Mechanical Ventilation to Minimize Progression of Lung Injury in Acute Respiratory Failure

Performance of helmet CPAP using different configurations: Turbine-driven ventilators vs Venturi devices

BACKGROUND

Traditionally, Venturi-based flow generators have been preferred over mechanical ventilators to provide continuous positive airway pressure (CPAP) through the helmet (h-CPAP). Recently, modern turbine-driven ventilators (TDVs) showed to be safe and effective in delivering h-CPAP. We aimed to compare the pressure stability during h-CPAP delivered by Venturi devices and TDVs and assess the impact of High Efficiency Particulate Air (HEPA) filters on their performance.

METHODS

We performed a bench study using an artificial lung simulator set in a restrictive respiratory condition, simulating two different levels of patient effort (high and low) with and without the interposition of the HEPA filter. We calculated the average of minimal (Pmin), maximal (Pmax) and mean (Pmean) airway pressure and the time product measured on the airway pressure curve (PTPinsp). We defined the pressure swing (Pswing) as Pmax - Pmin and pressure drop (Pdrop) as End Expiratory Pressure - Pmin.

RESULTS

Pswing across CPAP levels varied widely among all the tested devices. During "low effort", no difference in Pswing and Pdrop was found between Venturi devices and TDVs; during high effort, Pswing (p<0.001) and Pdrop (p<0.001) were significantly higher in TDVs compared to Venturi devices, but the PTPinsp was lower (1.50 SD 0.54 vs 1.67 SD 0.55, p<0.001). HEPA filter addition almost doubled Pswing and PTPinsp (p<0.001) but left unaltered the differences among Venturi and TDVs systems in favor of the latter (p<0.001).

CONCLUSIONS

TDVs performed better than Venturi systems in delivering a stable positive pressure level during h-CPAP in a bench setting.

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.

Association of Standardized Liberation Trials and Duration of Venovenous Extracorporeal Membrane Oxygenation in Patients with Acute Respiratory Failure

Rationale: There is a paucity of evidence around strategies to liberate patients from venovenous (VV) extracorporeal membrane oxygenation (ECMO) for acute respiratory failure. Objectives: The primary aim of this study was to determine if adopting standardized liberation trials (SLTs) for VV ECMO is associated with the duration of ECMO. The secondary aim was to identify factors associated with unsafe liberation and the effects of unsafe liberation on mortality to intensive care unit (ICU) discharge. Methods: This was a single-center retrospective cohort study of patients on VV ECMO for severe respiratory failure comparing endpoints between intervention (SLT) and control (no SLT) periods. Results: A total of 262 patients were included in the study, 13% (35 of 262) received SLTs, and 150 patients were decannulated from ECMO. Implementing SLTs was strongly associated with the duration of VV ECMO to first successful liberation trial (hazard ratio [HR], 1.88 [95% confidence interval (CI), 1.16 to 3.06]; P = 0.01) and decannulation (HR, 1.92 [95% CI, 1.0 to 3.06]; P = 0.01) without increasing the frequency of unsafe liberation (21% [5 of 23] with SLTs vs. 19% [24 of 127] without SLTs; odds ratio [OR], 1.19 [95% CI, -0.4 to 3.5]; P = 0.7). Unsafe liberation was strongly associated with ICU mortality (HR, 4.15 [95% CI, 1.24 to 13.9]; P = 0.02). Factors associated with unsafe liberation were respiratory rate (OR, 1.49 per 5 breaths/min increase [95% CI, 1.07 to 2.08]; P = 0.02) and ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (OR, 0.73 per 30 mm Hg increase [95% CI, 0.57 to 0.93]; P = 0.01) immediately before decannulation. Conclusions: Incorporating SLTs was significantly associated with the duration of VV ECMO, without increasing the frequency of unsafe liberation. Unsafe liberation was associated with increased ICU mortality.

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.

Factors influencing the transition phase in acute respiratory distress syndrome: an observational cohort study

BACKGROUND

Protective ventilation during the acute phase of ARDS and weaning from mechanical ventilation are well-established in current guidelines. However, the intermediate transition phase between these stages remains poorly characterized.

OBJECTIVES

To describe the transition phase in moderate-to-severe ARDS and evaluate the factors associated with neuromuscular blockade (NMBA) weaning failure and pressure support ventilation (PSV) failure.

METHODS

This bicentric observational cohort study included patients with moderate-to-severe ARDS requiring NMBA continuous infusion within 72 h post-intubation. The transition phase was defined as the 72 h following the first NMBA weaning attempt. The main endpoints were the rates of NMBA reintroduction and PSV failure. Secondary outcomes included predictive factors for NMBA weaning failure and PSV failure and the impact of tidal volume on patient outcomes.

MAIN RESULTS

A total of 196 patients were included. NMBA weaning failure occurred in 74 (38%) patients. COVID-19 (OR 3.98 [1.95-8.41], p < 0.001), pH (OR 0.50 [0.30-0.79], p = 0.004), PaO2/FiO2 ratio (OR 0.92 [0.87-0.97], p = 0.007), and high or low driving pressure before first NMBA weaning attempt (< 12 or ≥ 14 cmH2O) (OR 2.77 [1.16-7.14], p = 0.027) were significantly associated with NMBA reintroduction. PSV was initiated in 147 (75%) patients, with a failure rate of 57%, occurring after a median of 9 h [6-24]. Tidal volume (OR 1.28 [1.06-1.56], p = 0.012) was significantly associated with PSV failure. During PSV, 43% of patients exhibited high tidal volumes (> 8 mL/kg PBW). NMBA weaning failure was associated with fewer ventilator-free days and increased mortality at day 28. PSV failure was associated with fewer ventilator-free days.

CONCLUSION

The transition phase represents a high-risk period in ARDS, with significant failure rates for NMBA weaning and PSV trials that may influence patient outcomes. The transition phase therefore represents a critical area for future research to optimize management during this vulnerable period.

Knowledge, attitudes, practices, and burnout related to respiratory support among healthcare professionals in central China: a structural equation modeling study

BACKGROUND

Burnout, marked by emotional exhaustion and reduced clinical performance, may impair the effective application of noninvasive respiratory support (NIRS) and timely transition to invasive methods, potentially affecting patient outcomes. This study aims to identify the impact of burnout on the knowledge, attitudes, and practices (KAP) of healthcare professionals in the application of respiratory support, and further explore how other factors may influence these areas.

METHOD

A cross-sectional study was conducted from November 15, 2023, to December 14, 2023, at multiple hospitals in central China, involving key departments such as emergency, respiratory, cardiology, and critical care. Demographic information, alongside scores measuring KAP was gathered through the dissemination of questionnaires. Knowledge was assessed using a scoring system (range: 0-24), while attitude and practice were measured using 5-point Likert scales, with score ranges of 8-40 and 8-56, respectively. The Chinese version of the Maslach Burnout Inventory General Survey (MBI-GS) was used to assess occupational burnout.

RESULTS

A total of 517 valid questionnaires were enrolled, including 284 (54.9%) nurses, and 269 (52%) had worked for less than 10 years. The median scores for knowledge, attitude, practice, and burnout were 20, 26, 38, and 40, respectively. Participants from private hospitals exhibited burnout scores higher than 50. Burnout was negatively correlated with both attitude (r = -0.289) and practice (r = -0.206). Multivariate logistic regression showed that practice, as the dependent variable, was independently associated with a knowledge score below 20 (OR = 0.441, 95% CI: [0.297, 0.657]), an attitude score below 26 (OR = 0.493, 95% CI: [0.335, 0.724]), and burnout scores below 40 (OR = 0.539, 95% CI: [0.364-0.796]) were independently associated with practice. Age above 40 years (OR = 0.470, 95% CI: [0.264, 0.837]), being a nurse (OR = 0.627, 95% CI: [0.424, 0.928]), and lack of recent training in respiratory support (OR = 0.590, 95% CI: [0.403, 0.866]) were also associated with lower practice scores.

