odds of ICU mortality [p = 0.009, 95% confidence interval (CI) 1.22-4.21]. Frequency of extubation failure was lower in MICs but not significant after adjustment. Patients from MICs had 3.38 times the odds of tracheostomy (p ≤ 0.001, 95% CI 2.28-5.01), 5.59days shorter mean ICU stay (p < 0.001, 95% CI - 7.82 to - 3.36), and 1.96 times the odds of hospital mortality (p = 0.011, 95% CI 1.17-3.30). In an international registry of patients with ABI requiring invasive mechanical ventilation, MICs had higher odds of ICU mortality, tracheostomy placement, and hospital mortality compared with HICs, which may be due to difference in neurocritical care resources and management.

Reversion of Supra-Ventricular Tachycardia Through High Positive End-Expiratory Pressure During Mechanical Ventilation in Critically Ill Patients.

The Valsalva manoeuvre is widely recognised for its effectiveness in reverting supra-ventricular tachycardia (SVT) in patients with good coordination. However, this is not applicable in sedated ventilated patients and there is a dearth of literature regarding the application of Valsalva in unconscious patients on mechanical ventilation. The authors, for the first time, present a novel non-pharmacological method to treat SVT in critically ill patients on mechanical ventilation, employing the high positive end-expiratory pressure (PEEP) technique. This method successfully reverted SVT in two patients. While the exact mechanism remains unconfirmed, it is believed to be similar to that of the Valsalva manoeuvre. Further research is needed to validate this technique and determine the optimal ventilator settings, including the PEEP threshold, for such cases. Key Words: Valsalva manoeuvre, Supraventricular tachycardia, Positive end-expiratory pressure, Mechanical ventilation.

Initiating Mechanical Ventilation in Critically Ill Patients: Case-based Clinical Review

Abstract Mechanical Ventilation continues to be an integral part of critical care on which patients with respiratory failure often depend on for their survival. Specific criteria that need to be met to justify initiating MV include a patient dependency assessment, a clinical indication as well as the ventilator settings that are most appropriate. Hypoxemic respiratory failure, hypercapnic respiratory failure and the need for airway protection are the common indications to initiate MV. This review uses case-based to discuss the initiation of MV. Some of the clinical use settings include Acute Respiratory Distress Syndrome (ARDS), Pneumonia, Chronic Obstructive Pulmonary Disease (COPD) exacerbations, Trauma with altered mental status. Specific scenarios of patients, clinical management and intervention measures are described for every condition to help with the best approach. The review placed special focus on assessment before intubation, the type of mechanical ventilation to choose-VCV or PCV, and the settings to be used: TVs, RR, PEEP and FiO2. Further, it highlights the topic of focussed monitoring, common ventilator problems, and the Weaning phase from MV. The review outlines certain well-documented antecedent knowledge failures of young medicos and also intensivists that need to be corrected in their curriculums for enhancing their ventilator management competencies. Knowledge of MV initiation, strict supervision, and preparation for the cessation of MV is important in order to enhance the results of the patients within the Intensive Care Unit. It is mandatory and more important to see clinical signs like bilateral symmetric chest expansion than looking at the values on the ventilator alone. The presented case-based examples provide practical translation of theoretical information into the clinical practice and enhance the development of the clinical decision-making in the framework of critical care medicine. We definitely need a curriculum integration to decrease the phobia among the new entrants to the intensive care unit whether its medical or paramedical personnel.

Effects of Automated Versus Conventional Ventilation on Quality of Oxygenation—A Substudy of a Randomized Crossover Clinical Trial

