Lung- and Diaphragm-Protective Ventilation

Development of clinical tools to estimate the breathing effort during high-flow oxygen therapy: A multicenter cohort study

INTRODUCTION AND OBJECTIVES

Quantifying breathing effort in non-intubated patients is important but difficult. We aimed to develop two models to estimate it in patients treated with high-flow oxygen therapy.

PATIENTS AND METHODS

We analyzed the data of 260 patients from previous studies who received high-flow oxygen therapy. Their breathing effort was measured as the maximal deflection of esophageal pressure (ΔPes). We developed a multivariable linear regression model to estimate ΔPes (in cmH2O) and a multivariable logistic regression model to predict the risk of ΔPes being >10 cmH2O. Candidate predictors included age, sex, diagnosis of the coronavirus disease 2019 (COVID-19), respiratory rate, heart rate, mean arterial pressure, the results of arterial blood gas analysis, including base excess concentration (BEa) and the ratio of arterial tension to the inspiratory fraction of oxygen (PaO2:FiO2), and the product term between COVID-19 and PaO2:FiO2.

RESULTS

We found that ΔPes can be estimated from the presence or absence of COVID-19, BEa, respiratory rate, PaO2:FiO2, and the product term between COVID-19 and PaO2:FiO2. The adjusted R2 was 0.39. The risk of ΔPes being >10 cmH2O can be predicted from BEa, respiratory rate, and PaO2:FiO2. The area under the receiver operating characteristic curve was 0.79 (0.73-0.85). We called these two models BREF, where BREF stands for BReathing EFfort and the three common predictors: BEa (B), respiratory rate (RE), and PaO2:FiO2 (F).

CONCLUSIONS

We developed two models to estimate the breathing effort of patients on high-flow oxygen therapy. Our initial findings are promising and suggest that these models merit further evaluation.

Randomized Trial of Lung and Diaphragm Protective Ventilation in Children

BACKGROUND

Mechanical ventilation strategies that balance lung and diaphragm protection have not been extensively tested in clinical trials.

METHODS

We conducted a single-center, phase II randomized controlled trial in children with acute respiratory distress syndrome with two time points of random assignment: the acute and weaning phases of ventilation. Patients in the intervention group were managed with a computerized decision support (CDS) tool, named REDvent, and esophageal manometry to deliver lung and diaphragm protective ventilation. The control group received usual care. A daily standardized spontaneous breathing trial (SBT) was performed in both groups. The primary outcome was the length of weaning.

RESULTS

From October 2017 through March 2024, 248 children were randomly assigned to the acute phase. When participants were triggering the ventilator, the adjusted mean difference (REDvent-acute - usual care-acute) for peak inspiratory pressure was -3 cmH2O (95% CI, -5 to -2), positive end-expiratory pressure was -2 cmH2O (95% CI, -2 to -1), and the esophageal pressure swing was -1.8 cmH2O (95% CI, -3.2 to -0.3). For the primary outcome, 55% of REDvent-acute patients passed their SBT or were extubated on the day of the first SBT, compared with 39% in the usual care-acute group. After adjusting for age, immunosuppression, and oxygenation index value, the REDvent-acute intervention resulted in a 1.67 (95% CI, 1.01 to 2.77; P=0.045) odds of a shorter length of weaning than usual care. The median time from intubation to SBT passage was 3.83 days in the intervention group versus 4.75 days in the usual care group. The length of ventilation among survivors was 5.0 days in the intervention group versus 5.6 days in the usual care group. When comparing weaning phase random assignment, clinical outcomes were similar between groups. There were no differences in adverse events between the groups.

CONCLUSIONS

A lung and diaphragm protective ventilation strategy using a CDS tool during the acute phase of ventilation resulted in a shorter length of weaning than usual care. Phase III trials in mechanically ventilated patients are warranted. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT03266016.).

Early versus Delayed Switching from Controlled to Assisted Ventilation: A Target Trial Emulation

Rationale: In critically ill patients receiving invasive mechanical ventilation, switching from controlled to assisted ventilation is a crucial milestone toward ventilator liberation. The optimal timing for switching to assisted ventilation has not been studied. Objectives: Our objective was to determine whether a strategy of early compared with delayed switching affects the duration of invasive mechanical ventilation, ICU length of stay, and mortality. Methods: We conducted a target trial emulation using the prospective, global WEAN SAFE (the WorldwidE AssessmeNt of Separation of pAtients From ventilatory assistancE) dataset. Patients were eligible for switching if they were still on controlled mechanical ventilation, were not receiving neuromuscular blockers, and had PaO2:FiO2 ratios >150 mm Hg. We compared an "early switching" strategy (switch within 1 day after reaching switching eligibility criteria) with a "delayed switching" strategy (switch 1 or more days after reaching the switching eligibility criteria). The primary outcome was the 28-day cumulative incidence of successful extubation. Secondary outcomes included 28-day and 90-day ICU discharge and ICU mortality. Measurements and Main Results: A total of 1,489 patients met the switching eligibility criteria. The early-switch group had, on average, 4 additional days of being successfully extubated over the 28-day period (95% confidence interval [CI], 3-6 days; P < 0.001) compared with the delayed group, with a higher difference in cumulative incidence of successful extubation at Day 28 (7% [95% CI, 0-13%]; P = 0.04). Early switching was associated with an 11% higher cumulative incidence of ICU discharge at Day 28 (95% CI, 7-18%; P < 0.001) and an average of 7 additional days discharged from the ICU over the 90-day period (95% CI, 4-12 days; P < 0.001) compared with delayed switching. ICU mortality rates did not differ between the strategies. Conclusions: Early switching from controlled to assisted ventilation is associated with shorter duration of invasive mechanical ventilation and ICU stay compared with delayed switching.

Mechanical Ventilation in Patients with Acute Brain Injuries: A Pathophysiology-based Approach

Applying mechanical ventilation and selecting ventilatory strategies in patients with acute brain injuries, especially those with lung damage, is challenging. Static (positive end-expiratory pressure) and dynamic (intratidal) changes in ventilator pressure, via complex pathways, influence cerebral arterial inflow and cerebral venous pressure and thus cerebral blood volume and intracranial pressure. In this process, the relationship between airway pressure and pleural and transalveolar pressures, heavily affected by elastance of the chest wall and lung, respectively, plays a central role. This relationship determines the extent to which a static and dynamic increase in airway pressure affects the cardiac function and venous return curves, which govern the static and dynamic arterial and central venous pressures. The integrity of cerebral autoregulation determines whether static changes in arterial pressure alter cerebral arterial inflow. Conversely, dynamic changes in arterial pressure during the breath are followed by corresponding changes in cerebral arterial inflow because of the inability of autoregulation to control rapid arterial pressure fluctuations. The flow dynamics in the jugular veins and the relationship between intracranial and sagittal sinus pressures determine whether static and dynamic changes in central venous pressure alter cerebral venous pressure. Setting the ventilator and planning strategies should be individualized and guided by the complex, interactive effects among central nervous, respiratory, and cardiovascular systems on cerebral blood volume and cerebral perfusion and intracranial pressures. Following a logical framework, clinicians may anticipate the likely effects of ventilator settings and strategies on cerebral hemodynamics, enabling a more individualized approach in setting the ventilator and planning ventilatory strategies.

Diaphragm neurostimulation in mechanical ventilation: current status and future prospects

INTRODUCTION

Diaphragm neurostimulation is a muscle stimulation technique that, through electrodes placed directly on or at the vicinity of the phrenic nerves, induces diaphragm contractions independently of the patient's cooperation. Recently, the technical development of temporary diaphragm neurostimulation devices has paved the way for a new era in the management of critically ill patients.

AREAS COVERED

In this review, we describe the latest technical developments in diaphragm neurostimulation and its physiological effects. We searched MEDLINE of experimental and clinical studies in English language published from database inception until 31 October 2024. We also discuss the advances in terms of patients centered outcomes and the key areas for improvement. Lastly, we introduce possible future directions and the novel improvements in patient care.

EXPERT OPINION

The research on diaphragm neurostimulation promise as an emerging intervention which addresses common complications associated with mechanical ventilation. Large-scale clinical trials are necessary to validate diaphragm neurostimulation efficacy and safety in humans, establish treatment protocols, and determine cost-effectiveness, all of which are essential for diaphragm neurostimulation to be widely accepted in clinical practice.

Respiratory muscle ultrasound echo characteristics and weaning outcomes in mechanically ventilated patients with sepsis: a prospective observational study

AIM

This study aimed to determine the relationship between changes in the ultrasound echo intensity of respiratory muscles and weaning outcomes in mechanically ventilated patients with sepsis.

