Recruitment Maneuvers and PEEP Titration

One-lung ventilation with fixed and variable tidal volumes on oxygenation and pulmonary outcomes: A randomized trial

OBJECTIVE

Test the hypothesis that one-lung ventilation with variable tidal volume improves intraoperative oxygenation and reduces postoperative pulmonary complications after lung resection.

BACKGROUND

Constant tidal volume and respiratory rate ventilation can lead to atelectasis. Animal and human ARDS studies indicate that oxygenation improves with variable tidal volumes. Since one-lung ventilation shares characteristics with ARDS, we tested the hypothesis that one-lung ventilation with variable tidal volume improves intraoperative oxygenation and reduces postoperative pulmonary complications after lung resection.

DESIGN

Randomized trial.

SETTING

Operating rooms and a post-anesthesia care unit.

PATIENTS

Adults having elective open or video-assisted thoracoscopic lung resection surgery with general anesthesia were randomly assigned to intraoperative ventilation with fixed (n = 70) or with variable (n = 70) tidal volumes.

INTERVENTIONS

Patients assigned to fixed ventilation had a tidal volume of 6 ml/kgPBW, whereas those assigned to variable ventilation had tidal volumes ranging from 6 ml/kg PBW ± 33% which varied randomly at 5-min intervals.

MEASUREMENTS

The primary outcome was intraoperative oxygenation; secondary outcomes were postoperative pulmonary complications, mortality within 90 days of surgery, heart rate, and SpO2/FiO2 ratio.

RESULTS

Data from 128 patients were analyzed with 65 assigned to fixed-tidal volume ventilation and 63 to variable-tidal volume ventilation. The time-weighted average PaO2 during one-lung ventilation was 176 (86) mmHg in patients ventilated with fixed-tidal volume and 147 (72) mmHg in the patients ventilated with variable-tidal volume, a difference that was statistically significant (p < 0.01) but less than our pre-defined clinically meaningful threshold of 50 mmHg. At least one composite complication occurred in 11 (17%) of patients ventilated with variable-tidal volume and in 17 (26%) of patients assigned to fixed-tidal volume ventilation, with a relative risk of 0.67 (95% CI 0.34-1.31, p = 0.24). Atelectasis in the ventilated lung was less common with variable-tidal volumes (4.7%) than fixed-tidal volumes (20%) in the initial three postoperative days, with a relative risk of 0.24 (95% CI 0.01-0.8, p = 0.02), but there were no significant late postoperative differences. No other secondary outcomes were both statistically significant and clinically meaningful.

CONCLUSION

One-lung ventilation with variable tidal volume does not meaningfully improve intraoperative oxygenation, and does not reduce postoperative pulmonary complications.

Comparison of lung aeration loss in open abdominal oncologic surgeries after ventilation with electrical impedance tomography-guided PEEP versus conventional PEEP: a pilot feasibility study

BACKGROUND

Existing literature lacks high-quality evidence regarding the ideal intraoperative positive end-expiratory pressure (PEEP) to minimize postoperative pulmonary complications (PPCs). We hypothesized that applying individualized PEEP derived from electrical impedance tomography would reduce the severity of postoperative lung aeration loss, deterioration in oxygenation, and PPC incidence.

METHODS

A pilot feasibility study was conducted on 36 patients who underwent open abdominal oncologic surgery. The patients were randomized to receive individualized PEEP or conventional PEEP at 4 cmH2O. The primary outcome was the impact of individualized PEEP on changes in the modified lung ultrasound score (MLUS) derived from preoperative and postoperative lung ultrasonography. A higher MLUS indicated greater lung aeration loss. The secondary outcomes were the PaO2/FiO2 ratio and PPC incidence.

RESULTS

A significant increase in the postoperative MLUS (12.0 ± 3.6 vs 7.9 ± 2.1, P < 0.001) and a significant difference between the postoperative and preoperative MLUS values (7.0 ± 3.3 vs 3.0 ± 1.6, P < 0.001) were found in the conventional PEEP group, indicating increased lung aeration loss. In the conventional PEEP group, the intraoperative PaO2/FiO2 ratios were significantly lower but not the postoperative ratios. The PPC incidence was not significantly different between the groups. Post-hoc analysis showed the increase in lung aeration loss and deterioration of intraoperative oxygenation correlated with the deviation from the individualized PEEP.

CONCLUSIONS

Individualized PEEP appears to protect against lung aeration loss and intraoperative oxygenation deterioration. The advantage was greater in patients whose individualized PEEP deviated more from the conventional PEEP.

Early pathophysiology-driven airway pressure release ventilation versus low tidal volume ventilation strategy for patients with moderate-severe ARDS: study protocol for a randomized, multicenter, controlled trial

BACKGROUND

Conventional Mechanical ventilation modes used for individuals suffering from acute respiratory distress syndrome have the potential to exacerbate lung injury through regional alveolar overinflation and/or repetitive alveolar collapse with shearing, known as atelectrauma. Animal studies have demonstrated that airway pressure release ventilation (APRV) offers distinct advantages over conventional mechanical ventilation modes. However, the methodologies for implementing APRV vary widely, and the findings from clinical studies remain controversial. This study (APRVplus trial), aims to assess the impact of an early pathophysiology-driven APRV ventilation approach compared to a low tidal volume ventilation (LTV) strategy on the prognosis of patients with moderate to severe ARDS.

METHODS

The APRVplus trial is a prospective, multicenter, randomized clinical trial, building upon our prior single-center study, to enroll 840 patients from at least 35 hospitals in China. This investigation plans to compare the early pathophysiology-driven APRV ventilation approach with the control intervention of LTV lung-protective ventilation. The primary outcome measure will be all-cause mortality at 28 days after randomization in the intensive care units (ICU). Secondary outcome measures will include assessments of oxygenation, and physiology parameters at baseline, as well as on days 1, 2, and 3. Additionally, clinical outcomes such as ventilator-free days at 28 days, duration of ICU and hospital stay, ICU and hospital mortality, and the occurrence of adverse events will be evaluated.

TRIAL ETHICS AND DISSEMINATION

The research project has obtained approval from the Ethics Committee of West China Hospital of Sichuan University (2019-337). Informed consent is required. The results will be submitted for publication in a peer-reviewed journal and presented at one or more scientific conferences.

TRIAL REGISTRATION

The study was registered at Clinical Trials.gov (NCT03549910) on June 8, 2018.

Use of stepwise lung recruitment maneuver to predict fluid responsiveness under lung protective ventilation in the operating room

Recent research has revealed that hemodynamic changes caused by lung recruitment maneuvers (LRM) with continuous positive airway pressure can be used to identify fluid responders. We investigated the usefulness of stepwise LRM with increasing positive end-expiratory pressure and constant driving pressure for predicting fluid responsiveness in patients under lung protective ventilation (LPV). Forty-one patients under LPV were enrolled when PPV values were in a priori considered gray zone (4% to 17%). The FloTrac-Vigileo device measured stroke volume variation (SVV) and stroke volume (SV), while the patient monitor measured pulse pressure variation (PPV) before and at the end of stepwise LRM and before and 5 min after fluid challenge (6 ml/kg). Fluid responsiveness was defined as a ≥ 15% increase in the SV or SV index. Seventeen were fluid responders. The areas under the curve for the augmented values of PPV and SVV, as well as the decrease in SV by stepwise LRM to identify fluid responders, were 0.76 (95% confidence interval, 0.61-0.88), 0.78 (0.62-0.89), and 0.69 (0.53-0.82), respectively. The optimal cut-offs for the augmented values of PPV and SVV were > 18% and > 13%, respectively. Stepwise LRM -generated augmented PPV and SVV predicted fluid responsiveness under LPV.

Intraoperative lung protection: strategies and their impact on outcomes

PURPOSE OF REVIEW

The present review summarizes the current knowledge and the barriers encountered when implementing tailoring lung-protective ventilation strategies to individual patients based on advanced monitoring systems.

RECENT FINDINGS

Lung-protective ventilation has become a pivotal component of perioperative care, aiming to enhance patient outcomes and reduce the incidence of postoperative pulmonary complications (PPCs). High-quality research has established the benefits of strategies such as low tidal volume ventilation and low driving pressures. Debate is still ongoing on the most suitable levels of positive end-expiratory pressure (PEEP) and the role of recruitment maneuvers. Adapting PEEP according to patient-specific factors offers potential benefits in maintaining ventilation distribution uniformity, especially in challenging scenarios like pneumoperitoneum and steep Trendelenburg positions. Advanced monitoring systems, which continuously assess patient responses and enable the fine-tuning of ventilation parameters, offer real-time data analytics to predict and prevent impending lung complications. However, their impact on postoperative outcomes, particularly PPCs, is an ongoing area of research.

SUMMARY

Refining protective lung ventilation is crucial to provide patients with the best possible care during surgery, reduce the incidence of PPCs, and improve their overall surgical journey.

The Respiratory Mechanics of COVID-19 Acute Respiratory Distress Syndrome-Lessons Learned?

Acute respiratory distress syndrome (ARDS) is a well-defined clinical entity characterized by the acute onset of diffuse pulmonary injury and hypoxemia not explained by fluid overload. The COVID-19 pandemic brought about an unprecedented volume of patients with ARDS and challenged our understanding and clinical approach to treatment of this clinical syndrome. Unique to COVID-19 ARDS is the disruption and dysregulation of the pulmonary vascular compartment caused by the SARS-CoV-2 virus, which is a significant cause of hypoxemia in these patients. As a result, gas exchange does not necessarily correlate with respiratory system compliance and mechanics in COVID-19 ARDS as it does with other etiologies. The purpose of this review is to relate the mechanics of COVID-19 ARDS to its underlying pathophysiologic mechanisms and outline the lessons we have learned in the management of this clinic syndrome.

