Mechanical Ventilation–induced Diaphragm Atrophy Strongly Impacts Clinical Outcomes

Effects of proprioceptive neuromuscular facilitation combined with threshold inspiratory muscle training on respiratory function in neurocritical patients with weaning failure: a randomized controlled trial

The purpose of this study was to determine the effects of combining proprioceptive neuromuscular facilitation (PNF) with threshold inspiratory muscle training (TIMT), compared with TIMT alone, on respiratory function in neurocritical patients who experienced a weaning failure. Forty-seven participants (mostly after a stroke), were randomly divided into the experimental group ( n  = 24) and the control group ( n  = 23). The control group received usual care and TIMT, whereas the experimental group, in addition, underwent four 90-s periods of manual PNF. Both groups performed training in the ICU twice a day for 5 consecutive days. The main outcome measures included maximum inspiratory pressure, diaphragmatic excursions, diaphragm thickening fraction, oxygenation index, and forced expiratory volume in 1 s/forced vital capacity. The results showed a significant group-by-time interaction effect for maximum inspiratory pressure [ F (1, 45) = 17.84, η2  = 0.328, P  < 0.001] and oxygenation index [ F [1, 45) = 5.58, η2  = 0.11, P  = 0.023]. When compared with the control group, the experimental group showed overall significantly higher maximum inspiratory pressure [mean difference = 4.37 cm H 2 O, 95% confidence interval (CI) 0.25-8.50, P  = 0.038]. No other significant group differences were found. Combining PNF with TIMT may improve respiratory function in neurocritical patients with weaning failure. This combination approach may increase the likelihood of survival of neurocritical patients in the ICU.

Volatile anesthetics for lung- and diaphragm-protective sedation

This review explores the complex interactions between sedation and invasive ventilation and examines the potential of volatile anesthetics for lung- and diaphragm-protective sedation. In the early stages of invasive ventilation, many critically ill patients experience insufficient respiratory drive and effort, leading to compromised diaphragm function. Compared with common intravenous agents, inhaled sedation with volatile anesthetics better preserves respiratory drive, potentially helping to maintain diaphragm function during prolonged periods of invasive ventilation. In turn, higher concentrations of volatile anesthetics reduce the size of spontaneously generated tidal volumes, potentially reducing lung stress and strain and with that the risk of self-inflicted lung injury. Taken together, inhaled sedation may allow titration of respiratory drive to maintain inspiratory efforts within lung- and diaphragm-protective ranges. Particularly in patients who are expected to require prolonged invasive ventilation, in whom the restoration of adequate but safe inspiratory effort is crucial for successful weaning, inhaled sedation represents an attractive option for lung- and diaphragm-protective sedation. A technical limitation is ventilatory dead space introduced by volatile anesthetic reflectors, although this impact is minimal and comparable to ventilation with heat and moisture exchangers. Further studies are imperative for a comprehensive understanding of the specific effects of inhaled sedation on respiratory drive and effort and, ultimately, how this translates into patient-centered outcomes in critically ill patients.

Development and validation of a nomogram model for predicting 28-day mortality in patients with sepsis

Background

This study aimed to develop and validate a nomogram model for predicting 28-day mortality in patients with sepsis in the intensive care unit (ICU).

Methods

We retrospectively analyzed data from 331 patients with sepsis admitted to the ICU as a training set and collected a validation set of 120 patients. Both groups were followed for 28 days. Logistic regression analyses were performed to identify the potential prognostic factors for sepsis-related 28-day mortality. A nomogram model was generated to predict 28-day mortality in patients with sepsis in the ICU. Receiver operating characteristic (ROC) curve analysis, calibration curves, and decision curve analysis (DCA) were used to evaluate the model's prediction performance and clinical application. In addition, we used ROC curve analysis and DCA to compare this model with the sequential organ failure assessment (SOFA) and Acute Physiology and Chronic Health Evaluation (APACHE II) scores and further assessed the clinical value of our model.

Results

Logistic multivariate regression analysis revealed that mechanical ventilation, oxygenation index, and lactate and blood urea nitrogen (BUN) levels were independent predictors of 28-day mortality in patients with sepsis in the ICU. We developed a nomogram model based on these results to further predict 28-day mortality. The model demonstrated satisfactory calibration curves for both training and validation sets. Additionally, in the training set, the area under the ROC curve (AUC) for this model was 0.80. In the validation set, the AUC was 0.82. DCA showed that the high-risk thresholds ranged between 0 and 0.86 in the training set and between 0 and 0.75 in the validation set. We compared the ROC curve and DCA of this model with those of SOFA and APACHE II scores in both the training and validation sets. In the training set, the AUC of this model was significantly higher than those of the SOFA (P = 0.032) and APACHE II (P = 0.004) scores. Although the validation set showed a similar trend, the differences were not statistically significant for the SOFA (P = 0.273) and APACHE II (P = 0.320) scores. Additionally, the DCA showed comparable clinical utility in all three assessments.

Conclusion

The present study used four common clinical variables, including mechanical ventilation, oxygenation index and lactate and BUN levels, to develop a nomogram model to predict 28-day mortality in patients with sepsis in the ICU. Our model demonstrated robust prediction performance and clinical application after validation and comparison.

ICU patients receiving remifentanil do not experience reduced duration of mechanical ventilation: a systematic review of randomized controlled trials and network meta-analyses based on Bayesian theories

Background

The purpose of this network meta-analysis (NMA) was to evaluate the efficacy of intravenous opioid μ-receptor analgesics in shortening the duration of mechanical ventilation (MV) in ICU patients.

Methods

Randomized controlled trials comparing the efficacy of remifentanil, sufentanil, morphine, and fentanyl on the duration of MV in ICU patients were searched in Embase, Cochrane, Pubmed, and Web of Science electronic databases. The primary outcome was MV duration. The Bayesian random-effects framework was used to evaluate relative efficacy.

Results

In total 20 studies were included in this NMA involving 3,442 patients. Remifentanil was not associated with a reduction in the duration of MV compared with fentanyl (mean difference (MD) -0.16; 95% credible interval (CrI): -4.75 ~ 5.63) and morphine (MD 3.84; 95% CrI: -0.29 ~ 10.68). The secondary outcomes showed that, compared with remifentanil, sufentanil can prolong the duration of extubation. No regimen significantly shortened the ICU length of stay and improved the ICU mortality, efficacy, safety, and drug-related adverse events.

Conclusion

Among these analgesics, remifentanil did not appear to be associated with a reduction in MV duration. Clinicians should carefully titrate the analgesia of MV patients to prevent a potentially prolonged duration of MV due to excessive or inadequate analgesic therapy.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, CRD42021232604.

Rehabilitation in children with home invasive mechanical ventilation

Children with home invasive mechanical ventilation need special health care and rehabilitation services due to complications caused by both the pulmonary system and physical inactivity. Children who are dependent on invasive mechanical ventilators due to breathing difficulties and lung problems can benefit from rehabilitation programs. Rehabilitation requires a close relationship between the child, parents and/or caregivers, and healthcare professionals. The main goal of rehabilitation is to improve breathing, lung function and overall quality of life. In this review, although full standard approaches have not been determined yet, rehabilitation approaches for children dependent on home-type invasive mechanical ventilator will be discussed.

Tissue Doppler imaging of the diaphragm and outcome of weaning from mechanical ventilation

Purpose

This study aimed to employ tissue Doppler imaging to monitor diaphragmatic peak velocity and acceleration during contraction and relaxation in mechanically ventilated patients, with the objective of assessing the potential utility of this technique in predicting weaning outcomes.

Methods

A total of 89 adult subjects were recruited in this study. After 30 min of spontaneous breathing trial, the diaphragm motion parameters, including peak contraction velocity, peak relaxation velocity, contraction acceleration and relaxation acceleration, were measured in real time using tissue Doppler imaging. According to the results of weaning, the patients were divided into successful weaning group and failed weaning group. The differences of diaphragmatic tissue Doppler imaging monitoring indicators between the two groups were analysed, and the receiver operating characteristic curve was drawn to analyse the value of each ultrasound parameter in predicting weaning.

