Lesion characteristics using high-frequency low-tidal volume ventilation versus standard ventilation during ablation of paroxysmal atrial fibrillation.

INTRODUCTION: High-frequency low-tidal-volume (HFLTV) ventilation during radiofrequency catheter ablation (RFCA) for paroxysmal atrial fibrillation (PAF) has been shown to be superior to standard ventilation (SV) in terms of procedural efficiency, acute and long-term clinical outcomes. Our study aimed to compare ablation lesions characteristics utilizing HFLTV ventilation versus SV during RFCA of PAF. METHODS: A retrospective analysis was conducted on patients who underwent pulmonary vein isolation (PVI) for PAF between August 2022 and March 2023, using high-power short-duration ablation. Thirty-five patients underwent RFCA with HFLTV ventilation and were matched with another cohort of 35 patients who underwent RFCA with SV. Parameters including ablation duration, contact force (CF), impedance drop, and ablation index were extracted from the CARTONET database for each ablation lesion. RESULTS: A total of 70 patients were included (HFLTV = 35/2484 lesions, SV = 35/2830 lesions) in the analysis. There were no differences in baseline characteristics between the groups. While targeting the same ablation index, the HFLTV ventilation group demonstrated shorter average ablation duration per lesion (12.3 ± 5.0 vs. 15.4 ± 8.4 s, p < .001), higher average CF (17.0 ± 8.5 vs. 10.5 ± 4.6 g, p < .001), and greater impedance reduction (9.5 ± 4.6 vs. 7.7 ± 4.1 ohms, p < .001). HFLTV ventilation group also demonstrated shorter total procedural time (61.3 ± 25.5 vs. 90.8 ± 22.8 min, p < .001), ablation time (40.5 ± 18.6 vs. 65.8 ± 22.5 min, p < .001), and RF time (15.3 ± 4.8 vs. 22.9 ± 9.7 min, p < .001). CONCLUSION: HFLTV ventilation during PVI for PAF was associated with improved ablation lesion parameters and procedural efficiency compared to SV.

Con: Mechanical Ventilation During Cardiopulmonary Bypass.

The ventilatory strategy to adopt during cardiopulmonary bypass is still being debated. The rationale for using continuous positive airway pressure or mechanical ventilation would be to counteract alveolar collapse and improve ischemia phenomena and passive alveolar diffusion of oxygen. Although there are several studies supporting the hypothesis of a positive effect on oxygenation and systemic inflammatory response, the real clinical impact of ventilation during cardiopulmonary bypass is controversial. Furthermore, the biases present in the literature make the studies' results nonunique in their interpretation.

Anesthetic Techniques for Ablation in Atrial Fibrillation: A Comparative Review.

Atrial fibrillation, the most prevalent cardiac arrhythmia, has witnessed significant advancements in treatment modalities, transitioning from invasive procedures like the maze procedure to minimally invasive catheter ablation techniques. This review focuses on recent improvements in anesthetic approaches that enhance outcomes in catheter atrial fibrillation ablation. We highlight the efficacy of contact force sensing catheters with steerable introducer sheaths, which outperform traditional catheters by ensuring more effective contact time and lesion formation. Comparing general anesthesia with conscious sedation, we find that general anesthesia provides superior catheter stability due to reduced respiratory variability, resulting in more effective lesion formation, and reduced pulmonary vein reconnection. The use of high-frequency jet ventilation under general anesthesia, delivering low tidal volumes, effectively minimizes left atrial movement, decreasing catheter displacement and procedure time, and reducing recurrence in paroxysmal atrial fibrillation. An alternative, high-frequency low tidal volume ventilation using conventional ventilators, also shows improved catheter stability and lesion durability compared to traditional ventilation methods. However, a detailed comparative study of high-frequency jet ventilation, high-frequency low tidal volume ventilation, and conventional mechanical ventilation in catheter ablation for atrial fibrillation is lacking. This review emphasizes the need for such studies to identify optimal anesthetic techniques, potentially enhancing patient outcomes in atrial fibrillation treatment. Our findings suggest that careful selection of anesthetic methods, including ventilation strategies, plays a crucial role in the success of catheter ablation for atrial fibrillation, warranting further research for evidence-based practice.

Hospital Variation in Mortality and Ventilator Management among Mechanically Ventilated Patients with ARDS.