Setting positive end-expiratory pressure: does the 'best compliance' concept really work?

PURPOSE OF REVIEW

Determining the optimal positive end-expiratory pressure (PEEP) setting remains a central yet debated issue in the management of acute respiratory distress syndrome (ARDS).The 'best compliance' strategy set the PEEP to coincide with the peak respiratory system compliance (or 2 cmH 2 O higher) during a decremental PEEP trial, but evidence is conflicting.

RECENT FINDINGS

The physiological rationale that best compliance is always representative of functional residual capacity and recruitment has raised serious concerns about its efficacy and safety, due to its association with increased 28-day all-cause mortality in a randomized clinical trial in ARDS patients.Moreover, compliance measurement was shown to underestimate the effects of overdistension, and neglect intra-tidal recruitment, airway closure, and the interaction between lung and chest wall mechanics, especially in obese patients. In response to these concerns, alternative approaches such as recruitment-to-inflation ratio, the nitrogen wash-in/wash-out technique, and electrical impedance tomography (EIT) are gaining attention to assess recruitment and overdistention more reliably and precisely.

SUMMARY

The traditional 'best compliance' strategy for determining optimal PEEP settings in ARDS carries risks and overlooks some key physiological aspects. The advent of new technologies and methods presents more reliable strategies to assess recruitment and overdistention, facilitating personalized approaches to PEEP optimization.

Future directions in ventilator-induced lung injury associated cognitive impairment: a new sight

Mechanical ventilation is a widely used short-term life support technique, but an accompanying adverse consequence can be pulmonary damage which is called ventilator-induced lung injury (VILI). Mechanical ventilation can potentially affect the central nervous system and lead to long-term cognitive impairment. In recent years, many studies revealed that VILI, as a common lung injury, may be involved in the central pathogenesis of cognitive impairment by inducing hypoxia, inflammation, and changes in neural pathways. In addition, VILI has received attention in affecting the treatment of cognitive impairment and provides new insights into individualized therapy. The combination of lung protective ventilation and drug therapy can overcome the inevitable problems of poor prognosis from a new perspective. In this review, we summarized VILI and non-VILI factors as risk factors for cognitive impairment and concluded the latest mechanisms. Moreover, we retrospectively explored the role of improving VILI in cognitive impairment treatment. This work contributes to a better understanding of the pathogenesis of VILI-induced cognitive impairment and may provide future direction for the treatment and prognosis of cognitive impairment.

Reactive Oxygen Species and Strategies for Antioxidant Intervention in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening pulmonary condition characterized by the sudden onset of respiratory failure, pulmonary edema, dysfunction of endothelial and epithelial barriers, and the activation of inflammatory cascades. Despite the increasing number of deaths attributed to ARDS, a comprehensive therapeutic approach for managing patients with ARDS remains elusive. To elucidate the pathological mechanisms underlying ARDS, numerous studies have employed various preclinical models, often utilizing lipopolysaccharide as the ARDS inducer. Accumulating evidence emphasizes the pivotal role of reactive oxygen species (ROS) in the pathophysiology of ARDS. Both preclinical and clinical investigations have asserted the potential of antioxidants in ameliorating ARDS. This review focuses on various sources of ROS, including NADPH oxidase, uncoupled endothelial nitric oxide synthase, cytochrome P450, and xanthine oxidase, and provides a comprehensive overview of their roles in ARDS. Additionally, we discuss the potential of using antioxidants as a strategy for treating ARDS.

Setting the optimal positive end-expiratory pressure: a narrative review

The primary goals of positive end-expiratory pressure (PEEP) are to restore functional residual capacity through recruitment and prevention of alveolar collapse. Through these mechanisms, PEEP improves arterial oxygenation and may reduce the risk of ventilator-induced lung injury (VILI). Because of the many potential negative effects associated with the use of PEEP, much research has concentrated on determining the optimal PEEP setting. Arterial oxygenation targets and pressure-volume loops have been utilized to set the optimal PEEP for decades. Several other techniques have been suggested, including the use of PEEP tables, compliance, driving pressure (DP), stress index (SI), transpulmonary pressures, imaging, and electrical impedance tomography. Each of these techniques has its own benefits and limitations and there is currently not one technique that is recommended above all others.

Management of severe acute respiratory distress syndrome: a primer

This narrative review explores the physiology and evidence-based management of patients with severe acute respiratory distress syndrome (ARDS) and refractory hypoxemia, with a focus on mechanical ventilation, adjunctive therapies, and veno-venous extracorporeal membrane oxygenation (V-V ECMO). Severe ARDS cases increased dramatically worldwide during the Covid-19 pandemic and carry a high mortality. The mainstay of treatment to improve survival and ventilator-free days is proning, conservative fluid management, and lung protective ventilation. Ventilator settings should be individualized when possible to improve patient-ventilator synchrony and reduce ventilator-induced lung injury (VILI). Positive end-expiratory pressure can be individualized by titrating to best respiratory system compliance, or by using advanced methods, such as electrical impedance tomography or esophageal manometry. Adjustments to mitigate high driving pressure and mechanical power, two possible drivers of VILI, may be further beneficial. In patients with refractory hypoxemia, salvage modes of ventilation such as high frequency oscillatory ventilation and airway pressure release ventilation are additional options that may be appropriate in select patients. Adjunctive therapies also may be applied judiciously, such as recruitment maneuvers, inhaled pulmonary vasodilators, neuromuscular blockers, or glucocorticoids, and may improve oxygenation, but do not clearly reduce mortality. In select, refractory cases, the addition of V-V ECMO improves gas exchange and modestly improves survival by allowing for lung rest. In addition to VILI, patients with severe ARDS are at risk for complications including acute cor pulmonale, physical debility, and neurocognitive deficits. Even among the most severe cases, ARDS is a heterogeneous disease, and future studies are needed to identify ARDS subgroups to individualize therapies and advance care.

Efficacy of endotracheal tube clamping to prevent positive airways pressure loss and pressure behavior after reconnection: a bench study

BACKGROUND

Endotracheal tube (ETT) clamping before disconnecting the patient from the mechanical ventilator is routinely performed in patients with acute respiratory distress syndrome (ARDS) to minimize alveolar de-recruitment. Clinical data on the effects of ETT clamping are lacking, and bench data are sparse. We aimed to evaluate the effects of three different types of clamps applied to ETTs of different sizes at different clamping moments during the respiratory cycle and in addition to assess pressure behavior following reconnection to the ventilator after a clamping maneuver.

METHODS

A mechanical ventilator was connected to an ASL 5000 lung simulator using an ARDS simulated condition. Airway pressures and lung volumes were measured at three time points (5 s, 15 s and 30 s) after disconnection from the ventilator with different clamps (Klemmer, Chest-Tube and ECMO) on different ETT sizes (internal diameter of 6, 7 and 8 mm) at different clamping moments (end-expiration, end-inspiration and end-inspiration with tidal volume halved). In addition, we recorded airway pressures after reconnection to the ventilator. Pressures and volumes were compared among different clamps, different ETT-sizes and the different moments of clamp during the respiratory cycle.

RESULTS

The efficacy of clamping depended on the type of clamp, the duration of clamping, the size of the ETT and the clamping moment. With an ETT ID 6 mm all clamps showed similar pressure and volume results. With an ETT ID 7 and 8 mm only the ECMO clamp was effective in maintaining stable pressure and volume in the respiratory system during disconnection at all observation times. Clamping with Klemmer and Chest-Tube at end inspiration and at end inspiration with halved tidal volume was more efficient than clamping at end expiration (p < 0.03). After reconnection to the mechanical ventilator, end-inspiratory clamping generated higher alveolar pressures as compared with end-inspiratory clamping with halved tidal volume (p < 0.001).

CONCLUSIONS

ECMO was the most effective in preventing significant airway pressure and volume loss independently from tube size and clamp duration. Our findings support the use of ECMO clamp and clamping at end-expiration. ETT clamping at end-inspiration with tidal volume halved could minimize the risk of generating high alveolar pressures following reconnection to the ventilator and loss of airway pressure under PEEP.

SOLVe: a closed-loop system focused on protective mechanical ventilation

BACKGROUND

Mechanical ventilation is an essential component in the treatment of patients with acute respiratory distress syndrome. Prompt adaptation of the settings of a ventilator to the variable needs of patients is essential to ensure personalised and protective ventilation. Still, it is challenging and time-consuming for the therapist at the bedside. In addition, general implementation barriers hinder the timely incorporation of new evidence from clinical studies into routine clinical practice.

RESULTS

We present a system combing clinical evidence and expert knowledge within a physiological closed-loop control structure for mechanical ventilation. The system includes multiple controllers to support adequate gas exchange while adhering to multiple evidence-based components of lung protective ventilation. We performed a pilot study on three animals with an induced ARDS. The system achieved a time-in-target of over 75 % for all targets and avoided any critical phases of low oxygen saturation, despite provoked disturbances such as disconnections from the ventilator and positional changes of the subject.

CONCLUSIONS

The presented system can provide personalised and lung-protective ventilation and reduce clinician workload in clinical practice.

Acute Respiratory Distress Syndrome, Mechanical Ventilation, and Inhalation Injury in Burn Patients

Respiratory failure occurs with some frequency in seriously burned patients, driven by a combination of inflammatory and infection factors. Inhalation injury contributes to respiratory failure in some burn patients via direct mucosal injury and indirect inflammation. In burn patients, respiratory failure leading to acute respiratory distress syndrome, with or without inhalation injury, is effectively managed using principles evolved for non-burn critically ill patients.