Results

In the successful weaning group, there were 61 subjects, while in the failed weaning group, there were 28 subjects. The peak contraction velocity, peak relaxation velocity, contraction acceleration and relaxation acceleration of the diaphragm were significantly higher in the failed weaning group compared to the successful weaning group (P < 0.05). The area under the curve of diaphragmatic peak contraction velocity, peak relaxation velocity, diaphragmatic contraction acceleration and diaphragmatic relaxation acceleration were 0.81 (0.72-0.91), 0.85 (0.77-0.93), 0.74 (0.63-0.86) and 0.86 (0.78-0.94), respectively.

Conclusions

The diaphragm ultrasonic tissue Doppler imaging variables can serve as predictive indicators for weaning mechanical ventilation in patients, thus providing an effective tool to assist critical care physicians in determining the optimal timing for weaning mechanical ventilation.

Effect of different sedatives on the prognosis of patients with mechanical ventilation: a retrospective cohort study based on MIMIC-IV database

Aim

To compare the effects of midazolam, propofol, and dexmedetomidine monotherapy and combination therapy on the prognosis of intensive care unit (ICU) patients receiving continuous mechanical ventilation (MV).

Methods

11,491 participants from the Medical Information Mart for Intensive Care (MIMIC)-IV database 2008-2019 was included in this retrospective cohort study. The primary outcome was defined as incidence of ventilator-associated pneumonia (VAP), in-hospital mortality, and duration of MV. Univariate and multivariate logistic regression analyses were utilized to evaluate the association between sedation and the incidence of VAP. Univariate and multivariate Cox analyses were performed to investigate the correlation between sedative therapy and in-hospital mortality. Additionally, univariate and multivariate linear analyses were conducted to explore the relationship between sedation and duration of MV.

Results

Compared to patients not receiving these medications, propofol alone, dexmedetomidine alone, combination of midazolam and dexmedetomidine, combination of propofol and dexmedetomidine, combination of midazolam, propofol and dexmedetomidine were all association with an increased risk of VAP; dexmedetomidine alone, combination of midazolam and dexmedetomidine, combination of propofol and dexmedetomidine, combination of midazolam, propofol and dexmedetomidine may be protective factor for in-hospital mortality, while propofol alone was risk factor. There was a positive correlation between all types of tranquilizers and the duration of MV. Taking dexmedetomidine alone as the reference, all other drug groups were found to be associated with an increased risk of in-hospital mortality. The administration of propofol alone, in combination with midazolam and dexmedetomidine, in combination with propofol and dexmedetomidine, in combination with midazolam, propofol and dexmedetomidine were associated with an increased risk of VAP compared to the use of dexmedetomidine alone.

Conclusion

Dexmedetomidine alone may present as a favorable prognostic option for ICU patients with mechanical ventilation MV.

Effects of respiratory muscle training on post-stroke rehabilitation: A systematic review and meta-analysis

BACKGROUND

Stroke often results in significant respiratory dysfunction in patients. Respiratory muscle training (RMT) has been proposed as a rehabilitative intervention to address these challenges, but its effectiveness compared to routine training remains debated. This systematic review and meta-analysis aim to evaluate the effects of RMT on exercise tolerance, muscle strength, and pulmonary function in post-stroke patients.

AIM

To systematically assess the efficacy of RMT in improving exercise tolerance, respiratory muscle strength, and pulmonary function in patients recovering from a stroke, and to evaluate whether RMT offers a significant advantage over routine training modalities in enhancing these critical health outcomes in the post-stroke population.

METHODS

Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, a comprehensive search across PubMed, Embase, Web of Science, and the Cochrane Library was conducted on October 19, 2023, without temporal restrictions. Studies were selected based on the predefined inclusion and exclusion criteria focusing on various forms of RMT, control groups, and outcome measures [including forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), maximal voluntary ventilation (MVV), peak expiratory flow (PEF), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), and 6-min walking test (6MWT)]. Only randomized controlled trials (RCTs) were included. Data extraction and quality assessment were conducted independently by two reviewers using the Cochrane Collaboration's risk of bias tool. Statistical analyses, including those using the fixed-effect and random-effects models, sensitivity analysis, and publication bias assessment, were performed using Review Manager software.

RESULTS

A total of 15 RCTs were included. Results indicated significant improvements in MIP (12.51 cmH2O increase), MEP (6.24 cmH2O increase), and various pulmonary function parameters (including FEV1, FVC, MVV, and PEF). A substantial increase in 6MWT distance (22.26 meters) was also noted. However, the heterogeneity among studies was variable, and no significant publication bias was detected.

CONCLUSION

RMT significantly enhances walking ability, respiratory muscle strength (MIP and MEP), and key pulmonary function parameters (FEV1, FVC, MVV, and PEF) in post-stroke patients. These findings support the incorporation of RMT into post-stroke rehabilitative protocols.

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.

Diaphragm and Lung Transplantation

Mutual interactions between the diaphragm and lung transplantation (LTx) are known to exist. Before LTx, many factors can exert notable impact on the diaphragmatic function, such as the underlying respiratory disease, the comorbidities, and the chronic treatments of the patient. In the post-LTx setting, even the surgical procedure itself can cause a stressful trauma to the diaphragm, potentially leading to morphological and functional alterations. Conversely, the diaphragm can significantly influence various aspects of the LTx process, ranging from graft-to-chest cavity size matching to the long-term postoperative respiratory performance of the recipient. Despite this, there are still no standard criteria for evaluating, defining, and managing diaphragmatic dysfunction in the context of LTx to date. This deficiency hampers the accurate assessment of those factors which affect the diaphragm and its reciprocal influence on LTx outcomes. The objective of this narrative review is to delve into the complex role the diaphragm plays in the different stages of LTx and into the modifications of this muscle following surgery.

Ultrasound assessment of diaphragmatic dysfunction in non-critically ill patients: relevant indicators and update

Diaphragm dysfunction (DD) can be classified as mild, resulting in diaphragmatic weakness, or severe, resulting in diaphragmatic paralysis. Various factors such as prolonged mechanical ventilation, surgical trauma, and inflammation can cause diaphragmatic injury, leading to negative outcomes for patients, including extended bed rest and increased risk of pulmonary complications. Therefore, it is crucial to protect and monitor diaphragmatic function. Impaired diaphragmatic function directly impacts ventilation, as the diaphragm is the primary muscle involved in inhalation. Even unilateral DD can cause ventilation abnormalities, which in turn lead to impaired gas exchange, this makes weaning from mechanical ventilation challenging and contributes to a higher incidence of ventilator-induced diaphragm dysfunction and prolonged ICU stays. However, there is insufficient research on DD in non-ICU patients, and DD can occur in all phases of the perioperative period. Furthermore, the current literature lacks standardized ultrasound indicators and diagnostic criteria for assessing diaphragmatic dysfunction. As a result, the full potential of diaphragmatic ultrasound parameters in quickly and accurately assessing diaphragmatic function and guiding diagnostic and therapeutic decisions has not been realized.

Impact of extended lung protection during mechanical ventilation on lung recovery in patients with COVID-19 ARDS: a phase II randomized controlled trial

BACKGROUND

Protective ventilation seems crucial during early Acute Respiratory Distress Syndrome (ARDS), but the optimal duration of lung protection remains undefined. High driving pressures (ΔP) and excessive patient ventilatory drive may hinder lung recovery, resulting in self-inflicted lung injury. The hidden nature of the ΔP generated by patient effort complicates the situation further. Our study aimed to assess the feasibility of an extended lung protection strategy that includes a stepwise protocol to control the patient ventilatory drive, assessing its impact on lung recovery.

METHODS

We conducted a single-center randomized study on patients with moderate/severe COVID-19-ARDS with low respiratory system compliance (CRS < 0.6 (mL/Kg)/cmH2O). The intervention group received a ventilation strategy guided by Electrical Impedance Tomography aimed at minimizing ΔP and patient ventilatory drive. The control group received the ARDSNet low-PEEP strategy. The primary outcome was the modified lung injury score (mLIS), a composite measure that integrated daily measurements of CRS, along with oxygen requirements, oxygenation, and X-rays up to day 28. The mLIS score was also hierarchically adjusted for survival and extubation rates.