RATIONALE: Acute Respiratory Distress Syndrome (ARDS) is associated with significant mortality. Despite the mortality benefits of lung protective ventilation, adherence rates to evidence-based ventilator practice have remained low and ARDS mortality has remained high. OBJECTIVE: Determine variation in ARDS mortality and adherence to low tidal volume ventilation (LTV) across US hospitals. MATERIALS AND METHODS: We identified mechanically ventilated patients with ARDS using data from Philips eICU (2014-2015). We then used multi-variable hierarchical logistic regression models with hospital site as the random effect and patient and hospital level factors as fixed effects to assess the hospital risk adjusted mortality rate and median odds ratio for the association between mortality and hospital site. We then assessed associations between adherence to LTV (defined as 4-8 mL/kg PBW) and hospital risk adjusted mortality rates using Spearman correlation. RESULTS: Among 4441 patients admitted at 110 hospitals with ARDS, the hospital risk-adjusted mortality rate ranged from 19% to 39%, and the MOR for hospital of admission was 1.33 (95% CI 1.25-1.41). Among 3070 patients at 72 hospitals with available ventilator data, 73% of patients had a median set Vt between 4 to 8 mL/kg PBW; hospital adherence rates to LTV ranged from 13% to 95%. There was no association between hospital adherence to LTV and risk-adjusted mortality rate (spearman correlation coefficient -0.01, p = .93). Similarly, among 956 patients who started with a Vt > 8 mL/kg PBW, there was no association between the percent of patients at each hospital whose Vt was decreased to ≤ 8 mL/kg PBW and risk adjusted mortality rate (spearman correlation coefficient .05, p = .73). CONCLUSION: Risk adjusted mortality and use of LTV for patients with ARDS varied widely across hospitals. However, hospital adherence to LTV was not associated with ARDS mortality rates. Further evaluation of hospital practices associated with lower ARDS mortality are warranted.

Decreased Utilization of Low Tidal Volume Ventilation Outside of the Intensive Care Unit as Compared to Inside.

Background: Investigations into the use of low tidal volume ventilation (LTVV) have been performed for patients in emergency departments (EDs) or intensive care units (ICUs). Practice differences between the ICU and non-ICU care areas have not been described. We hypothesized that the initial implementation of LTVV would be better inside ICUs than outside. Methods: This is a retrospective observational study of patients initiated on invasive mechanical ventilation (IMV) between January 1, 2016, and July 17, 2019. Initial recorded tidal volumes after intubation were used to compare the use of LTVV between care areas. Low tidal volume was considered 6.5 cc/kg of ideal body weight (IBW) or less. The primary outcome was the initiation of low tidal volume. Sensitivity analyses used a tidal volume of 8 cc/kg of IBW or less, and direct comparisons were performed between the ICU, ED, and wards. Results: There were 6392 initiations of IMV: 2217 (34.7%) in the ICU and 4175 (65.3%) outside. LTVV was more likely to be initiated in the ICU than outside (46.5% vs 34.2%; adjusted odds ratio [aOR] 0.62, 95% confidence interval [CI] 0.56-0.71, P < .01). The ICU also had more implementation when PaO2/FiO2 ratio was less than 300, (48.0% vs 34.6%; aOR 0.59, 95% CI 0.48-0.71, P < .01). When comparing individual locations, wards had lower odds of LTVV than the ICU (aOR 0.82, 95% CI 0.70-0.96, P = .02), the ED had lower odds than the ICU (aOR 0.55, 95% CI 0.48-0.63, P < .01), and the ED had lower odds than the wards (aOR 0.66, 95% CI 0.56-0.77, P < .01). Interpretation: Initial low tidal volumes were more likely to be initiated in the ICU than outside. This finding remained when examining only patients with a PaO2/FiO2 ratio less than 300. Care areas outside of the ICU do not employ LTVV as often as ICUs and are, therefore, a possible target for process improvement.

Low tidal volume ventilation for patients undergoing laparoscopic surgery: a secondary analysis of a randomised clinical trial.

BACKGROUND: We recently reported the results for a large randomized controlled trial of low tidal volume ventilation (LTVV) versus conventional tidal volume (CTVV) during major surgery when positive end expiratory pressure (PEEP) was equal between groups. We found no difference in postoperative pulmonary complications (PPCs) in patients who received LTVV. However, in the subgroup of patients undergoing laparoscopic surgery, LTVV was associated with a numerically lower rate of PPCs after surgery. We aimed to further assess the relationship between LTVV versus CTVV during laparoscopic surgery. METHODS: We conducted a post-hoc analysis of this pre-specified subgroup. All patients received volume-controlled ventilation with an applied PEEP of 5 cmH2O and either LTVV (6 mL/kg predicted body weight [PBW]) or CTVV (10 mL/kg PBW). The primary outcome was the incidence of a composite of PPCs within seven days. RESULTS: Three hundred twenty-eight patients (27.2%) underwent laparoscopic surgeries, with 158 (48.2%) randomised to LTVV. Fifty two of 157 patients (33.1%) assigned to LTVV and 72 of 169 (42.6%) assigned to conventional tidal volume developed PPCs within 7 days (unadjusted absolute difference, - 9.48 [95% CI, - 19.86 to 1.05]; p = 0.076). After adjusting for pre-specified confounders, the LTVV group had a lower incidence of the primary outcome than patients receiving CTVV (adjusted absolute difference, - 10.36 [95% CI, - 20.52 to - 0.20]; p = 0.046). CONCLUSION: In this post-hoc analysis of a large, randomised trial of LTVV we found that during laparoscopic surgeries, LTVV was associated with a significantly reduced PPCs compared to CTVV when PEEP was applied equally between both groups. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry no: 12614000790640.