Background/Objectives: Attaining adequate oxygenation in critically ill patients undergoing invasive ventilation necessitates intense monitoring through pulse oximetry (SpO2) and frequent manual adjustments of ventilator settings like the fraction of inspired oxygen (FiO2) and the level of positive end-expiratory pressure (PEEP). Our aim was to compare the quality of oxygenation with the use of automated ventilation provided by INTELLiVENT–Adaptive Support Ventilation (ASV) vs. ventilation that is not automated, i.e., conventional pressure-controlled or pressure support ventilation. Methods: A substudy within a randomized crossover clinical trial in critically ill patients under invasive ventilation. The primary endpoint was the percentage of breaths in an optimal oxygenation zone, defined by predetermined levels of SpO2, FiO2, and PEEP. Secondary endpoints were the percentage of breaths in acceptable or critical oxygenation zones, the percentage of time spent in optimal, acceptable, and critical oxygenation zones, the number of manual interventions at the ventilator, and the number and duration of ventilator alarms related to oxygenation. Results: Of the 96 patients included in the parent study, 53 were eligible for this current subanalysis. Among them, 31 patients were randomized to start with automated ventilation, while 22 patients began with conventional ventilation. No significant differences were found in the percentage of breaths within the optimal zone between the two ventilation modes (median percentage of breaths during automated ventilation 19.4 [0.1–99.9]% vs. 25.3 [0.0–100.0]%; p = 0.963). Similarly, there were no differences in the percentage of breaths within the acceptable and critical zones, nor in the time spent in the three predefined oxygenation zones. Although the number of manual interventions was lower with automated ventilation, the number and duration of ventilator alarms were fewer with conventional ventilation. Conclusions: The quality of oxygenation with automated ventilation is not different from that with conventional ventilation. However, while automated ventilation comes with fewer manual interventions at the ventilator, it also comes with more ventilator alarms.

Impact of zero-positive end-expiratory pressure on blood transfusion rates in off-pump coronary artery bypass surgery: a retrospective cohort study

BackgroundBleeding are common in cardiac surgery, with significant impacts on transfusion-related complications and patient prognosis. This study aimed to determine the differences in perioperative blood loss, transfusion rates, and the incidence of postoperative pulmonary complications (PPCs) with and without the use of positive end-expiratory pressure (PEEP) in patients undergoing off-pump coronary artery bypass graft surgery (OPCAB).MethodsThis single-center, retrospective study included 106 adult patients undergoing coronary artery bypass surgery without cardiopulmonary bypass from January 2018 to March 2022. The patients were divided into two groups based on intraoperative ventilator settings: the zero-PEEP (ZEEP) group and the PEEP group. The primary outcome was the perioperative transfusion rate from the intraoperative period to postoperative 7 day. The incidence of PPCs was recorded for 1 week post-operatively. Logistic regression analysis was performed for statistical analysis.ResultsThe average PEEP in the PEEP group was 4.92 ± 0.42 cmH2O. Multiple regression analysis indicated that lower mean airway pressure during surgery tend to associate with intraoperative lower blood loss. The intraoperative transfusion rates in the ZEEP group were significantly lower than those in the PEEP group (ZEEP:14%, PEEP 38.4%, P = 0.02). Logistic regression analysis revealed that ZEEP (adjusted odds ratio [OR] 0.13, 95% confidence interval [CI] 0.04–0.78) and Society of Thoracic Surgeons(STS) scores (adjusted OR 2.31, 95% CI 1.53–3.49) were significantly associated with a reduced requirement for perioperative transfusions. No significant difference was observed between the two groups in terms of PPCs (p = 0.824). Atelectasis was the most common complication in both groups (ZEEP: 35.7%, PEEP: 40%, P = 0.832).ConclusionsZEEP and STS scores were associated with significantly reduced requirement for perioperative transfusion rates during elective OPCAB surgery. However, ZEEP did not significantly affect the incidence of PPCs.

Ecological impact of anesthesia: Analysis of sevoflurane consumption as a greenhouse gas

Abstract Background and Aims: According to the World Health Organization, climate change represents a threat to global health. Healthcare activities must understand their ecological impact and reduce their environmental footprint. Decreasing greenhouse gas emissions is a major health priority, to which all healthcare establishments should commit. We sought to understand whether anesthesiologists were aware of the impact of sevoflurane consumption on climate and whether they were inclined to implement eco-friendly strategies. Material and Methods: We assessed the knowledge of anesthesiologists about sevoflurane consumption and its impact on climate change. Overall, 152 anesthesiologists from Belgium, France, and Italy answered our questionnaire in April 2024. The database from the computerized anesthesia protocol was used to evaluate the average annual sevoflurane consumption at our Belgian institution between January 2015 and March 2022. The sevoflurane quantities used were obtained from information provided by the ventilator after each procedure. Potential savings were based on scientific recommendations regarding anesthesia ventilator settings. The analysis was based on the comparison between these data. Results: With optimized sevoflurane consumption conditions, the emission of 36.156 tons of CO2 could have been avoided, corresponding to 144,623 Km driven per year. The financial impact calculated was a saving of 533,525€ over 8 years. The survey highlighted that anesthesiologists were ready to embrace eco-friendly practices to reduce global pollution. Conclusions: We must invest in information and awareness-raising for anesthesiologists from the start of their medical training so that we can move toward a more eco-responsible practice to achieve major ecological and economic benefits.

