A Stimulating Approach to Ventilator-induced Diaphragmatic Dysfunction

Physical and Cognitive Impairment in Acute Respiratory Failure

Recent research has brought renewed attention to the multifaceted physical and cognitive dysfunction that accompanies acute respiratory failure (ARF). This state-of-the-art review provides an overview of the evidence landscape encompassing ARF-associated neuromuscular and neurocognitive impairments. Risk factors, mechanisms, assessment tools, rehabilitation strategies, approaches to ventilator liberation, and interventions to minimize post-intensive care syndrome are emphasized. The complex interrelationship between physical disability, cognitive dysfunction, and long-term patient-centered outcomes is explored. This review highlights the need for comprehensive, multidisciplinary approaches to mitigate morbidity and accelerate recovery.

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.

Rapid review of ventilator-induced diaphragm dysfunction

Ventilator-induced diaphragm dysfunction is gaining increased recognition. Evidence of diaphragm weakness can manifest within 12 h to a few days after the initiation of mechanical ventilation. Various noninvasive and invasive methods have been developed to assess diaphragm function. The implementation of diaphragm-protective ventilation strategies is crucial for preventing diaphragm injuries. Furthermore, diaphragm neurostimulation emerges as a promising and novel treatment option. In this rapid review, our objective is to discuss the current understanding of ventilator-induced diaphragm dysfunction, diagnostic approaches, and updates on strategies for prevention and management.

Lung, Pleura, and Diaphragm Point-of-Care Ultrasound

Thoracic Ultrasonography involves the ultrasonographic examination of the lungs, pleura, and diaphragm. This provides a plethora of clinical information during the point of care assessment of patients. The air filled lungs create consistent artifacts and careful examination and understanding of these artefactual signs can provide useful information on underlying clinicopathologic states. This review aims to provide a review of the ultrasound signs and features that can be seen in horacic ultrasonography and summarize the clinical evidence to support its use.

Effectiveness of abdominal sandbag training in enhancing diaphragm muscle function and exercise tolerance in patients with chronic respiratory failure

BACKGROUND

Chronic respiratory failure is a common cause of ventilator dependence in the intensive care unit (ICU). The causes of chronic respiratory failure include primary disease or complications, such as ICU-acquired weakness. Traditional practice requires patients to remain immobile and bedridden; however, recent evidence suggests that early adequate exercise promotes recovery without increasing risks. In this study, we explored the efficacy of planned progressive abdominal sandbag training in promoting the successful withdrawal of patients with chronic respiratory failure from mechanical ventilation.

METHODS

This study was conducted between April 2019 and November 2020. Patients were recruited and divided into two groups: abdominal sandbag training group and control group (no training). The training group participated in a 3-month daily pulmonary rehabilitation program, which involved a 30-min session of progressive sandbag loading on the upper abdomen as a form of diaphragmatic resistant exercise. The pressure support level of the ventilator was adjusted to maintain a tidal volume of 8 mL/kg. To investigate the effect of abdominal sandbag training on patients with chronic respiratory failure, we compared tidal volume, shallow breathing index, maximum respiratory pressure, and diaphragm characteristics between the training and control groups.

RESULTS

This study included 31 patients; of them, 17 (54.8 %) received abdominal sandbag training and 14 (45.2 %) did not. No significant between-group difference was found in baseline characteristics. Compared with the control group, the training group exhibited considerable improvements in ventilation-related parameters (p < 0.001): the tidal volume markedly increased (p = 0.012), rapid shallow breathing index declined (p = 0.016), and maximum respiratory pressure increased (p < 0.001) in the training group. The diaphragm motion value (p = 0.048) and diaphragm thickness (p = 0.041) were greater in the training group than in the control group. Nine patients (52.9 %) in the training group were removed from the ventilator compared with 1 (7.1 %) in the control group (p = 0.008).

CONCLUSIONS

Abdominal sandbag training may be beneficial for patients dependent on a ventilator. The training improves the function of the diaphragm muscle, thereby increasing tidal volume and reducing the respiratory rate and rapid shallow breathing index, thus facilitating withdrawal from ventilation. This training approach may also improve the thickness and motion of the diaphragm and the rate of ventilator detachment.

Pendelluft in hypoxemic patients resuming spontaneous breathing: proportional modes versus pressure support ventilation

BACKGROUND

Internal redistribution of gas, referred to as pendelluft, is a new potential mechanism of effort-dependent lung injury. Neurally-adjusted ventilatory assist (NAVA) and proportional assist ventilation (PAV +) follow the patient's respiratory effort and improve synchrony compared with pressure support ventilation (PSV). Whether these modes could prevent the development of pendelluft compared with PSV is unknown. We aimed to compare pendelluft magnitude during PAV + and NAVA versus PSV in patients with resolving acute respiratory distress syndrome (ARDS).

METHODS

Patients received either NAVA, PAV + , or PSV in a crossover trial for 20-min using comparable assistance levels after controlled ventilation (> 72 h). We assessed pendelluft (the percentage of lost volume from the non-dependent lung region displaced to the dependent region during inspiration), drive (as the delta esophageal swing of the first 100 ms [ΔPes 100 ms]) and inspiratory effort (as the esophageal pressure-time product per minute [PTPmin]). We performed repeated measures analysis with post-hoc tests and mixed-effects models.

RESULTS

Twenty patients mechanically ventilated for 9 [5-14] days were monitored. Despite matching for a similar tidal volume, respiratory drive and inspiratory effort were slightly higher with NAVA and PAV + compared with PSV (ΔPes 100 ms of -2.8 [-3.8--1.9] cm H2O, -3.6 [-3.9--2.4] cm H2O and -2.1 [-2.5--1.1] cm H2O, respectively, p < 0.001 for both comparisons; PTPmin of 155 [118-209] cm H2O s/min, 197 [145-269] cm H2O s/min, and 134 [93-169] cm H2O s/min, respectively, p < 0.001 for both comparisons). Pendelluft magnitude was higher in NAVA (12 ± 7%) and PAV + (13 ± 7%) compared with PSV (8 ± 6%), p < 0.001. Pendelluft magnitude was strongly associated with respiratory drive (β = -2.771, p-value < 0.001) and inspiratory effort (β = 0.026, p  < 0.001), independent of the ventilatory mode. A higher magnitude of pendelluft in proportional modes compared with PSV existed after adjusting for PTPmin (β = 2.606, p = 0.010 for NAVA, and β = 3.360, p = 0.004 for PAV +), and only for PAV + when adjusted for respiratory drive (β = 2.643, p = 0.009 for PAV +).