METHODS

We prospectively observed patients with sepsis receiving mechanical ventilation admitted to the Department of Critical Care Medicine at our hospital, and categorized them into weaning success (n = 75) and weaning failure (n = 35) groups according to their weaning outcomes. The baseline respiratory muscle echo intensity of the patients was observed, and the relationship between the respiratory muscle ultrasonographic echo characteristics and weaning outcomes was evaluated.

RESULTS

Baseline respiratory muscle echo intensity was significantly higher in the weaning failure group than in the weaning success group. The incidence of respiratory muscle echoes during mechanical ventilation was significantly higher in the weaning failure group than in the weaning success group. The respiratory muscle echo characteristics changed after ICU admission. Increased respiratory muscle echo intensity was detected earlier and more readily in patients with weaning failure than in those with respiratory muscle atrophy, and enhanced respiratory muscle echo was associated with a decrease in the incidence of cumulative weaning success.

CONCLUSION

Mechanically ventilated patients with sepsis with failed weaning had higher respiratory muscle echo intensities than those in the weaning success group. Futhermore, there was an association between the respiratory muscle echo intensity and weaning outcomes.

Tailoring non-invasive respiratory supports in acute hypoxemic respiratory failure: A practical approach for clinicians

The use of non-invasive respiratory support (NIRS) for acute respiratory failure (ARF), particularly hypoxemic respiratory failure, has advanced in recent years, especially during the COVID-19 pandemic. NIRS modalities like high-flow nasal cannula (HFNC), continuous positive airway pressure (CPAP), and non-invasive ventilation (NIV) have shown efficacy, though evidence is inconsistent, especially for "de novo" acute hypoxemic respiratory failure (AHRF). This review outlines the physiological rationale for NIRS and offers practical guidance on tailoring treatment to individual patients. Successful AHRF management with NIRS requires a personalized approach, guided by clinical expertise. Further research is needed to refine patient selection and optimize NIRS application.

ARDS Weaning: The Impact of Abnormal Breathing Patterns Detected by Electric Tomography Impedance and Respiratory Mechanics Monitoring

Background: After the improvement of the initial phase of ARDS, when the patients begin spontaneous breathing and weaning from mechanical ventilation, some patients may present abnormal breathing patterns, whose evaluation of the repercussions were poorly studied. This study proposed to evaluate abnormal breathing patterns through the use of electrical impedance tomography (EIT), and clinical, respiratory mechanics, and ventilatory parameters according to the types of weaning from mechanical ventilation. Methods: This was a prospective cohort study of subjects with ARDS who were considered able to be weaned from mechanical ventilation in the clinical-surgical ICU. Weaning types were defined as simple, difficult, and prolonged weaning. EIT, ventilatory, lung mechanics, and clinical data were collected. Data were collected at baseline in a controlled ventilatory mode and, after neuromuscular blocker withdrawal, data were collected after 30 min, 2 h, and 24 h. EIT parameter analysis was performed for ventilation distribution in the lung regions, pendelluft, breath-stacking, reverse-trigger, double-trigger, and asynchrony index. Results: The study included 25 subjects who were divided into 3 groups (9/25 simple, 8/25 difficult, and 8/25 prolonged weaning). The prolonged weaning group showed more delirium, ICU-acquired weakness, stay in ICU, and hospital and ICU mortality. During the change from controlled to spontaneous mode, we observed increased tidal volumes and driving pressures, which were mainly found in the prolonged weaning group when compared with the simple weaning group. The prolonged weaning group showed a higher flow index, more asynchronies during volume-assisted ventilation, a higher incidence of pendelluft, and redistribution of ventilation to posterior regions visualized by EIT. Conclusions: The present study showed abnormal breathing patterns in the prolonged weaning group. The clinical occult findings of abnormal breathing patterns could be monitored, mainly through EIT and with better assessment of pulmonary mechanics.

An overview of patient-ventilator asynchrony in children

INTRODUCTION

Mechanically ventilated children often have patient-ventilator asynchrony (PVA). When a ventilated patient has spontaneous effort, the ventilator attempts to synchronize with the patient, but PVA represents a mismatch between patient respiratory effort and ventilator delivered breaths.

AREAS COVERED

This review will focus on subtypes of patient ventilator asynchrony, methods to detect or measure PVA, risk factors for and characteristics of patients with PVA subtypes, potential clinical implications, treatment or prevention strategies, and future areas for research. Throughout this review, we will provide pediatric specific considerations.

EXPERT OPINION

PVA in pediatric patients supported by mechanical ventilation occurs frequently and is understudied. Pediatric patients have unique physiologic and pathophysiologic characteristics which affect PVA. While recognition of PVA and its subtypes is important for bedside clinicians, the clinical implications and risks versus benefits of treatment targeted at reducing PVA remain unknown. Future research should focus on harmonizing PVA terminology, refinement of automated detection technologies, determining which forms of PVA are harmful, and development of PVA-specific ventilator interventions.

Impact of Underassisted Ventilation on Diaphragm Function and Structure in a Porcine Model

BACKGROUND

Long-term controlled mechanical ventilation in the intensive care unit induces ventilator-induced diaphragm dysfunction (VIDD). The transition from controlled mechanical ventilation to assisted mechanical ventilation is a challenge that requires clinicians to balance overassistance and underassistance. While the effects of overassistance on the diaphragm are well known, the authors aimed to assess the impact of underassistance on diaphragm function and structure in a piglet model with preexisting VIDD (after long-term controlled mechanical ventilation) or without VIDD (short-term controlled mechanical ventilation).

METHODS

Twenty-two Large White female piglets were anesthetized, ventilated, and separated into two groups: a VIDD group (n = 10) with long-term 72-h controlled mechanical ventilation, and a no-VIDD group (n = 12) with short-term 2-h controlled mechanical ventilation. After sedation reduction at the end of the controlled mechanical ventilation period, each piglet was switched to underassisted ventilation for 2 h. Diaphragm function (supramaximal diaphragm pressure-generating capacity assessed by negative tracheal pressure after transvenous phrenic nerve stimulation) and diaphragm structure (mini-invasive in vivo biopsies) were assessed before and after underassisted ventilation.

RESULTS

In the VIDD group, supramaximal diaphragm pressure-generating capacity decreased by 22% from (mean ± SD) 69.9 ± 12.7 to 54.9 ± 19.7 cm H 2 O ( P = 0.04) after 72 h of controlled mechanical ventilation evidencing VIDD, then dropped by a further 29% from 54.9 ± 19.7 to 38.9 ± 15.5 cm H 2 O ( P < 0.01) after 2 h of underassisted ventilation. Diaphragm pressure-generating capacity remains stable from 55.3 ± 22.7 to 58.2 ± 24 cm H 2 O ( P = 0.24) in the no-VIDD group. Diaphragm structure showed that sarcomeric injuries increase from 13 ± 10% to 24 ± 19% ( P < 0.01) and lipid droplets decrease from 14 ± 8% to 11 ± 6% ( P = 0.03) of the total micrograph area after 2 h of underassisted ventilation in the VIDD group. Sarcomeric injuries and lipid droplets accounted, respectively, for 17 ± 16% and 2 ± 3% of the total micrograph area after underassisted ventilation in the no-VIDD group.

CONCLUSIONS

In this porcine model, a short 2-h exposure of underassisted ventilation induces impairment of diaphragm function with damage to the diaphragm structure in intensive care unit condition with preexisting VIDD.

Monitoring and preserving diaphragmatic function in mechanical ventilation

PURPOSE OF REVIEW

This review summarizes the evidence on clinical outcomes related to diaphragm dysfunction, providing an overview on available monitoring tools and strategies for its prevention and treatment.

RECENT FINDINGS

Long-term adverse functional outcomes in intensive care survivors are well documented, especially in patients with prolonged mechanical ventilation. Because diaphragm weakness is highly prevalent and strongly associated with weaning failure, a link between diaphragm weakness and adverse functional outcomes is probable. Mechanisms of critical illness-associated diaphragm weakness are complex and include ventilator-related myotrauma through various pathways (i.e. over-assistance, under-assistance, eccentric, expiratory). Given this potential clinical impact, research on preventive and therapeutic strategies is growing including the development of ventilation strategies aiming at protecting both the lung and the diaphragm. Phrenic nerve stimulation and specific rehabilitation strategies also appear promising.

SUMMARY

Diaphragm dysfunction is associated with adverse clinical outcomes in ventilated patients; therefore, their inspiratory effort and function should be monitored. Whenever possible, and without compromising lung protection, moderate inspiratory effort should be targeted. Phrenic nerve stimulation and specific rehabilitation strategies are promising to prevent and treat diaphragm dysfunction, but further evidence is needed before widespread implementation.