RESULTS

The study ended prematurely after three consecutive months without patient enrollment, attributed to the pandemic subsiding. The intention-to-treat analysis included 76 patients, with 37 randomized to the intervention group. The average mLIS score up to 28 days was not different between groups (P = 0.95, primary outcome). However, the intervention group showed a faster improvement in the mLIS (1.4 vs. 7.2 days to reach 63% of maximum improvement; P < 0.001), driven by oxygenation and sustained improvement of X-ray (P = 0.001). The intervention group demonstrated a sustained increase in CRS up to day 28 (P = 0.009) and also experienced a shorter time from randomization to room-air breathing (P = 0.02). Survival at 28 days and time until liberation from the ventilator were not different between groups.

CONCLUSIONS

The implementation of an individualized PEEP strategy alongside extended lung protection appears viable. Promising secondary outcomes suggested a faster lung recovery, endorsing further examination of this strategy in a larger trial. Clinical trial registration This trial was registered with ClinicalTrials.gov (number NCT04497454) on August 04, 2020.

Sex-Based Differences in the Sonographic Characterization of Diaphragm Thickness in Preterm Infants With Bronchopulmonary Dysplasia at Term Corrected Age: A Secondary Analysis of a Prospective Study

OBJECTIVE

To determine the sex-specific diaphragm thickness in infants with bronchopulmonary dysplasia (BPD) as well as in healthy term and near-term infants.

METHODS

We performed a secondary analysis of an observational study to compare the sonographic diaphragm thickness at end expiration (DTexp) in female and male infants. The study included infants with BPD and healthy near-term and term infants. To account for differences in anthropometric measurements, we calculated the DTexp as a ratio of body surface area (BSA). Statistical analysis was performed using R statistical software.

RESULTS

Of the 111 infants included, 54 (48.6%) were female. There were no significant differences in mean (SD) birth gestation [26.2 (2.1) vs 26.3 (2.1) weeks] and mean study age [38.0 (2.0) vs 37.4 (1.1) weeks] of male vs female infants with BPD. The mean (SD) DTexp [1.5 (0.4) mm vs 1.2 (0.3) mm, P = .02] and DTexp/BSA [8.3 (2.3) mm/m2 vs 6.7 (1.6) mm/m2, P < .01] were significantly thicker in female than male infants with BPD. In contrast, there were no significant differences in DTexp between sexes [1.5 (0.4) mm vs 1.5 (0.3) mm, P = .89] within the healthy control group. Moreover, there were no differences in inspiratory diaphragm thickness, diaphragm thickness fraction, or excursion between males and females in the BPD or healthy groups.

CONCLUSIONS

Male infants with BPD exhibit thinner diaphragm thickness compared with female infants. Its implication on higher rates of BPD in preterm males is unclear, but this finding highlights the need for further investigation.

Low-Medium and High-Intensity Inspiratory Muscle Training in Critically Ill Patients: A Systematic Review and Meta-Analysis

Background and objectives: Mechanical ventilation is often used in intensive care units to assist patients' breathing. This often leads to respiratory muscle weakness and diaphragmatic dysfunction, causing weaning difficulties. Inspiratory muscle training (IMT) has been found to be beneficial in increasing inspiratory muscle strength and facilitating weaning. Over the years, different protocols and devices have been used. Materials and Methods: The aim of this systematic review and meta-analysis was to investigate the effectiveness of low-medium (LM-IMT) and high-intensity (H-IMT) threshold inspiratory muscle training in critically ill patients. A systematic literature search was performed for randomized controlled trials (RCTs) in the electronic databases Google Scholar, PubMed, Scopus, and Science Direct. The search involved screening for studies examining the effectiveness of two different intensities of threshold IMT in critically ill patients published the last 10 years. The Physiotherapy Evidence Database (PEDro) scale was chosen as the tool to assess the quality of studies. A meta-analysis was performed where possible. Results: Fourteen studies were included in the systematic review, with five of them having high methodological quality. Conclusions: When examining LM-IMT and H-IMT though, neither was able to reach statistically significant improvement in their maximal inspiratory pressure (MIP), while LM-IMT reached it in terms of weaning duration. Additionally, no statistical difference was noticed in the duration of mechanical ventilation. The application of IMT is recommended to ICU patients in order to prevent diaphragmatic dysfunction and facilitate weaning from mechanical ventilation. Therefore, further research as well as additional RCTs regarding different protocols are needed to enhance its effectiveness.

Breath-by-breath comparison of a novel percutaneous phrenic nerve stimulation approach with mechanical ventilation in juvenile pigs: a pilot study

About one in three critically ill patients requires mechanical ventilation (MV). Prolonged MV, however, results in diaphragmatic weakness, which itself is associated with delayed weaning and increased mortality. Inducing active diaphragmatic contraction via electrical phrenic nerve stimulation (PNS) not only provides the potential to reduce diaphragmatic muscular atrophy but also generates physiological-like ventilation and therefore offers a promising alternative to MV. Reasons why PNS is not yet used in critical care medicine are high procedural invasiveness, insufficient evidence, and lack of side-by-side comparison to MV. This study aims to establish a minimal-invasive percutaneous, bilateral electrode placement approach for sole PNS breathing and thereby enable, for the first time, a breath-by-breath comparison to MV. Six juvenile German Landrace pigs received general anesthesia and orotracheal intubation. Following the novel ultrasound-guided, landmark-based, 4-step approach, two echogenic needles per phrenic nerve were successfully placed. Stimulation effectiveness was evaluated measuring tidal volume, diaphragmatic thickening and tomographic electrical impedance in a breath-by-breath comparison to MV. Following sufficient bilateral phrenic nerve stimulation in all pigs, PNS breaths showed a 2.2-fold increase in diaphragmatic thickening. It induced tidal volumes in the lung-protective range by negative pressure inspiration and improved dorso-caudal regional ventilation in contrast to MV. Our study demonstrated the feasibility of a novel ultrasound-guided, percutaneous phrenic nerve stimulation approach, which generated sufficient tidal volumes and showed more resemblance to physiological breathing than MV in a breath-by-breath comparison.

Imaging of the Diaphragm: A Primer

The diaphragm is a critical musculotendinous structure that contributes to respiratory function. Disorders of the diaphragm are rare and diagnostically challenging. Herein, the author reviews the radiologic options for the assessment of the diaphragm.

Irisin attenuates ventilator-induced diaphragmatic dysfunction by inhibiting endoplasmic reticulum stress through activation of AMPK

Mechanical ventilation (MV) is an essential life-saving technique, but prolonged MV can cause significant diaphragmatic dysfunction due to atrophy and decreased contractility of the diaphragm fibres, called ventilator-induced diaphragmatic dysfunction (VIDD). It is not clear about the mechanism of occurrence and prevention measures of VIDD. Irisin is a newly discovered muscle factor that regulates energy metabolism. Studies have shown that irisin can exhibit protective effects by downregulating endoplasmic reticulum (ER) stress in a variety of diseases; whether irisin plays a protective role in VIDD has not been reported. Sprague-Dawley rats were mechanically ventilated to construct a VIDD model, and intervention was performed by intravenous administration of irisin. Diaphragm contractility, degree of atrophy, cross-sectional areas (CSAs), ER stress markers, AMPK protein expression, oxidative stress indicators and apoptotic cell levels were measured at the end of the experiment.Our findings showed that as the duration of ventilation increased, the more severe the VIDD was, the degree of ER stress increased, and the expression of irisin decreased.ER stress may be one of the causes of VIDD. Intervention with irisin ameliorated VIDD by reducing the degree of ER stress, attenuating oxidative stress, and decreasing the apoptotic index. MV decreases the expression of phosphorylated AMPK in the diaphragm, whereas the use of irisin increases the expression of phosphorylated AMPK. Irisin may exert its protective effect by activating the phosphorylated AMPK pathway.