CONCLUSIONS

Pendelluft magnitude is associated with respiratory drive and inspiratory effort. Proportional modes do not prevent its occurrence in resolving ARDS compared with PSV.

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.

Cellular senescence contributes to mechanical ventilation-induced diaphragm dysfunction by upregulating p53 signalling pathways

BACKGROUND

Mechanical ventilation can cause acute atrophy and injury in the diaphragm, which are related to adverse clinical results. However, the underlying mechanisms of ventilation-induced diaphragm dysfunction (VIDD) have not been well elucidated. The current study aimed to explore the role of cellular senescence in VIDD.

METHODS

A total of twelve New Zealand rabbits were randomly divided into 2 groups: (1) spontaneously breathing anaesthetized animals (the CON group) and (2) mechanically ventilated animals (for 48 h) in V-ACV mode (the MV group). Respiratory parameters were collected during ventilation. Diaphragm were collected for further analyses.

RESULTS

Compared to those in the CON group, the percentage and density of sarcomere disruption in the MV group were much higher (p < 0.001, both). The mRNA expression of MAFbx and MuRF1 was upregulated in the MV group (p = 0.003 and p = 0.006, respectively). Compared to that in the CON group, the expression of MAFbx and MuRF1 detected by western blotting was also upregulated (p = 0.02 and p = 0.03, respectively). Moreover, RNA-seq showed that genes associated with senescence were remarkably enriched in the MV group. The mRNA expression of related genes was further verified by q-PCR (Pai1: p = 0.009; MMP9: p = 0.008). Transverse cross-sections of diaphragm myofibrils in the MV group showed more intensive positive staining of SA-βGal than those in the CON group. p53-p21 axis signalling was elevated in the MV group. The mRNA expression of p53 and p21 was significantly upregulated (p = 0.02 and p = 0.05, respectively). The western blot results also showed upregulation of p53 and p21 protein expression (p = 0.03 and p = 0.05, respectively). Moreover, the p21-positive staining in immunofluorescence and immunohistochemistry in the MV group was much more intense than that in the CON group (p < 0.001, both).

CONCLUSIONS

In a rabbit model, we demonstrated that mechanical ventilation in A/C mode for 48 h can still significantly induce ultrastructural damage and atrophy of the diaphragm. Moreover, p53-dependent senescence might play a role in mechanical ventilation-induced dysfunction. These findings might provide novel therapeutic targets for VIDD.

Outcomes in critically ill patients after diaphragmatic stimulation on ventilator-induced diaphragmatic dysfunction: a systematic review

INTRODUCTION

Mechanical ventilation (MV) is a lifesaving procedure for critically ill patients. Diaphragm activation and stimulation may counteract side effects, such as ventilator-induced diaphragm dysfunction (VIDD). The effects of stimulation on diaphragm atrophy and patient outcomes are reported in this systematic review.

EVIDENCE ACQUISITION

Studies investigating diaphragmatic stimulation versus standard of care in critically ill patients and evaluating clinical outcomes were extracted from a Medline database last on January 23, 2023, after registration in Prospero (CRD42021259353). Selected studies included the investigation of diaphragmatic stimulation versus standard of care in critically ill patients, an evaluation of the clinical outcomes. These included muscle atrophy, VIDD, weaning failure, mortality, quality of life, ventilation time, diaphragmatic function, length of stay in the Intensive Care Unit (ICU), and length of hospital stay. All articles were independently evaluated by two reviewers according to their abstract and title and, secondly, a full texts evaluation by two independent reviewers was performed. To resolve diverging evaluations, a third reviewer was consulted to reach a final decision. Data were extracted by the reviewers following the Oxford 2011 levels of evidence guidelines and summarized accordingly.

EVIDENCE SYNTHESIS

Seven studies were extracted and descriptively synthesized, since a metanalysis was not feasible. Patients undergoing diaphragm stimulation had moderate evidence of higher maximal inspiratory pressure (MIP), less atrophy, less mitochondrial respiratory dysfunction, less oxidative stress, less molecular atrophy, shorter MV time, shorter ICU length of stay, longer survival, and better SF-36 scores than control.

CONCLUSIONS

Evidence of the molecular and histological benefits of diaphragmatic stimulation is limited. The results indicate positive clinical effects of diaphragm activation with a moderate level of evidence for MIP and a low level of evidence for other outcomes. Diaphragm activation could be a therapeutic solution to avoid diaphragm atrophy, accelerate weaning, shorten MV time, and counteract VIDD; however, better-powered studies are needed to increase the level of evidence.

Diaphragm excursions as proxy for tidal volume during spontaneous breathing in invasively ventilated ICU patients

There is a need to monitor tidal volume in critically ill patients with acute respiratory failure, given its relation with adverse clinical outcome. However, quantification of tidal volume in non-intubated patients is challenging. In this proof-of-concept study, we evaluated whether ultrasound measurements of diaphragm excursion could be a valid surrogate for tidal volume in patients with respiratory failure. Diaphragm excursions and tidal volumes were simultaneously measured in invasively ventilated patients (N = 21) and healthy volunteers (N = 20). Linear mixed models were used to estimate the ratio between tidal volume and diaphragm excursion. The tidal volume-diaphragm excursion ratio was 201 mL/cm in ICU patients [95% confidence interval (CI) 161-240 mL/cm], and 361 (294-428) mL/cm in healthy volunteers. An excellent association was shown within participants (R2 = 0.96 in ICU patients, R2 = 0.90 in healthy volunteers). However, the differences between observed tidal volume and tidal volume as predicted by the linear mixed models were considerable: the 95% limits of agreement in Bland-Altman plots were ± 91 mL in ICU patients and ± 396 mL in healthy volunteers. Likewise, the variability in tidal volume estimation between participants was large. This study shows that diaphragm excursions measured with ultrasound correlate with tidal volume, yet quantification of absolute tidal volume from diaphragm excursion is unreliable.

Diaphragm function in patients with Covid-19-related acute respiratory distress syndrome on venovenous extracorporeal membrane oxygenation

BACKGROUND

Venovenous extracorporeal membrane oxygenation (VV ECMO) is frequently associated with deep sedation and neuromuscular blockades, that may lead to diaphragm dysfunction. However, the prevalence, risk factors, and evolution of diaphragm dysfunction in patients with VV ECMO are unknown. We hypothesized that the prevalence of diaphragm dysfunction is high and that diaphragm activity influences diaphragm function changes.