Heart Rate Variability During Weaning from Invasive Mechanical Ventilation: A Systematic Review.

Background: The role of Heart Rate Variability (HRV) indices in predicting the outcome of the weaning process remains a subject of debate. The aim of this study is to investigate HRV analysis in critically ill adult patients undergoing weaning from invasive mechanical ventilation (IMV). Methods: The protocol of this systematic review was registered with PROSPERO (CRD42024485800). We searched PubMed and Scopus databases from inception till March 2023 to identify randomized controlled trials and observational studies investigating HRV analysis in critically ill adult patients undergoing weaning from invasive mechanical ventilation. Our primary outcome was to investigate HRV changes occurring during the weaning from IMV. Results: Seven studies (n = 342 patients) were included in this review. All studies reported significant changes in at least one HRV parameter. The indices Low Frequency (LF), High Frequency (HF), and LF/HF ratio seem to be the most promising in predicting the outcome of weaning with reliability. Some HRV indices showed modification in response to different ventilator settings or modalities. Conclusions: Available data report HRV modifications during the process of weaning and suggest a promising role of some HRV indices in predicting weaning outcomes in critically ill patients. Point-of-care HRV monitoring systems might help to early detect patients at risk of weaning failure.

ECMO-weaning facilitated by neurally adjusted ventilatory assist (NAVA): a case for principal clarification.

The use of veno-venous extracorporeal membrane oxygenation (VV-ECMO) has become increasingly prevalent, particularly in respiratory disease pandemics such as H1N1-influenza and SARS-CoV-2. This surge has emphasized the importance of clear therapy recommendations, improved accessibility to ECMO technology, established ECMO teams, and structured networks to ensure access to specialized care throughout the course of the disease for patients with severe ARDS. Although the initiation criteria for VV-ECMO are well defined, treatment strategies while on ECMO regarding e.g., ventilator management or ECMO weaning strategies remain variable and with lack of consensus. NAVA (Neurally Adjusted Ventilatory Assist), as an assisted mechanical ventilation modality, offers real-time electromyographic feedback, which has been shown to enhance prolonged weaning processes from mechanical ventilation. We present a case of penetrating thoracic trauma complicated by ARDS, successfully managed with VV-ECMO. NAVA was employed to monitor and facilitate ECMO. This approach integrates ECMO weaning with ventilation settings, considering both gas exchange lung function, such as carbon dioxide removal, and respiratory mechanics in the form of neuromuscular coupling. This is a new approach to VV-ECMO weaning. More research is planned to validate the efficacy of this method in conjunction with additional parameters, such as diaphragm activity evaluated sonographically in a randomized design. This case underscores the potential of NAVA in VV-ECMO weaning, offering a promising avenue for optimizing patient care and outcomes.

Predictors of VILI risk: driving pressure, 4DPRR and mechanical power ratio—an experimental study

BackgroundVentilator-induced lung injury (VILI) is one of the side effects of mechanical ventilation during ARDS; a prerequisite for averting it is the quantification of its risk factors associated with a given ventilatory setting. Many clinical variables have been proposed as predictors of VILI, of which driving pressure is the most widely used. In this study, we compared the performance of driving pressure, four times the driving pressure added to respiratory rate (4DPRR) and mechanical power ratio.ResultsIn a study population of 121 previously healthy pigs exposed to harmful ventilation, we compared the association of driving pressure, 4DPRR and mechanical power ratio to lung weight, lung wet-to-dry and total histological score. All the three variables were associated with these outcomes. Driving pressure, 4DPRR and mechanical power ratio increase linearly with the lung weight (adjusted R2 of 0.27, 0.36 and 0.40, respectively), the lung wet-to-dry ratio (adjusted R2 of 0.19, 0.25 and 0.37) and the total histological score (adjusted R2 of 0.26, 0.38 and 0.26). Using a multiple linear regression model with forward analysis, starting with tidal volume and progressively adding respiratory rate and positive end-expiratory pressure, and comparing the topic with the outcome variables, we obtained R2 values, respectively, of 0.07, 0.20, 0.42 for lung weight, 0.09, 0.19, 0.26 for lung wet-to-dry ratio and 0.07, 0.27, 0.43 for total histological score.ConclusionsDriving pressure, 4DPRR and mechanical power ratio, were all associated with lung injury in healthy animals undergoing mechanical ventilation.

Rethinking ARDS classification: oxygenation impairment fails to predict VILI risk.