Enhanced protection against lipopolysaccharide-induced acute lung injury by autologous transplantation of adipose-derived stromal cells combined with low tidal volume ventilation in rats.

Adipose-derived stromal cells (ADSCs) showed excellent capacity in regeneration and tissue protection. Low tidal volume ventilation (LVT) strategy demonstrates a therapeutic benefit on the treatment of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). This study, therefore, aimed to undertaken determine whether the combined LVT and ADSCs treatment exerts additional protection against lipopolysaccharide (LPS)-induced ALI in rats. The animals were randomized into seven groups: Group I (control), Group II (instillation of LPS at 10 mg/kg intratracheally), Group III (LPS+LVT 6 ml/kg), Group IV (LPS+intravenous autologous 5 × 106 ADSCs which were pretreated with a scrambled small interfering RNA [siRNA] of keratinocyte growth factor [KGF] negative control), Group V (LPS+ADSCs which were pretreated with a scrambled siRNA of KGF, Group VI (LPS+LVT and ADSCs as in the Group IV), and Group VII (LPS+LVT and ADSCs as in the Group V). We found that levels of tumor necrosis factor-α, transforming growth factor-ß1, and interleukin (IL)-1ß and IL-6, the proinflammatory cytokines, were remarkably increased in LPS rats. Moreover, the expressions of ENaC, activity of Na, K-ATPase, and alveolar fluid clearance (AFC) were obviously reduced by LPS-induced ALI. The rats treated by ADSCs showed improved effects in all these changes of ALI and further enhanced by ADSCs combined with LVT treatment. Importantly, the treatment of ADSCs with siRNA-mediated knockdown of KGF partially eliminated the therapeutic effects. In conclusion, combined treatment with ADSCs and LVT not only is superior to either ADSCs or LVT therapy alone in the prevention of ALI. Evidence of the beneficial effect may be partly due to improving AFC by paracrine or systemic production of KGF and anti-inflammatory properties.

Lung-protective ventilation suppresses systemic and hepatic vein levels of cell-free DNA in porcine experimental post-operative sepsis.

BACKGROUND: Plasma levels of cell-free DNA (cf-DNA) are known to be elevated in sepsis and high levels are associated with a poor prognosis. Mechanical ventilation affects systemic inflammation in which lung-protective ventilation attenuates the inflammatory response. The aim was to study the effect of a lung protective ventilator regime on arterial and organ-specific venous blood as well as on trans-organ differences in cf-DNA levels in a porcine post-operative sepsis model. METHOD: One group of anaesthetised, domestic-breed, 9-12 weeks old, pigs were ventilated with protective ventilation (VT 6 mL x kg- 1, PEEP 10 cmH2O) n = 20. Another group, ventilated with a medium high tidal volume and lower PEEP, served as a control group (VT 10 mL x kg- 1, PEEP 5 cm H2O) n = 10. Blood samples were taken from four sources: artery, hepatic vein, portal vein and, jugular bulb. A continuous endotoxin infusion at 0.25 µg x kg- 1 x h- 1 for 5 h was started following 2 h of laparotomy, which simulated a surgical procedure. Inflammatory cytokines and cf-DNA in plasma were analysed and trans-organ differences calculated. RESULTS: The protective ventilation group had lower levels of cf-DNA in arterial (p = 0.02) and hepatic venous blood (p = 0.03) compared with the controls. Transhepatic differences in cf-DNA were lower in the protective group, compared with the controls (p = 0.03). No differences between the groups were noted as regards the transcerebral, transsplanchnic or the transpulmonary cf-DNA differences. CONCLUSIONS: Protective ventilation suppresses arterial levels of cf-DNA. The liver seems to be a net contributor to the systemic cf-DNA levels, but this effect is attenuated by protective ventilation.

Driving pressure is not associated with mortality in mechanically ventilated patients without ARDS.