CONCLUSIONS

Healthcare professionals had sufficient knowledge, positive attitudes, and proactive practices regarding the application of respiratory support. However, the impact of burnout must not be overlooked, even for those scoring below the threshold (50 points), as burnout can still significantly affect clinical performance. Healthcare institutions should prioritize continuous education and training programs focusing on respiratory support, especially for high stress environment professionals, to enhance clinical practice and patient outcomes.

CLINICAL TRIAL NUMBER

not applicable.

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.

Monitoring patients with acute respiratory failure during non-invasive respiratory support to minimize harm and identify treatment failure

Non-invasive respiratory support (NRS), including high flow nasal oxygen therapy, continuous positive airway pressure and non-invasive ventilation, is a cornerstone in the management of critically ill patients who develop acute respiratory failure (ARF). Overall, NRS reduces the work of breathing and relieves dyspnea in many patients with ARF, sometimes avoiding the need for intubation and invasive mechanical ventilation with variable efficacy across diverse clinical scenarios. Nonetheless, prolonged exposure to NRS in the presence of sustained high respiratory drive and effort can result in respiratory muscle fatigue, cardiovascular collapse, and impaired oxygen delivery to vital organs, leading to poor outcomes in patients who ultimately fail NRS and require intubation. Assessment of patients' baseline characteristics before starting NRS, close physiological monitoring to evaluate patients' response to respiratory support, adjustment of device settings and interface, and, most importantly, early identification of failure or of paramount importance to avoid the negative consequences of delayed intubation. This review highlights the role of respiratory monitoring across various modalities of NRS in patients with ARF including dyspnea, general respiratory parameters, measures of drive and effort, and lung imaging. It includes technical specificities related to the target population and emphasizes the importance of clinicians' physiological understanding and tailoring clinical decisions to individual patients' needs.

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.

Monitoring effort and respiratory drive in patients with acute respiratory failure

PURPOSE OF REVIEW

Accurate monitoring of respiratory drive and inspiratory effort is crucial for optimizing ventilatory support during acute respiratory failure. This review evaluates current and emerging bedside methods for assessing respiratory drive and effort.

RECENT FINDINGS

While electrical activity of the diaphragm and esophageal pressure remain the reference standards for assessing respiratory drive and effort, their clinical utility is largely limited to research. At the bedside, airway occlusion maneuvers are the most useful tools: P0.1 is a reliable marker of drive and detects abnormal inspiratory efforts, while occlusion pressure (Pocc) may outperform P0.1 in identifying excessive effort. The Pressure-Muscle-Index (PMI) can help detecting insufficient inspiratory effort, though its accuracy depends on obtaining a stable plateau pressure. Other techniques, such as central venous pressure swings (ΔCVP), are promising but require further investigation. Emerging machine learning and artificial intelligence based algorithms could play a pivotal role in automated respiratory monitoring in the near future.

SUMMARY

Although Pes and EAdi remain reference methods, airway occlusion maneuvers are currently the most practical bedside tools for monitoring respiratory drive and effort. Noninvasive alternatives such as ΔCVP deserve further evaluation. Artificial intelligence and machine learning may soon provide automated solutions for bedside monitoring of respiratory drive and effort.

Associations of mechanical power, ventilatory ratio, and other respiratory indices with mortality in patients with acute respiratory distress syndrome undergoing pressure-controlled mechanical ventilation

Background

Mechanical power (MP) and ventilatory ratio (VR) are crucial metrics in the management of acute respiratory distress syndrome (ARDS). This study aimed to evaluate the impact of these factors on ICU mortality in patients with ARDS undergoing pressure-controlled ventilation.

Methods

In this retrospective study, we included 600 adult patients with ARDS who required mechanical ventilation for > 48 h between March 2018 and February 2021 in a tertiary referral hospital in Korea. The MP was calculated using Becher's simplified equation, and the VR was determined using standard formulas. The ventilatory parameters were measured hourly during the first 12 h of ventilation. Clinical characteristics, ventilator settings, and outcomes were compared between the survivors and non-survivors. Multiple logistic regression models were used to assess the predictive performance of the respiratory and mechanical ventilation parameters for ICU mortality.

Results

Of the 600 patients, 61.5% (n = 369) survived to hospital discharge. Non-survivors had higher rates of chronic liver disease, hematologic malignancies, and solid tumors. The survivors demonstrated lower respiratory rates (21 vs. 22 breaths/min, p < 0.001), tidal volumes (491 vs. 445 mL, p = 0.048), and peak pressures (22.0 vs. 24.3 cm H2O, p < 0.001). Significant differences were observed in driving pressure (15.0 vs. 16.0 cm H2O, p = 0.001), MP (18.8 vs. 21.8 J/min, p < 0.001), LTCdyn-MP (7,371 vs. 8,780 cm H2O/min, p < 0.001), and power index (5,429 vs. 6,386 cm H2O/min, p = 0.005) between survivors and non-survivors. In adjusted models, MP (OR 1.03, 95% CI 1.01-1.05, p = 0.006), VR (OR 1.39, 95% CI 1.02-1.92, p = 0.040), and PBW-adjusted MP (OR 1.02, 95% CI 1.00-1.03, p = 0.009) were significant predictors of ICU mortality.

Conclusion

Our findings indicate that MP and VR were independently associated with ICU mortality in patients with ARDS undergoing pressure-controlled ventilation.

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.

Effect of Home Care on Physical Function in Post-Intensive Care Unit Patients: A Meta-Analysis

BACKGROUND

A decline in physical function is commonly observed after patients transition to their homes following hospital admission; this is especially true for patients requiring mechanical ventilation in an intensive care unit (ICU).

OBJECTIVE

This meta-analysis examines characteristics and effects of home-based or outpatient+home-based interventions used to improve physical function post-discharge in patients who received mechanical ventilation in an ICU.

METHODS

PRISMA guidelines were utilized. The literature search was conducted with the assistance of a medical librarian. Study inclusion criteria were post-ICU adult patients receiving mechanical ventilation who then had home-based or outpatient+home-based care to improve physical function after discharge. Effect size (Hedges' g) was calculated with random effects models.

RESULTS

Our search yielded 11 studies that met the inclusion criteria. The majority were randomized controlled trials, with 1 quasi-experimental study. All studies included physical therapists, and 2 included nurses. The 11 studies reported results for 39 physical function measurements. The overall pooled intervention effect across the 4 studies that utilized the 6-minute walk test was 0.32 (95% confidence intervals [CI]: 0.05 to 0.58), for the 3 studies that utilized the Timed Up and Go test it was 1.38 (95% CI: -0.09 to 2.84), and for the 8 studies that used the SF-36 Physical Function subscale, it was 0.31 (95% CI: 0.09 to 0.52).

CONCLUSIONS

This review's findings show that patients may improve their physical function after participating in specific intervention programs that are home-based alone or outpatient+home-based care. However, the effect sizes are small, so it may be useful to explore how to maximize the gains in physical function.

Airway Occlusion Pressure and P0.1 to Estimate Inspiratory Effort and Respiratory Drive in Ventilated Children

OBJECTIVE

To compare the level of agreement between proximal (near the subject) and distal (inside the ventilator) measured airway occlusion pressure at 100 ms (P0.1) and occlusion pressure (Δ Pocc ), and to study the correlation between Δ Pocc and peak-to-trough esophageal pressure (Δ Pes ).

DESIGN

Secondary analysis of prospectively collected physiology dataset (2021-2022).

SETTING

Medical-surgical 20-bed PICU.