Intraoperative Ventilator Management of the Critically Ill Patient

Strategies for the intraoperative ventilator management of the critically ill patient focus on parameters used for lung protective ventilation with acute respiratory distress syndrome, preventing or limiting the deleterious effects of mechanical ventilation, and optimizing anesthetic and surgical conditions to limit postoperative pulmonary complications for patients at risk. Patient conditions such as obesity, sepsis, the need for laparoscopic surgery, or one-lung ventilation may benefit from intraoperative lung protective ventilation strategies. Anesthesiologists can use risk evaluation and prediction tools, monitor advanced physiologic targets, and incorporate new innovative monitoring techniques to develop an individualized approach for patients.

Mechanical Ventilation in Patients with Traumatic Brain Injury: Is it so Different?

Patients with traumatic brain injury (TBI) frequently require invasive mechanical ventilation and admission to an intensive care unit. Ventilation of patients with TBI poses unique clinical challenges, and careful attention is required to ensure that the ventilatory strategy (including selection of appropriate tidal volume, plateau pressure, and positive end-expiratory pressure) does not cause significant additional injury to the brain and lungs. Selection of ventilatory targets may be guided by principles of lung protection but with careful attention to relevant intracranial effects. In patients with TBI and concomitant acute respiratory distress syndrome (ARDS), adjunctive strategies include sedation optimization, neuromuscular blockade, recruitment maneuvers, prone positioning, and extracorporeal life support. However, these approaches have been largely extrapolated from studies in patients with ARDS and without brain injury, with limited data in patients with TBI. This narrative review will summarize the existing evidence for mechanical ventilation in patients with TBI. Relevant literature in patients with ARDS will be summarized, and where available, direct data in the TBI population will be reviewed. Next, practical strategies to optimize the delivery of mechanical ventilation and determine readiness for extubation will be reviewed. Finally, future directions for research in this evolving clinical domain will be presented, with considerations for the design of studies to address relevant knowledge gaps.

Management of refractory hypoxemia using recruitment maneuvers and rescue therapies: A comprehensive review

Refractory hypoxemia in patients with acute respiratory distress syndrome treated with mechanical ventilation is one of the most challenging conditions in human and veterinary intensive care units. When a conventional lung protective approach fails to restore adequate oxygenation to the patient, the use of recruitment maneuvers and positive end-expiratory pressure to maximize alveolar recruitment, improve gas exchange and respiratory mechanics, while reducing the risk of ventilator-induced lung injury has been suggested in people as the open lung approach. Although the proposed physiological rationale of opening and keeping open previously collapsed or obstructed airways is sound, the technique for doing so, as well as the potential benefits regarding patient outcome are highly controversial in light of recent randomized controlled trials. Moreover, a variety of alternative therapies that provide even less robust evidence have been investigated, including prone positioning, neuromuscular blockade, inhaled pulmonary vasodilators, extracorporeal membrane oxygenation, and unconventional ventilatory modes such as airway pressure release ventilation. With the exception of prone positioning, these modalities are limited by their own balance of risks and benefits, which can be significantly influenced by the practitioner's experience. This review explores the rationale, evidence, advantages and disadvantages of each of these therapies as well as available methods to identify suitable candidates for recruitment maneuvers, with a summary on their application in veterinary medicine. Undoubtedly, the heterogeneous and evolving nature of acute respiratory distress syndrome and individual lung phenotypes call for a personalized approach using new non-invasive bedside assessment tools, such as electrical impedance tomography, lung ultrasound, and the recruitment-to-inflation ratio to assess lung recruitability. Data available in human medicine provide valuable insights that could, and should, be used to improve the management of veterinary patients with severe respiratory failure with respect to their intrinsic anatomy and physiology.

Flow-controlled expiration reduces positive end-expiratory pressure requirement in dorsally recumbent, anesthetized horses

Introduction

Equine peri-anesthetic mortality is higher than that for other commonly anesthetized veterinary species. Unique equine pulmonary pathophysiologic aspects are believed to contribute to this mortality due to impairment of gas exchange and subsequent hypoxemia. No consistently reliable solution for the treatment of peri-anesthetic gas exchange impairment is available. Flow-controlled expiration (FLEX) is a ventilatory mode that linearizes gas flow throughout the expiratory phase, reducing the rate of lung emptying and alveolar collapse. FLEX has been shown to improve gas exchange and pulmonary mechanics in anesthetized horses. This study further evaluated FLEX ventilation in anesthetized horses positioned in dorsal recumbency, hypothesizing that after alveolar recruitment, horses ventilated using FLEX would require a lower positive end-expiratory pressure (PEEP) to prevent alveolar closure than horses conventionally ventilated.

Methods

Twelve adult horses were used in this prospective, randomized study. Horses were assigned either to conventional volume-controlled ventilation (VCV) or to FLEX. Following induction of general anesthesia, horses were placed in dorsal recumbency mechanically ventilated for a total of approximately 6.5 hours. Thirty-minutes after starting ventilation with VCV or FLEX, a PEEP-titration alveolar recruitment maneuver was performed at the end of which the PEEP was reduced in decrements of 3 cmH₂O until the alveolar closure pressure was determined. The PEEP was then increased to the previous level and maintained for additional three hours. During this time, the mean arterial blood pressure, pulmonary arterial pressure, central venous blood pressure, cardiac output (CO), dynamic respiratory system compliance and arterial blood gas values were measured.

Results

The alveolar closure pressure was significantly lower (6.5 ± 1.2 vs 11.0 ± 1.5 cmH₂O) and significantly less PEEP was required to prevent alveolar closure (9.5 ± 1.2 vs 14.0 ± 1.5 cmH₂O) for horses ventilated using FLEX compared with VCV. The CO was significantly higher in the horses ventilated with FLEX (37.5 ± 4 vs 30 ± 6 l/min).

Discussion

We concluded that FLEX ventilation was associated with a lower PEEP requirement due to a more homogenous distribution of ventilation in the lungs during expiration. This lower PEEP requirement led to more stable and improved cardiovascular conditions in horses ventilated with FLEX.

Driving pressure-guided ventilation improves homogeneity in lung gas distribution for gynecological laparoscopy: a randomized controlled trial

To investigate whether driving pressure-guided ventilation could contribute to a more homogeneous distribution in the lung for gynecological laparoscopy. Chinese patients were randomized, after pneumoperitoneum, to receive either positive end expiratory pressure (PEEP) of 5 cm H₂O (control group), or individualized PEEP producing the lowest driving pressure (titration group). Ventilation homogeneity is quantified as the global inhomogeneity (GI) index based on electrical impedance tomography, with a lower index implying more homogeneous ventilation. The perioperative arterial oxygenation index and respiratory system mechanics were also recorded. Blood samples were collected for lung injury biomarkers including interleukin-10, neutrophil elastase, and Clara Cell protein-16. A total of 48 patients were included for analysis. We observed a significant increase in the GI index immediately after tracheal extubation compared to preinduction in the control group (p = 0.040) but not in the titration group (p = 0.279). Furthermore, the GI index was obviously lower in the titration group than in the control group [0.390 (0.066) vs 0.460 (0.074), p = 0.0012]. The oxygenation index and respiratory compliance were significantly higher in the titration group than in the control group. No significant differences in biomarkers or hemodynamics were detected between the two groups. Driving pressure-guided PEEP led to more homogeneous ventilation, as well as improved gas exchange and respiratory compliance for patients undergoing gynecological laparoscopy.Trial Registration: ClinicalTrials.gov NCT04374162; first registration on 05/05/2020.

Assessment of Heterogeneity in Lung Structure and Function During Mechanical Ventilation: A Review of Methodologies

The mammalian lung is characterized by heterogeneity in both its structure and function, by incorporating an asymmetric branching airway tree optimized for maintenance of efficient ventilation, perfusion, and gas exchange. Despite potential benefits of naturally occurring heterogeneity in the lungs, there may also be detrimental effects arising from pathologic processes, which may result in deficiencies in gas transport and exchange. Regardless of etiology, pathologic heterogeneity results in the maldistribution of regional ventilation and perfusion, impairments in gas exchange, and increased work of breathing. In extreme situations, heterogeneity may result in respiratory failure, necessitating support with a mechanical ventilator. This review will present a summary of measurement techniques for assessing and quantifying heterogeneity in respiratory system structure and function during mechanical ventilation. These methods have been grouped according to four broad categories: (1) inverse modeling of heterogeneous mechanical function; (2) capnography and washout techniques to measure heterogeneity of gas transport; (3) measurements of heterogeneous deformation on the surface of the lung; and finally (4) imaging techniques used to observe spatially-distributed ventilation or regional deformation. Each technique varies with regard to spatial and temporal resolution, degrees of invasiveness, risks posed to patients, as well as suitability for clinical implementation. Nonetheless, each technique provides a unique perspective on the manifestations and consequences of mechanical heterogeneity in the diseased lung.

PEEP titration by EIT strategies for patients with ARDS: A systematic review and meta-analysis

OBJECTIVE

To determine which method of Positive End-expiratory Pressure (PEEP) titration is more useful, and to establish an evidence base for the clinical impact of Electrical Impedance Tomography (EIT) based individual PEEP setting which appears to be a promising method to optimize PEEP in Acute Respiratory Distress Syndrome (ARDS) patients.

DESIGN

A systematic review and meta-analysis.

SETTING

4 databases (PUBMED, EMBASE, Web Of Science, and the Cochrane Library) from 1980 to December 2020 were performed.

PARTICIPANTS

Randomized clinical trials patients with ARDS.

MAIN VARIABLES

PaO₂/FiO₂-ratio and respiratory system compliance.

INTERVENSION

The quality of the studies was assessed with the Cochrane risk and bias tool.

RESULTS

8 trials, including a total of 222 participants, were eligible for analysis. Meta-analysis demonstrates a significantly EIT-based individual PEEP setting for patients receiving higher PaO₂/FiO₂ ratio as compared to other PEEP titration strategies [5 trials, 202 patients, SMD 0.636, (95% CI 0.364-0.908)]. EIT-drived PEEP titration strategy did not significantly increase respiratory system compliance when compared to other peep titration strategies, [7 trials, 202 patients, SMD -0.085, (95% CI -0.342 to 0.172)].