BACKGROUND: In patients with acute respiratory distress syndrome (ARDS), low tidal volume ventilation has been associated with reduced mortality. Driving pressure (tidal volume normalized to respiratory system compliance) may be an even stronger predictor of ARDS survival than tidal volume. We sought to study whether these associations hold true in acute respiratory failure patients without ARDS. METHODS: This is a retrospectively cohort analysis of mechanically ventilated adult patients admitted to ICUs from 12 hospitals over 2 years. We used natural language processing of chest radiograph reports and data from the electronic medical record to identify patients who had ARDS. We used multivariable logistic regression and generalized linear models to estimate associations between tidal volume, driving pressure, and respiratory system compliance with adjusted 30-day mortality using covariates of Acute Physiology Score (APS), Charlson Comorbidity Index (CCI), age, and PaO2/FiO2 ratio. RESULTS: We studied 2641 patients; 48% had ARDS (n = 1273). Patients with ARDS had higher mean APS (25 vs. 23, p < .001) but similar CCI (4 vs. 3, p = 0.6) scores. For non-ARDS patients, tidal volume was associated with increased adjusted mortality (OR 1.18 per 1 mL/kg PBW increase in tidal volume, CI 1.04 to 1.35, p = 0.010). We observed no association between driving pressure or respiratory compliance and mortality in patients without ARDS. In ARDS patients, both ΔP (OR1.1, CI 1.06-1.14, p < 0.001) and tidal volume (OR 1.17, CI 1.04-1.31, p = 0.007) were associated with mortality. CONCLUSIONS: In a large retrospective analysis of critically ill non-ARDS patients receiving mechanical ventilation, we found that tidal volume was associated with 30-day mortality, while driving pressure was not.

Acetylcholine receptor antagonists in acute respiratory distress syndrome: much more than muscle relaxants.

Acetylcholine receptor antagonists have been shown to improve outcome in patients with severe acute respiratory distress syndrome. However, it is incompletely understood how these agents improve outcome. In the current editorial, we discuss the mechanisms of action of acetylcholine receptor antagonists beyond neuromuscular blockade.

Apneic Oxygenation Versus Low-Tidal-Volume Ventilation in Anesthetized Cardiac Surgical Patients: A Prospective, Single-Center, Randomized Controlled Trial.

OBJECTIVES: To compare the physiology of apneic oxygenation with low-tidal-volume (VT) ventilation during harvesting of the left internal mammary artery. DESIGN: Prospective, single-center, randomized trial. SETTING: Single-center teaching hospital. PARTICIPANTS: The study comprised 24 patients who underwent elective coronary artery bypass grafting surgery. INTERVENTIONS: Apneic oxygenation (apneic group: 12 participants) and low-VT ventilation (low-VT group: 12 participants) (2.5 mL/kg ideal body weight) for 15 minutes during harvesting of the left internal mammary artery. MEASUREMENT AND MAIN RESULTS: The primary endpoint was an absolute change in partial pressure of arterial carbon dioxide (PaCO2). Secondary endpoints were changes in arterial pH, pulmonary artery pressures (PAP), cardiac index, and pulmonary artery acceleration time and ease of surgical access. The mean (standard deviation) absolute increase in PaCO2 was 31.8 mmHg (7.6) in the apneic group and 17.6 mmHg (8.2) in the low-VT group (baseline-adjusted difference 14.2 mmHg [95% confidence interval 21.0-7.3], p<0.001). The mean (standard deviation) absolute decrease in pH was 0.15 (0.03) in the apneic group and 0.09 (0.03) in the low-VT group baseline-adjusted difference 0.06 [95% confidence interval 0.03-0.09], p<0.001. Differences in the rate of change over time between groups (time-by-treatment interaction) were observed for PaCO2 (p<0.001), pH (p<0.001), systolic PAP (p = 0.002), diastolic PAP (p = 0.023), and mean PAP (p = 0.034). Both techniques provided adequate ease of surgical access; however, apneic oxygenation was preferred predominantly. CONCLUSIONS: Apneic oxygenation caused a greater degree of hypercarbia and respiratory acidemia compared with low-VT ventilation. Neither technique had deleterious effects on PAP or cardiac function. Both techniques provided adequate ease of surgical access.

Low Tidal Volume Ventilation Is Poorly Implemented for Patients in North American and United Kingdom ICUs Using Electronic Health Records.