PATIENTS

Children younger than 18 years with and without acute lung injury ventilated greater than 24 hours and spontaneously breathing with appropriate triggering of the ventilator.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data from three expiratory hold maneuvers (with a maximum of three breaths during each maneuver) in 74 subjects (118 measurements) with median age 3 months (interquartile range 1-17), and primary respiratory failure due to a pulmonary infection in 41/74 (55.4%) were studied. The median proximal ∆ Pocc was 6.7 cm H 2 O (3.1-10.7) and median P0.1 4.9 cm H 2 O (4.1-6.0) for the first breath from the maneuver; both increased significantly ( p < 0.001) with the subsequent two breaths during the same maneuver. Median distal ∆ Pocc was 6.8 (2.9-10.8) and P0.1 4.6 (3.9-5.6) cm H 2 O; both increased significantly ( p < 0.001) with the two subsequent breaths. Proximal and distal Δ Pocc ( r > 0.99, p < 0.001) and P0.1 ( r > 0.80, p < 0.001) were correlated. Correlation between ventilator displayed and Y-piece measured Δ Pocc ( r > 0.99) and P0.1 ( r = 0.85) was good. Mean ( sd ) difference for Δ Pocc was 0.13 (0.21); levels of agreement were -0.28 and 0.54. For P0.1, mean ( sd ) difference was -0.36 (1.14) and levels of agreement -2.61 and 1.88. There was a high correlation between Δ Pes and ∆ Pocc ( r = 0.92) for the same breath and a good correlation with Δ Pes from the preceding breath ( r = 0.76). There was a poor correlation with the transpulmonary pressure ( r = 0.37).

CONCLUSIONS

Δ Pocc is not affected by measurement site, whereas P0.1 may be overestimated or underestimated. Δ Pocc was highly correlated with the peak-to-trough esophageal pressure, supporting the concept that inspiratory effort can also be quantified noninvasively by measuring Δ Pocc .

High-flow nasal oxygen therapy in patients with hypercapnic respiratory failure: A systematic review and meta-analysis

BACKGROUND

Noninvasive ventilation (NIV) is recommended as the first-line respiratory support method for patients with hypercapnic respiratory failure (HRF). However, the need for well-trained operators and the occurrence of treatment discomfort may limit its efficacy. High-flow nasal oxygen therapy (HFNO) is a convenient respiratory support with user-friendly operation, high comfort, and good compliance. This systematic review and meta-analysis was performed to compare the therapeutic effects of HFNO and other noninvasive respiratory support methods [NIV or conventional oxygen therapy (COT)] in patients with acute HRF (AHRF) or chronic HRF (CHRF).

METHODS

We searched the PubMed, Web of Science, Embase, and Cochrane Library databases from inception to May 2024 to identify randomized clinical trials comparing the impact of HFNO and NIV/COT in adults with HRF.

RESULTS

Sixteen studies (1630 patients) were included. Compared with NIV, HFNO did not improve the primary outcome of PaCO2 in patients with AHRF or CHRF [AHRF: MD = -0.81, 95 % CI = -3.40 to 1.77; CHRF: MD = 1.82, 95 % CI = 0.44 to 3.20]. However, HFNO showed advantages over COT (AHRF: MD = -2.03, 95 % CI = -3.48 to -0.59; CHRF: MD = -2.64, 95 % CI = -4.24 to -1.03).

CONCLUSIONS

The evidence of its clinical efficacy in hypercapnic patients remains inconclusive. Further studies are needed to generate more evidence for the application of HFNO in patients with HRF and to determine the subset of patients for whom may be preferable.

Role of InterLeukin-6 monitoring during weaning from volume-controlled ventilation in patients with COVID-19 acute respiratory distress syndrome

ObjectiveThe aim of this study was to assess the ability of plasma InterLeukin-6 (IL-6) monitoring to predict the failure to switch from volume-controlled ventilation to spontaneous ventilation (SV) in patients with COVID-19-related acute respiratory distress syndrome (ARDS).MethodsWe conducted an observational, single-center and prospective cohort study in the medico-surgical intensive care unit of Avignon Hospital Center. Participants were adult patients requiring invasive mechanical ventilation for COVID-19-related ARDS between August 2021 and August 2022, who were eligible for switching from volume-controlled ventilation to SV.ResultsAmong the 35 patients included in the study, 13 (37%) successfully switched from controlled ventilation to SV, while 22 failed (63%). In the failure group, mean plasma IL-6 levels were higher than in the successful group from hour 0 (defined as the moment of the switch to SV mode) to 48 h. However, differences between groups became significant from 24 h (362.8 vs. 33.6 pg/mL, P = 0.002). Interestingly, between-group differences in plasma C-reactive protein (CRP) levels were only significant between groups from 48 h (129.3 vs. 52.2 mg/L, P = 0.017). Finally, IL-6 and CRP had a similar ability to predict the failure to switch to SV mode: area under the receiving operative curves 0.763 [95%CI: 0.633-0.893] and 0.753 [95%CI: 0.595-0.911], respectively (P = 0.87).ConclusionsIL-6 and CRP are inflammatory biomarkers predictive of failure to switch to SV mode in COVID-19 ARDS patients. Our results showed that IL-6 can detect failure earlier than CRP. However, larger multicenter studies are needed to confirm our results, particularly in other ARDS models.

Evaluation of limiting PEEP effectiveness in preventing barotrauma in critically ill COVID-19 patients: A retrospective study

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 can cause acute respiratory distress syndrome, requiring prolonged invasive mechanical ventilation. However, patients with coronavirus disease 2019 (COVID-19) undergoing invasive mechanical ventilation experience barotrauma. We assessed whether limiting the maximum positive end-expiratory pressure (PEEP) may prevent barotrauma more effectively than using PEEP/fraction of inspired oxygen (FiO2) in patients with COVID-19 undergoing invasive mechanical ventilation.

MATERIALS AND METHODS

We retrospectively included patients who met the diagnostic criteria at our center; they were divided into an ordinary PEEP group (PEEP/higher FiO2 table) and a limited PEEP group (maximum PEEP of <10 cmH2O) during intensive care unit admission. We evaluated the maximum ventilator variables for mechanical ventilation and limited PEEP to inhibit barotrauma as the primary outcome.

RESULTS

Patients in the ordinary PEEP group (n = 34) were significantly older and had higher body mass indexes than those in the limited PEEP group (n = 27). The maximum PEEP and maximum peak inspiratory pressure were significantly higher in the ordinary PEEP group than in the limited PEEP group. The ordinary PEEP group had a significantly higher incidence of barotrauma than the limited PEEP group.

CONCLUSIONS

Limiting the maximum PEEP to <10 cmH2O may prevent barotrauma in patients with COVID-19 undergoing invasive mechanical ventilation.

Selenium nanoparticles activate selenoproteins to mitigate septic lung injury through miR-20b-mediated RORγt/STAT3/Th17 axis inhibition and enhanced mitochondrial transfer in BMSCs

Sepsis-induced acute lung injury (ALI) remains a critical clinical challenge with complex inflammatory pathogenesis. While bone marrow mesenchymal stem cells (BMSCs) demonstrate therapeutic potential through anti-inflammatory and cytoprotective effects, their age-related functional decline limits clinical utility. This study developed chitosan-functionalized selenium nanoparticles (SeNPs@CS, 100 nm) to rejuvenate BMSCs through miR-20b-mediated selenoprotein biosynthesis. Mechanistic investigations revealed that SeNPs@CS-treated BMSCs exhibited enhanced mitochondrial transfer capacity, delivering functional mitochondria to damaged alveolar epithelial cells (AECII) for cellular repair. Concurrently, miR-20b upregulation suppressed the RORγt/STAT3/Th17 axis, reducing pro-inflammatory Th17 cell differentiation in CD4+ T lymphocytes. The dual-target mechanism integrates immunomodulation via Th17 pathway inhibition with mitochondrial rejuvenation therapy, representing a paradigm-shifting approach for ALI management. These engineered BMSCs mitigated inflammatory markers in murine models, demonstrating superior efficacy to conventional BMSC therapies. Our findings establish SeNPs@CS-modified BMSCs as a novel therapeutic platform combining nanotechnology-enhanced stem cell engineering with precision immunometabolic regulation, providing new avenues for the treatment of sepsis-induced ALI.