Advanced Respiratory Monitoring during Extracorporeal Membrane Oxygenation

Advanced respiratory monitoring encompasses a diverse range of mini- or noninvasive tools used to evaluate various aspects of respiratory function in patients experiencing acute respiratory failure, including those requiring extracorporeal membrane oxygenation (ECMO) support. Among these techniques, key modalities include esophageal pressure measurement (including derived pressures), lung and respiratory muscle ultrasounds, electrical impedance tomography, the monitoring of diaphragm electrical activity, and assessment of flow index. These tools play a critical role in assessing essential parameters such as lung recruitment and overdistention, lung aeration and morphology, ventilation/perfusion distribution, inspiratory effort, respiratory drive, respiratory muscle contraction, and patient-ventilator synchrony. In contrast to conventional methods, advanced respiratory monitoring offers a deeper understanding of pathological changes in lung aeration caused by underlying diseases. Moreover, it allows for meticulous tracking of responses to therapeutic interventions, aiding in the development of personalized respiratory support strategies aimed at preserving lung function and respiratory muscle integrity. The integration of advanced respiratory monitoring represents a significant advancement in the clinical management of acute respiratory failure. It serves as a cornerstone in scenarios where treatment strategies rely on tailored approaches, empowering clinicians to make informed decisions about intervention selection and adjustment. By enabling real-time assessment and modification of respiratory support, advanced monitoring not only optimizes care for patients with acute respiratory distress syndrome but also contributes to improved outcomes and enhanced patient safety.

Diaphragmatic morphological post-mortem findings in critically ill COVID-19 patients: an observational study

Our study investigates the post-mortem findings of the diaphragm's muscular structural changes in mechanically ventilated COVID-19 patients. Diaphragm samples of the right side from 42 COVID-19 critically ill patients were analyzed and correlated with the type and length of mechanical ventilation (MV), ventilatory parameters, prone positioning, and use of sedative drugs. The mean number of fibers was 550±626. The cross-sectional area was 4120±3280 μm2, while the muscular fraction was 0.607±0.126. The overall population was clustered into two distinct populations (clusters 1 and 2). Cluster 1 showed a lower percentage of slow myosin fiber and higher fast fiber content than cluster 2, 68% versus 82%, p<0.00001, and 29.8% versus 18.8%, p=0.00045 respectively. The median duration of MV was 180 (41-346) hours. In cluster 1, a relationship between assisted ventilation and fast myosin fiber percentage (R2=-0.355, p=0.014) was found. In cluster 2, fast fiber content increased with increasing the length of the controlled MV (R2=0.446, p=0.006). A high grade of fibrosis was reported. Cluster 1 was characterized by fibers' atrophy and cluster 2 by hypertrophy, supposing different effects of ventilation on the diaphragm but without excluding a possible direct viral effect on diaphragmatic fibers.

Combined cardiac, lung, and diaphragm ultrasound for predicting weaning failure during spontaneous breathing trial

BACKGROUND

Weaning from invasive mechanical ventilation (MV) is a complex and challenging process that involves multiple pathophysiological mechanisms. A combined ultrasound evaluation of the heart, lungs, and diaphragm during the weaning phase can help to identify risk factors and underlying mechanisms for weaning failure. This study aimed to investigate the accuracy of lung ultrasound (LUS), transthoracic echocardiography (TTE), and diaphragm ultrasound for predicting weaning failure in critically ill patients.

METHODS

Patients undergoing invasive MV for > 48 h and who were readied for their first spontaneous breathing trial (SBT) were studied. Patients were scheduled for a 2-h SBT using low-level pressure support ventilation. LUS and TTE were performed prospectively before and 30 min after starting the SBT, and diaphragm ultrasound was only performed 30 min after starting the SBT. Weaning failure was defined as failure of SBT, re-intubation, or non-invasive ventilation within 48 h.

RESULTS

Fifty-one patients were included, of whom 15 experienced weaning failure. During the SBT, the global, anterior, and antero-lateral LUS scores were higher in the failed group than in the successful group. Receiver operating characteristic curve analysis showed that the areas under the curves for diaphragm thickening fraction (DTF) and global and antero-lateral LUS scores during the SBT to predict weaning failure were 0.678, 0.719, and 0.721, respectively. There was no correlation between the LUS scores and the average E/e' ratio during the SBT. Multivariate analysis identified antero-lateral LUS score > 7 and DTF < 31% during the SBT as independent predictors of weaning failure.

CONCLUSION

LUS and diaphragm ultrasound can help to predict weaning failure in patients undergoing an SBT with low-level pressure support. An antero-lateral LUS score > 7 and DTF < 31% during the SBT were associated with weaning failure.

Dyssynchronous diaphragm contractions impair diaphragm function in mechanically ventilated patients

BACKGROUND

Pre-clinical studies suggest that dyssynchronous diaphragm contractions during mechanical ventilation may cause acute diaphragm dysfunction. We aimed to describe the variability in diaphragm contractile loading conditions during mechanical ventilation and to establish whether dyssynchronous diaphragm contractions are associated with the development of impaired diaphragm dysfunction.

METHODS

In patients receiving invasive mechanical ventilation for pneumonia, septic shock, acute respiratory distress syndrome, or acute brain injury, airway flow and pressure and diaphragm electrical activity (Edi) were recorded hourly around the clock for up to 7 days. Dyssynchronous post-inspiratory diaphragm loading was defined based on the duration of neural inspiration after expiratory cycling of the ventilator. Diaphragm function was assessed on a daily basis by neuromuscular coupling (NMC, the ratio of transdiaphragmatic pressure to diaphragm electrical activity).

RESULTS

A total of 4508 hourly recordings were collected in 45 patients. Edi was low or absent (≤ 5 µV) in 51% of study hours (median 71 h per patient, interquartile range 39-101 h). Dyssynchronous post-inspiratory loading was present in 13% of study hours (median 7 h per patient, interquartile range 2-22 h). The probability of dyssynchronous post-inspiratory loading was increased with reverse triggering (odds ratio 15, 95% CI 8-35) and premature cycling (odds ratio 8, 95% CI 6-10). The duration and magnitude of dyssynchronous post-inspiratory loading were associated with a progressive decline in diaphragm NMC (p < 0.01 for interaction with time).

CONCLUSIONS

Dyssynchronous diaphragm contractions may impair diaphragm function during mechanical ventilation.

TRIAL REGISTRATION

MYOTRAUMA, ClinicalTrials.gov NCT03108118. Registered 04 April 2017 (retrospectively registered).

Critical illness-associated limb and diaphragmatic weakness

PURPOSE OF REVIEW

In the current review, we aim to highlight the evolving evidence on the diagnosis, prevention and treatment of critical illness weakness (CIW) and critical illness associated diaphragmatic weakness (CIDW).

RECENT FINDINGS

In the ICU, several risk factors can lead to CIW and CIDW. Recent evidence suggests that they have different pathophysiological mechanisms and impact on outcomes, although they share common risk factors and may overlap in several patients. Their diagnosis is challenging, because CIW diagnosis is primarily clinical and, therefore, difficult to obtain in the ICU population, and CIDW diagnosis is complex and not easily performed at the bedside. All of these issues lead to underdiagnosis of CIW and CIDW, which significantly increases the risk of complications and the impact on both short and long term outcomes. Moreover, recent studies have explored promising diagnostic techniques that are may be easily implemented in daily clinical practice. In addition, this review summarizes the latest research aimed at improving how to prevent and treat CIW and CIDW.

SUMMARY

This review aims to clarify some uncertain aspects and provide helpful information on developing monitoring techniques and therapeutic interventions for managing CIW and CIDW.

The depth of neuromuscular blockade is not related to chest wall elastance and respiratory mechanics in moderate to severe acute respiratory distress syndrome patients. A prospective cohort study

BACKGROUND

Data concerning the depth of neuromuscular blockade (NMB) required for effective relaxation of the respiratory muscles in ARDS are scarce. We hypothesised that complete versus partial NMB can modify respiratory mechanics.

METHOD

Prospective study to compare the respiratory mechanics of ARDS patients according to the NMB depth. Each patient was analysed at two times: deep NMB (facial train of four count (TOFC) = 0) and intermediate NMB (TOFC >0). The primary endpoint was the comparison of chest wall elastance (ELCW) according to the NMB level.

RESULTS

33 ARDS patients were analysed. There was no statistical difference between the ELCW at TOFC = 0 compared to TOFC >0: 7 cmH2O/l [5.7-9.5] versus 7 cmH2O/l [5.3-10.8] (p = 0.36). The depth of NMB did not modify the expiratory nor inspiratory oesophageal pressure (Pesexp = 8 cmH2O [5-9.5] at TOFC = 0 versus 7 cmH2O [5-10] at TOFC >0; (p = 0.16) and Pesinsp = 10 cmH2O [8.2-13] at TOFC = 0 versus 10 cmH2O [8-13] at TOFC >0; (p = 0.12)).