BACKGROUND: Low tidal volume ventilation (LTVV; < 8 mL/kg predicted body weight [PBW]) is a well-established standard of care associated with improved outcomes. This study used data collated in multicenter electronic health record ICU databases from the United Kingdom and the United States to analyze the use of LTVV in routine clinical practice. RESEARCH QUESTION: What factors are associated with adherence to LTVV in the United Kingdom and North America? STUDY DESIGN: This was a retrospective, multicenter study across the United Kingdom and United States of patients who were mechanically ventilated. METHODS: Factors associated with adherence to LTVV were assessed in all patients in both databases who were mechanically ventilated for > 48 h. We observed trends over time and investigated whether LTVV was associated with patient outcomes (30-day mortality and duration of ventilation) and identified strategies to improve adherence to LTVV. RESULTS: A total of 5,466 (Critical Care Health Informatics Collaborative [CCHIC]) and 7,384 electronic ICU collaborative research database [eICU-CRD] patients were ventilated for > 48 h and had data of suitable quality for analysis. The median tidal volume (VT) values were 7.48 mL/kg PBW (CCHIC) and 7.91 mL/kg PBW (eICU-CRD). The patients at highest risk of not receiving LTVV were shorter than 160 cm (CCHIC) and 165 cm (eICU-CRD). Those with BMI > 30 kg/m2 (CCHIC OR, 1.9 [95% CI, 1.7-2.13]; eICU-CRD OR, 1.61 [95% CI, 1.49-1.75]) and female patients (CCHIC OR, 2.39 [95% CI, 2.16-2.65]; eICU-CRD OR, 2.29 [95% CI, 2.26-2.31]) were at increased risk of having median VT > 8 mL/kg PBW. Patients with median VT < 8 mL/kg PBW had decreased 30-day mortality in the CCHIC database (CCHIC cause-specific hazard ratio, 0.86 [95% CI, 0.76-0.97]; eICU-CRD cause-specific hazard ratio, 0.9 [95% CI, 0.86-1.00]). There was a significant reduction in VT over time in the CCHIC database. INTERPRETATION: There has been limited implementation of LTVV in routine clinical practice in the United Kingdom and the United States. VT > 8 mL/kg PBW was associated with worse patient outcomes.

Lung Protective Ventilation during Pregnancy: An Observational Cohort Study.

Objectives We sought to describe characteristics of mechanically ventilated pregnant patients, evaluate utilization of low-tidal-volume ventilation (LTVV) and high-tidal-volume ventilation (HTVV) by trimester, and describe maternal and fetal outcomes by ventilation strategy. Study Design This is a retrospective cohort study of pregnant women with mechanical ventilation for greater than 24 hours between July 2012 and August 2020 at a tertiary care academic medical center. We defined LTVV as average daily tidal volume 8 mL/kg of less of predicted body weight, and HTVV as greater than 8 mL/kg. We examined demographic characteristics, maternal and fetal characteristics, and outcomes by ventilation strategy. Results We identified 52 ventilated pregnant women, 43 had LTVV, and 9 had HTVV. Acute respiratory distress syndrome occurred in 73% ( N = 38) of patients, and infection was a common indication for ventilation ( N = 33, 63%). Patients had LTVV more often than HTVV in all trimesters. Obstetric complications occurred frequently, 21% ( N = 11) experienced preeclampsia or eclampsia, and among 43 patients with available delivery data, 60% delivered preterm ( N = 26) and 16% had fetal demise ( N = 7). Conclusion LTVV was utilized more often than HTVV among pregnant women in all trimesters. There was a high prevalence of maternal and fetal morbidity and fetal mortality among our cohort. Key Points Our center utilized low tidal more often than high-tidal-volume ventilation during all trimesters of pregnancy.Prone positioning can be performed at advanced gestations.Infection is a common cause of antepartum ventilation.

High-frequency low-tidal volume ventilation improves procedural and long-term clinical outcomes in persistent atrial fibrillation ablation: Prospective multicenter registry.

BACKGROUND: High-frequency, low-tidal volume (HFLTV) ventilation increases the efficacy and efficiency of radiofrequency catheter ablation (RFCA) of paroxysmal atrial fibrillation. Whether those benefits can be extrapolated to RFCA of persistent atrial fibrillation (PeAF) is undetermined. OBJECTIVE: The purpose of this study was to evaluate whether using HFLTV ventilation during RFCA in patients with PeAF is associated with improved procedural and long-term clinical outcomes compared to standard ventilation (SV). METHODS: In this prospective multicenter registry (REAL-AF), patients who had undergone pulmonary vein isolation (PVI) + posterior wall isolation (PWI) for PeAF using either HFLTV ventilation or SV were included. The primary efficacy outcome was freedom from all-atrial arrhythmias at 12 months. Secondary outcomes included procedural and long-term clinical outcomes and complications. RESULTS: A total of 210 patients were included (HFLTV=95 vs. SV=115) in the analysis. There were no differences in baseline characteristics between the groups. Procedural time (80 [66-103.5] minutes vs 110 [85-141] minutes; P <.001), total radiofrequency (RF) time (18.73 [13.93-26.53] minutes vs 26.15 [20.30-35.25] minutes; P <.001), and pulmonary vein RF time (11.35 [8.78-16.69] minutes vs 18 [13.74-24.14] minutes; P <.001) were significantly shorter using HFLTV ventilation compared with SV. Freedom from all-atrial arrhythmias was significantly higher with HFLTV ventilation compared with SV (82.1% vs 68.7%; hazard ratio 0.41; 95% confidence interval [0.21-0.82]; P = .012), indicating a 43% relative risk reduction and a 13.4% absolute risk reduction in all-atrial arrhythmia recurrence. There was no difference in long-term procedure-related complications between the groups (HFLTV 1.1% vs SV 0%, P = .270). CONCLUSION: In patients undergoing RFCA with PVI + PWI for PeAF, the use of HFLTV ventilation was associated with higher freedom from all-atrial arrhythmias at 12-month follow-up, with significantly shorter procedural and RF times compared to SV, while reporting a similar safety profile.