Patient-Self Inflicted Lung Injury (P-SILI): An Insight into the Pathophysiology of Lung Injury and Management

Acute respiratory distress syndrome (ARDS) is a heterogeneous group of disease entities that are associated with acute hypoxic respiratory failure and significant morbidity and mortality. With a better understanding and phenotyping of lung injury, novel pathophysiologic mechanisms demonstrate the impact of a patient's excessive spontaneous breathing effort on perpetuating lung injury. Patient self-inflicted lung injury (P-SILI) is a recently identified phenomenon that delves into the impact of spontaneous breathing on respiratory mechanics in patients with lung injury. While the studies are hypothesis-generating and have been demonstrated in animal and human studies, further clinical trials are needed to identify its impact on ARDS management. The purpose of this review article is to highlight the physiologic mechanisms of P-SILI, novel tools and methods to detect P-SILI, and to review the current literature on non-invasive and invasive respiratory management in patients with ARDS.

Gravitational distribution of regional intrapulmonary shunt assessed by EIT in ARDS

BACKGROUND

Regional ventilation/perfusion (V/Q) mismatch in intrapulmonary shunt in dependent regions has always been considered a hallmark of ARDS. However, little is known about the spatial distribution of shunt, and a clear definition has been lacking. The aim of the study was to propose two phenotypes for the spatial distribution of intrapulmonary shunt using electrical impedance tomography (EIT) and to investigate the clinical characteristics and outcomes in the two preset phenotypes.

METHODS

A total of 76 ARDS patients who received EIT saline contrast examination were included in this retrospective study. Deadspace(%), Shunt(%), and V/Qmismatch(%) were calculated based on the lung V/Q matching map. EIT maps were divided into two horizontal anterior-to-posterior regions of interest, ranging from gravity-independent regions to gravity-dependent regions. The dosal shunt proportion (Shuntdosal/Shuntglobal%) was defined as the percentage of shunt in gravity-dependent regions. Based on Shuntdosal/Shuntglobal%, the patients were divided into a dependent-shunt group (D-shunt, Shuntdosal/Shuntglobal% > 50%) and a nondependent-shunt group (ND-shunt, Shuntdosal/Shuntglobal% ≤ 50%).

RESULTS

The D-shunt group (n = 46) had lower dorsal ventilation, lower dorsal deadspace, and a higher Shuntdosal/Shuntglobal% than the ND-shunt group (n = 30). Multivariable Cox regression analysis showed that Shuntdosal/Shuntglobal% was an independent predictive factor for 28-day mortality (HR = 0.06; 95% CI, 0.01-0.36; P = 0.002). There was no significant difference in regional perfusion distribution, global shunt, global deadspace and global V/Q mismatch between the two groups. Moreover, a higher BMI (25.4 [22.9, 29.2] vs. 22.9 [20.8, 26.4], P = 0.04) and more extrapulmonary ARDS patients [65% (30/46) vs. 33% (10/30), P = 0.01] were found in the D-shunt group. A similar PaO2/FiO2 ratio was found between the two groups on Day 0, but the D-shunt group had a higher PaO2/FiO2 ratio on Day 4. A higher 28-day mortality (40% vs. 17%, P = 0.03) and fewer ventilation-free days (VFDs) on day 28 (11.0 [0, 21.8] vs. 20.5 [4.8, 24.0], P = 0.04) were found in the ND-shunt group.

CONCLUSION

Two phenotypes of regional shunt gravitational distribution can be revealed by EIT. Patients exhibiting a predominance of dependent shunt were characterized by a higher BMI and extrapulmonary ARDS and may experience faster improvement in oxygenation as well as better clinical outcomes. Further research is necessary to evaluate shunt distribution patterns to guide the individualized treatment of ARDS patients.

Beyond the Lungs: Extrapulmonary Effects of Non-Invasive and Invasive Ventilation Strategies

Background/Objectives: Non-invasive respiratory support and invasive mechanical ventilation are critical interventions that can induce significant changes not only in the lungs but also in extra-pulmonary organs, which are often overlooked. Understanding the extra-pulmonary effects of non-invasive respiratory support and invasive mechanical ventilation is crucial since it can help prevent or mitigate complications and improve outcomes. This narrative review explores these consequences in detail and highlights areas that require further research. Main Text: Non-invasive respiratory support and invasive mechanical ventilation can significantly impact various extrapulmonary organs. For instance, some ventilation strategies can affect venous return from the brain, which may lead to neurological sequelae. In the heart, regardless of the chosen ventilation method, increased intrathoracic pressure (ITP) can also reduce venous return to the heart. This reduction in turn can decrease cardiac output, resulting in hypotension and diminished perfusion of vital organs. Conversely, in certain situations, both ventilation strategies may enhance cardiac function by decreasing the work of breathing and lowering oxygen consumption. In the kidneys, these ventilation methods can impair renal perfusion and function through various mechanisms, including hemodynamic changes and the release of stress hormones. Such alterations can lead to acute kidney injury or exacerbate pre-existing renal conditions. Conclusions: This review emphasizes the critical importance of understanding the extensive mechanisms by which non-invasive respiratory support and invasive mechanical ventilation affect extrapulmonary organs, including neurological, cardiovascular, and renal systems. Such knowledge is essential for optimizing patient care and improving outcomes in critical care settings.

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.

Mechanical power density, spontaneous breathing indexes, and weaning readiness following prolonged mechanical ventilation

INTRODUCTION

Evidence suggests that mechanical power (MP) normalized to dynamic compliance, which equals power density, may help identify prolonged ventilated patients at risk for spontaneous breathing trial (SBT) failure. This study compared MP density with traditional spontaneous breathing indexes to predict a patient's capacity to sustain a short trial of unassisted breathing.

METHODS

A prospective observational study on 186 prolonged ventilated, tracheotomized patients. We analyzed the first 30-min SBT upon weaning center admission, comparing MP density with spontaneous breathing indexes (e.g., predicted body weight normalized tidal volume (VT/PBW), rapid shallow breathing index (RSBI), and the integrative weaning index (IWI)) regarding SBT failure prediction, with diagnostic accuracy expressed as the area under the receiver operating characteristic curve (AUROC).

RESULTS

SBT failure occurred in 51 out of 186 patients (27 %), who demonstrated significantly lower dynamic compliance (median 29 mL/cmH2O [IQR 26-37] vs. 39 mL/cmH2O [33-45]) and higher MP density (5837 cmH2O2/min [4512-7758] vs. 2922 cmH2O2/min [2001-4094]) before SBT, as well as lower spontaneous VT/PBW (5.7 mL∗kg-1 [5.0-6.7] vs. 6.6 mL∗kg-1 [5.9-7.8]), higher RSBI (73 min-1∗L-1 [57-100] vs. 59 min-1∗L-1 [45-76]), and lower IWI (40 L2/cmH2O∗%∗min∗10-3 [27-50] vs. 63 L2/cmH2O∗%∗min∗10-3 [46-91]) after 5 min of unassisted breathing. MP density was more accurate at predicting SBT failures (AUROC 0.86 [95%CI 0.80-0.91]) than VT/PBW (0.58 [0.50-0.65]), RSBI (0.54 [0.47-0.61]), or IWI (0.66 [0.58-0.73])).

CONCLUSIONS

MP density as a readiness criterion was more accurate at predicting weaning trial failures in prolonged ventilated, tracheotomized patients than traditional indexes assessed during unassisted breathing.