METHODS

Patients with acute respiratory distress syndrome (ARDS) requiring VV ECMO were included in two centers. Diaphragm function was serially assessed by measuring the tracheal pressure in response to phrenic nerve stimulation (Ptr,stim) from ECMO initiation (Day 1) until ECMO weaning. Diaphragm activity was estimated from the percentage of spontaneous breathing ventilation and by measuring the diaphragm thickening fraction (TFdi) with ultrasound.

RESULTS

Sixty-three patients were included after a median of 4 days (3-6) of invasive mechanical ventilation. Diaphragm dysfunction, defined by Ptr, stim ≤ 11 cmH2O, was present in 39 patients (62%) on Day 1 of ECMO. Diaphragm function did not change over the study period and was not influenced by the percentage of spontaneous breathing ventilation or the TFdi during the 1 week. Among the 63 patients enrolled in the study, 24 (38%) were still alive at the end of the study period (60 days).

CONCLUSIONS

Sixty-two percent of patients undergoing ECMO for ARDS related to SARS CoV-2 infection had a diaphragm dysfunction on Day 1 of ECMO initiation. Diaphragm function remains stable over time and was not associated with the percentage of time with spontaneous breathing.

CLINICALTRIALS

gov Identifier NCT04613752 (date of registration February 15, 2021).

Timing of parenteral nutrition initiation in critically ill children: a randomized clinical trial

BACKGROUND

The optimal timing of parenteral nutrition (PN) initiation in critically ill children remains controversial.

PURPOSE

To identify the optimal timing of PN initiation in critically ill children.

METHODS

This randomized clinical trial was conducted in the pediatric intensive care unit (PICU) of Menoufia University Hospital. A total of 140 patients were randomized to receive early or late PN. The early PN group consisted of 71 well-nourished and malnourished patients who received PN on the first day of PICU admission. Malnourished (42%) and well-nourished children randomized to the late PN group (42%) started PN on the fourth versus seventh day after admission, respectively. Mechanical ventilation (MV) was the primary outcome, while PICU length of stay and mortality were secondary outcomes.

RESULTS

Patients who received early PN started enteral feeding significantly earlier (median, 6 days; interquartile range, 2-20 days) than those not provided early PN (median, 12 days; interquartile range, 3-30 days; P<0.001) and had a significantly lower risk of feeding intolerance (5.6% vs.18.8%, P=0.035). The median time required to obtain full calories enterally was shorter in the early versus late PN group (P=0.004). Furthermore, patients in the early versus late PN group had a significantly shorter median PICU stay (P<0.001) and were less likely to require MV (P=0.018).

CONCLUSION

Patients who received early PN had a lower MV need and duration than those who received later PN and had more favorable clinical outcomes in terms of morbidity.

Acute dyspnea in the emergency department: a clinical review

Acute dyspnea represents one of the most frequent symptoms leading to emergency room evaluation. Its significant prognostic value warrants a careful evaluation. The differential diagnosis of dyspnea is complex due to the lack of specificity and the loose association between its intensity and the severity of the underlying pathological condition. The initial assessment of dyspnea calls for prompt diagnostic evaluation and identification of optimal monitoring strategy and provides information useful to allocate the patient to the most appropriate setting of care. In recent years, accumulating evidence indicated that lung ultrasound, along with echocardiography, represents the first rapid and non-invasive line of assessment that accurately differentiates heart, lung or extra-pulmonary involvement in patients with dyspnea. Moreover, non-invasive respiratory support modalities such as high-flow nasal oxygen and continuous positive airway pressure have aroused major clinical interest, in light of their efficacy and practicality to treat patients with dyspnea requiring ventilatory support, without using invasive mechanical ventilation. This clinical review is focused on the pathophysiology of acute dyspnea, on its clinical presentation and evaluation, including ultrasound-based diagnostic workup, and on available non-invasive modalities of respiratory support that may be required in patients with acute dyspnea secondary or associated with respiratory failure.

Managing respiratory muscle weakness during weaning from invasive ventilation

Weaning is a critical stage of an intensive care unit (ICU) stay, in which the respiratory muscles play a major role. Weakness of the respiratory muscles, which is associated with significant morbidity in the ICU, is not limited to atrophy and subsequent dysfunction of the diaphragm; the extradiaphragmatic inspiratory and expiratory muscles also play important parts. In addition to the well-established deleterious effect of mechanical ventilation on the respiratory muscles, other risk factors such as sepsis may be involved. Weakness of the respiratory muscles can be suspected visually in a patient with paradoxical movement of the abdominal compartment. Measurement of maximal inspiratory pressure is the simplest way to assess respiratory muscle function, but it does not specifically take the diaphragm into account. A cut-off value of -30 cmH₂O could identify patients at risk for prolonged ventilatory weaning; however, ultrasound may be better for assessing respiratory muscle function in the ICU. Although diaphragm dysfunction has been associated with weaning failure, this diagnosis should not discourage clinicians from performing spontaneous breathing trials and considering extubation. Recent therapeutic developments aimed at preserving or restoring respiratory muscle function are promising.

The Effects of Positive End Expiratory Pressure and Lung Volume on Diaphragm Thickness and Thickening

Introduction: Diaphragm dysfunction is common in patients undergoing mechanical ventilation. The application of positive end-expiratory pressure (PEEP) and the varying end-expiratory lung volume cause changes in diaphragm geometry. We aimed to assess the impact of the level of PEEP and lung inflation on diaphragm thickness, thickening fraction and displacement. Methods: An observational study in a mixed medical and surgical ICU was conducted. The patients underwent a PEEP-titration trial with the application of three random levels of PEEP: 0 cmH₂O (PEEP0), 8 cmH₂O (PEEP8) and 15 cmH₂O (PEEP15). At each step, the indices of respiratory effort were assessed, together with arterial blood and diaphragm ultrasound; end-expiratory lung volume was measured. Results: 14 patients were enrolled. The tidal volume, diaphragm displacement and thickening fraction were significantly lower with higher levels of PEEP, while both the expiratory and inspiratory thickness increased with higher PEEP levels. The inspiratory effort, as evaluated by the esophageal pressure swing, was unchanged. Both the diaphragm thickening fraction and displacement were significantly correlated with inspiratory effort in the whole dataset. For both measurements, the correlation was stronger at lower levels of PEEP. The difference in the diaphragm thickening fraction during tidal breathing between PEEP 15 and PEEP 0 was negatively related to the change in the functional residual capacity and the change in alveolar dead space. Conclusions: Different levels of PEEP significantly modified the diaphragmatic thickness and thickening fraction, showing a PEEP-induced decrease in the diaphragm contractile efficiency. When using ultrasound to assess diaphragm size and function, the potential effect of lung inflation should be taken into account.