The selection and intensity of respiratory support for ARDS are guided by PaO2/FiO2. However, ventilator-induced lung injury (VILI) is linked to respiratory mechanics and ventilator settings. We explored whether the VILI risk is related to ARDS severity based on oxygenation. We analysed data on 228 ARDS subjects with PaO2/FiO2 < 200mmHg, categorized into three severity groups: one based on PaO2/FiO2 ratio, and the others based on tertiles of predictors of VILI: mechanical power ratio (MPR) and driving pressure (DP). In each group of oxygenation-based ARDS severity and MPR and DP tertiles, we measured CT anatomy, gas exchange, respiratory mechanics, VILI prerequisites (lung elastance and lung gas volume), and VILI determinants (tidal volume, PEEP, airway pressures). Predictors of VILI, such as MPR and DP, were similar across ARDS severity groups based on PaO2/FiO2 ratio, while oxygenation remained comparable across different levels of VILI risk defined by MPR and DP. Oxygenation impairment was associated with increased lung weight, recruitability, and reduced well-inflated tissue. In contrast, MPR and DP tertiles affected variables associated with the baby lung size, such as lung gas volume and well-inflated tissue. Mechanical ventilation intensity increased progressively across MPR and DP tertiles, but remained similar across PaO2/FiO2 severity groups. ARDS severity based on oxygenation impairment does not reflect the prerequisites and determinants of VILI. This should prompt a reconsideration of recommending respiratory support based on oxygenation impairment, rather than VILI determinants.

Effects of different ventilatory settings on alveolar and pulmonary microvessel dimensions in pigs

Mechanical ventilation with high tidal volume (TV) or positive end-expiratory pressure (PEEP) may induce lung overinflation and increased pulmonary vascular resistance to flow. In 8 healthy mechanically ventilated pigs, we evaluated whether incident dark field (IDF) vital microscopy, applied through a small thoracotomy, could be used to evaluate changes in alveolar and pulmonary microvessel dimensions under different ventilator settings. High TV (12 ml/kg) increased alveolar diameters (from 99 ± 13 to 114 ± 6 μm, p < 0.05 repeated measures one way analysis of variance) and reduced septal capillary diameters (from 12.1 ± 1.7 to 10.5 ± 1.4 μm, p < 0.001) as compared to 8 ml/kg TV. This effect was more pronounced in non-dependent lung. Alveolar and microvessel diameters did not change with high PEEP (12 cmH2O Vs. 5 cmH2O). High FiO2 (100%) led to pulmonary vasodilation (from 12.1 ± 1.7 to 14.7 ± 1.4 μm, p < 0.001), with no change in alveolar dimensions as compared to 50% FiO2. In conclusion, IDF imaging enabled to obtain high-quality images of subpleural alveoli and microvessels. High TV ventilation may induce alveolar distension with compression of septal capillaries, thus potentially increasing dead space ventilation.

Immediate postinjury extracorporeal carbon dioxide removal reduces ventilator requirements and mitigates acute respiratory distress syndrome in swine.

Awareness of ventilator-induced lung injury contributed to increased use of extracorporeal interventions, but not immediately after injury, before acute respiratory distress syndrome (ARDS) ensues. Our objective was to evaluate the role of venovenous extracorporeal carbon dioxide removal (ECCO2R) in management of mechanically ventilated swine with smoke inhalation injury and 40% body surface area burns. Yorkshire swine (n = 29, 43.2 ± 0.5 kg) underwent anesthesia, instrumentation, severe smoke inhalation, and 40% body surface area burns, followed by 72 hours of round-the-clock intensive care unit care with mechanical ventilation, fluids, pressors, bronchoscopic cast removal, computer tomography scans, and arterial blood assays. Within 1 hour after injury, animals received ECCO2R with either MiniLung (Xenios AG, Heilbronn, Germany; n = 10) or Hemolung (ALung Technologies, Pittsburgh, PA; n = 10), or no ECCO2R in injured controls (INJC, n = 12). Immediate postinjury ECCO2R reduced minute ventilation (p < 0.001) and prevented ARDS in 37.5% of MiniLung and 11.1% of Hemolung animals. Time to ARDS (partial pressure of arterial oxygen to fraction of inspired oxygen ratio below 300) was shortest (14 ± 2.2 hours) in INJC, intermediate (21.6 ± 3.5 hours) in Hemolung (HEMO), and most delayed in MiniLung (31.1 ± 7.2 hours, p = 0.0121, log-rank test vs. INJC). Driving pressure was lower in MiniLung versus INJC (p < 0.0001) and HEMO versus INJC (p = 0.0005) at 48 hours. Extracorporeal CO2 removal reduced systemic levels of tumor necrosis factor α versus INJC. In swine with severe smoke inhalation and burns, immediate postinjury ECCO2R reduced ventilator settings, delayed or prevented ARDS, and reduced its severity. Proactive early percutaneous ECCO2R initiation via simplified, purpose-built devices should be considered as a low-maintenance lung injury management approach with significant disease modifying clinical benefit potential.