Physiological Comparison of Airway Pressure Release Ventilation and Low Tidal Volume Ventilation in Acute Respiratory Distress Syndrome: A Randomized Controlled Trial.

BACKGROUND: The physiological effects of different ventilation strategies on patients with acute respiratory distress syndrome (ARDS) need to be better understood. RESEARCH QUESTION: In patients with ARDS under controlled mandatory ventilation, does airway pressure release ventilation (APRV) improve lung ventilation-perfusion matching and ventilation homogeneity compared to low tidal volume ventilation (LTV)? STUDY DESIGN AND METHODS: This study was a single-center randomized controlled trial. Patients with moderate-to-severe ARDS were randomly ventilated on APRV or LTV. Electrical impedance tomography (EIT) was utilized to assess lung ventilation and perfusion. EIT-based data and clinical variables related to respiratory and hemodynamic conditions were collected shortly before randomization (0h), and at 12 and 24 hours after randomization. RESULTS: A total of 40 subjects were included and randomized to the APRV or LTV group (20 per group). During the 24-hour trial period, patients on APRV exhibited significantly increased dorsal ventilation (difference value (24h-0h), median [25-75 percentiles]: 10.82% [2.62-13.74] vs 0.12% [-2.81-4.76], P = .017), decreased dorsal shunt (-4.67% [-6.83-0.59] vs 1.73% [-0.95-5.53], P = .008) and increased dorsal ventilation-perfusion matching (4.13% [-0.26-10.47] vs -3.29% [-5.05-2.81], P = .026) than those on LTV; no difference in ventral dead space was observed between study groups (P = .903). Additionally, two indicators of ventilation distribution heterogeneity: global inhomogeneity index significantly decreased, and center of ventilation significantly increased in the APRV group compared to the LTV group. Patients on APRV had significantly higher PaO2/FiO2, higher respiratory system static compliance (Crs) and lower PaCO2 than those on LTV at 24h. The cardiac output was comparable in both groups. INTERPRETATION: APRV, as compared to LTV, could recruit dorsal region, reduce dorsal shunt, increase dorsal ventilation-perfusion matching, and improve ventilation homogeneity of the lungs, leading to better gas exchange and Crs in patients with moderate-to-severe ARDS.

Delivery of Lung-protective Ventilation for Acute Respiratory Distress Syndrome: A Hybrid Implementation-Effectiveness Trial.

Rationale: Lung-protective ventilation (LPV) improves outcomes for patients with acute respiratory distress syndrome (ARDS), but adherence remains inadequate. Objectives: To measure the process and clinical impacts of implementation of a science-based intervention to improve LPV adherence for patients with ARDS, in part by increased use of clinical decision support (CDS). Methods: We conducted a type III hybrid implementation/effectiveness pilot trial enrolling adult patients with ARDS admitted to three hospitals before and after the launch of a multimodal implementation intervention to increase the use of mechanical ventilation CDS and improve LPV adherence. The primary outcome was patients' percentage of time adherent to low tidal volume (⩽6.5 ml/kg predicted body weight) ventilation (LTVV). Secondary outcomes included adherence to prescribed oxygenation settings, the use of the CDS tool's independent oxygenation and ventilation components, ventilator-free days, and mortality. Analyses employed multivariable regression to compare adjusted pre- versus postintervention outcomes after the exclusion of a postintervention wash-in period. A sensitivity analysis measured process outcomes' level and trend change postintervention using segmented regression. Results: The 446 included patients had a mean age of 60 years, and 43% were female. Demographic and clinical characteristics were similar pre- versus postintervention. The adjusted proportion of adherent time increased postintervention for LTVV (9.2%; 95% confidence interval [CI], 3.8-14.5%) and prescribed oxygenation settings (11.9%; 95% CI, 7.2-16.5%), as did the probability patients spent ⩾90% of ventilated time on LTVV (adjusted odds ratio [aOR] 2.58; 95% CI, 1.64-4.10) and use of ventilation CDS (aOR, 41.3%; 95% CI, 35.9-46.7%) and oxygenation CDS (aOR, 54.3%; 95% CI, 50.9-57.7%). Ventilator-free days (aOR, 1.15; 95% CI, 0.81-1.62) and 28-day mortality (aOR, 0.78; 95% CI, 0.50-1.20) did not change significantly after intervention. Segmented regression analysis supported a causal relationship between the intervention and improved CDS usage but suggested trends before intervention rather than the studied intervention could explain increased LPV adherence after the intervention. Conclusions: In this pilot trial, a multimodal implementation intervention was associated with increased use of ventilator management CDS for patients with ARDS but was not associated with differences in clinical outcomes and may not have independently caused the observed postintervention improvements in LPV adherence. Clinical trial registered with www.clinicaltrials.gov (NCT03984175).