Awake Venovenous Extracorporeal Membrane Oxygenation in the Intensive Care Unit: Challenges and Emerging Concepts

Extracorporeal membrane oxygenation (ECMO) is an advanced treatment for severe respiratory failure. Implantation of ECMO before invasive ventilation or extubation during ECMO has been reported and is becoming increasingly popular. Avoidance of sedation and invasive ventilation during ECMO (commonly referred to as "awake ECMO") may have potential advantages, including a lower rate of delirium, shorter mechanical ventilation time, and the possibility of undergoing early rehabilitation and/or physiotherapy. However, awake ECMO is also associated with several risks, such as self-inflicted lung injury and cannula displacement or self-removal. Accordingly, invasive ventilation before ECMO, as well as weaning from ECMO before weaning from mechanical ventilation, remain the most common approaches. In this review, the authors describe indications, contraindications, advantages, disadvantages, and current evidence on the use of ECMO without invasive ventilation in patients with respiratory failure.

Validation of Airway Occlusion Pressure as a Method of Assessing Breathing Effort During Noninvasive Ventilation

Background: The airway-occlusion pressure is used to estimate the muscle pressure (P mus ) and the occlusion pressure at 100 ms (P 0 .1 ) to assess respiratory drive in patients on mechanical ventilation. However, the validity of these maneuvers during noninvasive ventilation (NIV) has not been evaluated. This study was designed to validate the airway-occlusion pressure and the P 0 .1 described for mechanical ventilation during NIV in a bench model. Methods: This was a bench observational prospective study carried out during January and February 2024 in the ICU laboratory of the Hospital Británico of Buenos Aires. Results: In the non-leakage NIV scenarios with oronasal and total face mask, the NIV-airway-occlusion pressure increased with greater P mus (P < .001). For a programmed P mus of 5 cm H2O, values around 4.5 cm H2O were recorded for both oronasal and total face masks. At 10 cm H2O, the values were ∼8 cm H2O, and at 15 cm H2O, they were ∼11 cm H2O. With leaks, this difference worsened as leakage increased and the effort decreased. In the Bland-Altman analysis between mechanical ventilation-airway-occlusion pressure and NIV-airway-occlusion pressure without leakage for oronasal and total face masks, we found a good agreement for the 3 levels of P mus with both types of masks. With regard to the values of NIV-airway-occlusion pressure with the helmet, Bland-Altman analysis showed a high bias and random error. Multivariate analysis found that NIV-airway-occlusion pressure depends on the type of interface, increased with P mus , and decreased as leakage increased. The agreement of NIV-P 0 .1 was not good across all noninvasive measurements. Conclusions: This study constitutes a relevant contribution in the validation of indices to assess P mus during NIV. In a laboratory setting, the measurement of airway-occlusion pressure in NIV may be used to assess effort estimation in the absence of leakage; however, it will likely be underestimated. P 0 .1 proved to be an unreliable method. These findings suggest the feasibility of assessing muscle effort during NIV.

Impact of patient safety on outcomes. From prevention to the treatment of post-intensive care syndrome

Survivors of critical illness may present physical, psychological, or cognitive symptoms after hospital discharge, encompassed within what is known as post-intensive care syndrome. These alterations result from both the critical illness itself and the medical interventions surrounding it. For its prevention, the implementation of the ABCDEF bundle (Assess/treat pain, Breathing/awakening trials, Choice of sedatives, Delirium reduction, Early mobility and exercise, Family) has been proposed, along with additional strategies grouped under the acronym GHIRN (Good communication, Handout materials, Redefined ICU architectural design, Respirator, Nutrition). In addition to these preventive measures during the ICU stay, high-risk patients should be identified for subsequent follow-up through multidisciplinary teams coordinated by Intensive Care Medicine Departments.

Inhaled sedation versus propofol in respiratory failure in the ICU (INSPiRE-ICU2): study protocol for a multicenter randomized controlled trial

BACKGROUND

Patients undergoing invasive mechanical ventilation often require pharmacologic sedation to facilitate tolerance of this life-sustaining intervention, but sedatives currently used in routine care have substantial limitations. Isoflurane is an inhaled volatile anesthetic with pharmacologic properties potentially suitable to sedation of ventilator-dependent critically ill patients, but need for specialized drug administration equipment has limited its use historically to general anesthesia in the operating theatre. This trial will evaluate isoflurane, administered using a novel drug delivery system, for sedation of ventilator-dependent adult intensive care unit (ICU) patients in the United States (US).

METHODS

The Inhaled Sedation versus Propofol in Respiratory Failure in the ICU (INSPiRE-ICU2) is a phase 3, multicenter, randomized, controlled, assessor-blinded non-inferiority trial that will evaluate efficacy and safety of inhaled isoflurane delivered via the Sedaconda ACD-S, compared to intravenous propofol, for sedation of mechanically ventilated adult ICU patients. At 16 US hospitals, 235 enrolled patients requiring continuous sedation during invasive mechanical ventilation will be randomized in 1.5:1 ratio to inhaled isoflurane or intravenous propofol for sedation. Treatment duration is expected to be at least 12 h and may last up to 48 (± 6) h or until no longer needing continuous sedation, whichever occurs first. The primary endpoint is the percentage of time sedation depth is maintained within the targeted range (Richmond Agitation Sedation Scale - 1 to - 4), in the absence of rescue sedation, during the treatment period. Secondary superiority outcomes include opioid exposure, wake-up time, cognitive recovery after end-of-treatment, and preservation of spontaneous breathing effort.

DISCUSSION

The INSPiRE-ICU2 trial will help determine the potential role of isoflurane for sedation of ventilator-dependent adult patients in the ICU. Key trial design features, including adoption of the estimand framework and blinded assessments of sedation depth, pain, and cognitive recovery, will ensure a rigorous evaluation of isoflurane for ICU sedation. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05327296. First registered on April 5, 2022.

Effects of 'Head Up' Prone Position on Transcranial Color Doppler-Based Estimators of Intracranial Pressure in Moderate to Severe Acute Respiratory Distress Syndrome Without Brain Injury: A Cross-Over, Longitudinal, Physiological Study

BACKGROUND

Prone positioning is recommended in acute respiratory distress syndrome (ARDS) to ensure adequate gas exchange. However, it may lead to an increase in intracranial pressure (ICP), mostly due to a reduction of venous return from the brain. ICP can be noninvasively estimated with transcranial color-coded Doppler (TCCD) using methods based on the relationships between the pulsatility index (PI) and ICP or methods based on the estimate of cerebral perfusion pressure (eCPP) and estimate of ICP (eICP). This study was aimed at assessing the effects of a 30° reverse Trendelenburg ('head up') prone position on two noninvasive estimators of ICP (eICP and PI).

METHODS

This is a cross-over, longitudinal, physiological study conducted on a cohort of adult patients fulfilling Berlin definition criteria for moderate to severe ARDS without brain injury but with clinical indication to prone positioning. We registered TCCD parameters of cerebral hemodynamic and systemic hemodynamic parameters, blood gas exchange data, and respiratory mechanics parameters in a horizonal supine position, in a 30° semirecumbent supine position, in the standard prone position, and, finally, in the 30° 'head up' prone position, obtained by tilting the entire bed to a reverse Trendelenburg position. One-way repeated measures analysis of variance was used to analyze data.

RESULTS

In 20 patients included, switching from a supine position to the standard prone position resulted in a significant increase in mean ± SD PI (from 0.99 ± 0.22 to 1.29 ± 0.25, p < 0.01) and eICP (from 12.5 ± 3.8 to 17.5 ± 4.1, p < 0.01), whereas moving from this latter position to the 'head up' prone position resulted in a decrease in the mean ± SD PI (from 1.29 ± 0.25 to 1.0 ± 0.23, p < 0.01). Hemodynamic and respiratory mechanics parameters did not differ.

CONCLUSIONS

The 30° 'head up' prone position may limit the increase in PI in moderate to severe ARDS without brain injury. As a noninvasive estimator of ICP, PI may allow detection of changes in ICP when moving from the 'head up' semirecumbent supine position to the standard prone position and from this latter position to the 'head up' prone position.

Weakness acquired in the cardiac intensive care unit: still the elephant in the room?