CONCLUSIONS

The benefits of PEEP titration with EIT on clinical outcomes of ARDS in placebo-controlled trials probably result from the visible regional ventilation of EIT. These findings offer clinicians and stakeholders a comprehensive assessment and high-quality evidence for the safety and efficacy of the EIT-based individual PEEP setting as a superior option for patients who undergo ARDS.

Chest wall loading during supine and prone position in patients with COVID-19 ARDS: effects on respiratory mechanics and gas exchange

Background

Recent reports of patients with severe, late-stage COVID-19 ARDS with reduced respiratory system compliance described paradoxical decreases in plateau pressure and increases in respiratory system compliance in response to anterior chest wall loading. We aimed to assess the effect of chest wall loading during supine and prone position in ill patients with COVID-19-related ARDS and to investigate the effect of a low or normal baseline respiratory system compliance on the findings.

Methods

This is a single-center, prospective, cohort study in the intensive care unit of a COVID-19 referral center. Consecutive mechanically ventilated, critically ill patients with COVID-19-related ARDS were enrolled and classified as higher (≥ 40 ml/cmH₂O) or lower respiratory system compliance (< 40 ml/cmH₂O). The study included four steps, each lasting 6 h: Step 1, supine position, Step 2, 10-kg continuous chest wall compression (supine + weight), Step 3, prone position, Step 4, 10-kg continuous chest wall compression (prone + weight). The mechanical properties of the respiratory system, gas exchange and alveolar dead space were measured at the end of each step.

Results

Totally, 40 patients were enrolled. In the whole cohort, neither oxygenation nor respiratory system compliance changed between supine and supine + weight; both increased during prone positioning and were unaffected by chest wall loading in the prone position. Alveolar dead space was unchanged during all the steps. In 16 patients with reduced compliance, PaO₂/FiO₂ significantly increased from supine to supine + weight and further with prone and prone + weight (107 ± 15.4 vs. 120 ± 18.5 vs. 146 ± 27.0 vs. 159 ± 30.4, respectively; p < 0.001); alveolar dead space decreased from both supine and prone position after chest wall loading, and respiratory system compliance significantly increased from supine to supine + weight and from prone to prone + weight (23.9 ± 3.5 vs. 30.9 ± 5.7 and 31.1 ± 5.7 vs. 37.8 ± 8.7 ml/cmH₂O, p < 0.001). The improvement was higher the lower the baseline compliance.

Conclusions

Unlike prone positioning, chest wall loading had no effects on respiratory system compliance, gas exchange or alveolar dead space in an unselected cohort of critically ill patients with C-ARDS. Only patients with a low respiratory system compliance experienced an improvement, with a higher response the lower the baseline compliance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04141-7.

Effects of two alveolar recruitment maneuvers in an “open-lung” approach during laparoscopy in dogs

Objectives

The aim of this study was to compare the effects of a sustained inflation alveolar recruiting maneuver (ARM) followed by 5 cmH₂O of PEEP and a stepwise ARM, in dogs undergoing laparoscopic surgery.

Materials and methods

Twenty adult dogs were enrolled in this prospective randomized clinical study. Dogs were premedicated with methadone intramuscularly (IM); anesthesia was induced with propofol intravenously (IV) and maintained with inhaled isoflurane in pure oxygen. The baseline ventilatory setting (BVS) was as follows: tidal volume of 15 mL/kg, inspiratory pause of 25%, inspiratory to expiratory ratio of 1:2, and the respiratory rate to maintain the end-tidal carbon dioxide between 45 and 55 mmHg. 10 min after pneumoperitoneum, randomly, 10 dogs underwent sustained inflation ARM followed by 5 cmH₂O of PEEP (ARMi), while 10 dogs underwent a stepwise recruitment maneuver followed by the setting of the “best PEEP” (ARMc). Gas exchange, respiratory system mechanics, and hemodynamic were evaluated before the pneumoperitoneum induction (BASE), 10 min after the pneumoperitoneum (PP), 10 min after the recruitment (ARM), and 10 min after the pneumoperitoneum resolution (PostPP). Statistical analysis was performed with the ANOVA test (p < 0.05).

Results

Static compliance decreased in both groups at PP (ARMc = 1.35 ± 0.21; ARMi = 1.16 ± 0.26 mL/cmH₂O/kg) compared to BASE (ARMc = 1.78 ± 0.60; ARMi = 1.66 ± 0.66 mL/cmH₂O/kg) and at ARM (ARMc = 1.71 ± 0.41; ARMi = 1.44 ± 0.84 mL/cmH₂O/kg) and PostPP (ARMc = 1.75 ± 0.45; ARMi = 1.89 ± 0.59 mL/cmH₂O/kg), and it was higher compared to PP and similar to BASE. The PaO₂/FiO₂, in both groups, was higher at ARM (ARMc = 455.11 ± 85.90; ARMi = 505.40 ± 31.70) and PostPP (ARMc = 521.30 ± 66.20; ARMi = 450.90 ± 70.60) compared to PP (ARMc = 369.53 ± 49.31; ARMi = 394.32 ± 37.72).

Conclusion and clinical relevance

The two ARMs improve lung function in dogs undergoing laparoscopic surgery similarly. Application of PEEP at the end of the ARMs prolonged the effects of the open-lung strategy.

Effect of positive end expiratory pressure on central venous pressure in closed and open thorax

OBJECTIVE

The magnitude and mechanism of the rise of central venous pressure (CVP) after positive end-expiratory pressure (PEEP) among patients with cardiac disease is poorly understood. Therefore, the study aimed to compare the magnitude of change in CVP after PEEP in patients with TR (tricuspid regurgitation), high CVP and high PCWP (pulmonary capillary wedge pressure) with no TR, low CVP and low PCWP. Additionally, we hypothesized that PEEP in the open thorax would also lead to a rise in CVP.

APPROACH

This prospective, quasi-experimental study was conducted in patients undergoing cardiac surgery. Three consecutive readings of variables were obtained at 1-minute intervals after PEEP (5 and 10 cm H2O) application in the closed and open thorax. Patients were stratified a priori into low CVP (<10 cm H2O) and high CVP (≥10 cm H2O), no TR and TR and low PCWP (<15 mm Hg) and high PCWP (≥15 mm Hg) in the closed and open thorax.

MAIN RESULTS

Sixty-two patients were eligible for final analysis. The mean difference (MD) in ∆CVP (CVP10 cm H2O of PEEP - CVP zero end-expiratory pressure) was 2.33±1.13 (95% CI, 2.04-2.62, P=0.000) and 1.02±0.77 (95% CI, 0.82-1.22, P=0.000) in the closed and open thorax, respectively. The increase in CVP was higher among patients who had a lower CVP (2.64 ± 0.9 mm Hg vs 1.45± 1.17 mm Hg; p=0.000), without TR (2.64 ± 0.97 mm Hg vs 2.14 ± 1.2 mm Hg, p=0.09) and lower PCWP (2.4 ± 0.9 mm Hg vs 2.3 ± 1.4 mm Hg, p=0.67) at 10 cm H2O PEEP in the closed thorax.

SIGNIFICANCE

The rise in CVP was higher among patients without TR, low CVP and low PCWP. Zero intrathoracic pressure in the open thorax did not abolish the effect of PEEP on CVP rise altogether.

Lung UltraSound Targeted Recruitment (LUSTR): A Novel Protocol to Optimize Open Lung Ventilation in Critically Ill Neonates

This study investigated the effectiveness of an original Lung UltraSound Targeted Recruitment (LUSTR) protocol to improve the success of lung recruitment maneuvers (LRMs), which are performed as a rescue approach in critically ill neonates. All the LUSTR maneuvers, performed on infants with an oxygen saturation/fraction of inspired oxygen (S/F) ratio below 200, were included in this case−control study (LUSTR-group). The LUSTR-group was matched by the initial S/F ratio and underlying respiratory disease with a control group of lung recruitments performed following the standard oxygenation-guided procedure (Ox-group). The primary outcome was the improvement of the S/F ratio (Delta S/F) throughout the LRM. Secondary outcomes included the rate of air leaks. Each group was comprised of fourteen LRMs. As compared to the standard approach, the LUSTR protocol was associated with a higher success of the procedure in terms of Delta S/F (110 ± 47.3 vs. 64.1 ± 54.6, p = 0.02). This result remained significant after adjusting for confounding variables through multiple linear regressions. The incidence of pneumothorax was lower, although not reaching statistical significance, in the LUSTR-group (0 vs. 14.3%, p = 0.15). The LUSTR protocol may be a more effective and safer option than the oxygenation-based procedure to guide open lung ventilation in neonates, potentially improving ventilation and reducing the impact of ventilator-induced lung injury.

A novel lung recruitment technique in pediatric patients with congenital heart diseases: A case series

Background

Lung recruitment techniques are employed to help in improvement of pulmonary mechanics, facilitate early weaning, and shorten the duration of mechanical ventilation. We are reporting a novel lung recruitment technique employed in four children with left lung atelectasis, who underwent corrective surgery for congenital heart disease.

Materials and Methods

From January 2020 to March 2021, four pediatric cardiac patients having left lung atelectasis, undergoing corrective surgery were subjected to lung recruitment technique and had elective endobronchial intubation and suctioning with chest physiotherapy in the form of vibration and percussion. This was done along with intermittent ventilation with 100% oxygen.

Results

Successful recruitment of lung segments and clearance of atelectasis were confirmed by auscultation and chest X-ray in all four patients. All the cases were successfully weaned off the ventilator within 24-48 h. One patient had an opposite lung collapse after extubation, which was managed conservatively with chest physiotherapy. Another patient had bradycardia and desaturation during the procedure, which was improved after withdrawing the tube and instituting two lung ventilation with 100% oxygen.