Diaphragm Ultrasound in Critically Ill Patients on Mechanical Ventilation—Evolving Concepts

Mechanical ventilation (MV) is a life-saving respiratory support therapy, but MV can lead to diaphragm muscle injury (myotrauma) and induce diaphragmatic dysfunction (DD). DD is relevant because it is highly prevalent and associated with significant adverse outcomes, including prolonged ventilation, weaning failures, and mortality. The main mechanisms involved in the occurrence of myotrauma are associated with inadequate MV support in adapting to the patient’s respiratory effort (over- and under-assistance) and as a result of patient-ventilator asynchrony (PVA). The recognition of these mechanisms associated with myotrauma forced the development of myotrauma prevention strategies (MV with diaphragm protection), mainly based on titration of appropriate levels of inspiratory effort (to avoid over- and under-assistance) and to avoid PVA. Protecting the diaphragm during MV therefore requires the use of tools to monitor diaphragmatic effort and detect PVA. Diaphragm ultrasound is a non-invasive technique that can be used to monitor diaphragm function, to assess PVA, and potentially help to define diaphragmatic effort with protective ventilation. This review aims to provide clinicians with an overview of the relevance of DD and the main mechanisms underlying myotrauma, as well as the most current strategies aimed at minimizing the occurrence of myotrauma with special emphasis on the role of ultrasound in monitoring diaphragm function.

Update on Lean Body Mass Diagnostic Assessment in Critical Illness

Acute critical illnesses can alter vital functions with profound biological, biochemical, metabolic, and functional modifications. Despite etiology, patient's nutritional status is pivotal to guide metabolic support. The assessment of nutritional status remains complex and not completely elucidated. Loss of lean body mass is a clear marker of malnutrition; however, the question of how to investigate it still remains unanswered. Several tools have been implemented to measure lean body mass, including a computed tomography scan, ultrasound, and bioelectrical impedance analysis, although such methods unfortunately require validation. A lack of uniform bedside measurement tools could impact the nutrition outcome. Metabolic assessment, nutritional status, and nutritional risk have a pivotal role in critical care. Therefore, knowledge about the methods used to assess lean body mass in critical illnesses is increasingly required. The aim of the present review is to update the scientific evidence regarding lean body mass diagnostic assessment in critical illness to provide the diagnostic key points for metabolic and nutritional support.

Validation of a non-invasive pressure-time index of the inspiratory muscles in spontaneously breathing newborn infants

To validate the pressure-time index of the inspiratory muscles as a non-invasive index of inspiratory muscle function in spontaneously breathing infants by comparing it against the gold-standard pressure-time index of the diaphragm. Prospective observational cohort study of consecutive infants breathing unsupported in room air in a tertiary neonatal intensive care unit, studied prior to discharge from neonatal care. The invasive pressure-time index of the diaphragm was calculated using a transdiaphragmatic dual-pressure catheter that measured transdiaphragmatic pressure by subtraction of the oesophageal from the gastric pressure. The non-invasive pressure-time index of the inspiratory muscles was calculated using pressure measurements at the level of the mouth via a differential pressure transducer connected to a face mask. Both indices were calculated as the product of the ratio of the mean inspiratory pressure divided by the maximum inspiratory pressure and the ratio of the inspiratory time divided by the total time of a respiratory cycle. One hundred and thirty infants (79 male) were included with a mean (SD) gestational age of 35.2 (3.2) weeks, studied at a median (IQR) postnatal age of 9 (6-20) days. The mean (SD) pressure-time index of the diaphragm was 0.063 (0.019) and the mean (SD) pressure-time index of the inspiratory muscles was 0.065 (0.023). The correlation coefficient for the two indices was 0.509 (p < 0.001). The mean (SD) absolute difference between the pressure-time index of the inspiratory muscles and pressure-time index of the diaphragm was 0.002 (0.021). In convalescent infants, the non-invasive pressure-time index of the inspiratory muscles had a moderate degree of correlation with the invasively derived pressure time index of the diaphragm measured with a transdiaphragmatic catheter.

Ultrasonographic Assessment of Diaphragmatic Function and Its Clinical Application in the Management of Patients with Acute Respiratory Failure

Acute respiratory failure (ARF) is a common life-threatening medical condition, with multiple underlying etiologies. In these cases, many factors related to systemic inflammation, prolonged use of steroids, and lung mechanical abnormalities (such as hyperinflation or increased elastic recoil due to pulmonary oedema or fibrosis) may act as synergic mechanisms leading to diaphragm dysfunction. The assessment of diaphragm function with ultrasound has been increasingly investigated in the emergency department and during hospital stay as a valuable tool for providing additional anatomical and functional information in many acute respiratory diseases. The diaphragmatic ultrasound is a noninvasive and repeatable bedside tool, has no contraindications, and allows the physician to rapidly assess the presence of diaphragmatic dysfunction; this evaluation may help in estimating the need for mechanical ventilation (and the risk of weaning failure), as well as the risk of longer hospital stay and higher mortality rate. This study presents an overview of the recent evidence regarding the evaluation of diaphragmatic function with bedside ultrasound and its clinical applications, including a discussion of real-life clinical cases.

Treatment with levosimendan in an experimental model of early ventilator-induced diaphragmatic dysfunction

Introduction

Mechanical ventilation (MV) is a life-saving approach in critically ill patients. However, it may affect the diaphragmatic structure and function, beyond the lungs. Levosimendan is a calcium sensitizer widely used in clinics to improve cardiac contractility in acute heart failure patients. In vitro studies have demonstrated that levosimendan increased force-generating capacity of the diaphragm in chronic obstructive pulmonary disease patients. Thus the aim of this study was to evaluate the effects of levosimendan administration in an animal model of ventilator-induced diaphragmatic dysfunction (VIDD) on muscle contraction and diaphragm muscle cell viability.

Methods

Sprague-Dawley rats underwent prolonged MV (5 hours). VIDD+Levo group received a starting bolus of levosimendan immediately after intratracheal intubation and then an intravenous infusion of levosimendan throughout the study. Diaphragms were collected for ex vivo contractility measurement (with electric stimulation), histological analysis and Western blot analysis. Healthy rats were used as the control.