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.

Monitoring and modulating respiratory drive in mechanically ventilated patients

PURPOSE OF REVIEW

Respiratory drive is frequently deranged in the ICU, being associated with adverse clinical outcomes. Monitoring and modulating respiratory drive to prevent potentially injurious consequences merits attention. This review gives a general overview of the available monitoring tools and interventions to modulate drive.

RECENT FINDINGS

Airway occlusion pressure (P0.1) is an excellent measure of drive and is displayed on ventilators. Respiratory drive can also be estimated based on the electrical activity of respiratory muscles and measures of respiratory effort; however, high respiratory drive might be present in the context of low effort with neuromuscular weakness. Modulating a deranged drive requires a multifaceted intervention, prioritizing treatment of the underlying cause and adjusting ventilator settings for comfort. Additional tools include changes in PEEP, peak inspiratory flow, fraction of inspired oxygen, and sweep gas flow (in patients receiving extracorporeal life-support). Sedatives and opioids have differential effects on drive according to drug category. Monitoring response to any intervention is warranted and modulating drive should not preclude readiness to wean assessment or delay ventilation liberation.

SUMMARY

Monitoring and modulating respiratory drive are feasible based on physiological principles presented in this review. However, evidence arising from clinical trials will help determine precise thresholds and optimal interventions.

Effect of Higher or Lower PEEP on Pendelluft During Spontaneous Breathing Efforts in Acute Hypoxemic Respiratory Failure

Background: In acute hypoxemic respiratory failure (AHRF), spontaneous breathing effort can generate excessive regional lung stress and strain manifesting as pendelluft. Higher PEEP may reduce pendelluft and reduce regional lung stress and strain during spontaneous breathing. This study aimed to establish whether higher or lower PEEP ameliorates pendelluft and to characterize factors determining the presence and magnitude of pendelluft during spontaneous breathing efforts. Methods: This study was a randomized crossover trial of higher versus lower PEEP applied after systematically initiating spontaneous breathing in subjects with moderate or severe AHRF. The presence and volume of pendelluft were assessed by electrical impedance tomography (EIT). Results: EIT recordings were available for 20 of 30 subjects enrolled in the trial. After initiating spontaneous breathing, 11/20 exhibited pendelluft (proportion 55% [95% CI 32-76]). Following PEEP titration, the prevalence of pendelluft was not different between higher versus lower PEEP levels (50% vs 50%, P = .55). When present, pendelluft volume was generally small (median 28 [interquartile range 8-93] mL) but ranged as high as 364 mL. Pendelluft was associated with higher respiratory effort (esophageal pressure [Pes] swing [ΔPes] median -15 cm H2O vs ΔPes median -8 cm H2O, P = .01), higher pulmonary flow resistance (median 8 cm H2O/L/s vs median 3 cm H2O/L/s, P < .001), and higher dynamic pulmonary elastance (median 5.0 cm H2O/mL/kg predicted body weight vs median 3.2 cm H2O/mL/kg predicted body weight, P = .03). Conclusions: Pendelluft reflecting increased regional lung stress and strain is likely common during spontaneous breathing effort in patients with AHRF but was not systematically affected by applying higher PEEP. The presence and magnitude of pendelluft depended on respiratory effort and lung mechanics.

Impact of the Early Use of High-flow Nasal Cannula in Patients with Post-traumatic Lung Contusion: A Randomized Clinical Trial

Background

Patients with pulmonary contusion (PC) following blunt chest trauma are at risk of developing acute lung injury. High-flow nasal cannula (HFNC) is an established method for managing hypoxic respiratory failure (HRF).

Aim

This study aims to evaluate the efficacy of oxygen therapy delivered through HFNC vs venturi mask (VM) in patients with hypoxia following traumatic lung contusion, to reduce the need for intubation and ventilation.

Materials and methods

This is an open-label randomized controlled trial conducted on 120 patients with HRF following traumatic PC and a PaO2/FiO2 of 100-200 mm Hg. Patients were divided into two groups: Group A (60 patients) received oxygen therapy through HFNC, while group B (60 patients) received oxygen therapy through VM.

Results

High-flow nasal cannula significantly improved pulmonary oxygenation as early as 1 hour after randomization and the after with statistically significant improvement of PaO2/FiO2 over time (p < 0.001). However, it was associated with a nonsignificant reduction in the rate of intubation and mechanical ventilation (p = 0.255) and a nonsignificant reduction in the mortality rate (p = 0.491). The extent of PC was found to be an independent predictor of mortality (p = 0.589) and length of hospital stay (p = 0.581) by multivariate analysis.

Conclusion

The early use of HFNC is associated with a significant improvement in pulmonary oxygenation. We suggest that HFNC can be used as a first-line oxygen therapy in hypoxic patients with lung contusion following blunt chest trauma.

How to cite this article

Elsayed RG, Hafez AF, Maarouf MM, AbdElAziz FKE. Impact of the Early Use of High-flow Nasal Cannula in Patients with Post-traumatic Lung Contusion: A Randomized Clinical Trial. Indian J Crit Care Med 2025;29(2):117-124.

Ultrafast humidity sensor and transient humidity detections in high dynamic environments

Limited by the adsorption and diffusion rate of water molecules, traditional humidity sensors, such as those based on polymer electrolytes, porous ceramics, and metal oxides, typically have long response times, which hinder their application in monitoring transient humidity changes. Here we present an ultrafast humidity sensor with a millisecond-level response. The sensor is prepared by assembling monolayer graphene oxide quantum dots on silica microspheres using a simple electrostatic self-assembly technique. Benefiting from the joint action of the micro spheres and the ultrathin humidity-sensitive film, it displays the fastest response time (2.76 ms) and recovery time (12.4 ms) among electronic humidity sensors. With the ultrafast response of the sensor, we revealed the correlation between humidity changes in speech airflow and speech activities, demonstrated the noise immunity of humidity speech activity detection, confirmed the humidity shock caused by explosions, realized ultrahigh frequency respiratory monitoring, and verified the effect of humidity-triggering in the non-invasive ventilator. This ultrafast humidity sensor has broad application prospects in monitoring transient humidity changes.

The use of protective mechanical ventilation during extracorporeal membrane oxygenation for the treatment of acute respiratory failure

Acute respiratory failure (ARF) strikes an estimated two million people in the United States each year, with care exceeding US$50 billion. The hallmark of ARF is a heterogeneous injury, with normal tissue intermingled with a large volume of low compliance and collapsed tissue. Mechanical ventilation is necessary to oxygenate and ventilate patients with ARF, but if set inappropriately, it can cause an unintended ventilator-induced lung injury (VILI). The mechanism of VILI is believed to be overdistension of the remaining normal tissue known as the 'baby' lung, causing volutrauma, repetitive collapse and reopening of lung tissue with each breath, causing atelectrauma, and inflammation secondary to this mechanical damage, causing biotrauma. To avoid VILI, extracorporeal membrane oxygenation (ECMO) can temporally replace the pulmonary function of gas exchange without requiring high tidal volumes (VT) or airway pressures. In theory, the lower VT and airway pressure will minimize all three VILI mechanisms, allowing the lung to 'rest' and heal in the collapsed state. The optimal method of mechanical ventilation for the patient on ECMO is unknown. The ARDSNetwork Acute Respiratory Management Approach (ARMA) is a Rest Lung Approach (RLA) that attempts to reduce the excessive stress and strain on the remaining normal lung tissue and buys time for the lung to heal in the collapsed state. Theoretically, excessive tissue stress and strain can also be avoided if the lung is fully open, as long as the alveolar re-collapse is prevented during expiration, an approach known as the Open Lung Approach (OLA). A third lung-protective strategy is the Stabilize Lung Approach (SLA), in which the lung is initially stabilized and gradually reopened over time. This review will analyze the physiologic efficacy and pathophysiologic potential of the above lung-protective approaches.