Conclusions

This novel lung recruitment technique helps in recruitment of collapsed lung segments and thus helps in early weaning and shortens the duration of mechanical ventilation.

Efficacy analysis of the lung recruitment maneuver in correcting pulmonary atelectasis in neurological intensive care unit-a retrospective study

Background

Atelectasis after supratentorial craniotomy is common. It can lead to the decrease of arterial partial pressure of oxygen (PaO₂) in patients with neurosurgical intensive care units (NICU), and the recovery of neurological function is more and more difficult. However, due to the particularity of maintaining the stability of intracranial pressure (ICP), there are few reports on effective ways to alleviate atelectasis and improve oxygenation in patients with NICU effectively.

Methods

A retrospective analysis was conducted to analyze the clinical data of patients with atelectasis who received lung recruitment maneuver in the NICU. This study collected data on 33 patients. Of these, 17 patients had traumatic brain injury and 16 patients had spontaneous intracranial hemorrhage. PaO₂, oxygenation index (OI), tidal volume, positive end-expiratory pressure (PEEP), respiratory system compliance, plateau pressure, respiratory rate, minute ventilation and chest computed tomography (CT) or portable chest X-ray images were compared before and after recruitment. As for safety evaluation indicators, we reviewed the invasive arterial blood pressure, heart rate, heart rhythm, and subcutaneous emphysema in all patients. Before and after lung recruitment, the data were compared using the paired t-test and the Wilcoxon test.

Results

Compared with tidal volume 8.1 [6.85-10.05] mL/kg, minute ventilation volume (9.3±1.3 L/min), respiratory system compliance 60 [39-80] mL/cmH₂O, respiratory rate 17 [16-21.5] breaths/min, PEEP 4 [4-6] cmH₂O, plateau pressure 19 [17-23] cmH₂O, PaO₂ (104.2±33.17 mmHg) and OI (250.6±87.65 mmHg) before lung recruitment, tidal volume 9 [8.05-10.65] mL/kg, minute ventilation (9.7±1.1 L/min), respiratory system compliance 69 [50-82.5] mL/cmH₂O, respiratory rate 17 [14-18.5] breaths/min, PEEP 4 [4-5] cmH₂O, plateau pressure 18 [16-19.5] cmH₂O, PaO₂ (127.3±34.95 mmHg) and OI (306.9±96.52 mmHg) of patients were significantly improved after recruitment after recruitment (all P<0.05). In all patients, chest CT showed a decrease in atelectasis area and bilateral pulmonary exudates in 25 patients after lung recruitment maneuver. X-ray after recruitment in 2 patients showed increased lung tissue transparency and decreased ground-glass shadowing, while improvements were not obvious in 6 patients.

Conclusions

For patients diagnosed with atelectasis in the NICU, lung recruitment maneuver can improve atelectasis, increase PaO₂, and improve oxygenation.

The incidence, clinical characteristics, and outcome of polytrauma patients with the combination of pulmonary contusion, flail chest and upper thoracic spinal injury

BACKGROUND

Chest trauma was the third most common cause of death in polytrauma patients, accounting for 25% of all deaths from traumatic injury. Chest trauma involves in injury to the bony thorax, intrathoracic organs and thoracic medulla. This study aimed to investigate the incidence, clinical characteristics, and outcome of polytrauma patients with pulmonary contusion, flail chest and upper thoracic spinal injury.

METHODS

Patients who met inclusion criteria were divided into groups: Pulmonary contusion group (PC); Pulmonary contusion and flail chest group (PC + FC); Pulmonary contusion and upper thoracic spinal cord injury group (PC + UTSCI); Thoracic trauma triad group (TTT): included patients with flail chest, pulmonary contusion and the upper thoracic spinal cord injury coexisted. Outcomes were determined, including 30-day mortality and 6-month mortality.

RESULTS

A total 84 patients (2.0%) with TTT out of 4176 polytrauma patients presented to Tongji trauma center. There was no difference in mean ISS among PC + FC group, PC + UTSCI group and TTT group. Patients with TTT had a longer ICU stay (21.4 days vs. 7.5 and 6.2; p<0.01), relatively higher 30-day mortality (40.5% vs. 6.0% and 4.3%; p<0.01), and especially higher 6-month mortality (71.4% vs. 6.5%, 13.0%; p<0.01), compared to patients with PC + FC or with PC + UTSCI. The leading causes of death for patients with TTT were ARDS (44.1%) and pulmonary infection (26.5%) during first 30 days after admission. For those patients who died later than 30 days during the 6 months, the predominant underlying cause of death was MOF (53.8%).

CONCLUSIONS

Lethal triad of thoracic trauma (LTTT) were described in this study, which consisting of pulmonary contusion,flail chest and the upper thoracic spine cord injury. Like the classic "lethal triad", there was a synergy between the factors when they coexist, resulting in especially high mortality rates. Polytrauma patients with LTTT were presented relatively high 30-day mortality and 6 months mortality. We should pay much more attention to the patients with LTTT for further minimizing complications and mortality.

Respiratory effects of lung recruitment maneuvers depend on the recruitment-to-inflation ratio in patients with COVID-19-related acute respiratory distress syndrome

Background

In the context of acute respiratory distress syndrome (ARDS), the response to lung recruitment maneuvers (LRMs) varies considerably from one patient to another and so is difficult to predict. The aim of the study was to determine whether or not the recruitment-to-inflation (R/I) ratio could differentiate between patients according to the change in lung mechanics during the LRM.

Methods

We evaluated the changes in gas exchange and respiratory mechanics induced by a stepwise LRM at a constant driving pressure of 15 cmH₂O during pressure-controlled ventilation. We assessed lung recruitability by measuring the R/I ratio. Patients were dichotomized with regard to the median R/I ratio.

Results

We included 30 patients with moderate-to-severe ARDS and a median [interquartile range] R/I ratio of 0.62 [0.42–0.83]. After the LRM, patients with high recruitability (R/I ratio ≥ 0.62) presented an improvement in the P_aO₂/F_iO₂ ratio, due to significant increase in respiratory system compliance (33 [27–42] vs. 42 [35–60] mL/cmH₂O; p < 0.001). In low recruitability patients (R/I < 0.62), the increase in P_aO₂/F_iO₂ ratio was associated with a significant decrease in pulse pressure as a surrogate of cardiac output (70 [55–85] vs. 50 [51–67] mmHg; p = 0.01) but not with a significant change in respiratory system compliance (33 [24–47] vs. 35 [25–47] mL/cmH₂O; p = 0.74).

Conclusion

After the LRM, patients with high recruitability presented a significant increase in respiratory system compliance (indicating a gain in ventilated area), while those with low recruitability presented a decrease in pulse pressure suggesting a drop in cardiac output and therefore in intrapulmonary shunt.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03876-z.

Noninvasive and invasive mechanical ventilation for neurologic disorders

Patients with acute neurologic injuries frequently require mechanical ventilation due to diminished airway protective reflexes, cardiopulmonary failure secondary to neurologic insults, or to facilitate gas exchange to precise targets. Mechanical ventilation enables tight control of oxygenation and carbon dioxide levels, enabling clinicians to modulate cerebral hemodynamics and intracranial pressure with the goal of minimizing secondary brain injury. In patients with acute spinal cord injuries, neuromuscular conditions, or diseases of the peripheral nerve, mechanical ventilation enables respiratory support under conditions of impending or established respiratory failure. Noninvasive ventilatory approaches may be carefully considered for certain disease conditions, including myasthenia gravis and amyotrophic lateral sclerosis, but may be inappropriate in patients with Guillain-Barré syndrome or when relevant contra-indications exist. With regard to discontinuing mechanical ventilation, considerable uncertainty persists about the best approach to wean patients, how to identify patients ready for extubation, and when to consider primary tracheostomy. Recent consensus guidelines highlight these and other knowledge gaps that are the focus of active research efforts. This chapter outlines important general principles to consider when initiating, titrating, and discontinuing mechanical ventilation in patients with acute neurologic injuries. Important disease-specific considerations are also reviewed where appropriate.

Lung Recruitment Using High-Frequency Oscillation Volume Guarantee in Preterm Infants with Evolving Bronchopulmonary Dysplasia

BACKGROUND

Stepwise lung recruitment maneuvers (LRMs) may be used in ventilated preterm infants. However, its use in high-frequency oscillation with volume guarantee (HFO-VG) is not well studied.

METHODS

Preterm infants treated with HFO-VG who had LRMs were identified. Patient and respiratory parameters were recorded.

RESULTS

Ten infants, median GA 25+6 (IQR 24+2-27+0) weeks, and 21 LRMs were identified. LRMs were performed at a median age of 26 days, with a starting MAP of 16 (14-17) cm H2O and the highest MAP of 23.5 (22.0-24.8) cm H2O. Most (76%) resulted in immediate improved SpO2/FiO2. There were no sustained differences in median oxygen saturation index (8.4 vs. 9, p = 0.09), SpO2/FiO2 (1.8 vs. 1.8, p = 0.8), ∆P (21 vs. 23, p = 0.64), or transcutaneous CO2 (58 vs. 60, p = 0.84) in 24 h before and after LRMs.

CONCLUSIONS

In preterm infants with evolving bronchopulmonary dysplasia, LRMs on HFO-VG did not result in sustained improvement to oxygenation or ventilation.

Over-distension prediction via hysteresis loop analysis and patient-specific basis functions in a virtual patient model

BACKGROUND AND OBJECTIVE

Recruitment maneuvers (RMs) with subsequent positive-end-expiratory-pressure (PEEP) have proven effective in recruiting lung volume and preventing alveolar collapse. However, a suboptimal PEEP could induce undesired injury in lungs by insufficient or excessive breath support. Thus, a predictive model for patient response under PEEP changes could improve clinical care and lower risks.