Results

Levosimendan treatment maintained an adequate mean arterial pressure during the entire experimental protocol, preserved levels of autophagy-related proteins (LC3BI and LC3BII) and the muscular cell diameter demonstrated by histological analysis. Levosimendan did not affect the diaphragmatic contraction or the levels of proteins involved in the protein degradation (atrogin).

Conclusions

Our data suggest that levosimendan preserves muscular cell structure (cross-sectional area) and muscle autophagy after 5 hours of MV in a rat model of VIDD. However, levosimendan did not improve diaphragm contractile efficiency.

Spontaneous Breathing and Pendelluft in Patients with Acute Lung Injury: A Narrative Review

Acute respiratory distress syndrome (ARDS) is characterized by acute-onset rapid-deteriorating inflammatory lung injury. Although the preservation of spontaneous breathing may have physiological benefits in oxygenation, increasing evidence shows that vigorous spontaneous breathing may aggravate lung injury (i.e., patient self-inflicted lung injury). Increased lung stress and pendelluft, which is defined as intrapulmonary gas redistribution without a significant change in tidal volume, are important mechanisms of patient self-inflicted lung injury. The presence of pendelluft may be considered a surrogate marker of vigorous inspiratory effort, which can cause the dependent lung to overstretch. In this review, we summarized three major methods for electrical impedance tomography-based pendelluft monitoring. Future studies are warranted to compare and validate the different methods of pendelluft estimation in patients with ARDS.

Intensive Care Unit Acquired Weakness Is Associated with Rapid Changes to Skeletal Muscle Proteostasis

Intensive care unit (ICU)-acquired weakness is a frequent consequence of critical illness that impacts both the limb and respiratory muscles. The cause of ICU-acquired weakness is multifactorial, but both prolonged limb muscle inactivity and mechanical ventilation are risk factors for muscle wasting, which predisposes ICU patients to both short-term complications and long-term disabilities resulting from muscle weakness. Unfortunately, the current research does not provide a detailed understanding of the cellular etiology of ICU-acquired weakness, and no standard treatment exists. Therefore, improving knowledge of the mechanisms promoting muscle atrophy in critically ill patients is essential to developing therapeutic strategies to protect against ICU-induced skeletal muscle wasting. To advance our understanding of the mechanism(s) responsible for ICU-acquired weakness, we tested the hypothesis that ICU-induced muscle inactivity promotes a rapid decrease in anabolic signaling/protein synthesis and accelerates proteolysis in both limb and respiratory muscles. To investigate ICU-induced changes in skeletal muscle proteostasis, adult Sprague Dawley rats were anesthetized and mechanically ventilated for 12 h to simulate ICU care. Measurements of anabolic signaling, protein synthesis, and proteolytic activity in the limb muscles (plantaris and soleus) and respiratory muscles (parasternal and intercostal) revealed ICU-induced reductions in both anabolic signaling (i.e., AKT/mTOR pathway) and muscle protein synthesis. Moreover, simulated ICU care resulted in increased biomarkers of accelerated proteolysis in both limb and respiratory muscles. These novel findings reveal that disturbances in limb and respiratory muscle proteostasis occur rapidly during ICU-induced muscle inactivity, irrespective of the muscle function or muscle fiber type.

Ultrasound Versus Computed Tomography for Diaphragmatic Thickness and Skeletal Muscle Index during Mechanical Ventilation

Background: Diaphragmatic alterations occurring during mechanical ventilation (MV) can be monitored using ultrasound (US). The performance of computed tomography (CT) to evaluate diaphragmatic thickness is limited. Further, the association between muscle mass and outcome is increasingly recognized. However, no data are available on its correlation with diaphragmatic thickness. We aimed to determine correlation and agreement of diaphragmatic thickness between CT and US; and its association with muscle mass and MV parameters. Methods: Prospective observational study. US measurements of the diaphragmatic thickness were collected in patients undergoing MV within 12 h before or after performing a CT scan of the thorax and/or upper abdomen. Data on skeletal muscle index (SMI), baseline, and ventilatory data were recorded and correlated with US and CT measures of diaphragmatic thickness. Agreement was explored between US and CT data. Results: Twenty-nine patients were enrolled and the diaphragm measured by CT resulted overall thicker than US-based measurement of the right hemidiaphragm. The US thickness showed the strongest correlation with the left posterior pillar at CT (r = 0.49, p = 0.008). The duration of the controlled MV was negatively correlated with US thickness (r = -0.45, p = 0.017), the thickness of the right anterior pillar (r = -0.41, p = 0.029), and splenic dome by CT (r = -0.43, p = 0.023). SMI was positively correlated with US diaphragmatic thickness (r = 0.50, p = 0.007) and inversely correlated with the duration of MV before enrollment (r = -0.426, p = 0.027). Conclusions: CT scan of the left posterior pillar can estimate diaphragmatic thickness and is moderately correlated with US measurements. Both techniques show that diaphragm thickness decreases with MV duration. The diaphragmatic thickness by US showed a good correlation with SMI.

Immediate Effect of Mechanical Ventilation Mode and Sedative Infusion on Measured Diaphragm Thickness

Rationale: In patients who are mechanically ventilated, diaphragm thinning on ultrasound is thought to correlate with diaphragm atrophy and has been associated with prolonged intubation. Factors other than atrophy, however, may cause changes in diaphragm thickness, which may confound studies examining changes in diaphragm thickness over time. Objectives: To determine if changes in the mode of mechanical ventilation or an interruption of sedatives have immediate effects on diaphragm thickness measurements in adult patients in the intensive care unit who are mechanically ventilated. Methods: Adult patients receiving invasive mechanical ventilation for less than 48 hours were included. Diaphragm thickness was measured at end-expiration and peak inspiration using ultrasound while patients were receiving both volume assist-control and pressure-support modes in a randomized crossover fashion. In patients receiving sedatives, additional measurements were taken after an interruption of sedatives. Measurements were compared between modes and on assist-control before and after an interruption of sedatives. Results: Of 85 patients enrolled, 66 had measurements on assist-control and spontaneous modes, and 40 had measurements before and after an interruption of sedatives. End-expiratory diaphragm thickness increased by a median of 0.08 mm after an interruption of sedatives (95% confidence interval [CI], 0.002 mm to 0.164 mm; P = 0.017), corresponding to a median increase of 6.5%. No difference was seen when comparing measurements taken on volume assist-control and pressure support (median difference, 0 mm; 95% CI, -0.07 mm to 0.08 mm; P = 0.98). Conclusions: End-expiratory diaphragm thickness increased by 6.5% after an interruption of sedatives. The effect of sedatives on measured diaphragm thickness should be considered in future studies examining changes in diaphragm thickness over time. Clinical trial registered with Clinicaltrials.gov (NCT04319939).