Over the past two decades, the cardiac critical care population has shifted to increasingly comorbid and elderly patients often presenting with nonprimary cardiac conditions that exacerbate underlying advanced cardiac disease. Consequently, the modern cardiac intensive care unit (CICU) patient has poor outcome regardless of left ventricular ejection fraction. Importantly, delayed liberation from organ support, independent from premorbid health status and admission severity of illness, has been associated with increased morbidity and mortality up to years post-general critical care. Although a constellation of several acquired morbidities is at play, the most prominent enactor of poor long-term outcome in this population appears to be intensive care unit acquired weakness. Although the specific burden of ICU-acquired morbidities in CICU patients is yet to be clearly defined, it seems unfathomable that patients will not accrue some sort of ICU-related morbidity. There is hence an urgent need to better establish the exact benefit and cost of resource-intensive strategies in both short- and long-term survival of the CICU patient. Consequent and standardized documentation of admission comorbidities, severity of illness indicators, relevant ICU-related complications including weakness, and long-term post-ICU morbidity outcomes can help our understanding of the disease continuum and how to better care for the CICU survivor and their families and caregivers. Given increasing budgetary pressure on healthcare systems worldwide, interventions targeting CICU patients should focus on improving patient-centred long-term outcomes in a cost-effective manner. It will require a holistic and transmural continuity of care model to meet the challenges associated with treating critically ill cardiac patients in the future.

Pathophysiological mechanisms of ARDS: a narrative review from molecular to organ-level perspectives

BACKGROUND

Acute respiratory distress syndrome (ARDS) remains a life-threatening pulmonary condition with persistently high mortality rates despite significant advancements in supportive care. Its complex pathophysiology involves an intricate interplay of molecular and cellular processes, including cytokine storms, oxidative stress, programmed cell death, and disruption of the alveolar-capillary barrier. These mechanisms drive localized lung injury and contribute to systemic inflammatory response syndrome and multiple organ dysfunction syndrome. Unlike prior reviews that primarily focus on isolated mechanisms, this narrative review synthesizes the key pathophysiological processes of ARDS across molecular, cellular, tissue, and organ levels.

MAIN BODY

By integrating classical theories with recent research advancements, we provide a comprehensive analysis of how inflammatory mediators, metabolic reprogramming, oxidative stress, and immune dysregulation synergistically drive ARDS onset and progression. Furthermore, we critically evaluate current evidence-based therapeutic strategies, such as lung-protective ventilation and prone positioning, while exploring innovative therapies, including stem cell therapy, gene therapy, and immunotherapy. We emphasize the significance of ARDS subtypes and their inherent heterogeneity in guiding the development of personalized treatment strategies.

CONCLUSIONS

This narrative review provides fresh perspectives for future research, ultimately enhancing patient outcomes and optimizing management approaches in ARDS.

Advances in achieving lung and diaphragm-protective ventilation

PURPOSE OF REVIEW

Mechanical ventilation may have adverse effects on diaphragm and lung function. Lung- and diaphragm-protective ventilation is an approach that challenges the clinician to facilitate physiological respiratory efforts, while maintaining minimal lung stress and strain. Here, we discuss the latest advances in monitoring and interventions to achieve lung- and diaphragm protective ventilation.

RECENT FINDINGS

Noninvasive ventilator maneuvers (P0.1, airway occlusion pressure, pressure-muscle index) can accurately detect low and excessive respiratory efforts and high lung stress. Additional monitoring techniques include esophageal manometry, ultrasound, electrical activity of the diaphragm, and electrical impedance tomography. Recent trials demonstrate that a systematic approach to titrating inspiratory support and sedation facilitates lung- and diaphragm protective ventilation. Titration of positive-end expiratory pressure and, if available, veno-venous extracorporeal membrane oxygenation sweep gas flow may further modulate neural respiratory drive and effort to facilitate lung- and diaphragm protective ventilation.

SUMMARY

Achieving lung- and diaphragm-protective ventilation may require more than a single intervention; it demands a comprehensive understanding of the (neuro)physiology of breathing and mechanical ventilation, along with the application of a series of interventions under close monitoring. We suggest a bedside-approach to achieve lung- and diaphragm protective ventilation targets.

Monitoring respiratory muscles effort during mechanical ventilation

PURPOSE OF REVIEW

To summarize basic physiological concepts of breathing effort and outline various methods for monitoring effort of inspiratory and expiratory muscles.

RECENT FINDINGS

Esophageal pressure (Pes) measurement is the reference standard for respiratory muscle effort quantification, but various noninvasive screening tools have been proposed. Expiratory occlusion pressures (P0.1 and Pocc) could inform about low and high effort and the resulting lung stress, with Pocc outperforming P0.1 in identifying high effort. The pressure muscle index during an inspiratory hold could unveil inspiratory muscle effort, however obtaining a reliable inspiratory plateau can be difficult. Surface electromyography has the potential for inspiratory effort estimation, yet this is technically challenging for real-time assessment. Expiratory muscle activation is common in the critically ill warranting their assessment, that is, via gastric pressure monitoring. Expiratory muscle activation also impacts inspiratory effort interpretation which could result in both under- and overestimation of the resulting lung stress. There is likely a future role for machine learning applications to automate breathing effort monitoring at the bedside.

SUMMARY

Different tools are available for monitoring the respiratory muscles' effort during mechanical ventilation - from noninvasive screening tools to more invasive quantification methods. This could facilitate a lung and respiratory muscle-protective ventilation approach.

Pressure Support Ventilation During Extracorporeal Membrane Oxygenation Support in Patients With Acute Respiratory Distress Syndrome

In the initial phases of veno-venous extracorporeal membrane oxygenation (VV ECMO) support for severe acute respiratory distress syndrome (ARDS), ultraprotective controlled mechanical ventilation (CMV) is typically employed to limit the progression of lung injury. As patients recover, transitioning to assisted mechanical ventilation can be considered to reduce the need for prolonged sedation and paralysis. This study aimed to evaluate the feasibility of transitioning to pressure support ventilation (PSV) during VV ECMO and to explore variations in respiratory mechanics and oxygenation parameters following the transition to PSV. This retrospective monocentric study included 191 adult ARDS patients treated with VV ECMO between 2009 and 2022. Within this population, 131 (69%) patients were successfully switched to PSV during ECMO. Pressure support ventilation was associated with an increase in respiratory system compliance ( p = 0.02) and a reduction in pulmonary shunt fraction ( p < 0.001). Additionally, improvements in the cardiovascular Sequential Organ Failure Assessment score and a reduction in pulmonary arterial pressures ( p < 0.05) were recorded. Ninety-four percent of patients who successfully transitioned to PSV were weaned from ECMO, and 118 (90%) were discharged alive from the intensive care unit (ICU). Of those who did not reach PSV, 74% died on ECMO, whereas the remaining patients were successfully weaned from extracorporeal support. In conclusion, PSV is feasible during VV ECMO and potentially correlates with improvements in respiratory function and hemodynamics.

Comparison of programmed sedation care with conventional care in patients receiving mechanical ventilation for acute respiratory failure

OBJECTIVE

The aim of this study is to evaluate the effectiveness of planned sedation therapy in comparison to standard care for patients receiving mechanical ventilation for acute respiratory failure (ARF).

METHOD

The research included a total of sixty individuals who underwent mechanical ventilation for acute respiratory failure (ARF). Utilizing the random number table method, these patients were randomized at random to either the planned sedation care group (Group PSC) or the conventional care group (Group C). The objective was to assess and contrast the impact of treatment on the two groups. Significantly shorter durations of mechanical ventilation, sedative use, ICU therapy, length of stay, incidence of delirium, and adverse events were observed in Group PSC compared with Group C (P < 0.05). A higher 1-month survival rate following mechanical ventilation, a higher post-intervention forced expiratory volume in one second (FEV1) as a percentage of the expected value, a higher post-intervention forced vital capacity (FVC), and a higher patient family care satisfaction rate were observed in Group PSC compared to Group C (P < 0.05).

CONCLUSION

The scheduled administration of sedative therapy in patients receiving mechanical ventilation for acute respiratory failure (ARF) offers significant, reliable, and effective therapeutic benefits.

Does patient-ventilator asynchrony really matter?

PURPOSE OF REVIEW

Past observational studies have reported the association between patient-ventilator asynchronies and poor clinical outcomes, namely longer duration of mechanical ventilation and higher mortality. But causality has remained undetermined. During the era of lung and diaphragm protective ventilation, should we revolutionize our clinical practice to detect and treat dyssynchrony?

RECENT FINDINGS

Clinicians' ability to recognize asynchronies is typically low. Automatized softwares based on artificial intelligence have been trained to largely outperform human eyesight and are close to be implemented at the bedside. There is growing evidence that in susceptible patients, dyssynchrony may lead to ventilation-induced lung injury (or patient self-inflicted lung injury) and that clusters of such dyssynchronous events have the highest association with poor outcomes. Dyssynchrony may also be associated with harm indirectly when it reflects over-assistance or over-sedation. However, the occurrence of reverse triggering by means of low inspiratory efforts during passive ventilation may prevent diaphragm dysfunction and atrophy and be beneficial.

SUMMARY

Most recent evidence on the topic suggests that synchrony between the patient and the mechanical ventilator is a critical element for protecting lung and diaphragm during the time of invasive mechanical ventilation or may reflect inadequate settings or sedation. Therefore, it is a complex situation, and clinical trials are still needed to test the effectiveness of keeping patient-ventilator interaction synchronous on clinical outcomes.