METHODS

This research adds novel elements to a virtual patient model to identify and predict patient-specific lung distension to optimise and personalise care. Model validity and accuracy are validated using data from 18 volume-controlled ventilation (VCV) patients at 7 different baseline PEEP levels (0-12cmH₂O), yielding 623 prediction cases. Predictions were made up to ΔPEEP = 12cmH₂O ahead covering 6x2cmH₂O PEEP steps.

RESULTS

Using the proposed lung distension model, 90% of absolute peak inspiratory pressure (PIP) prediction errors compared to clinical measurement are within 3.95cmH₂O, compared with 4.76cmH₂O without this distension term. Comparing model-predicted and clinically measured distension had high correlation increasing to R² = 0.93-0.95 if maximum ΔPEEP ≤ 6cmH₂O. Predicted dynamic functional residual capacity (V_frc) changes as PEEP rises yield 0.013L median prediction error for both prediction groups and overall R² of 0.84.

CONCLUSIONS

Overall results demonstrate nonlinear distension mechanics are accurately captured in virtual lung mechanics patients for mechanical ventilation, for the first time. This result can minimise the risk of lung injury by predicting its potential occurrence of distension before changing ventilator settings. The overall outcomes significantly extend and more fully validate this virtual mechanical ventilation patient model.

COVID-19 ARDS: Points to Be Considered in Mechanical Ventilation and Weaning

The COVID-19 disease can cause hypoxemic respiratory failure due to ARDS, requiring invasive mechanical ventilation. Although early studies reported that COVID-19-associated ARDS has distinctive features from ARDS of other causes, recent observational studies have demonstrated that ARDS related to COVID-19 shares common clinical characteristics and respiratory system mechanics with ARDS of other origins. Therefore, mechanical ventilation in these patients should be based on strategies aiming to mitigate ventilator-induced lung injury. Assisted mechanical ventilation should be applied early in the course of mechanical ventilation by considering evaluation and minimizing factors associated with patient-inflicted lung injury. Extracorporeal membrane oxygenation should be considered in selected patients with refractory hypoxia not responding to conventional ventilation strategies. This review highlights the current and evolving practice in managing mechanically ventilated patients with ARDS related to COVID-19.

Programmed Multi-Level Ventilation: A Strategy for Ventilating Non-Homogenous Lungs

Mechanical ventilation (MV) has been an integral method used in ICU care for decades. MV is typically viewed as a life-supporting intervention. However, it can also contribute to lung injury through stress and strain, as evidenced by ventilator-induced lung injury (VILI), even in previously healthy lungs. The negative impact may be worsened when significant lung non-homogeneity is present, eg. ALI and ARDS. Protective lung strategies to minimize VILI are to use low tidal volumes (Vt 4–6 mL/kg/PBW), plateau pressures (P_plat) <30 cmH₂O and relatively high positive end-expiratory pressures (PEEP). Yet, use of constantly high PEEP levels is well recognized to result in hemodynamic compromise of the right ventricle, increased stress and strain through high mechanical energy impact on the lung and overdistension of relatively healthy lung tissue. Taking these issues into consideration, a different approach to mechanical ventilation was developed specifically for patients with non-homogeneity. This review focuses on a feature called programmed multi-level ventilation (PMLV). It is not a ventilation mode per se, but rather a form of extension that adjusts and modifies any ventilation mode (eg PCV,PSV, VCV, SIMV, etc.). PMLV is based on measured time constants (Tau) of the whole respiratory system, including artificial airways, breathing circuits, humidification devices and mechanical ventilator. Using a physiology-based approach presents a method to ventilate non-homogenous lungs through cyclic changes of different PEEP levels; recruitment takes place in lung areas with long time constants but protects relatively healthy lung areas from overdistension thus minimizing excessive mechanical power to the lung tissue.

Transoesophageal Ultrasound Assessment of Lung Aeration in Patients With Acute Respiratory Distress Syndrome

Introduction: The effect of positive end-expiratory pressure (PEEP) depends closely on the potential for lung recruitment. Bedside assessment of lung recruitability is crucial for personalized lung-protective mechanical ventilation in acute respiratory distress syndrome (ARDS) patients. Methods: We developed a transoesophageal lung ultrasound (TE-LUS) method in which a quantitative (computer-assisted) grayscale determination served as a guide to PEEP-induced lung recruitment. The method is based on the following hypothesis: when the PEEP increases, inflation of the recruited alveoli leads to significant changes in the air/water ratio. Normally ventilated areas are hypoechoic because the ultrasound waves are weakly reflected while poorly aerated areas or non-aerated areas are hyperechoic. We calculated the TE-LUS re-aeration score (RAS) as the ratio of the mean gray scale level at low PEEP to that value at high PEEP for the lower and upper lobes. A RAS > 1 indicated an increase in ventilated area. We used this new method to detect changes in ventilation in patients with a low (<0.5) vs. high (≥0.5) recruitment-to-inflation (R/I) ratio (i.e., the ratio between the recruited lung compliance and the respiratory system compliance at low PEEP). Results: We included 30 patients with moderate-to-severe ARDS. In patients with a high R/I ratio, the TE-LUS RAS was significantly higher in the lower lobes than in the upper lobes (1.20 [1.12-1.63] vs. 1.05 [0.89-1.38]; p = 0.05). Likewise, the TE-LUS RAS in the lower lobes was significantly higher in the high R/I group than in the low R/I group (1.20 [1.12-1.63] vs. 1.07 [1.00-1.20]; p = 0.04). Conclusion: The increase in PEEP induces a substantial gain in the ventilation detected by TE-LUS of poorly or non-aerated lower lobes (dependent lung regions), especially in patients with a high R/I ratio.

Safety and efficacy evaluation of the automatic stepwise recruitment maneuver in the neonatal population: An in vivo interventional study. Can anesthesiologists safely perform automatic lung recruitment maneuvers in neonates?

BACKGROUND

A new software has recently been incorporated in almost all new anesthesia machines to enable automatic lung recruitment maneuvers. To date, no studies have assessed the safety and efficacy of these automatic software programs in the neonatal population.

AIMS

We aimed to evaluate the safety and efficacy of the lung recruitment maneuver performed using the automatic stepwise recruitment maneuver software of the FLOW-i 4.3 Anesthesia System^® in a healthy and live neonatal model.

METHODS

Eight male newborn piglets were included in the study. The lung recruitment maneuver was performed in pressure-controlled ventilation with a constant driving pressure (15 cmH₂ O) in a stepwise increasing positive end-expiratory pressure (PEEP) model. The target peak inspiratory pressure (PIP) was 30 cmH₂ O and PEEP was 15 cmH₂ O. The maneuver lasted for 39 seconds. The hemodynamic variables were monitored using the PICCO^® system. The following respiratory parameters were monitored: oxygen saturation, fraction of inspired oxygen, partial pressure of oxygen and carbon dioxide in the arterial blood, end-tidal carbon dioxide pressure, PIP, plateau pressure, PEEP, static compliance (C_stat ), and dynamic compliance (C_dyn ). Safety was evaluated by assessing the accuracy of the software, need for not interrupting the maneuver, hemodynamic stability, and absence of adverse respiratory events with the lung recruitment maneuver. Efficacy was evaluated by improvement in C_stat and C_dyn after performing the lung recruitment maneuver.

RESULTS

All lung recruitment maneuvers were safely performed as scheduled without any interruptions. No pneumothorax or other side effects were observed. Hemodynamic stability was maintained during the lung recruitment maneuver. We observed an improvement of 33% in C_dyn and 24% in C_stat after the maneuver.

CONCLUSIONS

The automatic stepwise recruitment maneuver software of the FLOW-i 4.3 Anesthesia System^® is safe and efficacious in a healthy neonatal model. We did not observe any adverse respiratory or hemodynamic events during the implementation of the lung recruitment maneuver in the pressure-controlled ventilation mode using a stepwise increasing PEEP (30/15 cmH₂ O) approach.

A Nationwide Cross-Sectional Online Survey on the Treatment of COVID-19-ARDS: High Variance in Standard of Care in German ICUs

INTRODUCTION

Coronavirus disease (COVID-19) has recently dominated scientific literature. Incomplete understanding and a lack of data concerning the pathophysiology, epidemiology, and optimal treatment of the disease has resulted in conflicting recommendations. Adherence to existing guidelines and actual treatment strategies have thus far not been studied systematically. We hypothesized that capturing the variance in care would lead to the discovery of aspects that need further research and-in case of proven benefits of interventions not being performed-better communication to care providers.

METHODS

This article is based on a quantitative and qualitative cross-sectional mixed-methods online survey among intensive-care physicians in Germany during the COVID-19 pandemic by the CEOsys (COVID-19 Evidence Ecosystem) network, endorsed by the German Interdisciplinary Association for Intensive Care and Emergency Medicine (DIVI) conducted from December 3 to 31 December 2020.

RESULTS

We identified several areas of care with an especially high variance in treatment among hospitals in Germany. Crucially, 51.5% of the participating ICUs (n = 205) reported using intubation as a last resort for respiratory failure in COVID-19 patients, while 21.8% used intubation early after admission. Furthermore, 11.5% considered extracorporeal membrane oxygenation (ECMO) in awake patients. Finally, 72.3% of respondents used the ARDS-network-table to titrate positive end-expiratory-pressure (PEEP) levels, with 36.9% choosing the low-PEEP table and 41.8% the high-PEEP table.

CONCLUSIONS

We found that significant differences exist between reported treatment strategies and that adherence to published guidelines is variable. We describe necessary steps for future research based on our results highlighting significant clinical variability in care.