Association between histological diaphragm atrophy and ultrasound diaphragm expiratory thickness in ventilated patients

Background

Diaphragm fiber atrophy has been evidenced after short periods of mechanical ventilation (MV) and related to critical illness-associated diaphragm weakness. Atrophy is described as a decrease in diaphragm fiber cross-sectional area (CSA) in human diaphragm biopsy, but human samples are still difficult to obtain in clinics. In recent years, ultrasound has become a useful tool in intensive care to evaluate diaphragm anatomy. The present study aimed to evaluate the ability of diaphragm expiratory thickness (Tdi) measured by ultrasound to predict diaphragm atrophy, defined by a decrease in diaphragm fiber CSA obtained through diaphragm biopsy (the gold standard technique) in ventilated patients.

Methods

Diaphragm biopsies and diaphragm ultrasound were performed in ventilated donors and in control subjects. Demographic variables, comorbidities, severity on admission, treatment, laboratory test results and evolution variables were evaluated. Immunohistochemical analysis to determine CSA and ultrasound measurements of Tdi at end-expiration were performed, and median values of the control group were used as thresholds to determine agreement between them in further analysis. Sensitivity, specificity, and positive and negative predictive values of an ultrasound Tdi cutoff for detecting histologic atrophy were calculated. Agreement between two ultrasound observers was also assessed.

Results

Thirty-five ventilated organ donors and 5 ventilated controls were included, without differences in basic characteristics. CSA and Tdi were lower in donors than in controls. All donors presented lower CSA, but only 74% lower Tdi regarding control group thresholds. The cut-off value for lower diaphragm expiratory thickness (Tdi < 1.7 mm) presented a sensitivity of 73%, a specificity of 67%, a positive predictive value of 96% and a negative predictive value of 17% for determining the presence of diaphragm atrophy (CSA < 2851 μm²).

Conclusions

Diaphragm atrophy and thickness reduction is associated to MV. While a lower Tdi in diaphragm ultrasound is a good tool for diagnosing atrophy, normal or increased Tdi cannot rule atrophy out showing that both parameters should not be considered as synonymous.

Point-of-care application of diaphragmatic ultrasonography in the emergency department for the prediction of development of respiratory failure in community-acquired pneumonia: A pilot study

Background

Early recognition of patients with community-acquired pneumonia (CAP) at risk of poor outcomes is crucial. However, there is no effective assessment tool for predicting the development of respiratory failure in patients with CAP. Diaphragmatic ultrasonography (DUS) is a novel technique developed for evaluating diaphragmatic function via measurements of the diaphragm thickening fraction (DTF) and diaphragm excursion (DE). This study evaluated the accuracy of DUS in predicting the development of respiratory failure in patients with CAP, as well as the feasibility of its use in the emergency department (ED) setting.

Materials and methods

This was a single-center prospective cohort study. We invited all patients with ED aged ≥ 20 years who were diagnosed with CAP of pneumonia severity index (PSI) SIe diagnosed with CAP of pneumonia severe with respiratory failure or septic shock were excluded. Two emergency physicians performed DUS to obtain DTF and DE measurements. Data were collected to calculate PSI, CURB-65 score, and Infectious Diseases Society of America/American Thoracic Society severity criteria. Study endpoints were taken at the development of respiratory failure or 30 days post-ED presentation. Continuous variables were analyzed using T-tests, while categorical variables were analyzed using chi-square tests. Further logistic regression and receiver operating characteristic curve analyses were performed to examine the ability to predict the development of respiratory failure. Intra- and inter-rater reliability was examined with intraclass correlation coefficients (ICCs).

Results

In this study, 13 of 50 patients with CAP enrolled developed respiratory failure. DTF was found to be an independent predictor (OR: 0.939, p = 0.0416). At the optimal cut-off point of 23.95%, DTF had 69.23% of sensitivity, 83.78% of specificity, 88.57% of negative predictive value, and 80% of accuracy. Intra- and inter-rater analysis demonstrated good consistency (intra-rater ICC 0.817, 0.789; inter-rater ICC 0.774, 0.781).

Conclusion

DUS assessment of DTF may reliably predict the development of respiratory failure in patients with CAP presenting to the ED. Patients with DTF > 23.95% may be considered for outpatient management.

Relationships between double cycling and inspiratory effort with diaphragm thickness during the early phase of mechanical ventilation: A prospective observational study

Background

Increased and decreased diaphragm thickness during mechanical ventilation is associated with poor outcomes. Some types of patient-ventilator asynchrony theoretically cause myotrauma of the diaphragm. However, the effects of double cycling on structural changes in the diaphragm have not been previously evaluated. Hence, this study aimed to investigate the relationship between double cycling during the early phase of mechanical ventilation and changes in diaphragm thickness, and the involvement of inspiratory effort in the occurrence of double cycling.

Methods

We evaluated adult patients receiving invasive mechanical ventilation for more than 48 h. The end-expiratory diaphragm thickness (Tdi_ee) was assessed via ultrasonography on days 1, 2, 3, 5 and 7 after the initiation of mechanical ventilation. Then, the maximum rate of change from day 1 (ΔTdi_ee%) was evaluated. Concurrently, we recorded esophageal pressure and airway pressure on days 1, 2 and 3 for 1 h during spontaneous breathing. Then, the waveforms were retrospectively analyzed to calculate the incidence of double cycling (double cycling index) and inspiratory esophageal pressure swing (ΔP_es). Finally, the correlation between double cycling index as well as ΔP_es and ΔTdi_ee% was investigated using linear regression models.

Results

In total, 19 patients with a median age of 69 (interquartile range: 65–78) years were enrolled in this study, and all received pressure assist-control ventilation. The Tdi_ee increased by more than 10% from baseline in nine patients, decreased by more than 10% in nine and remained unchanged in one. The double cycling indexes on days 1, 2 and 3 were 2.2%, 1.3% and 4.5%, respectively. There was a linear correlation between the double cycling index on day 3 and ΔTdi_ee% (R² = 0.446, p = 0.002). The double cycling index was correlated with the ΔP_es on days 2 (R² = 0.319, p = 0.004) and 3 (R² = 0.635, p < 0.001).