How to protect the diaphragm and the lung with diaphragm neurostimulation

PURPOSE OF REVIEW

In the current review, we aim to highlight the evolving evidence on using diaphragm neurostimulation to develop lung and diaphragm protective mechanical ventilation.

RECENT FINDINGS

Positive-pressure ventilation (PPV) causes stress and strain to the lungs which leads to ventilator-induced lung injury (VILI). In addition, PPV is frequently associated with sedatives that induce excessive diaphragm unloading which contributes to ventilator-induced diaphragmatic dysfunction (VIDD). The nonvolitional diaphragmatic contractions entrained by diaphragm neurostimulation generate negative pressure ventilation, which may be a beneficial alternative or complement to PPV. Although well established as a permanent treatment of central apnea syndromes, temporary diaphragm neurostimulation rapidly evolves to prevent and treat VILI and VIDD. Experimental and small clinical studies report comprehensive data showing that diaphragm neurostimulation has the potential to mitigate VIDD and to decrease the stress and strain applied to the lungs.

SUMMARY

Scientific interest in temporary diaphragm neurostimulation has dramatically evolved in the last few years. Despite a solid physiological rationale and promising preliminary findings confirming a beneficial effect on the diaphragm and lungs, more studies and further technological advances will be needed to establish optimal standardized settings and lead to clinical implementation and improved outcomes.

An artificial intelligence application to predict prolonged dependence on mechanical ventilation among patients with critical orthopaedic trauma: an establishment and validation study

BACKGROUND

Prolonged dependence on mechanical ventilation is a common occurrence in clinical ICU patients and presents significant challenges for patient care and resource allocation. Predicting prolonged dependence on mechanical ventilation is crucial for improving patient outcomes, preventing ventilator-associated complications, and guiding targeted clinical interventions. However, specific tools for predicting prolonged mechanical ventilation among ICU patients, particularly those with critical orthopaedic trauma, are currently lacking. The purpose of the study was to establish and validate an artificial intelligence (AI) platform to assess the prolonged dependence on mechanical ventilation among patients with critical orthopaedic trauma.

METHODS

This study analyzed 1400 patients with critical orthopaedic trauma who received mechanical ventilation, and the prolonged dependence on mechanical ventilation was defined as not weaning from mechanical ventilation for ≧ 7 days. Patients were randomly classified into a training cohort and a validation cohort based on the ratio of 8:2. Patients in the training cohort were used to establish models using machine learning techniques, including logistic regression (LR), extreme gradient boosting machine (eXGBM), decision tree (DT), random forest (RF), support vector machine (SVM), and light gradient boosting machine (LightGBM), whereas patients in the validation cohort were used to validate these models. The prediction performance of these models was evaluated using discrimination and calibration. A scoring system was used to comprehensively assess and compare the prediction performance of the models, based on ten evaluation metrics. External validation of the model was performed in 122 patients with critical orthopaedic trauma from a university teaching hospital. Furthermore, the optimal model was deployed as an AI calculator, which was accessible online, to assess the risk of prolonged dependence on mechanical ventilation.

RESULTS

Among the developed models, the eXGBM model had the highest score of 50, followed by the LightGBM model (48) and the RF model (37). In detail, the eXGBM model outperformed other models in terms of recall (0.892), Brier score (0.088), log loss (0.291), and calibration slope (0.999), and the model was the second best in terms of area under the curve value (0.949, 95%: 0.933-0.961), accuracy (0.871), F1 score (0.873), and discrimination slope (0.647). The SHAP revealed that the most important five features were respiratory rate, lower limb fracture, glucose, PaO2, and PaCO2. External validation of the eXGBM model also demonstrated favorable prediction performance, with an AUC value of 0.893 (95%CI: 0.819-0.967). The eXGBM model was successfully deployed as an AI platform, which was at https://prolongedmechanicalventilation-lqsfm6ecky6dpd4ybkvohu.streamlit.app/ . By simply clicking the link and inputting features, users were able to obtain the risk of experiencing prolonged dependence on mechanical ventilation for individuals. Based on the risk of prolonged dependence on mechanical ventilation, patients were stratified into the high-risk or the low-risk groups, and corresponding therapeutic interventions were recommended, accordingly.

CONCLUSIONS

The AI model shows potential as a valuable tool for stratifying patients with a high risk of prolonged dependence on mechanical ventilation. The AI model may offer a promising approach for optimizing patient care and resource allocation in critical care settings.

CLINICAL TRIAL NUMBER

Not applicable.

Serial sonographic assessment of diaphragmatic atrophy and lung injury patterns in mechanically ventilated preterm infants to predict extubation failure: a prospective observational study

Diaphragmatic atrophy (DA) and lung injury (LI) have been associated with mechanical ventilation (MV). We aimed to assess the ultrasonographic changes in diaphragmatic thickness and LI during MV and their prediction for extubation failure in preterm infants. In this prospective observational study, mechanically ventilated preterm infants, < 30 weeks gestation, within the first 24 h of life underwent a baseline, within 24 h of MV, and serial diaphragmatic and lung ultrasounds scans until their first extubation attempt. DA was defined as a decline in pre-extubation expiratory diaphragmatic thickness (DTexp) by ≥ 10% compared to baseline. A total of 251 ultrasound scans were performed on 38 preterm infants with a mean gestational age of 26.6 ± 1.7 weeks. Of these, 18 infants (47%) had DA. Among infants with DA, a pattern of progressive decline in DTexp was associated with a concomitant pattern of increase in the lung ultrasound score (LUS). Infants in the DA group experienced a significantly higher percentage of extubation failure [13 (72%) versus 5 (25%), p = 0.004] compared to the no-DA group. Pre-extubation LUS was significantly higher in the DA compared to the no-DA group (14.2 ± 6.0 versus 10.3 ± 5.2, p = 0.04). Logistic regression analysis controlling for gestational age, pre-extubation weight, and mean airway pressure at extubation showed that LUS [OR 1.27, 95% CI (1.04-1.56), p = 0.02] was an independent predictor of for extubation failure.

CONCLUSION

In this cohort of preterm infants, lung ultrasound score has proved to be a stronger predictor of successful extubation compared to diaphragmatic thickness.

WHAT IS KNOWN

• Ultrasonographic assessment of the diaphragm and lungs is a sensitive tool in diagnosis of ventilator induced diaphragmatic atrophy and lung injury in preterm infants. Accuracy of lung and diaphragmatic ultrasound in predicting extubation outcome in preterm infants is questionable.

WHAT IS NEW

• A pattern of progressive decline in diaphragmatic thickness was associated with a concomitant pattern of increase in the lung ultrasound score in mechanically ventilated preterm infants. Lung ultrasound score has proved to be a stronger predictor of successful extubation compared to diaphragmatic thickness.

Personalized positive end-expiratory pressure in spontaneously breathing patients with acute respiratory distress syndrome by simultaneous electrical impedance tomography and transpulmonary pressure monitoring: a randomized crossover trial

PURPOSE

Personalized positive end-expiratory pressure (PEEP) might foster lung and diaphragm protection in patients with acute respiratory distress syndrome (ARDS) who are undergoing pressure support ventilation (PSV). We aimed to compare the physiologic effects of personalized PEEP set according to synchronized electrical impedance tomography (EIT) and driving transpulmonary pressure (∆PL) monitoring against a classical lower PEEP/FiO2 table in intubated ARDS patients undergoing PSV.

METHODS

A cross-over randomized multicenter study was conducted in 30 ARDS patients with simultaneous recording of the airway, esophageal and transpulmonary pressure, together with EIT during PSV. Following a decremental PEEP trial (18 cmH2O to 4 cmH2O), PEEPEIT-∆PL was identified as the level with the smallest difference between lung overdistension and collapse. A low PEEP/FiO2 table was used to select PEEPTABLE. Each PEEP strategy was applied for 20 min, and physiologic data were collected at the end of each step.

RESULTS

The PEEP trial was well tolerated. Median PEEPEIT-∆PL was higher than PEEPTABLE (10 [8-12] vs. 8 [5-10] cmH2O; P = 0.021) and, at the individual patient level, PEEPEIT-∆PL level differed from PEEPTABLE in all patients. Overall, PEEPEIT-∆PL was associated with lower dynamic ∆PL (P < 0.001) and pressure-time product (P < 0.001), but there was variability among patients. PEEPEIT-∆PL also decreased respiratory drive and effort (P < 0.001), improved regional lung mechanics (P < 0.05) and reversed lung collapse (P = 0.007) without increasing overdistension (P = 0.695).