Effect of fluid and driving pressure on cyclical "on-off" flow of pulmonary microcirculation during mechanical ventilation

OBJECTIVES

This study aimed to identify the cyclical "on-off" flow of pulmonary microcirculation during inspiration and expiration by sidestream dark field imaging (SDF) technology in vivo and investigate the effects of volume status and driving pressure on cyclical "on-off" flow of microcirculation.

METHODS

24 ARDS-modeled rabbits were randomly divided into high-driving pressure group (HDP group) and low-driving pressure group (LDP group). Lung microcirculation measurements were performed using the SDF microscope at two timepoints (T1 CVP 2-4 mmHg, T2 CVP 8-10 mmHg). From T1 to T2, 10 ml/kg saline was infused to increase CVP. The cyclical "on-off" pulmonary microcirculation was quantitatively assessed by the change of microcirculation between expiration and inspiration.

RESULTS

Proportion of perfused vessels (PPV), microvascular flow index (MFI), perfused vessel density (PVD), and total vessel density (TVD) at expiration were significantly higher than inspiration in the HDP group. The HDP group has a higher ΔPPV and ΔPVD. After fluid loading, ΔPPV and ΔMFI decreased. TNF-α, IL-6, Ang-2, and vWF levels in the HDP group were higher. The HDP group also has a higher lung wet-weight/body weight ratio, lung wet-to-dry weight ratio, and more severe damage of pulmonary capillaries than the LDP group.

CONCLUSIONS

The difference in alveolar perfused microcirculation between inspiration and expiration defined as cyclical "on-off flow" can be detected. High driving pressure can enhance the cyclical "on-off" flow, and fluid loading can relieve it. High driving pressure can potentially cause injury to pulmonary capillaries due to the phenomenon of "on-off" flow, thereby exacerbating ARDS.

Noninvasive Respiratory Support in Acute Respiratory Distress Syndrome

Noninvasive respiratory supports have been successfully used as an alternative to endotracheal intubation especially in patients with a milder degree of hypoxemia. In patients with acute respiratory distress syndrome (ARDS), the main goals of noninvasive oxygenation strategies are to improve oxygenation, unload the respiratory muscles, and relieve dyspnea. On the other hand, recent studies have suggested that spontaneous breathing could represent an additional mechanism of lung injury, especially in the more severe forms. The aim of this review is to describe the role of different noninvasive respiratory supports in ARDS, to optimize its use in clinical practice.

The impact of a lung-protective ventilation mode using transpulmonary driving pressure titrated positive end-expiratory pressure on the prognosis of patients with acute respiratory distress syndrome

OBJECTIVE

This study aimed to assess the impact of a lung-protective ventilation strategy utilizing transpulmonary driving pressure titrated positive end-expiratory pressure (PEEP) on the prognosis [mechanical ventilation duration, hospital stay, 28-day mortality rate and incidence of ventilator-associated pneumonia (VAP), survival outcome] of patients with Acute Respiratory Distress Syndrome (ARDS).

METHODS

A total of 105 ARDS patients were randomly assigned to either the control group (n = 51) or the study group (n = 53). The control group received PEEP titration based on tidal volume [A tidal volume of 6 mL/kg, flow rate of 30-60 L/min, frequency of 16-20 breaths/min, constant flow rate, inspiratory-to-expiratory ratio of 1:1 to 1:1.5, and a plateau pressure ≤ 30-35 cmH2O. PEEP was adjusted to maintain oxygen saturation (SaO2) at or above 90%, taking into account blood pressure], while the study group received PEEP titration based on transpulmonary driving pressure (Esophageal pressure was measured as a surrogate for pleural pressure using an esophageal pressure measurement catheter connected to the ventilator. Tidal volume and PEEP were adjusted based on the observed end-inspiratory and end-expiratory transpulmonary pressures, aiming to maintain a transpulmonary driving pressure below 15 cmH2O during mechanical ventilation. Adjustments were made 2-4 times per day). Statistical analysis and comparison were conducted on lung function indicators [oxygenation index (OI), arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2)] as well as other measures such as heart rate, mean arterial pressure, and central venous pressure in two groups of patients after 48 h of mechanical ventilation. The 28-day mortality rate, duration of mechanical ventilation, length of hospital stay, and ventilator-associated pneumonia (VAP) incidence were compared between the two groups. A 60-day follow-up was performed to record the survival status of the patients.

RESULTS

In the control group, the mean age was (55.55 ± 10.51) years, with 33 females and 18 males. The pre-ICU hospital stay was (32.56 ± 9.89) hours. The mean Acute Physiology and Chronic Health Evaluation (APACHE) II score was (19.08 ± 4.67), and the mean Murray Acute Lung Injury score was (4.31 ± 0.94). In the study group, the mean age was (57.33 ± 12.21) years, with 29 females and 25 males. The pre-ICU hospital stay was (33.42 ± 10.75) hours. The mean APACHE II score was (20.23 ± 5.00), and the mean Murray Acute Lung Injury score was (4.45 ± 0.88). They presented a homogeneous profile (all P > 0.05). Following intervention, significant improvements were observed in PaO2 and OI compared to pre-intervention values. The study group exhibited significantly higher PaO2 and OI compared to the control group, with statistically significant differences (all P < 0.05). After intervention, the study group exhibited a significant increase in PaCO2 (43.69 ± 6.71 mmHg) compared to pre-intervention levels (34.19 ± 5.39 mmHg). The study group's PaCO2 was higher than the control group (42.15 ± 7.25 mmHg), but the difference was not statistically significant (P > 0.05). There were no significant differences in hemodynamic indicators between the two groups post-intervention (all P > 0.05). The study group demonstrated significantly shorter mechanical ventilation duration and hospital stay, while 28-day mortality rate and incidence of ventilator-associated pneumonia (VAP) showed no significant differences. Kaplan-Meier survival analysis revealed a significantly better survival outcome in the study group at the 60-day follow-up (HR = 0.565, 95% CI: 0.320-0.999).

CONCLUSION

Lung-protective mechanical ventilation using transpulmonary driving pressure titrated PEEP effectively improves lung function, reduces mechanical ventilation duration and hospital stay, and enhances survival outcomes in patients with ARDS. However, further study is needed to facilitate the wider adoption of this approach.

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.

Carbon Dioxide Targets in Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome

Target values for arterial carbon dioxide tension (PaCO 2 ) in extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome (ARDS) are unknown. We hypothesized that lower PaCO 2 values on ECMO would be associated with lighter sedation. We used data from two independent patient cohorts with ARDS spending 1,177 days (discovery cohort, 69 patients) and 516 days (validation cohort, 70 patients) on ECMO and evaluated the associations between daily PaCO 2 , pH, and bicarbonate (HCO 3 ) with sedation. Median PaCO 2 was 41 (interquartile range [IQR] = 37-46) mm Hg and 41 (IQR = 37-45) mm Hg in the discovery and the validation cohort, respectively. Lower PaCO 2 and higher pH but not bicarbonate (HCO 3 ) served as significant predictors for reaching a Richmond Agitation Sedation Scale (RASS) target range of -2 to +1 (lightly sedated to restless). After multivariable adjustment for mortality, tracheostomy, prone positioning, vasoactive inotropic score, Simplified Acute Physiology Score (SAPS) II or Sequential Organ Failure Assessment (SOFA) Score and day on ECMO, only PaCO 2 remained significantly associated with the RASS target range (adjusted odds ratio 1.1 [95% confidence interval (CI) = 1.01-1.21], p = 0.032 and 1.29 [95% CI = 1.1-1.51], p = 0.001 per mm Hg decrease in PaCO 2 for the discovery and the validation cohort, respectively). A PaCO 2 ≤40 mm Hg, as determined by the concordance probability method, was associated with a significantly increased probability of a sedation level within the RASS target range in both patient cohorts (adjusted odds ratio = 2.92 [95% CI = 1.17-7.24], p = 0.021 and 6.82 [95% CI = 1.50-31.0], p = 0.013 for the discovery and the validation cohort, respectively).