Conclusions

Double cycling on the third day of mechanical ventilation was associated with strong inspiratory efforts and, possibly, changes in diaphragm thickness.

Point of care diaphragm ultrasound in mechanically ventilated children: A predictive tool to detect extubation failure

BACKGROUND

Children should be weaned from the ventilator once their clinical condition improves. Extubation failure is associated with poorer clinical outcomes in children. Predictive indicators of successful extubation are needed. This study aims to evaluate the predictive value of ultrasonographic diaphragm imaging could help predict weaning success.

METHODS

In this prospective, observational study conducted between March and December 2021, children between 1 month and 10 years of age who were mechanically ventilated for more than 48 h were included. Diaphragm ultrasound (DUS) examinations were performed at the end of 2-h extubation readiness test (ERT). The end-inspiratory thickness (DTi), end-expiratory thickness (DTe), diaphragmatic thickening fraction (DTF), diaphragmatic excursion (DE), inspiratory slope (IS), and expiratory slope (ES) were evaluated.

RESULTS

Twenty-four (60%) patients were successfully extubated, while 16 (40%) required invasive or noninvasive mechanical ventilation support which were classified as failed extubation group. Three of the sixteen patients in the failed extubation group required reintubation. DTF was significantly greater in the successful weaning group (55.05 ± 23.75% vs. 30.9 ± 10.38%) (p < 0.001). DE was significantly greater in the successful weaning group (14 ± 4.4 mm vs. 11.05 ± 3.25 mm) (p < 0.001). DTF and DE were found to have a sensitivity and specificity of 91.67%, 87.50%, 83.33%, and 81.25%, respectively.

CONCLUSION

Diaphragm ultrasound is a feasible and promising tool to guide physicians during weaning from invasive mechanical ventilation. Among all DUS measurements, the DE and DTF indexes showed better performance in extubation failure than other diaphragmatic parameters.

Integrated lung ultrasound score for early clinical decision-making in patients with COVID-19: results and implications

Background and objectives

Lung Ultrasound Score (LUS) identifies and monitors pneumonia by assigning increasing scores. However, it does not include parameters, such as inferior vena cava (IVC) diameter and index of collapse, diaphragmatic excursions and search for pleural and pericardial effusions. Therefore, we propose a new improved scoring system, termed “integrated” lung ultrasound score (i-LUS) which incorporates previously mentioned parameters that can help in prediction of disease severity and survival, choice of oxygenation mode/ventilation and assignment to subsequent areas of care in patients with COVID-19 pneumonia.

Methods

Upon admission at the sub-intensive section of the emergency medical department (SEMD), 143 consecutively examined COVID-19 patients underwent i-LUS together with all other routine analysis. A database for anamnestic information, laboratory data, gas analysis and i-LUS parameters was created and analyzed.

Results

Of 143 enrolled patients, 59.4% were male (mean age 71 years) and 40.6% female. (mean age 79 years: p = 0.005). Patients that survived at 1 month had i-LUS score of 16, which was lower than that of non-survivors (median 20; p = 0.005). Survivors had a higher PaO2/FiO2 (median 321.5) compared to non-survivors (median 229, p < 0.001). There was a correlation between i-LUS and PaO2/FiO2 ratio (rho:-0.4452; p < 0.001), PaO2/FiO2 and survival status (rho:-0.3452; p < 0.001), as well as i-LUS score and disease outcome (rho:0.24; p = 0.005). In non-survivors, the serum values of different significant COVID indicators were severely expressed. The i-LUS score was higher (median 20) in patients who required non-invasive ventilation (NIV) than in those treated only by oxygen therapy (median 15.42; p = 0.003). The odds ratio for death outcome was 1.08 (confidence interval 1.02–1.15) for each point increased. At 1-month follow-up, 65 patients (45.5%) died and 78 (54.5%) survived. Patients admitted to the high critical ward had higher i-LUS score than those admitted to the low critical one (p < 0.003).

Conclusions

i-LUS could be used as a helpful clinical tool for early decision-making in patients with COVID-19 pneumonia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13089-022-00264-8.

Effect of Acupuncture on Diaphragm Function in Healthy Volunteers: A Pilot Clinical Study

Introduction

In western medicine, the diaphragm is the main inspiratory muscle. It is involved in the postural control of the trunk and contributes to balance performance. In traditional Chinese medicine (TCM), the diaphragm represents a gateway between the lower and upper parts of the body, and it regulates the descending and ascending functions of the whole organism. The aim of this study was to assess the effect of acupuncture on diaphragm function.

Methods

A proof-of-concept, prospective, controlled, pilot trial in healthy volunteers. Respiratory rate, inspired volume, diaphragm excursion, and thickening were measured during tidal and maximal breathing at baseline and after sham or real acupuncture. Acupuncture was performed on Yanglingquan (GB34), Tai Chong (LV3), Danzhong (CV17), Geshu (BL17), and Geguan (BL46).

Results

Ten participants were enrolled (6 males, weight 71 ± 12 kg, height 173 ± 9 cm, BMI 21 ± 1.3 kg/m²). During tidal breathing, tidal volume, diaphragm displacement, and end-expiratory diaphragm thickness did not change with sham or real acupuncture as compared to baseline; thickening ratio was 43.5 ± 16.6 vs. 31.3 ± 14.9 (sham) vs. 30.8 ± 15.3% (baseline), p=0.1066. During breaths at vital capacity, the acupuncture group, as compared to both baseline and sham acupuncture, had a trend toward a larger tidal volume (3840 ± 690 vs. 3110 ± 880 vs. 3230 ± 750 ml, p=0.1247) and showed a significantly higher thickening ratio (270.6 ± 136.4 vs. 172.4 ± 57.4 vs. 188.6 ± 41.7%, p=0.0414).

Conclusions

Acupuncture significantly influenced diaphragm function in healthy volunteers, improving its inspiratory thickening fraction during breaths at vital capacity, as compared to no or sham acupuncture.