CONCLUSION

Personalized PEEP selected using synchronized EIT and transpulmonary pressure monitoring could be associated with reduced dynamic lung stress and metabolic work of breathing in ARDS patients undergoing PSV.

Rehabilitation effects of acupuncture on the diaphragmatic dysfunction in respiratory insufficiency: A systematic review and meta-analysis

INTRODUCTION

Mechanical ventilation after respiratory insufficiency can induce diaphragm dysfunction through various hypothesized mechanisms. In this study, we evaluated the rehabilitative effect of acupuncture on diaphragm function in patients with respiratory insufficiency using meta-analysis and summarised the rules of acupoints through association rules analysis.

METHODS

Articles (published from January 2000 to February 2024) were retrieved from the following databases: PubMed, Cochrane Library, Embase, Web of Science, CNKI, VIP, SinoMed, and Wanfang. Two researchers conducted literature selection, data extraction, and statistical analysis independently. The risk of bias was assessed utilizing the Physical Therapy Evidence Database (PEDro) scale. The meta-analysis was performed with RevMan 5.4 software, and the quality of each outcome evidence was assessed via the online software GRADEpro GDT. The regularity of acupoint selection was summarized using association rules analysis. This study is registered on PROSPERO, number CRD42024526705.

RESULTS

Eleven articles were eventually included, all of which were of low to moderate quality. Results of the meta-analysis showed a significant increase in diaphragmatic thickening fraction (MD 3.40 [1.52, 5.27]) and diaphragmatic excursion (MD 0.95 [0.58, 1.31]) in patients with respiratory insufficiency after acupuncture treatment. Also, OI (MD 28.52 [15.93, 41.11]) and PaO2 (MD 7.18 [2.22, 12.13]) were significantly elevated and PaCO2 (MD -6.94 [-12.30, -1.59]) was decreased. Mechanical ventilation time (MD-1.86 [-2.28, -1.45]) was also significantly improved. The overall quality of the outcome evidence is deemed moderate. Association rules analysis showed that ST36, RN4, RN6, and others are core acupoints for the treatment of diaphragmatic dysfunction in patients with respiratory insufficiency by acupuncture.

CONCLUSION

Acupuncture shows potential in the rehabilitation of patients with respiratory insufficiency and may serve as a complementary and alternative therapy for related conditions. We suggest the use of ST36 as a core acupoint, in combination with other acupoints. Due to the potential publication bias and high heterogeneity of the current data, further high-quality RCTs are needed to confirm these findings.

Lung and Diaphragm Protection During Mechanical Ventilation in Patients with Acute Respiratory Distress Syndrome

Patients with acute respiratory distress syndrome often require mechanical ventilation to maintain adequate gas exchange and to reduce the workload of the respiratory muscles. Although lifesaving, positive pressure mechanical ventilation can potentially injure the lungs and diaphragm, further worsening patient outcomes. While the effect of mechanical ventilation on the risk of developing lung injury is widely appreciated, its potentially deleterious effects on the diaphragm have only recently come to be considered by the broader intensive care unit community. Importantly, both ventilator-induced lung injury and ventilator-induced diaphragm dysfunction are associated with worse patient-centered outcomes.

What every paediatrician needs to know about mechanical ventilation

Invasive mechanical ventilation (MV) is one of the most practiced interventions in the intensive care unit (ICU) and is unmistakably lifesaving for children with acute respiratory failure (ARF). However, if delivered inappropriately (i.e. ignoring the respiratory system mechanics and not targeted to the need of the individual patient at a specific time point in the disease trajectory), the side effects will outweigh the benefits. Decades of experimental and clinical investigations have resulted in a better understanding of three important detrimental effects of MV. These are ventilation-induced lung injury (VILI), patient self-inflicted lung injury (P-SILI), and ventilation-induced diaphragmatic injury (VIDD). VILI, P-SILI, and VIDD have in common that they occur when there is either too much or too little ventilatory assistance.Conclusion: The purpose of this review is to give the paediatrician an overview of the challenges to prevent these detrimental effects and titrate MV to the individual patient needs.

Transvenous phrenic nerve stimulation reduces diaphragm injury during controlled mechanical ventilation in a preclinical model of ARDS

Patients with acute respiratory distress syndrome (ARDS) require periods of deep sedation and mechanical ventilation, leading to diaphragm dysfunction. Our study seeks to determine whether the combination of temporary transvenous diaphragm neurostimulation (TTDN) and mechanical ventilation changes the degree of diaphragm injury and cytokines concentration in a preclinical ARDS model. Moderate ARDS was induced in pigs using oleic acid, followed by ventilation for 12 h post-injury with volume-control at 8 mL/kg, positive end-expiratory pressure (PEEP) 5 cmH2O, respiratory rate and [Formula: see text] set to achieve normal arterial blood gases. Two groups received TTDN: every second breath (MV + TTDN50%, n = 6) or every breath (MV + TTDN100%, n = 6). One group received ventilation only (MV, n = 6). Full-thickness diaphragm and quadricep muscle biopsies were taken at study end. Samples were fixed and stained with hematoxylin and eosin and a point-counting technique was applied to calculate abnormal muscle area fraction. Cytokine concentrations were measured in homogenized tissue using porcine-specific enzyme-linked immunosorbent assay (ELISA) and compared with serum samples. Percentage of abnormal diaphragm tissue was different between MV [8.1% (6.0-8.8)] versus MV + TTDN50% [3.4% (2.1-4.8)], P = 0.010 and MV versus MV + TTDN100% [3.1% (2.5-4.0)], P = 0.005. Percentage of abnormal quadriceps tissue was not different between groups. Cytokine concentration patterns in diaphragm samples were different between all groups (P < 0.001) and the interaction between TTDN application and resultant cytokine concentration pattern was significant (P = 0.025). TTDN, delivered in synchrony with mechanical ventilation, mitigated diaphragm injury, as evidenced by less abnormal tissue in the diaphragm samples, in pigs with oleic acid-induced ARDS and is an exciting tool for lung and diaphragm-protective ventilation.NEW & NOTEWORTHY This study adds to our understanding of applying transvenous diaphragm neurostimulation synchronously with mechanical ventilation by examining its effects on diaphragm muscle injury and cytokine concentration patterns in pigs with acute respiratory distress syndrome (ARDS). We observed that using this therapy for 12 h post lung injury mitigated ventilator-induced diaphragm injury and changed the pattern of cytokine concentration measured in diaphragm tissue. These findings suggest that transvenous diaphragm neurostimulation is an exciting tool for lung and diaphragm protective ventilation.

Phenotypes based on respiratory drive and effort to identify the risk factors when P0.1 fails to estimate ∆PES in ventilated children

BACKGROUND

Monitoring respiratory effort and drive during mechanical ventilation is needed to deliver lung and diaphragm protection. Esophageal pressure (∆PES) is the gold standard measure of respiratory effort but is not routinely available. Airway occlusion pressure in the first 100 ms of the breath (P0.1) is a readily available surrogate for both respiratory effort and drive but is only modestly correlated with ∆PES in children. We sought to identify risk factors for P0.1 over or underestimating ∆PES in ventilated children.

METHODS

Secondary analysis of physiological data from children and young adults enrolled in a randomized controlled trial testing lung and diaphragm protective ventilation in pediatric acute respiratory distress syndrome (PARDS) (NCT03266016). ∆PES (∆PES-REAL), P0.1 and predicted ∆PES (∆PES-PRED = 5.91*P0.1) were measured daily to identify phenotypes based upon the level of respiratory effort and drive: one passive (no spontaneous breathing), three where ∆PES-REAL and ∆PES-PRED were aligned (low, normal, and high effort and drive), two where ∆PES-REAL and ∆PES-PRED were mismatched (high underestimated effort, and overestimated effort). Logistic regression models were used to identify factors associated with each mismatch phenotype (High underestimated effort, or overestimated effort) as compared to all other spontaneous breathing phenotypes.

RESULTS

We analyzed 953 patient days (222 patients). ∆PES-REAL and ∆PES-PRED were aligned in 536 (77%) of the active patient days. High underestimated effort (n = 119 (12%)) was associated with higher airway resistance (adjusted OR 5.62 (95%CI 2.58, 12.26) per log unit increase, p < 0.001), higher tidal volume (adjusted OR 1.53 (95%CI 1.04, 2.24) per cubic unit increase, p = 0.03), higher opioid use (adjusted OR 2.4 (95%CI 1.12, 5.13, p = 0.024), and lower set ventilator rate (adjusted OR 0.96 (95%CI 0.93, 0.99), p = 0.005). Overestimated effort was rare (n = 37 (4%)) and associated with higher alveolar dead space (adjusted OR 1.05 (95%CI 1.01, 1.09), p = 0.007) and lower respiratory resistance (adjusted OR 0.32 (95%CI 0.13, 0.81), p = 0.017).