Driving Pressure-Guided Individualized Positive End-Expiratory Pressure in Abdominal Surgery: A Randomized Controlled Trial

BACKGROUND

The optimal positive end-expiratory pressure (PEEP) to prevent postoperative pulmonary complications (PPCs) remains unclear. Recent evidence showed that driving pressure was closely related to PPCs. In this study, we tested the hypothesis that an individualized PEEP guided by minimum driving pressure during abdominal surgery would reduce the incidence of PPCs.

METHODS

This single-centered, randomized controlled trial included a total of 148 patients scheduled for open upper abdominal surgery. Patients were randomly assigned to receive an individualized PEEP guided by minimum driving pressure or an empiric fixed PEEP of 6 cm H2O. The primary outcome was the incidence of clinically significant PPCs within the first 7 days after surgery, using a χ2 test. Secondary outcomes were the severity of PPCs, the area of atelectasis, and pleural effusion. Other outcomes, such as the incidence of different types of PPCs (including hypoxemia, atelectasis, pleural effusion, dyspnea, pneumonia, pneumothorax, and acute respiratory distress syndrome), intensive care unit (ICU) admission rate, length of hospital stay, and 30-day mortality were also explored.

RESULTS

The median value of PEEP in the individualized group was 10 cm H2O. The incidence of clinically significant PPCs was significantly lower in the individualized PEEP group compared with that in the fixed PEEP group (26 of 67 [38.8%] vs 42 of 67 [62.7%], relative risk = 0.619, 95% confidence intervals, 0.435-0.881; P = .006). The overall severity of PPCs and the area of atelectasis were also significantly diminished in the individualized PEEP group. Higher respiratory compliance during surgery and improved intra- and postoperative oxygenation was observed in the individualized group. No significant differences were found in other outcomes between the 2 groups, such as ICU admission rate or 30-day mortality.

CONCLUSIONS

The application of individualized PEEP based on minimum driving pressure may effectively decrease the severity of atelectasis, improve oxygenation, and reduce the incidence of clinically significant PPCs after open upper abdominal surgery.

Serious complications in COVID-19 ARDS cases: pneumothorax, pneumomediastinum, subcutaneous emphysema and haemothorax

The novel coronavirus identified as severe acute respiratory syndrome-coronavirus-2 causes acute respiratory distress syndrome (ARDS). Our aim in this study is to assess the incidence of life-threatening complications like pneumothorax, haemothorax, pneumomediastinum and subcutaneous emphysema, probable risk factors and effect on mortality in coronavirus disease-2019 (COVID-19) ARDS patients treated with mechanical ventilation (MV). Data from 96 adult patients admitted to the intensive care unit with COVID-19 ARDS diagnosis from 11 March to 31 July 2020 were retrospectively assessed. A total of 75 patients abiding by the study criteria were divided into two groups as the group developing ventilator-related barotrauma (BG) (N = 10) and the group not developing ventilator-related barotrauma (NBG) (N = 65). In 10 patients (13%), barotrauma findings occurred 22 ± 3.6 days after the onset of symptoms. The mortality rate was 40% in the BG-group, while it was 29% in the NBG-group with no statistical difference identified. The BG-group had longer intensive care admission duration, duration of time in prone position and total MV duration, with higher max positive end-expiratory pressure (PEEP) levels and lower min pO₂/FiO₂ levels. The peak lactate dehydrogenase levels in blood were higher by statistically significant level in the BG-group (P < 0.05). The contribution of MV to alveolar injury caused by infection in COVID-19 ARDS patients may cause more frequent barotrauma compared to classic ARDS and this situation significantly increases the MV and intensive care admission durations of patients. In terms of reducing mortality and morbidity in these patients, MV treatment should be carefully maintained within the framework of lung-protective strategies and the studies researching barotrauma pathophysiology should be increased.

Assessment of the Effect of Recruitment Maneuver on Lung Aeration Through Imaging Analysis in Invasively Ventilated Patients: A Systematic Review

Background: Recruitment maneuvers (RMs) have heterogeneous effects on lung aeration and have adverse side effects. We aimed to identify morphological, anatomical, and functional imaging characteristics that might be used to predict the RMs on lung aeration in invasively ventilated patients.

Methods: We performed a systemic review. Studies included invasively ventilated patients who received an RM and in whom re-aeration was examined with chest computed tomography (CT), electrical impedance tomography (EIT), and lung ultrasound (LUS) were included.

Results: Twenty studies were identified. Different types of RMs were applied. The amount of re-aerated lung tissue after an RM was highly variable between patients in all studies, irrespective of the used imaging technique and the type of patients (ARDS or non-ARDS). Imaging findings suggesting a non-focal morphology (i.e., radiologic findings consistent with attenuations with diffuse or patchy loss of aeration) were associated with higher likelihood of recruitment and lower chance of overdistention than a focal morphology (i.e., radiological findings suggestive of lobar or segmental loss of aeration). This was independent of the used imaging technique but only observed in patients with ARDS. In patients without ARDS, the results were inconclusive.

Conclusions: ARDS patients with imaging findings suggestive of non-focal morphology show most re-aeration of previously consolidated lung tissue after RMs. The role of imaging techniques in predicting the effect of RMs on re-aeration in patients without ARDS remains uncertain.

Airway Pressure Release Ventilation Mode Improves Circulatory and Respiratory Function in Patients After Cardiopulmonary Bypass, a Randomized Trial

Importance

Postoperative pulmonary complications and cardiovascular complications are major causes of morbidity, mortality, and resource utilization in cardiac surgery patients.

Objectives

To investigate the effects of airway pressure release ventilation (APRV) on respiration and hemodynamics in post cardiac surgery patients.

Main Outcomes and Measures

A single-center randomized control trial was performed. In total, 138 patients undergoing cardiopulmonary bypass were prospectively screened. Ultimately 39 patients met the inclusion criteria and were randomized into two groups: 19 patients were managed with pressure control ventilation (PCV) and 20 patients were managed with APRV. Respiratory mechanics after 4 h, hemodynamics within the first day, and Chest radiograph score (CRS) and blood gasses within the first three days were recorded and compared.

Results

A higher cardiac index (3.1 ± 0.7 vs. 2.8 ± 0.8 L⋅min^–1⋅m²; p < 0.05), and shock volume index (35.4 ± 9.2 vs. 33.1 ± 9.7 ml m^–2; p < 0.05) were also observed in the APRV group after 4 h as well as within the first day (p < 0.05). Compared to the PCV group, the PaO2/FiO₂ was significantly higher after 4 h in patients of APRV group (340 ± 97 vs. 301 ± 82, p < 0.05) and within the first three days (p < 0.05) in the APRV group. CRS revealed less overall lung injury in the APRV group (p < 0.001). The duration of mechanical ventilation and ICU length of stay were not significantly (p = 0.248 and 0.424, respectively).

Conclusions and Relevance

Compared to PCV, APRV may be associated with increased cardiac output improved oxygenation, and decreased lung injury in postoperative cardiac surgery patients.

Effectiveness of postural lung recruitment on postoperative atelectasis assessed by lung ultrasound in children undergoing lateral thoracotomy cardiac surgery with cardiopulmonary bypass

OBJECTIVES

To assess the effects of postural lung recruitment maneuvers on the postoperative atelectasis assessed by lung ultrasound (LUS) compared with supine position recruitment maneuvers in children undergoing right lateral thoracotomy cardiac surgery with cardiopulmonary bypass.

METHODS

In this randomized and controlled trial, 84 patients aged 3 years or younger, scheduled for right lateral thoracotomy cardiac surgery with cardiopulmonary bypass (CPB) were randomly allocated to postural lung recruitment group or control group. The first LUS exam was performed immediately upon completion of the cardiac surgery (T1), and a repeat ultrasound exam started 1 min after lung recruitment maneuvers (T2). The primary outcome was the incidence of significant atelectasis at T2.

RESULTS

The incidence of significant atelectasis at T2 in the postural lung recruitment maneuver group was lower compared with that in the control group (30.2% vs. 58.1%; odds ratio: 0.31; 95% confidence interval: 0.13-0.76; p = .009). The LUS scores for consolidations and B-lines of the left lung were higher than those of the right lung in both groups at T1. More significant reduction of the left LUS scores and sizes of atelectatic areas were found in the postural lung recruitment group than those in the control group.

CONCLUSIONS

Postoperative postural recruitment maneuver was more effective to improve reaeration of lung than supine position recruitment maneuver in children undergoing right lateral thoracotomy cardiac surgery with CPB.

Non-specialist therapeutic strategies in acute respiratory distress syndrome

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is associated with significant morbidity and mortality. We undertook a meta-analysis of randomized controlled trials (RCTs) to determine the mortality benefit of non-specialist therapeutic interventions for ARDS available to general critical care units.

EVIDENCE ACQUISITION

A systematic search of MEDLINE, Embase, and the Cochrane Central Register for RCTs investigating therapeutic interventions in ARDS including corticosteroids, fluid management strategy, high PEEP, low tidal volume ventilation, neuromuscular blockade, prone position ventilation, or recruitment maneuvers. Data was collected on demographic information, treatment strategy, duration and dose of treatment, and primary (28 or 30-day mortality) and secondary (P<inf>a</inf>O<inf>2</inf>:FiO<inf>2</inf> ratio at 24-48 hours) outcomes.

EVIDENCE SYNTHESIS

No improvement in 28-day mortality could be demonstrated in three RCTs investigating high PEEP (28.0% vs. 30.2% control; risk ratio [confidence interval] 0.93 [0.82-1.06]; eight assessing prone position ventilation (39.3% vs. 44.5%; RR 0.83 [0.68-1.01]; seven investigating neuromuscular blockade (37.8% vs. 42.0%; RR 0.91 [0.81-1.03]); ten investigating recruitment maneuvers (42.4% vs. 42.1%; RR 1.01 [0.91-1.12]); eight investigating steroids (34.8% vs. 41.1%; RR 0.81 [0.59-1.12]); and one investigating conservative fluid strategies (25.4% vs. 28.4%; RR 0.90 [0.73-1.10]). Three studies assessing low tidal volume ventilation (33.1% vs. 41.9%; RR 0.79 (0.68-0.91); P=0.001), and subgroup analyses within studies investigating prone position ventilation greater than 12 hours (33.1% vs. 44.4%; RR 0.75 [0.59-0.95), P=0.02) did reveal outcome benefit.