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.

High flow nasal cannula and low level continuous positive airway pressure have different physiological effects during de novo acute hypoxemic respiratory failure

BACKGROUND

Large tidal volumes during de novo acute hypoxemic respiratory failure (AHRF) may promote patient self-inflicted lung injury. Tidal volume assessment under high flow nasal cannula (HFNC) is not routinely feasible at the bedside. Our objective was to determine whether tidal volume during low-level continuous positive airway pressure (CPAP) could predict tidal volume during HFNC and to compare the physiological effects of HFNC and low-level CPAP.

METHODS

Prospective, single-center study including 29 de novo AHRF patients treated with HFNC (50 to 60 L.min- 1). Patients were monitored using electrical impedance tomography during HFNC then CPAP at 4 cmH2O. Tidal volume during HFNC was calculated based on tidal impedance variation. The ability of tidal volume under low-level CPAP to predict tidal volume under HFNC was explored using Bland-Altman analysis. CPAP and HFNC were compared in terms of tidal volume, minute ventilation, respiratory comfort, dyspnea, oxygenation, ventilation distribution, end-expiratory lung volume, thoraco-abdominal asynchrony and recruitment.

RESULTS

Under HFNC, patients had a tidal volume of 6.6 (5.9-8.7) mL.kg- 1 PBW. 20 (69%) patients exhibited a tidal volume between 4 and 8 mL.kg- 1 PBW, while in 5 (17%) patients it exceeded 9 mL.kg- 1 PBW. Tidal volume under CPAP was higher (9.4 (8.3-11) mL.kg- 1 PBW, p < 0.001). Tidal volumes under CPAP and under HFNC were modestly correlated (Spearman r = 0.50, p = 0.005). Bland-Altman analysis showed a bias of 2.4 mL.kg- 1, with limits of agreement ranging from - 1.1 mL.kg- 1to 5.9 mL.kg- 1. Nevertheless, a larger (> 11.5 mL.kg- 1 PBW ) tidal volume under low-level CPAP predicted a larger (> 9 mL.kg- 1 PBW ) tidal volume under HFNC with 80% sensitivity and 96% specificity. Low-level CPAP was associated with increased minute ventilation, end-expiratory lung volume, and oxygenation as compared to HFNC. It decreased signs of respiratory distress in the most severe patients but was associated with lower comfort compared to HFNC.

CONCLUSION

Among ICU patients with de novo AHRF, tidal volume under HFNC was mostly protective. Tidal volume during CPAP at 4 cmH2O did not predict tidal volume during HFNC. Such low-level CPAP was associated with increased tidal volume, minute ventilation, end-expiratory volume, and oxygenation.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT03919331. Registration date: 2019-03-26.

Electrical impedance tomography monitoring in adult ICU patients: state-of-the-art, recommendations for standardized acquisition, processing, and clinical use, and future directions

Electrical impedance tomography (EIT) is an emerging technology for the non-invasive monitoring of regional distribution of ventilation and perfusion, offering real-time and continuous data that can greatly enhance our understanding and management of various respiratory conditions and lung perfusion. Its application may be especially beneficial for critically ill mechanically ventilated patients. Despite its potential, clear evidence of clinical benefits is still lacking, in part due to a lack of standardization and transparent reporting, which is essential for ensuring reproducible research and enhancing the use of EIT for personalized mechanical ventilation. This report is the result of a four-day expert meeting where we aimed to promote the consistent and reliable use of EIT, facilitating its integration into both clinical practice and research, focusing on the adult intensive care patient. We discuss the state-of-the-art regarding EIT acquisition and processing, applications during controlled ventilation and spontaneous breathing, ventilation-perfusion assessment, and novel future directions.

A cluster randomized trial on inspiratory effort-targeted pressure support adjustment strategy in patients undergoing assisted mechanical ventilation: protocol for the IT-PSV study

Background

Pressure support ventilation (PSV) is one of the most frequently used ventilator modes in the intensive care unit (ICU). The successful implementation of PSV depends on matching the patient's inspiratory effort with the ventilator support. In clinical practice, the pressure support level is usually set and adjusted according to tidal volume and respiratory rate. However, these parameters may not fully represent the patient's effort. Previous studies have shown that pressure muscle index (PMI), which is measured as the difference between the peak and plateau airway pressure during an end-inspiratory airway occlusion, could reliably determine the low and high inspiratory effort during PSV. Herein we present the study protocol for the Inspiratory effort-Targeted Pressure Support Ventilation (IT-PSV) trial to determine the effect of a PMI-targeted pressure support setting strategy on clinical outcomes in patients undergoing PSV.

Methods and analysis

This is a cluster randomized controlled trial. Sixteen ICUs in academic hospitals will be included, eight of which will be randomly allocated to the PMI-targeted group and eight to the tidal volume/respiratory rate-targeted group. Before the initiation of the study, a four-week comprehensive training program, which includes courses of PSV initiation, pressure support adjustment, and weaning process, will be conducted for all staff in the participating ICUs. Adult patients with acute hypoxic respiratory failure and undergoing PSV within 24 h will be included. Pressure support setting and adjustment will follow the strategy according to the grouping. The primary outcome is the ventilator-free days at 28 days after enrollment. The patients will be followed up until successful weaning or separation of mechanical ventilation, death, hospital discharge, or until 28 days after randomization, whichever comes first.

Discussion

The IT-PSV trial will examine the effect of an inspiratory effort-targeted PSV setting strategy on the duration of mechanical ventilation. If positive, it will provide a new physiological-based PSV management that could potentially facilitate protective assisted ventilation.

Clinical trial registration

ClinicalTrials.gov, identifier NCT06526598.

Association Between Dyscapnia, Ventilatory Variables, and Mortality in Patients With Acute Respiratory Distress Syndrome-A Retrospective Cohort Study

Background: This study aimed to investigate the associations between dyscapnia, ventilatory variables, and mortality. We hypothesized that the association between mechanical power or ventilatory ratio and survival is mediated by dyscapnia. Methods: Patients with moderate or severe acute respiratory distress syndrome (ARDS), who received mechanical ventilation within the first 48 h after admission to the intensive care unit for at least 48 h, were included in this retrospective single-center study. Values of arterial carbon dioxide (PaCO2) were categorized into "hypercapnia" (PaCO2 ≥ 50 mm Hg), "normocapnia" (PaCO2 36-49 mmHg), and "hypocapnia" (PaCO2 ≤ 35 mm Hg). We used path analyses to assess the associations between ventilatory variables (mechanical power and ventilatory ratio) and mortality, where hypocapnia or hypercapnia were included as mediating variables. Results: Between December 2017 and April 2021, 435 patients were included. While there was a significant association between mechanical power and hypercapnia (BEM = 0.24 [95% CI: 0.15; 0.34], P < .01), there was no significant association between mechanical power or hypercapnia and ICU mortality. The association between mechanical power and intensive care unit (ICU) mortality was fully mediated by hypocapnia (BEM = -0.10 [95% CI: -0.19; 0.00], P = .05; BMO = 0.38 [95% CI: 0.13; 0.63], P < .01). Ventilatory ratio was significantly associated with hypercapnia (B = 0.23 [95% CI: 0.14; 0.32], P < .01). There was no significant association between ventilatory ratio, hypercapnia, and mortality. There was a significant effect of ventilatory ratio on mortality, which was fully mediated by hypocapnia (BEM = -0.14 [95% CI: -0.24; -0.05], P < .01; BMO = 0.37 [95% CI: 0.12; 0.62], P < .01). Conclusion: In mechanically ventilated patients with moderate or severe ARDS, the association between mechanical power and mortality was fully mediated by hypocapnia. Likewise, there was a mediating effect of hypocapnia on the association between ventilatory ratio and ICU mortality. Our results indicate that the debate on dyscapnia and outcome after ARDS should consider the impact of ventilatory variables.