Effect of tissue viscoelasticity on delivered mechanical power in a physical respiratory system model: distinguishing between airway and tissue resistance

Understanding the mechanics of the respiratory system is crucial for optimizing ventilator settings and ensuring patient safety. While simple models of the respiratory system typically consider only flow resistance and lung compliance, lung tissue resistance is usually neglected. This study investigated the effect of lung tissue viscoelasticity on delivered mechanical power in a physical model of the respiratory system and the possibility of distinguishing tissue resistance from airway resistance using proximal pressure measured at the airway opening. Three different configurations of a passive physical model of the respiratory system representing different mechanical properties (Tissue resistance model, Airway resistance model, and No-resistance model) were tested. The same volume-controlled ventilation and parameters were set for each configuration, with only the inspiratory flow rates being adjusted. Pressure and flow were measured with a Datex-Ohmeda S/5 vital signs monitor (Datex-Ohmeda, Madison, WI, USA). Tissue resistance was intentionally tuned so that peak pressures and delivered mechanical energy measured at airway opening were similar in Tissue and Airway Resistance models. However, measurements inside the artificial lung revealed significant differences, with Tissue resistance model yielding up to 20% higher values for delivered mechanical energy. The results indicate the need to revise current methods of calculating mechanical power delivery, which do not distinguish between tissue resistance and airway flow resistance, making it difficult to evaluate and interpret the significance of mechanical power delivery in terms of lung ventilation protectivity.

The role of pleural pressure in inducing pneumothorax and other adverse effects of positive pressure ventilation.

Mechanical ventilation, essential for critically ill patients, contrasts with natural respiration, primarily due to differences in pleural pressure (Ppleural ). Natural inspiration decreases Ppleural , pulling the lungs away from the thoracic wall, whereas positive pressure inspiration increases Ppleural , pushing the lungs against the thoracic wall. This shift has several consequences. First, elevated Ppleural during positive pressure ventilation can lead to cyclic airway closure, particularly in the dependent lung regions. This increases the risk of atelectasis, that impairs oxygenation and may lead to further complications such as pneumonia. Second, the increase in Ppleural disrupts the balance maintained by negative Ppleural and capillary forces. This disruption reduces the lubricating pleural fluid between the pleurae, increasing friction and shear stress on the lung tissues, which may lead to damage and conditions such as ventilator-induced lung injury and pneumothorax. Furthermore, airway closure can worsen lung compliance, making mechanical ventilation more challenging and increasing the risk of lung overstretching. This necessitates careful management of ventilation settings, particularly the use of positive end-expiratory pressure (PEEP) and recruitment maneuvers to minimize these adverse effects. Protective strategies, such as synchronizing mechanical ventilation with the patient's breathing efforts, prone positioning, and careful application of PEEP, are crucial in reducing Ppleural and its associated risks. Since negative pressure ventilation (NPV) inherently lowers Ppleural , it may help avoid many of the adverse side effects previously discussed. Therefore, reconsidering and reintroducing NPV in a modern context should be seriously explored.

Development and Verification of Microclimate Control System for Enhanced Driver Comfort and Safety Based on Skin Resistance Measurements

Abstract This study deals with the design and construction of a device that enhances driver comfort and safety by automatically adjusting the microclimate in the vehicle cabin based on real-time skin resistance measurements. Using electrodes attached to driver‘s skin and an Arduino microcontroller, the system monitors and evaluates skin conductivity and adjusts heating, ventilation, and air conditioning (HVAC) settings accordingly. Experimental verification in laboratory conditions demonstrated device‘s functionality in changing microclimate parameters. Preliminary results suggest a potential correlation between baseline skin resistance values and the magnitude of observed changes in response to ambient conditions. Subjects with lower baseline skin resistance (≤100,000 Ω) showed smaller changes compared to those with higher baseline resistance (≥100,000 Ω). The current results are graphically processed as the course of skin resistance changes depending on the changing parameters of microclimate.