Hospital Variation in Management and Outcomes of Acute Respiratory Distress Syndrome Due to COVID-19.

OBJECTIVES: To describe hospital variation in use of "guideline-based care" for acute respiratory distress syndrome (ARDS) due to COVID-19. DESIGN: Retrospective, observational study. SETTING: The Society of Critical Care Medicine's Discovery Viral Infection and RESPIRATORY ILLNESS UNIVERSAL STUDY COVID-19 REGISTRY. PATIENTS: Adult patients with ARDS due to COVID-19 between February 15, 2020, and April 12, 2021. INTERVENTIONS: Hospital-level use of "guideline-based care" for ARDS including low-tidal-volume ventilation, plateau pressure less than 30 cm H2O, and prone ventilation for a Pao2/Fio2 ratio less than 100. MEASUREMENTS AND MAIN RESULTS: Among 1,495 adults with COVID-19 ARDS receiving care across 42 hospitals, 50.4% ever received care consistent with ARDS clinical practice guidelines. After adjusting for patient demographics and severity of illness, hospital characteristics, and pandemic timing, hospital of admission contributed to 14% of the risk-adjusted variation in "guideline-based care." A patient treated at a randomly selected hospital with higher use of guideline-based care had a median odds ratio of 2.0 (95% CI, 1.1-3.4) for receipt of "guideline-based care" compared with a patient receiving treatment at a randomly selected hospital with low use of recommended therapies. Median-adjusted inhospital mortality was 53% (interquartile range, 47-62%), with a nonsignificantly decreased risk of mortality for patients admitted to hospitals in the highest use "guideline-based care" quartile (49%) compared with the lowest use quartile (60%) (odds ratio, 0.7; 95% CI, 0.3-1.9; p = 0.49). CONCLUSIONS: During the first year of the COVID-19 pandemic, only half of patients received "guideline-based care" for ARDS management, with wide practice variation across hospitals. Strategies that improve adherence to recommended ARDS management strategies are needed.

Lung-Protective Ventilation Over 6 Years at a Large Academic Medical Center: An Evaluation of Trends, Adherence, and Perceptions of Benefit.

The main objective of this study was to evaluate trends in set tidal volumes across all adult ICUs at a large academic medical center over 6 years, with a focus on adherence to lung-protective ventilation (≤ 8-cc/kg ideal body weight). A secondary objective was to survey providers on their perceptions of lung-protective ventilation and barriers to its implementation. DESIGN: Retrospective observational analysis (primary objective) and cross-sectional survey study (secondary objective), both at a single center. PARTICIPANTS: Mechanically ventilated adult patients with a set tidal volume (primary objective) and providers rotating through the Medical and Neurosciences ICUs (secondary objective). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: From 2013 to 2018, the average initial set tidal volume (cc/kg ideal body weight) decreased from 8.99 ± 2.19 to 7.45±1.34 (p < 0.001). The cardiothoracic ICU had the largest change in tidal volume from 11.09 ± 1.96 in 2013 to 7.97 ± 1.03 in 2018 (p < 0.001). Although the majority of tidal volumes across all ICUs were between 6.58 and 8.01 (interquartile range) in 2018, 27% of patients were still being ventilated at volumes greater than 8-cc/kg ideal body weight. Most surveyed respondents felt there was benefit to lung-protective ventilation, though many did not routinely calculate the set tidal volume in cc/kg ideal body weight, and most did not feel it was easily calculable with the current electronic medical record system. CONCLUSIONS: Despite a trend toward lower tidal volumes over the years, in 2018, over a quarter of mechanically ventilated adult patients were being ventilated with tidal volumes greater than 8 cc/kg. Survey data indicate that despite respondents acknowledging the benefits of lung-protective ventilation, there are barriers to its optimal implementation. Future modifications of the electronic medical record, including a calculator to set tidal volume in cc/kg and the use of default set tidal volumes, may help facilitate the delivery of and adherence to lung-protective ventilation.