Comparison of Weaning Strategies in Patients Receiving Venovenous Extracorporeal Membrane Oxygenation: An Exploratory Retrospective Study

Venovenous extracorporeal membrane oxygenation (VV ECMO) facilitates the reduction of mechanical ventilation (MV) support in acute respiratory failure. Contrary to increasing evidence regarding its initiation, the optimal timing of VV ECMO weaning in interaction with MV weaning is undetermined. In this retrospective study, 47 patients who received VV ECMO between 2013 and 2021 and survived ≥1 day after ECMO cessation were divided according to their MV status before ECMO removal: 28 patients were classified into an "ECMO weaning during assisted MV/spontaneous breathing" group and 19 into an "ECMO weaning during controlled MV" group. Extracorporeal membrane oxygenation duration was longer in the "assisted MV/spontaneous breathing" group (17 [Interquartile range (IQR) = 11-35] vs. 6 [5-11] days, p < 0.001). These patients had a longer intensive care unit (ICU) stay after ECMO start (48 [29-66] vs. 31 [15-40] days, p = 0.01). No significant differences were found for MV duration after ECMO start (30 [19-45] vs. 19 [12-30] days, p = 0.06) and further ICU survival (86% vs. 89%, p ≥ 0.9). There was a trend toward more patients with mechanical ECMO complications in the "assisted MV/spontaneous breathing" group (57% vs. 32%, p = 0.08). Thus, our results suggest a possible benefit of early ECMO weaning during controlled MV.

Monitoring and modulation of respiratory drive in patients with acute hypoxemic respiratory failure in spontaneous breathing

Non-invasive respiratory support, namely, non-invasive ventilation, continuous positive airway pressure, and high-flow nasal cannula, has been increasingly used worldwide to treat acute hypoxemic respiratory failure, giving the benefits of keeping spontaneous breathing preserved. In this scenario, monitoring and controlling respiratory drive could be helpful to avoid patient self-inflicted lung injury and promptly identify those patients that require an upgrade to invasive mechanical ventilation. In this review, we first describe the physiological components affecting respiratory drive to outline the risks associated with its hyperactivation. Further, we analyze and compare the leading strategies implemented for respiratory drive monitoring and discuss the sedative drugs and the non-pharmacological approaches used to modulate respiratory drive during non-invasive respiratory support. Refining the available techniques and rethinking our therapeutic and monitoring targets can help critical care physicians develop a personalized and minimally invasive approach.

The implication of dendritic cells in lung diseases: Immunological role of toll-like receptor 4

The immune responses play a profound role in the progression of lung lesions in both infectious and non-infectious diseases. Dendritic cells, as the "frontline" immune cells responsible for antigen presentation, set up a bridge between innate and adaptive immunity in the course of these diseases. Among the receptors equipped in dendritic cells, Toll-like receptors are a group of specialized receptors as one type of pattern recognition receptors, capable of sensing environmental signals including invading pathogens and self-antigens. Toll-like receptor 4, a pivotal member of the Toll-like receptor family, was formerly recognized as a receptor sensitive to the outer membrane component lipopolysaccharide derived from Gram-negative bacteria, triggering the subsequent response. Moreover, its other essential roles in immune responses have drawn significant attention in the past decade. A better understanding of the implication of Toll-like receptor 4 in dendritic cells could contribute to the management of pulmonary diseases including pneumonia, pulmonary tuberculosis, asthma, acute lung injury, and lung cancer.

Impact of low dose inhaled nitric oxide treatment in spontaneously breathing and intubated COVID-19 patients: a retrospective propensity-matched study

BACKGROUND

The benefit of Inhaled nitric oxide (iNO) therapy in the setting of COVID-19-related ARDS is obscure. We performed a multicenter retrospective study to evaluate the impact of iNO on patients with COVID-19 who require respiratory support.

METHODS

This retrospective multicenter study included COVID-19 patients enrolled in the SCCM VIRUS COVID-19 registry who were admitted to different Mayo Clinic sites between March 2020 and June 2022 and required high-flow nasal cannula (HFNC), non-invasive ventilation (NIV), or invasive mechanical ventilation (IMV). Patients were included in the 'spontaneously breathing' group if they remained non-intubated or were initiated on an HFNC (± NIV) before intubation. Patients who got intubated without prior use of an HFNC (± NIV) were included in the 'intubated group.' They were further divided into categories based on their iNO usage. Propensity score matching (PSM) and inverse propensity of treatment weighting (IPTW) were performed to examine outcomes.

RESULTS

Among 2767 patients included in our analysis, 1879 belonged to spontaneously breathing (153 received iNO), and 888 belonged to the intubated group (193 received iNO). There was a consistent improvement in FiO2 requirement, P/F ratio, and respiratory rate within 48 h of iNO use among both spontaneously breathing and intubated groups. However, there was no significant difference in intubation risk with iNO use among spontaneously breathing patients (PSM OR 1.08, CI 0.71-1.65; IPTW OR 1.10, CI 0.90-1.33). In a time-to-event analysis using Cox proportional hazard model, spontaneously breathing patients initiated on iNO had a lower hazard ratio of in-hospital mortality (PSM HR 0.49, CI 0.32-0.75, IPTW HR 0.40, 95% CI 0.26-0.62) but intubated patients did not (PSM HR: 0.90; CI 0.66-1.24, IPTW HR 0.98, 95% CI 0.73-1.31). iNO use was associated with longer in-hospital stays, ICU stays, ventilation duration, and a higher incidence of creatinine rise.

CONCLUSIONS

This retrospective propensity-score matched study showed that spontaneously breathing COVID-19 patients on HFNC/ NIV support had a decreased in-hospital mortality risk with iNO use in a time-to-event analysis. Both intubated and spontaneously breathing patients had improvement in oxygenation parameters with iNO therapy but were associated with longer in-hospital stays, ICU stays, ventilation duration, and higher incidence of creatinine rise.

Effect of high-flow nasal cannula oxygen versus standard oxygen on mortality in patients with acute hypoxaemic respiratory failure: protocol for a multicentre, randomised controlled trial (SOHO)

INTRODUCTION

First-line oxygenation strategy in patients with acute hypoxaemic respiratory failure consists in standard oxygen or high-flow nasal oxygen therapy. Clinical practice guidelines suggest the use of high-flow nasal oxygen rather than standard oxygen. However, findings remain contradictory with a low level of certainty. We hypothesise that compared with standard oxygen, high-flow nasal oxygen may reduce mortality in patients with acute hypoxaemic respiratory failure.

METHOD AND ANALYSIS

The Standard Oxygen versus High-flow nasal Oxygen-trial is an investigator-initiated, multicentre, open-label, randomised controlled trial comparing high-flow nasal oxygen versus standard oxygen in patients admitted to an intensive care unit (ICU) for acute respiratory failure with moderate-to-severe hypoxaemia. 1110 patients will be randomly assigned to one of the two groups with a ratio of 1:1. The primary outcome is the number of patients who died 28 days after randomisation. Secondary outcomes include comfort, dyspnoea and oxygenation 1 hour after treatment initiation, the number of patients intubated at day 28, mortality in ICU, in hospital and until day 90, and complications during ICU stay.

ETHICS AND DISSEMINATION

The study has been approved by the central Ethics Committee 'Sud Méditerranée III' (2020-07-05) and patients will be included after informed consent. The results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04468126.