CONCLUSION

In ARDS, the relaxation of the respiratory muscles seems to be independent of the NMB level.

Noninvasive respiratory support in the emergency department: Controversies and state-of-the-art recommendations

Acute respiratory failure is a common reason for emergency department visits and hospital admissions. Diverse underlying physiologic abnormalities lead to unique aspects about the most common causes of acute respiratory failure: acute decompensated heart failure, acute exacerbation of chronic obstructive pulmonary disease, and acute de novo hypoxemic respiratory failure. Noninvasive respiratory support strategies are increasingly used methods to support work of breathing and improve gas exchange abnormalities to improve outcomes relative to conventional oxygen therapy or invasive mechanical ventilation. Noninvasive respiratory support includes noninvasive positive pressure ventilation and nasal high flow, each with unique physiologic mechanisms. This paper will review the physiology of respiratory failure and noninvasive respiratory support modalities and offer data and guideline-driven recommendations in the context of key clinical controversies.

Effects of structured protocolized physical therapy on the duration of mechanical ventilation in patients with prolonged weaning

PURPOSE

20% of patients with mechanical ventilation (MV) have a prolonged, complex weaning process, often experiencing a condition of ICU-acquired weakness (ICUAW), with a severe decrease in muscle function and restricted long-term prognosis. We aimed to analyze a protocolized, systematic approach of physiotherapy in prolonged weaning patients and hypothesized that the duration of weaning from MV would be shortened.

METHODS

ICU patients with prolonged weaning were included before (group 1) and after (group 2) introduction of a quality control measure of a structured and protocolized physiotherapy program. Primary endpoint was the tested dynamometric handgrip strength and the Surgical Intensive Care Unit Optimal Mobilization Score (SOMS). Secondary endpoints were weaning success rate, ventilator-free days, hospital mortality, the prevalence of ICUAW, infections and delirium.

RESULTS

106 patients were included. Both the SOMS and the handgrip test were significantly improved after introducing the program. Despite no differences in weaning success rates at discharge, the total length of MV was significantly shorter in group 2, which also had lower prevalence of infection and higher probability of survival.

CONCLUSIONS

Protocolized, systematic physiotherapy resulted in an improvement of the clinical outcome in patients with prolonged weaning. Results were objectifiable with the SOMS and the handgrip test.

Diaphragm atrophy during invasive mechanical ventilation is related to extubation failure in preterm infants: An ultrasound study

Background

Diaphragm dysfunction is associated with poor outcomes in critically ill patients. Ventilator‐induced diaphragmatic dysfunction (VIDD), including diaphragm atrophy (DA), is poorly studied in newborns. We aimed to assess VIDD and its associations in newborns.

Methods

Single‐center prospective study. Diaphragm thickness was measured at end‐inspiration (TDI) and end‐expiration (TDE) on the right midaxillary line. DA was defined as decrease in TDE ≥ 10%. Daily measurements were recorded in preterm newborns on invasive mechanical ventilation (IMV) for ≥2 days. Clinical characteristics of patients and extubation failure were recorded. Univariate analysis, logistic regression, and mixed models were performed to describe VIDD and associated factors.

Results

We studied 17 patients (median gestational age 270/7 weeks) and 22 IMV cycles (median duration 9 days). Median TDE decreased from 0.118 cm (interquartile range [IQR] 0.094–0.165) on the first IMV day to 0.104 cm (IQR 0.083–0.120) on the last IMV day (p = .092). DA occurred in 11 IMV cycles (50%) from 10 infants early during IMV (median: second IMV day). Mean airway pressure (MAP) and lung ultrasound score (LUS) on the first IMV day were significantly higher in patients who developed DA. DA was more frequent in patients with extubation failure than in those with extubation success within 7 days (83.3 vs. 33.3%, p = .038).

Conclusions

DA, significantly associated with extubation failure, occurred in 58.8% of the study infants on IMV. Higher MAP and LUS at IMV start were associated with DA. Our results suggest a potential role of diaphragm ultrasound to assess DA and predict extubation failure in clinical practice.

Early Mobilization and Rehabilitation of Critically-Ill Patients

Post-intensive care unit (ICU) syndrome may occur after ICU treatment and includes ICU-acquired weakness (ICU-AW), cognitive decline, and mental problems. ICU-AW is muscle weakness in patients treated in the ICU and is affected by the period of mechanical ventilation. Diaphragmatic weakness may also occur because of respiratory muscle unloading using mechanical ventilators. ICU-AW is an independent predictor of mortality and is associated with longer duration of mechanical ventilation and hospital stay. Diaphragm weakness is also associated with poor outcomes. Therefore, pulmonary rehabilitation with early mobilization and respiratory muscle training is necessary in the ICU after appropriate patient screening and evaluation and can improve ICU-related muscle weakness and functional deterioration.

Diaphragm thickness modifications and associated factors during VA-ECMO for a cardiogenic shock: a cohort study

BACKGROUND

The incidence, causes and impact of diaphragm thickness evolution in veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for cardiogenic shock are unknown. Our study investigates its evolution during the first week of VA-ECMO and its relationship with sweep gas flow settings.

METHODS

We conducted a prospective monocentric observational study in a 12-bed ICU in France, enrolling patients on the day of the VA-ECMO implantation. The diaphragm thickness and the diaphragm thickening fraction (as index of contractile activity, dTF; dTF < 20% defined a low contractile activity) were daily measured for one week using ultrasound. Factors associated with diaphragm thickness evolution (categorized as increased, stable, or atrophic based on > 10% modification from baseline to the last measurement), early extubation role (< day4), and patients outcome at 60 days were investigated. Changes in diaphragm thickness, the primary endpoint, was analysed using a mixed-effect linear model (MLM).

RESULTS

Of the 29 included patients, seven (23%) presented diaphragm atrophy, 18 remained stable (60%) and 4 exhibited an increase (17%). None of the 13 early-extubated patients experienced diaphragm atrophy, while 7 (46%) presented a decrease when extubated later (p-value = 0.008). Diaphragm thickness changes were not associated with the dTF (p-value = 0.13) but with sweep gas flow (Beta = - 3; Confidence Interval at 95% (CI) [- 4.8; - 1.2]. p-value = 0.001) and pH (Beta = - 2; CI [- 2.9; - 1]. p-value < 0.001) in MLM. The dTF remained low (< 20%) in 20 patients (69%) at the study's end and was associated with sweep gas flow evolution in MLM (Beta = - 2.8; 95% CI [- 5.2; - 0.5], p-value = 0.017). Odds ratio of death at 60 days in case of diaphragm atrophy by day 7 was 8.50 ([1.4-74], p = 0.029).

CONCLUSION

In our study, diaphragm thickness evolution was frequent and not associated with the diaphragm thickening fraction. Diaphragm was preserved from atrophy in case of early extubation with ongoing VA-ECMO assistance. Metabolic disorders resulting from organ failures and sweep gas flow were linked with diaphragm thickness evolution. Preserved diaphragm thickness in VA-ECMO survivors emphasizes the importance of diaphragm-protective strategies, including meticulous sweep gas flow titration.

Changes in temporal muscle dimensions and their clinical impact in out-of-hospital cardiac arrest survivors

OBJECTIVE

This study investigates temporal muscle atrophy in out-of-hospital cardiac arrest patients post-resuscitation, seeking associations with neurological outcomes and factors associated with atrophy.

METHODS

Using data from six Japanese intensive care units, adult patients' post-resuscitation who underwent head computed tomography scans on admission and two to five days post-admission were assessed. Temporal muscle area, thickness, and density were quantified from a single cross-sectional image. Patients were categorized into 'atrophy' or 'no atrophy' groups based on median daily temporal muscle atrophy rates. The primary outcome was changes in temporal muscle dimensions between admission and follow-up two to five days later. Secondary outcomes included assessing the impact of temporal muscle atrophy on 30-day survival, as well as identifying any clinical factors associated with temporal muscle atrophy.

RESULTS

A total of 185 patients were analyzed. Measurements at follow-up revealed significant decreases in temporal muscle area (214 vs. 191 mm2, p < 0.001), thickness (4.9 vs. 4.7 mm, p < 0.001), and density (46 vs. 44 HU, p < 0.001) compared to those at admission. The median daily rate for temporal muscle area atrophy was 2.0% per day. There was no significant association between temporal muscle atrophy and 30-day survival (hazard ratios, 0.71; 95% CI, 0.41-1.23, p = 0.231). Multivariable logistic regression found no clinical factors significantly associated with temporal muscle atrophy.