Effect of Intraoperative Ventilation Strategies on Postoperative Pulmonary Complications: A Meta-Analysis.

Introduction: The role of intraoperative ventilation strategies in subjects undergoing surgery is still contested. This meta-analysis study was performed to assess the relationship between the low tidal volumes strategy and conventional mechanical ventilation in subjects undergoing surgery. Methods: A systematic literature search up to December 2020 was performed in OVID, Embase, Cochrane Library, PubMed, and Google scholar, and 28 studies including 11,846 subjects undergoing surgery at baseline and reporting a total of 2,638 receiving the low tidal volumes strategy and 3,632 receiving conventional mechanical ventilation, were found recording relationships between low tidal volumes strategy and conventional mechanical ventilation in subjects undergoing surgery. Odds ratio (OR) or mean difference (MD) with 95% confidence intervals (CIs) were calculated between the low tidal volumes strategy vs. conventional mechanical ventilation using dichotomous and continuous methods with a random or fixed-effect model. Results: The low tidal volumes strategy during surgery was significantly related to a lower rate of postoperative pulmonary complications (OR, 0.60; 95% CI, 0.44-0.83, p < 0.001), aspiration pneumonitis (OR, 0.63; 95% CI, 0.46-0.86, p < 0.001), and pleural effusion (OR, 0.72; 95% CI, 0.56-0.92, p < 0.001) compared to conventional mechanical ventilation. However, the low tidal volumes strategy during surgery was not significantly correlated with length of hospital stay (MD, -0.48; 95% CI, -0.99-0.02, p = 0.06), short-term mortality (OR, 0.88; 95% CI, 0.70-1.10, p = 0.25), atelectasis (OR, 0.76; 95% CI, 0.57-1.01, p = 0.06), acute respiratory distress (OR, 1.06; 95% CI, 0.67-1.66, p = 0.81), pneumothorax (OR, 1.37; 95% CI, 0.88-2.15, p = 0.17), pulmonary edema (OR, 0.70; 95% CI, 0.38-1.26, p = 0.23), and pulmonary embolism (OR, 0.65; 95% CI, 0.26-1.60, p = 0.35) compared to conventional mechanical ventilation. Conclusions: The low tidal volumes strategy during surgery may have an independent relationship with lower postoperative pulmonary complications, aspiration pneumonitis, and pleural effusion compared to conventional mechanical ventilation. This relationship encouraged us to recommend the low tidal volumes strategy during surgery to avoid any possible complications.

Sex Differences in Use of Low Tidal Volume Ventilation in COVID-19-Insights From the PRoVENT-COVID Study.

The purpose of this study was to compare and understand differences in the use of low tidal volume ventilation (LTVV) between females and males with acute respiratory distress syndrome (ARDS) related to coronavirus disease 2019 (COVID-19). This is a post-hoc analysis of an observational study in invasively ventilated patients with ARDS related to COVID-19 in 22 ICUs in the Netherlands. The primary endpoint was the use of LTVV, defined as having received a median tidal volume (VT) ≤6 ml/kg predicted body weight (PBW) during controlled ventilation. A mediation analysis was used to investigate the impact of anthropometric factors, next to the impact of sex per se. The analysis included 934 patients, 251 females and 683 males. All the patients had ARDS, and there were no differences in ARDS severity between the sexes. On the first day of ventilation, females received ventilation with a higher median VT compared with males [6.8 (interquartile range (IQR) 6.0-7.6 vs. 6.3 (IQR 5.8-6.9) ml/kg PBW; p < 0.001]. Consequently, females received LTVV less often than males (23 vs. 34%; p = 0.003). The difference in the use of LTVV became smaller but persisted over the next days (27 vs. 36%; p = 0.046 at day 2 and 28 vs. 38%; p = 0.030 at day 3). The difference in the use LTVV was significantly mediated by sex per se [average direct effect of the female sex, 7.5% (95% CI, 1.7-13.3%); p = 0.011] and by differences in the body height [average causal mediation effect, -17.5% (-21.5 to -13.5%); p < 0.001], but not by the differences in actual body weight [average causal mediation effect, 0.2% (-0.8 to 1.2%); p = 0.715]. In conclusion, in this cohort of patients with ARDS related to COVID-19, females received LTVV less often than males in the first days of invasive ventilation. The difference in the use of LTVV was mainly driven by an anthropometric factor, namely, body height. Use of LTVV may improve by paying attention to correct titration of VT, which should be based on PBW, which is a function of body height.