CONCLUSIONS

Among non-specialist therapeutic strategies available to general critical care units, low tidal volumes and prone position ventilation for greater than 12 hours improve mortality in ARDS.

Virtual patients for mechanical ventilation in the intensive care unit

BACKGROUND

Mechanical ventilation (MV) is a core intensive care unit (ICU) therapy. Significant inter- and intra- patient variability in lung mechanics and condition makes managing MV difficult. Accurate prediction of patient-specific response to changes in MV settings would enable optimised, personalised, and more productive care, improving outcomes and reducing cost. This study develops a generalised digital clone model, or in-silico virtual patient, to accurately predict lung mechanics in response to changes in MV.

METHODS

An identifiable, nonlinear hysteresis loop model (HLM) captures patient-specific lung dynamics identified from measured ventilator data. Identification and creation of the virtual patient model is fully automated using the hysteresis loop analysis (HLA) method to identify lung elastances from clinical data. Performance is evaluated using clinical data from 18 volume-control (VC) and 14 pressure-control (PC) ventilated patients who underwent step-wise recruitment maneuvers.

RESULTS

Patient-specific virtual patient models accurately predict lung response for changes in PEEP up to 12 cmH₂O for both volume and pressure control cohorts. R² values for predicting peak inspiration pressure (PIP) and additional retained lung volume, V_frc in VC, are R²=0.86 and R²=0.90 for 106 predictions over 18 patients. For 14 PC patients and 84 predictions, predicting peak inspiratory volume (PIV) and V_frc yield R²=0.86 and R²=0.83. Absolute PIP, PIV and V_frc errors are relatively small.

CONCLUSIONS

Overall results validate the accuracy and versatility of the virtual patient model for capturing and predicting nonlinear changes in patient-specific lung mechanics. Accurate response prediction enables mechanically and physiologically relevant virtual patients to guide personalised and optimised MV therapy.

Lung Recruitment, Individualized PEEP, and Prone Position Ventilation for COVID-19-Associated Severe ARDS: A Single Center Observational Study

Background: Patients with coronavirus disease 2019 (COVID-19) may develop severe acute respiratory distress syndrome (ARDS). The aim of the study was to explore the lung recruitability, individualized positive end-expiratory pressure (PEEP), and prone position in COVID-19-associated severe ARDS. Methods: Twenty patients who met the inclusion criteria were studied retrospectively (PaO₂/FiO₂ 68.0 ± 10.3 mmHg). The patients were ventilated under volume-controlled mode with tidal volume of 6 mL/kg predicted body weight. The lung recruitability was assessed via the improvement of PaO₂, PaCO₂, and static respiratory system compliance (C_stat) from low to high PEEP (5-15 cmH₂O). Patients were considered recruitable if two out of three parameters improved. Subsequently, PEEP was titrated according to the best C_stat. The patients were turned to prone position for further 18-20 h. Results: For recruitability assessment, average value of PaO₂ was slightly improved at PEEP 15 cmH₂O (68.0 ± 10.3 vs. 69.7 ± 7.9 mmHg, baseline vs. PEEP 15 cmH₂O; p = 0.31). However, both PaCO₂ and C_stat worsened (PaCO₂: 72.5 ± 7.1 vs. 75.1 ± 9.0 mmHg; p < 0.01. C_stat: 17.5 ± 3.5 vs. 16.6 ± 3.9 ml/cmH₂O; p = 0.05). Only four patients (20%) were considered lung recruitable. Individually titrated PEEP was higher than the baseline PEEP (8.0 ± 2.1 cmH₂O vs. 5 cmH₂O, p < 0.001). After 18-20 h of prone positioning, investigated parameters were significantly improved compared to the baseline (PaO₂: 82.4 ± 15.5 mmHg. PaCO₂: 67.2 ± 6.4 mmHg. C_stat: 20.6 ± 4.4 ml/cmH₂O. All p < 0.001 vs. baseline). Conclusions: Lung recruitability was very low in COVID-19-associated severe ARDS. Individually titrated PEEP and prone positioning might improve lung mechanics and blood gasses.

Surfactant therapy for COVID-19 related ARDS: a retrospective case-control pilot study

Background

COVID-19 causes acute respiratory distress syndrome (ARDS) and depletes the lungs of surfactant, leading to prolonged mechanical ventilation and death. The feasibility and safety of surfactant delivery in COVID-19 ARDS patients have not been established.

Methods

We performed retrospective analyses of data from patients receiving off-label use of exogenous natural surfactant during the COVID-19 pandemic. Seven COVID-19 PCR positive ARDS patients received liquid Curosurf (720 mg) in 150 ml normal saline, divided into five 30 ml aliquots) and delivered via a bronchoscope into second-generation bronchi. Patients were matched with 14 comparable subjects receiving supportive care for ARDS during the same time period. Feasibility and safety were examined as well as the duration of mechanical ventilation and mortality.

Results

Patients showed no evidence of acute decompensation following surfactant installation into minor bronchi. Cox regression showed a reduction of 28-days mortality within the surfactant group, though not significant. The surfactant did not increase the duration of ventilation, and health care providers did not convert to COVID-19 positive.

Conclusions

Surfactant delivery through bronchoscopy at a dose of 720 mg in 150 ml normal saline is feasible and safe for COVID-19 ARDS patients and health care providers during the pandemic. Surfactant administration did not cause acute decompensation, may reduce mortality and mechanical ventilation duration in COVID-19 ARDS patients. This study supports the future performance of randomized clinical trials evaluating the efficacy of meticulous sub-bronchial lavage with surfactant as treatment for patients with COVID-19 ARDS.

Management of Pediatric Septic Shock and Acute Respiratory Distress Syndrome in Thailand: A Survey of Pediatricians

Introduction: Pediatric septic shock and acute respiratory distress syndrome (pARDS) are major causes of morbidity and mortality in pediatric intensive care units (PICUs). While standardized guidelines for sepsis and pARDS are published regularly, their implementation and adherence to guidelines are different in resource-rich and resource-limited countries. The purpose of this study was to conduct a survey to ascertain variation in current clinician-reported practice in pediatric septic shock and acute respiratory distress syndrome, and the clinician skills in a variety of hospital settings throughout Thailand. Methods: We conducted an electronic survey in pediatricians throughout the country between August 2020 and February 2021 using multiple choice questions and clinical case scenarios based on the 2017 American College of Critical Care Medicine's Consensus guideline for pediatric and neonatal septic shock and the 2015 Pediatric Acute Lung Injury Consensus Conference. Results: The survey elicited responses from 255 pediatricians (125 general pediatricians, 38 pulmonologists, 27 cardiologists, 32 intensivists, and 33 other subspecialists), with 54.5% of the respondents having <5 years of PICU experience. Among the six sepsis scenarios, 72.5 and 78.4% of the respondents had good adherence to the guidelines for managing fluid refractory shock and sedation for intubation, respectively. The ICU physicians reported greater adherence during more complex shock. In ARDS scenarios, 80.8% of the respondents reported having difficulty diagnosing ARDS mimic conditions and used lesser PEEP than the recommendation. Acceptance of permissive hypercapnia and mild hypoxemia was accepted by 62.4 and 49.4% of respondents, respectively. The ICU physicians preferred decremental PEEP titration, whereas general pediatricians preferred incremental PEEP titration. Conclusion: This survey variation could be the result of resource constraints, knowledge gaps, or ambiguous guidelines. Understanding the perspective and rationale for variation in pediatricians' practices is critical for successful guideline implementation.

Effect of lung recruitment on blood gas index, hemodynamics, lung compliance, and rehabilitation index in children with acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a common pediatric disease, with an increasing mortality rate in recent years. This study aims to explore the effects of lung recruitment on blood gas indexes, hemodynamics, lung compliance, and rehabilitation index in children with ARDS.

METHODS

Seventy children with ARDS admitted to our hospital from December 2017 to December 2018 were selected as the study subjects, and were divided into a study group (35 cases, treated with lung recruitment strategy) and a control group (35 cases, treated with routine therapy). The changes of blood gas indexes, such as partial pressure of oxygen (PO₂), partial pressure of carbon dioxide (PCO₂), and partial pressure of oxygen/fraction of inspired oxygen (PO₂/FiO₂) levels, as well as hemodynamic indexes, including cardiac output (CO), heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), were compared before and after treatment in the two groups.

RESULTS

Results showed that the difference in blood gas indexes between the two groups was statistically significant after treatment (P<0.05), and that the levels of PaO₂, PaCO₂, pondus Hydrogenii (pH), and PO₂/FiO₂ in the study group were all higher compared to the control group (P<0.05). The hemodynamic indexes showed that CO was significantly different between the two groups (P<0.05), but HR, MAP, and CVP were not (P>0.05). The lung compliance values of the two groups continued to increase at different time points after treatment (P<0.05), and the lung compliance of the study group was higher than that of the control group immediately after recruitment, as well as at 10 and 60 min of lung recruitment (P<0.05). In addition, the ventilator use, ICU stay, and hospital stay times of the study group were shorter than those in the control group (P<0.05), and the mortality rate of the study group was lower than that of the control group (P>0.05).

CONCLUSIONS

The lung recruitment strategy has a significant therapeutic effect on children with ARDS. It can effectively improve blood and gas function and lung compliance, and has a positive effect on the hemodynamic stability of children with ARDS.