CONCLUSIONS

Temporal muscle atrophy in post-resuscitation patients occurs rapidly at 2.0% per day. However, there was no significant association with 30-day mortality or any identified clinical factors. Further investigation into its long-term functional implications is warranted.

From bedside to recovery: exercise therapy for prevention of post-intensive care syndrome

BACKGROUND

As advancements in critical care medicine continue to improve Intensive Care Unit (ICU) survival rates, clinical and research attention is urgently shifting toward improving the quality of survival. Post-Intensive Care Syndrome (PICS) is a complex constellation of physical, cognitive, and mental dysfunctions that severely impact patients' lives after hospital discharge. This review provides a comprehensive and multi-dimensional summary of the current evidence and practice of exercise therapy (ET) during and after an ICU admission to prevent and manage the various domains of PICS. The review aims to elucidate the evidence of the mechanisms and effects of ET in ICU rehabilitation and highlight that suboptimal clinical and functional outcomes of ICU patients is a growing public health concern that needs to be urgently addressed.

MAIN BODY

This review commences with a brief overview of the current relationship between PICS and ET, describing the latest research on this topic. It subsequently summarises the use of ET in ICU, hospital wards, and post-hospital discharge, illuminating the problematic transition between these settings. The following chapters focus on the effects of ET on physical, cognitive, and mental function, detailing the multi-faceted biological and pathophysiological mechanisms of dysfunctions and the benefits of ET in all three domains. This is followed by a chapter focusing on co-interventions and how to maximise and enhance the effect of ET, outlining practical strategies for how to optimise the effectiveness of ET. The review next describes several emerging technologies that have been introduced/suggested to augment and support the provision of ET during and after ICU admission. Lastly, the review discusses future research directions.

CONCLUSION

PICS is a growing global healthcare concern. This review aims to guide clinicians, researchers, policymakers, and healthcare providers in utilising ET as a therapeutic and preventive measure for patients during and after an ICU admission to address this problem. An improved understanding of the effectiveness of ET and the clinical and research gaps that needs to be urgently addressed will greatly assist clinicians in their efforts to rehabilitate ICU survivors, improving patients' quality of survival and helping them return to their normal lives after hospital discharge.

Lung- and diaphragm-protective strategies in acute respiratory failure: an in silico trial

BACKGROUND

Lung- and diaphragm-protective (LDP) ventilation may prevent diaphragm atrophy and patient self-inflicted lung injury in acute respiratory failure, but feasibility is uncertain. The objectives of this study were to estimate the proportion of patients achieving LDP targets in different modes of ventilation, and to identify predictors of need for extracorporeal carbon dioxide removal (ECCO2R) to achieve LDP targets.

METHODS

An in silico clinical trial was conducted using a previously published mathematical model of patient-ventilator interaction in a simulated patient population (n = 5000) with clinically relevant physiological characteristics. Ventilation and sedation were titrated according to a pre-defined algorithm in pressure support ventilation (PSV) and proportional assist ventilation (PAV+) modes, with or without adjunctive ECCO2R, and using ECCO2R alone (without ventilation or sedation). Random forest modelling was employed to identify patient-level factors associated with achieving targets.

RESULTS

After titration, the proportion of patients achieving targets was lower in PAV+ vs. PSV (37% vs. 43%, odds ratio 0.78, 95% CI 0.73-0.85). Adjunctive ECCO2R substantially increased the probability of achieving targets in both PSV and PAV+ (85% vs. 84%). ECCO2R alone without ventilation or sedation achieved LDP targets in 9%. The main determinants of success without ECCO2R were lung compliance, ventilatory ratio, and strong ion difference. In silico trial results corresponded closely with the results obtained in a clinical trial of the LDP titration algorithm (n = 30).

CONCLUSIONS

In this in silico trial, many patients required ECCO2R in combination with mechanical ventilation and sedation to achieve LDP targets. ECCO2R increased the probability of achieving LDP targets in patients with intermediate degrees of derangement in elastance and ventilatory ratio.

Management of Neuromuscular Blocking Agents in Critically Ill Patients with Lung Diseases

The use of neuromuscular blocking agents (NMBAs) is common in the intensive care unit (ICU). NMBAs have been used in critically ill patients with lung diseases to optimize mechanical ventilation, prevent spontaneous respiratory efforts, reduce the work of breathing and oxygen consumption, and avoid patient-ventilator asynchrony. In patients with acute respiratory distress syndrome (ARDS), NMBAs reduce the risk of barotrauma and improve oxygenation. Nevertheless, current guidelines and evidence are contrasting regarding the routine use of NMBAs. In status asthmaticus and acute exacerbation of chronic obstructive pulmonary disease, NMBAs are used in specific conditions to ameliorate patient-ventilator synchronism and oxygenation, although their routine use is controversial. Indeed, the use of NMBAs has decreased over the last decade due to potential adverse effects, such as immobilization, venous thrombosis, patient awareness during paralysis, development of critical illness myopathy, autonomic interactions, ICU-acquired weakness, and residual paralysis after cessation of NMBAs use. The aim of this review is to highlight current knowledge and synthesize the evidence for the effects of NMBAs for critically ill patients with lung diseases, focusing on patient-ventilator asynchrony, ARDS, status asthmaticus, and chronic obstructive pulmonary disease.

Association between nutritional risk status and both diaphragmatic dysfunction and diaphragm atrophy in medical ıntensive care unit patients

AIM

critical illness often leads to malnutrition and diaphragmatic dysfunction (DD), common in intensive care units (ICU). Ultrasonography (US) is a potent tool for detecting DD. This study examines the connection between malnutrition risk and DD in ICU patients using ultrasonographic diaphragm measurements in medical ICU patients.

METHODS

we assessed nutritional risk using risk screening tools and mid-upper arm circumference measurements (MUAC). Diaphragm atrophy (DA) and DD were evaluated by measuring diaphragmatic excursion (DE), thickness, and thickening fraction (TF) by US. We then compared these diaphragmatic measurements in patients based on their nutritional risk scores.

RESULTS

of the fifty patients studied, 54 % to 78 % were at risk of malnutrition, 28 % exhibited diaphragm atrophy (DA), and 24 % showed DD upon ICU admission. Malnutrition risk diagnosed by all nutritional risk screening tools was significantly more frequent in patients with DD, while diagnosed by MUAC was considerably higher in patients with DA. A total of 16 patients (32 %) died during their ICU stay, with DD, DA, and malnutrition risks (as identified by the mNUTRIC Score) being more prevalent among non-survivors (p < 0.05). Malnutrition risk (as determined by the mNUTRIC Score) was an independent risk factor for DD [OR (95 % CI): 6.6 (1.3-34), p = 0.03].

CONCLUSION

malnutrition risk may be significantly associated with DD and DA in medical ICU patients upon ICU admission.

Predictive values of ultrasonic diaphragm thickening fraction combined with integrative weaning index in weaning patients with mechanical ventilation: a retrospective study

OBJECTIVE

We aimed to explore the predictive values of ultrasonic diaphragm thickening fraction (DTF) combined with integrative weaning index (IWI) in weaning patients with mechanical ventilation.

METHODS

Patients with mechanical ventilation who received oral endotracheal intubation from September 2020 to September 2021 were included in this retrospective study. Before the start of the spontaneous breathing test (SBT), IWI was calculated according to the blood gas analysis parameters and parameters read in volume control mode. After the start of SBT, DTF was calculated according to the end-expiratory thickness and end-inspiratory thickness of the right diaphragm. The receiver operating curve (ROC) was used to evaluate the predictive value of DTF and IWI for successful weaning, and the sensitivity and specificity were calculated according to the best critical value.

RESULTS

The sensitivity, specificity, and best cutoff value of DTF to predict successful weaning was 0.772, 0.727, and 0.293, respectively, and the area under the curve (AUC) was 0.72 (95%CI 0.59-0.86, p = 0.003). The sensitivity, specificity, and best cutoff value of IWI to predict successful weaning was 0.614, 0.909, 53.00, respectively, and AUC was 0.82 (95%CI 0.72-0.91, p < 0.001). The sensitivity, specificity, and best cutoff value of the combination of DTF and IWI to predict successful weaning was 0.614, 0.909, 17.848, respectively, and AUC was 0.84 (95%CI 0.75-0.93, p < 0.001).