CONCLUSIONS

In patients with PARDS, P0.1 commonly underestimated high respiratory effort particularly with high airway resistance, high tidal volume, and high doses of opioids. Future studies are needed to investigate the impact of measures of respiratory effort, drive, and the presence of a mismatch phenotype on clinical outcome.

TRIAL REGISTRATION

NCT03266016; August 23, 2017.

Pressure control plus spontaneous ventilation versus volume assist-control ventilation in acute respiratory distress syndrome. A randomised clinical trial

PURPOSE

The aim of this study was to compare the effect of a pressure-controlled strategy allowing non-synchronised unassisted spontaneous ventilation (PC-SV) to a conventional volume assist-control strategy (ACV) on the outcome of patients with acute respiratory distress syndrome (ARDS).

METHODS

Open-label randomised clinical trial in 22 intensive care units (ICU) in France. Seven hundred adults with moderate or severe ARDS (PaO2/FiO2 < 200 mmHg) were enrolled from February 2013 to October 2018. Patients were randomly assigned to PC-SV (n = 348) or ACV (n = 352) with similar objectives of tidal volume (6 mL/kg predicted body weight) and positive end-expiratory pressure (PEEP). Paralysis was stopped after 24 h and sedation adapted to favour patients' spontaneous ventilation. The primary endpoint was in-hospital death from any cause at day 60.

RESULTS

Hospital mortality [34.6% vs 33.5%, p = 0.77, risk ratio (RR) = 1.03 (95% confidence interval [CI] 0.84-1.27)], 28-day mortality, as well as the number of ventilator-free days and organ failure-free days at day 28 did not differ between PC-SV and ACV groups. Patients in the PC-SV group received significantly less sedation and neuro-muscular blocking agents than in the ACV group. A lower proportion of patients required adjunctive therapy of hypoxemia (including prone positioning) in the PC-SV group than in the ACV group [33.1% vs 41.3%, p = 0.03, RR = 0.80 (95% CI 0.66-0.98)]. The incidences of pneumothorax and refractory hypoxemia did not differ between the groups.

CONCLUSIONS

A strategy based on PC-SV mode that favours spontaneous ventilation reduced the need for sedation and adjunctive therapies of hypoxemia but did not significantly reduce mortality compared to ACV with similar tidal volume and PEEP levels.

Respiratory muscle dysfunction in acute and chronic respiratory failure: how to diagnose and how to treat?

Assessing and treating respiratory muscle dysfunction is crucial for patients with both acute and chronic respiratory failure. Respiratory muscle dysfunction can contribute to the onset of respiratory failure and may also worsen due to interventions aimed at treatment. Evaluating respiratory muscle function is particularly valuable for diagnosing, phenotyping and assessing treatment efficacy in these patients. This review outlines established methods, such as measuring respiratory pressures, and explores novel techniques, including respiratory muscle neurophysiology assessments using electromyography and imaging with ultrasound.Additionally, we review various treatment strategies designed to support and alleviate the burden on overworked respiratory muscles or to enhance their capacity through training interventions. These strategies range from invasive and noninvasive mechanical ventilation approaches to specialised respiratory muscle training programmes. By summarising both established techniques and recent methodological advancements, this review aims to provide a comprehensive overview of the tools available in clinical practice for evaluating and treating respiratory muscle dysfunction. Our goal is to present a clear understanding of the current capabilities and limitations of these diagnostic and therapeutic approaches. Integrating advanced diagnostic methods and innovative treatment strategies should help improve patient management and outcomes. This comprehensive review serves as a resource for clinicians, equipping them with the necessary knowledge to effectively diagnose and treat respiratory muscle dysfunction in both acute and chronic respiratory failure scenarios.

Post-insufflation diaphragm contractions in patients receiving various modes of mechanical ventilation

BACKGROUND

During mechanical ventilation, post-insufflation diaphragm contractions (PIDCs) are non-physiologic and could be injurious. PIDCs could be frequent during reverse-triggering, where diaphragm contractions follow the ventilator rhythm. Whether PIDCs happens with different modes of assisted ventilation is unknown. In mechanically ventilated patients with hypoxemic respiratory failure, we aimed to examine whether PIDCs are associated with ventilator settings, patients' characteristics or both.

METHODS

One-hour recordings of diaphragm electromyography (EAdi), airway pressure and flow were collected once per day for up to five days from intubation until full recovery of diaphragm activity or death. Each breath was classified as mandatory (without-reverse-triggering), reverse-triggering, or patient triggered. Reverse triggering was further subclassified according to EAdi timing relative to ventilator cycle or reverse triggering leading to breath-stacking. EAdi timing (onset, offset), peak and neural inspiratory time (Tineuro) were measured breath-by-breath and compared to the ventilator expiratory time. A multivariable logistic regression model was used to investigate factors independently associated with PIDCs, including EAdi timing, amplitude, Tineuro, ventilator settings and APACHE II.

RESULTS

Forty-seven patients (median[25%-75%IQR] age: 63[52-77] years, BMI: 24.9[22.9-33.7] kg/m2, 49% male, APACHE II: 21[19-28]) contributed 2 ± 1 recordings each, totaling 183,962 breaths. PIDCs occurred in 74% of reverse-triggering, 27% of pressure support breaths, 21% of assist-control breaths, 5% of Neurally Adjusted Ventilatory Assist (NAVA) breaths. PIDCs were associated with higher EAdi peak (odds ratio [OR][95%CI] 1.01[1.01;1.01], longer Tineuro (OR 37.59[34.50;40.98]), shorter ventilator inspiratory time (OR 0.27[0.24;0.30]), high peak inspiratory flow (OR 0.22[0.20;0.26]), and small tidal volumes (OR 0.31[0.25;0.37]) (all P ≤ 0.008). NAVA was associated with absence of PIDCs (OR 0.03[0.02;0.03]; P < 0.001). Reverse triggering was characterized by lower EAdi peak than breaths triggered under pressure support and associated with small tidal volume and shorter set inspiratory time than breaths triggered under assist-control (all P < 0.05). Reverse triggering leading to breath stacking was characterized by higher peak EAdi and longer Tineuro and associated with small tidal volumes compared to all other reverse-triggering phenotypes (all P < 0.05).

CONCLUSIONS

In critically ill mechanically ventilated patients, PIDCs and reverse triggering phenotypes were associated with potentially modifiable factors, including ventilator settings. Proportional modes like NAVA represent a solution abolishing PIDCs.

Respiratory Drive, Effort, and Lung-Distending Pressure during Transitioning from Controlled to Spontaneous Assisted Ventilation in Patients with ARDS: A Multicenter Prospective Cohort Study

Objectives: To investigate the impact of patient characteristics and treatment factors on excessive respiratory drive, effort, and lung-distending pressure during transitioning from controlled to spontaneous assisted ventilation in patients with acute respiratory distress syndrome (ARDS). Methods: Multicenter cohort observational study of patients with ARDS at four academic intensive care units. Respiratory drive (P0.1), diaphragm electrical activity (EAdi), inspiratory effort derived from EAdi (∆PmusEAdi) and from occlusion of airway pressure (∆Pocc) (PmusΔPocc), and dynamic transpulmonary driving pressure (ΔPL,dyn) were measured at the first transition to assisted spontaneous breathing. Results: A total of 4171 breaths were analyzed in 48 patients. P0.1 was >3.5 cmH2O in 10%, EAdiPEAK > 15 µV in 29%, ∆PmusEAdi > 15 cmH2O in 28%, and ΔPL,dyn > 15 cmH2O in 60% of the studied breaths. COVID-19 etiology of ARDS was the strongest independent risk factor for a higher proportion of breaths with excessive respiratory drive (RR 3.00 [2.43-3.71], p < 0.0001), inspiratory effort (RR 1.84 [1.58-2.15], p < 0.0001), and transpulmonary driving pressure (RR 1.48 [1.36-1.62], p < 0.0001). The P/F ratio at ICU admission, days of deep sedation, and dose of steroids were additional risk factors for vigorous inspiratory effort. Age and dose of steroids were risk factors for high transpulmonary driving pressure. Days of deep sedation (aHR 1.15 [1.07-1.24], p = 0.0002) and COVID-19 diagnosis (aHR 6.96 [1-48.5], p = 0.05) of ARDS were independently associated with composite outcome of transitioning from light to deep sedation (RASS from 0/-3 to -4/-5) or return to controlled ventilation within 48 h of spontaneous assisted breathing. Conclusions: This study identified that specific patient characteristics, including age, COVID-19-related ARDS, and P/F ratio, along with treatment factors such as the duration of deep sedation and the dosage of steroids, are independently associated with an increased likelihood of assisted breaths reaching potentially harmful thresholds of drive, effort, and lung-distending pressure during the initial transition to spontaneous assisted breathing. It is noteworthy that patients who were subjected to prolonged deep sedation under controlled mechanical ventilation, as well as those with COVID-19, were more susceptible to failing the transition from controlled to assisted breathing.