CONCLUSION

DTF and IWI can guide the selection of weaning, while DTF combined with IWI can improve the effect of weaning prediction and provide support for patients' weaning safety.

Positive end-expiratory pressure limits inspiratory effort through modulation of the effort-to-drive ratio: an experimental crossover study

BACKGROUND

How assisted spontaneous breathing should be used during acute respiratory distress syndrome is questioned. Recent evidence suggests that high positive end-expiratory pressure (PEEP) may limit the risk of patient self-inflicted lung injury (P-SILI). The aim of this study was to assess the effects of PEEP on esophageal pressure swings, inspiratory drive, and the neuromuscular efficiency of ventilation. We hypothesized that high PEEP would reduce esophageal pressure swings, regardless of inspiratory drive changes, by modulating the effort-to-drive ratio (EDR). This was tested retrospectively in an experimental animal crossover study. Anesthetized pigs (n = 15) were subjected to mild to moderate lung injury and different PEEP levels were applied, changing PEEP from 0 to 15 cmH2O and back to 0 cmH2O in steps of 3 cmH2O. Airway pressure, esophageal pressure (Pes), and electric activity of the diaphragm (Edi) were collected. The EDR was calculated as the tidal change in Pes divided by the tidal change in Edi. Statistical differences were tested using the Wilcoxon signed-rank test.

RESULTS

Inspiratory esophageal pressure swings decreased from - 4.2 ± 3.1 cmH2O to - 1.9 ± 1.5 cmH2O (p < 0.01), and the mean EDR fell from - 1.12 ± 1.05 cmH2O/µV to - 0.24 ± 0.20 (p < 0.01) as PEEP was increased from 0 to 15 cmH2O. The EDR was significantly correlated to the PEEP level (rs = 0.35, p < 0.01).

CONCLUSIONS

Higher PEEP limits inspiratory effort by modulating the EDR of the respiratory system. These findings indicate that PEEP may be used in titration of the spontaneous impact on ventilation and in P-SILI risk reduction, potentially facilitating safe assisted spontaneous breathing. Similarly, ventilation may be shifted from highly spontaneous to predominantly controlled ventilation using PEEP. These findings need to be confirmed in clinical settings.

Setting positive end-expiratory pressure: role in diaphragm-protective ventilation

PURPOSE OF REVIEW

With mechanical ventilation, positive end-expiratory pressure (PEEP) is applied to improve oxygenation and lung homogeneity. However, PEEP setting has been hypothesized to contribute to critical illness associated diaphragm dysfunction via several mechanisms. Here, we discuss the impact of PEEP on diaphragm function, activity and geometry.

RECENT FINDINGS

PEEP affects diaphragm geometry: it induces a caudal movement of the diaphragm dome and shortening of the zone of apposition. This results in reduced diaphragm neuromechanical efficiency. After prolonged PEEP application, the zone of apposition adapts by reducing muscle fiber length, so-called longitudinal muscle atrophy. When PEEP is withdrawn, for instance during a spontaneous breathing trial, the shortened diaphragm muscle fibers may over-stretch which may lead to (additional) diaphragm myotrauma. Furthermore, PEEP may either increase or decrease respiratory drive and resulting respiratory effort, probably depending on lung recruitability. Finally, the level of PEEP can also influence diaphragm activity in the expiratory phase, which may be an additional mechanism for diaphragm myotrauma.

SUMMARY

Setting PEEP could play an important role in both lung and diaphragm protective ventilation. Both high and low PEEP levels could potentially introduce or exacerbate diaphragm myotrauma. Today, the impact of PEEP setting on diaphragm structure and function is in its infancy, and clinical implications are largely unknown.

Setting positive end-expiratory pressure: lung and diaphragm ultrasound

PURPOSE OF REVIEW

The purpose of this review is to summarize the role of lung ultrasound and diaphragm ultrasound in guiding ventilator settings with an emphasis on positive end-expiratory pressure (PEEP). Recent advances for using ultrasound to assess the effects of PEEP on the lungs and diaphragm are discussed.

RECENT FINDINGS

Lung ultrasound can accurately diagnose the cause of acute respiratory failure, including acute respiratory distress syndrome and can identify focal and nonfocal lung morphology in these patients. This is essential in determining optimal ventilator strategy and PEEP level. Assessment of the effect of PEEP on lung recruitment using lung ultrasound is promising, especially in the perioperative setting. Diaphragm ultrasound can monitor the effects of PEEP on the diaphragm, but this needs further validation. In patients with an acute exacerbation of chronic obstructive pulmonary disease, diaphragm ultrasound can be used to predict noninvasive ventilation failure. Lung and diaphragm ultrasound can be used to predict weaning outcome and accurately diagnose the cause of weaning failure.

SUMMARY

Lung and diaphragm ultrasound are useful for diagnosing the cause of respiratory failure and subsequently setting the ventilator including PEEP. Effects of PEEP on lung and diaphragm can be monitored using ultrasound.

Ultrasonography to Access Diaphragm Dysfunction and Predict the Success of Mechanical Ventilation Weaning in Critical Care: A Narrative Review

INTRODUCTION

Weaning failure is common in mechanically ventilated patients, and whether ultrasound (US) can predict weaning outcome remains controversial. This review aims to evaluate the diaphragmatic function measured by US as a predictor of weaning outcome.

METHODS

PubMed was searched to identify original articles about the use of diaphragmatic US in ICU patients. A total of 61 citations were retrieved initially; available data of 26 studies were included in this review.

RESULTS

To assess diaphragmatic dysfunction in adults, six studies evaluated excursion, five evaluated thickening fraction, and both in nine. Despite heterogeneity in the diagnostic accuracy of diaphragm US among the studies, the sonographic indices showed good diagnostic performance for predicting weaning outcome.

CONCLUSIONS

Diaphragmatic US can be a useful and accurate tool to detect diaphragmatic dysfunction in critically ill patients and predict weaning outcome.

Time-Controlled Adaptive Ventilation (TCAV): a personalized strategy for lung protection

Acute respiratory distress syndrome (ARDS) alters the dynamics of lung inflation during mechanical ventilation. Repetitive alveolar collapse and expansion (RACE) predisposes the lung to ventilator-induced lung injury (VILI). Two broad approaches are currently used to minimize VILI: (1) low tidal volume (LVT) with low-moderate positive end-expiratory pressure (PEEP); and (2) open lung approach (OLA). The LVT approach attempts to protect already open lung tissue from overdistension, while simultaneously resting collapsed tissue by excluding it from the cycle of mechanical ventilation. By contrast, the OLA attempts to reinflate potentially recruitable lung, usually over a period of seconds to minutes using higher PEEP used to prevent progressive loss of end-expiratory lung volume (EELV) and RACE. However, even with these protective strategies, clinical studies have shown that ARDS-related mortality remains unacceptably high with a scarcity of effective interventions over the last two decades. One of the main limitations these varied interventions demonstrate to benefit is the observed clinical and pathologic heterogeneity in ARDS. We have developed an alternative ventilation strategy known as the Time Controlled Adaptive Ventilation (TCAV) method of applying the Airway Pressure Release Ventilation (APRV) mode, which takes advantage of the heterogeneous time- and pressure-dependent collapse and reopening of lung units. The TCAV method is a closed-loop system where the expiratory duration personalizes VT and EELV. Personalization of TCAV is informed and tuned with changes in respiratory system compliance (CRS) measured by the slope of the expiratory flow curve during passive exhalation. Two potentially beneficial features of TCAV are: (i) the expiratory duration is personalized to a given patient's lung physiology, which promotes alveolar stabilization by halting the progressive collapse of alveoli, thereby minimizing the time for the reopened lung to collapse again in the next expiration, and (ii) an extended inspiratory phase at a fixed inflation pressure after alveolar stabilization gradually reopens a small amount of tissue with each breath. Subsequently, densely collapsed regions are slowly ratcheted open over a period of hours, or even days. Thus, TCAV has the potential to minimize VILI, reducing ARDS-related morbidity and mortality.