Use of pressure muscle index to guide pressure support ventilation setting: a study protocol and statistical plan for a prospective randomised controlled proof-of-concept trial

INTRODUCTION

Although pressure support ventilation is one of the most commonly used assisted ventilation modes in intensive care units, there is still a lack of precise strategies for setting pressure support. By performing an end-inspiratory airway occlusion, the difference between the peak and plateau airway pressure, which is defined as pressure muscle index (PMI), can be easily measured on the ventilator screen. Previous studies have shown that PMI is accurate in detecting high and low inspiratory effort. No study has been conducted to investigate the use of PMI as an indicator for setting inspiratory pressure support.

METHOD AND ANALYSIS

This is a study protocol for a prospective, single-centre, randomised controlled, pilot trial. Sixty participants undergoing pressure support ventilation will be randomly assigned in a 1:1 ratio to the control group or intervention group, with pressure support adjusted according to standard care or guided by the PMI strategy for 48 hours, respectively. The feasibility of the PMI-guided strategy will be evaluated. The primary endpoint is the proportion of inspiratory effort measurements within a well-accepted 'normal' range, which is predefined as oesophageal pressure-time product per minute between 50 and 200 cmH2O⋅s/min, for each patient during 48 hours of pressure support adjustment.

ETHICS AND DISSEMINATION

The study protocol has been approved by Beijing Tiantan Hospital (KY2023-005-02). The data generated in the present study will be available from the corresponding author on reasonable request. The results of the trial will be submitted to international peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05963737; ClinicalTrials.org.

Reliability and reference values for diaphragmatic excursion, thickness, and thickening fraction and quadriceps femoris muscle thickness in full-term newborns evaluated by ultrasound

To determine the diaphragm thickness, thickening fraction, and excursion and thickness of the quadriceps femoris muscle in full-term newborns and to evaluate the intra- and interrater reliability of these measurements. This was a prospective, observational clinical study including full-term newborns born within the first 48 h after birth. Serial measurements of the thickness, thickening fraction, and mobility of the diaphragm muscles and the thickness of the quadriceps muscle were obtained using ultrasound images. A total of 69 newborns with a mean gestational age of 39 weeks were included. The following measurements were obtained and are expressed as the mean (standard deviation): inspiratory diaphragm thickness, 0.19 cm (0.04); expiratory diaphragm thickness, 0.16 cm (0.04); diaphragm thickness fraction, 16.70 cm (10.27); diaphragmatic excursion, 0.68 cm (0.22); and quadriceps thickness, 0.99 cm (0.14). Intrarater reliability was assessed using intraclass correlation coefficients (ICCs). Excellent intrarater agreement was observed for the two groups of operators (ICC > 0.86, p < 0.001) for all measurements except for the diaphragm thickening fraction, which showed good agreement for both operator groups (ICC = 0.70, p < 0.001). Regarding interrater reliability, moderate agreement between the raters was observed in the means of all measures (ICC > 0.49, p < 0.001), except for the diaphragm thickening fraction, which showed poor agreement.    Conclusion: Good intrarater and moderate interrater reliability were achieved in ultrasound evaluations of the thickness and mobility of the diaphragm and quadriceps femoris muscles in full-term newborns, demonstrating the feasibility of this technique for clinical use. This pioneering study offers reference values for these muscles in a single study, allowing comparisons between different clinical conditions. What is Known: • Ultrasound is a highly reliable tool for muscle assessment that can be used to assess muscular atrophy in critically ill patients. • Muscle atrophy worsens the patient's condition and has been associated with worse outcomes. What is New: • To our knowledge, this is the first study to jointly evaluate the diaphragm and quadriceps muscle thickness and evaluate the reliability of all measurements. • Our study presents reference values for both muscles, enabling comparisons between different clinical conditions.

AARC Clinical Practice Guideline: Patient-Ventilator Assessment

Given the important role of patient-ventilator assessments in ensuring the safety and efficacy of mechanical ventilation, a team of respiratory therapists and a librarian used Grading of Recommendations, Assessment, Development, and Evaluation methodology to make the following recommendations: (1) We recommend assessment of plateau pressure to ensure lung-protective ventilator settings (strong recommendation, high certainty); (2) We recommend an assessment of tidal volume (VT) to ensure lung-protective ventilation (4-8 mL/kg/predicted body weight) (strong recommendation, high certainty); (3) We recommend documenting VT as mL/kg predicted body weight (strong recommendation, high certainty); (4) We recommend an assessment of PEEP and auto-PEEP (strong recommendation, high certainty); (5) We suggest assessing driving pressure to prevent ventilator-induced injury (conditional recommendation, low certainty); (6) We suggest assessing FIO2 to ensure normoxemia (conditional recommendation, very low certainty); (7) We suggest telemonitoring to supplement direct bedside assessment in settings with limited resources (conditional recommendation, low certainty); (8) We suggest direct bedside assessment rather than telemonitoring when resources are adequate (conditional recommendation, low certainty); (9) We suggest assessing adequate humidification for patients receiving noninvasive ventilation (NIV) and invasive mechanical ventilation (conditional recommendation, very low certainty); (10) We suggest assessing the appropriateness of the humidification device during NIV and invasive mechanical ventilation (conditional recommendation, low certainty); (11) We recommend that the skin surrounding artificial airways and NIV interfaces be assessed (strong recommendation, high certainty); (12) We suggest assessing the dressing used for tracheostomy tubes and NIV interfaces (conditional recommendation, low certainty); (13) We recommend assessing the pressure inside the cuff of artificial airways using a manometer (strong recommendation, high certainty); (14) We recommend that continuous cuff pressure assessment should not be implemented to decrease the risk of ventilator-associated pneumonia (strong recommendation, high certainty); and (15) We suggest assessing the proper placement and securement of artificial airways (conditional recommendation, very low certainty).

High Airway Occlusion Pressure Is Associated with Dyspnea and Increased Mortality in Critically Ill Mechanically Ventilated Patients

Rationale: Airway occlusion pressure at 100 ms (P0.1) reflects central respiratory drive. Objectives: We aimed to assess factors associated with P0.1 and whether an abnormally low or high P0.1 value is associated with higher mortality and longer duration of mechanical ventilation (MV). Methods: We performed a secondary analysis of a prospective cohort study conducted in 10 ICUs in France to evaluate dyspnea in communicative MV patients. In patients intubated for more than 24 hours, P0.1 was measured with dyspnea as soon as patients could communicate and the next day. Measurements and Main Results: Among 260 patients assessed after a median time of ventilation of 4 days, P0.1 was 1.9 (1-3.5) cm H2O at enrollment, 24% had P0.1 values >3.5 cm H2O, 37% had P0.1 values between 1.5 and 3.5 cm H2O, and 39% had P0.1 values <1.5 cm H2O. In multivariable linear regression, independent factors associated with P0.1 were the presence of dyspnea (P = 0.037), respiratory rate (P < 0.001), and PaO2 (P = 0.008). Ninety-day mortality was 33% in patients with P0.1 > 3.5 cm H2O versus 19% in those with P0.1 between 1.5 and 3.5 cm H2O and 17% in those with P0.1 < 1.5 cm H2O (P = 0.046). After adjustment for the main risk factors, P0.1 was associated with 90-day mortality (hazard ratio per 1 cm H2O, 1.19 [95% confidence interval, 1.04-1.37]; P = 0.011). P0.1 was also independently associated with a longer duration of MV (hazard ratio per 1 cm H2O, 1.10 [95% confidence interval, 1.02-1.19]; P = 0.016). Conclusions: In patients receiving invasive MV, abnormally high P0.1 values may suggest dyspnea and are associated with higher mortality and prolonged duration of MV.

Ultrasonographic Assessment of the Diaphragm

Mechanical ventilation injures not only the lungs but also the diaphragm, resulting in dysfunction associated with poor outcomes. Diaphragm ultrasonography is a noninvasive, cost-effective, and reproducible diagnostic method used to monitor the condition and function of the diaphragm. With advances in ultrasound technology and the expansion of its clinical applications, diaphragm ultrasonography has become increasingly important as a tool to visualize and quantify diaphragmatic morphology and function across multiple medical specialties, including pulmonology, critical care, and rehabilitation medicine. This comprehensive review aims to provide an in-depth analysis of the role and limitations of ultrasonography in assessing the diaphragm, especially among critically ill patients. Furthermore, we discuss a recently published expert consensus and provide a perspective for the future.