Perioperative Diaphragm Dysfunction

Diaphragm Dysfunction (DD) is a respiratory disorder with multiple causes. Although both unilateral and bilateral DD could ultimately lead to respiratory failure, the former is more common. Increasing research has recently delved into perioperative diaphragm protection. It has been established that DD promotes atelectasis development by affecting lung and chest wall mechanics. Diaphragm function must be specifically assessed for clinicians to optimally select an anesthetic approach, prepare for adequate monitoring, and implement the perioperative plan. Recent technological advancements, including dynamic MRI, ultrasound, and esophageal manometry, have critically aided disease diagnosis and management. In this context, it is noteworthy that therapeutic approaches for DD vary depending on its etiology and include various interventions, either noninvasive or invasive, aimed at promoting diaphragm recruitment. This review aims to unravel alternative anesthetic and operative strategies that minimize postoperative dysfunction by elucidating the identification of patients at a higher risk of DD and procedures that could cause postoperative DD, facilitating the recognition and avoidance of anesthetic and surgical interventions likely to impair diaphragmatic function.

Risk factors for prolonged mechanical ventilation in critically ill patients with influenza-related acute respiratory distress syndrome

BACKGROUND

Patients with influenza-related acute respiratory distress syndrome (ARDS) are critically ill and require mechanical ventilation (MV) support. Prolonged mechanical ventilation (PMV) is often seen in these cases and the optimal management strategy is not established. This study aimed to investigate risk factors for PMV and factors related to weaning failure in these patients.

METHODS

This retrospective cohort study was conducted by eight medical centers in Taiwan. All patients in the intensive care unit with virology-proven influenza-related ARDS requiring invasive MV from January 1 to March 31, 2016, were included. Demographic data, critical illness data and clinical outcomes were collected and analyzed. PMV is defined as mechanical ventilation use for more than 21 days.

RESULTS

There were 263 patients with influenza-related ARDS requiring invasive MV enrolled during the study period. Seventy-eight patients had PMV. The final weaning rate was 68.8% during 60 days of observation. The mortality rate in PMV group was 39.7%. Risk factors for PMV were body mass index (BMI) > 25 (kg/m2) [odds ratio (OR) 2.087; 95% confidence interval (CI) 1.006-4.329], extracorporeal membrane oxygenation (ECMO) use (OR 6.181; 95% CI 2.338-16.336), combined bacterial pneumonia (OR 4.115; 95% CI 2.002-8.456) and neuromuscular blockade use over 48 h (OR 2.8; 95% CI 1.334-5.879). In addition, risk factors for weaning failure in PMV patients were ECMO (OR 5.05; 95% CI 1.75-14.58) use and bacteremia (OR 3.91; 95% CI 1.20-12.69).

CONCLUSIONS

Patients with influenza-related ARDS and PMV have a high mortality rate. Risk factors for PMV include BMI > 25, ECMO use, combined bacterial pneumonia and neuromuscular blockade use over 48 h. In addition, ECMO use and bacteremia predict unsuccessful weaning in PMV patients.

The predictive value of neurally adjusted ventilatory assist indexes for the prognosis of patients with severe cerebral hemorrhage

OBJECTIVE

This study assessed the predictive value of electrical activity of the diaphragm (EAdi) and the EAdi-derived monitoring index in the prognosis of patients with severe cerebral hemorrhage.

METHODS

Ninety patients with severe cerebral hemorrhage were admitted to the Neurosurgery Intensive Care Unit of Yijishan Hospital from April 2019 to June 2021 and were divided into the good prognosis group (Glasgow Outcome Scale [GOS] ≥ 4) and poor prognosis group (GOS ≤ 3). The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to evaluate prediction accuracy.

RESULTS

EAdi, neuro-ventilatory efficiency (NVE), and neuro-muscular efficiency (NME) in patients with good prognosis were significantly higher than those in patients with poor prognosis (4.707 µV vs 2.80 µV, P < 0.001; 141.85 ml/µV vs 66.01 ml/µV, P = 0.000; 2.57 cm H2O/µV vs 1.37 cm H2O/µV, P = 0.000). The area under the ROC curve for the EAdi score was 0.719, with sensitivity of 69.70% and specificity of 68.42% when EAdi was 3.6 µV. The AUC for NVE score was 0.793, with sensitivity of 75.76% and specificity of 75.44% when the NVE value was 95.32 ml/µV. The AUC for NME score was 0.792, with sensitivity of 69.70% and specificity of 78.95% when the NME value was 2.06 H2O/µV. The 6-month survival time of patients with higher EAdi, NVE, and NME was significantly longer than that of patients with lower EAdi, NVE, and NME CONCLUSION: EAdi, NVE, and NME can be used as indices for predicting the prognosis of patients with severe cerebral hemorrhage.

TRIAL REGISTRATION NO

ChiCTR1900022861. Registered April 28, 2019, http://www.chictr.org.cn .

[Diaphragmatic ultrasonography for the pulmonologist: Technique and clinical use]

INTRODUCTION

Ultrasonography is an emerging tool that helps to assess diaphragmatic function. It is now widely used in ICUs to predict weaning from mechanical ventilation. Ultrasonography is readily available, harmless (no radiation), and repeatable with good interoperator reproducibility. Over the past few years, ultrasonography has seen increasing use in patients with chronic pulmonary pathologies.

STATE OF THE ART

The aim of this review is (1) to describe the ultrasound techniques used to assess diaphragmatic excursion and thickening, (2) to indicate the expected, normal values in healthy patients, and (3) to summarize the main findings and clinical applications in treatment of chronic respiratory disorders.

CONCLUSIONS

Chronic pulmonary diseases are associated with diaphragmatic dysfunction that can be assessed with ultrasound. Diaphragmatic dysfunction is primary in neuromuscular disorders and secondary to respiratory disease in other chronic pulmonary conditions (COPD, ILD). Ultrasound is correlated with the severity of the underlying disease (functional and clinical parameters).

PERSPECTIVES

The prognostic interest of diaphragm ultrasonography remains to be established, after which its utilization should become routine.

Phrenic nerve stimulation to prevent diaphragmatic dysfunction and ventilator-induced lung injury

Side effects of mechanical ventilation, such as ventilator-induced diaphragmatic dysfunction (VIDD) and ventilator-induced lung injury (VILI), occur frequently in critically ill patients. Phrenic nerve stimulation (PNS) has been a valuable tool for diagnosing VIDD by assessing respiratory muscle strength in response to magnetic PNS. The detection of pathophysiologically reduced respiratory muscle strength is correlated with weaning failure, longer mechanical ventilation time, and mortality. Non-invasive electromagnetic PNS designed for diagnostic use is a reference technique that allows clinicians to measure transdiaphragm pressure as a surrogate parameter for diaphragm strength and functionality. This helps to identify diaphragm-related issues that may impact weaning readiness and respiratory support requirements, although lack of lung volume measurement poses a challenge to interpretation. In recent years, therapeutic PNS has been demonstrated as feasible and safe in lung-healthy and critically ill patients. Effects on critically ill patients' VIDD or diaphragm atrophy outcomes are the subject of ongoing research. The currently investigated application forms are diverse and vary from invasive to non-invasive and from electrical to (electro)magnetic PNS, with most data available for electrical stimulation. Increased inspiratory muscle strength and improved diaphragm activity (e.g., excursion, thickening fraction, and thickness) indicate the potential of the technique for beneficial effects on clinical outcomes as it has been successfully used in spinal cord injured patients. Concerning the potential for electrophrenic respiration, the data obtained with non-invasive electromagnetic PNS suggest that the induced diaphragmatic contractions result in airway pressure swings and tidal volumes remaining within the thresholds of lung-protective mechanical ventilation. PNS holds significant promise as a therapeutic intervention in the critical care setting, with potential applications for ameliorating VIDD and the ability for diaphragm training in a safe lung-protective spectrum, thereby possibly reducing the risk of VILI indirectly. Outcomes of such diaphragm training have not been sufficiently explored to date but offer the perspective for enhanced patient care and reducing weaning failure. Future research might focus on using PNS in combination with invasive and non-invasive assisted ventilation with automatic synchronisation and the modulation of PNS with spontaneous breathing efforts. Explorative approaches may investigate the feasibility of long-term electrophrenic ventilation as an alternative to positive pressure-based ventilation.