Randomized Clinical Study of Temporary Transvenous Phrenic Nerve Stimulation in Difficult-to-Wean Patients

Rationale: Diaphragm dysfunction is frequently observed in critically ill patients with difficult weaning from mechanical ventilation. Objectives: To evaluate the effects of temporary transvenous diaphragm neurostimulation on weaning outcome and maximal inspiratory pressure. Methods: Multicenter, open-label, randomized, controlled study. Patients aged ⩾18 years on invasive mechanical ventilation for ⩾4 days and having failed at least two weaning attempts received temporary transvenous diaphragm neurostimulation using a multielectrode stimulating central venous catheter (bilateral phrenic stimulation) and standard of care (treatment) (n = 57) or standard of care (control) (n = 55). In seven patients, the catheter could not be inserted, and in seven others, pacing therapy could not be delivered; consequently, data were available for 43 patients. The primary outcome was the proportion of patients successfully weaned. Other endpoints were mechanical ventilation duration, 30-day survival, maximal inspiratory pressure, diaphragm-thickening fraction, adverse events, and stimulation-related pain. Measurements and Main Results: The incidences of successful weaning were 82% (treatment) and 74% (control) (absolute difference [95% confidence interval (CI)], 7% [-10 to 25]), P = 0.59. Mechanical ventilation duration (mean ± SD) was 12.7 ± 9.9 days and 14.1 ± 10.8 days, respectively, P = 0.50; maximal inspiratory pressure increased by 16.6 cm H₂O and 4.8 cm H₂O, respectively (difference [95% CI], 11.8 [5 to 19]), P = 0.001; and right hemidiaphragm thickening fraction during unassisted spontaneous breathing was +17% and -14%, respectively, P = 0.006, without correlation with changes in maximal inspiratory pressure. Serious adverse event frequency was similar in both groups. Median stimulation-related pain in the treatment group was 0 (no pain). Conclusions: Temporary transvenous diaphragm neurostimulation did not increase the proportion of successful weaning from mechanical ventilation. It was associated with a significant increase in maximal inspiratory pressure, suggesting reversal of the course of diaphragm dysfunction. Clinical trial registered with www.clinicaltrials.gov (NCT03096639) and the European Database on Medical Devices (CIV-17-06-020004).

Supplemental oxygen administration during mechanical ventilation reduces diaphragm blood flow and oxygen delivery

During mechanical ventilation (MV), supplemental oxygen (O2) is commonly administered to critically ill patients to combat hypoxemia. Previous studies demonstrate that hyperoxia exacerbates MV-induced diaphragm oxidative stress and contractile dysfunction. Whereas normoxic MV (i.e., 21% O2) diminishes diaphragm perfusion and O2 delivery in the quiescent diaphragm, the effect of MV with 100% O2 is unknown. We tested the hypothesis that MV supplemented with hyperoxic gas (100% O2) would increase diaphragm vascular resistance and reduce diaphragmatic blood flow and O2 delivery to a greater extent than MV alone. Female Sprague-Dawley rats (4-6 mo) were randomly divided into two groups: 1) MV + 100% O2 followed by MV + 21% O2 (n = 9) or 2) MV + 21% O2 followed by MV + 100% O2 (n = 10). Diaphragmatic blood flow (mL/min/100 g) and vascular resistance were determined, via fluorescent microspheres, during spontaneous breathing (SB), MV + 100% O2, and MV + 21% O2. Compared with SB, total diaphragm vascular resistance was increased, and blood flow was decreased with both MV + 100% O2 and MV + 21% O2 (all P < 0.05). Medial costal diaphragmatic blood flow was lower with MV + 100% O2 (26 ± 6 mL/min/100 g) versus MV + 21% O2 (51 ± 15 mL/min/100 g; P < 0.05). Second, the addition of 100% O2 during normoxic MV exacerbated the MV-induced reductions in medial costal diaphragm perfusion (23 ± 7 vs. 51 ± 15 mL/min/100 g; P < 0.05) and O2 delivery (3.4 ± 0.2 vs. 6.4 ± 0.3 mL O2/min/100 g; P < 0.05). These data demonstrate that administration of supplemental 100% O2 during MV increases diaphragm vascular resistance and diminishes perfusion and O2 delivery to a significantly greater degree than normoxic MV. This suggests that prolonged bouts of MV (i.e., 6 h) with hyperoxia may accelerate MV-induced vascular dysfunction in the quiescent diaphragm and potentially exacerbate downstream contractile dysfunction.NEW & NOTEWORTHY This is the first study, to our knowledge, demonstrating that supplemental oxygen (i.e., 100% O2) during mechanical ventilation (MV) augments the MV-induced reductions in diaphragmatic blood flow and O2 delivery. The accelerated reduction in diaphragmatic blood flow with hyperoxic MV would be expected to potentiate MV-induced diaphragm vascular dysfunction and consequently, downstream contractile dysfunction. The data presented herein provide a putative mechanism for the exacerbated oxidative stress and diaphragm dysfunction reported with prolonged hyperoxic MV.

Diaphragm dysfunction and peripheral muscle wasting in septic shock patients: Exploring their relationship over time using ultrasound technology (the MUSiShock protocol)

Background

Intensive Care Unit (ICU) patients are known to lose muscle mass and function during ICU stay. Ultrasonography (US) application for the assessment of the skeletal muscle is a promising tool and might help detecting muscle changes and thus several dysfunctions during early stages of ICU stay. MUSiShock is a research project aiming to investigate structure and function of diaphragm and peripheral muscles using ultrasound techniques in septic shock patients, and to assess their relevance in several clinical outcomes such as the weaning process.

Methods and design

This is a research protocol from an observational prospective cohort study. We plan to assess eighty-four septic shock patients during their ICU stay at the following time-points: at 24 hours of ICU admission, then daily until day 5, then weekly, at extubation time and at ICU discharge. At each time-point, we will measure the quadriceps rectus femoris and diaphragm muscles, using innovative US muscle markers such as Shear-Wave Elastography (SWE). In parallel, the Medical Research Council (MRC) sum score for muscle testing and the Airway occlusion pressure (P_0.1) will also be collected. We will describe the association between SWE assessment and other US markers for each muscle. The association between the changes in both diaphragm and rectus femoris US markers over time will be explored as well; finally, the analysis of a combined model of one diaphragm US marker and one limb muscle US marker to predict weaning success/failure will be tested.

Discussion

By using muscle ultrasound at both diaphragm and limb levels, MUSiShock aims to improve knowledge in the early detection of muscle dysfunction and weakness, and their relationship with muscle strength and MV weaning, in critically ill patients. A better anticipation of these short-term muscle structure and function outcomes may allow clinicians to rapidly implement measures to counteract it.

Trial registration

ClinicalTrials.gov, NCT04550143. Registered on 16 September 2020.

Activation of Calpain Contributes to Mechanical Ventilation-Induced Depression of Protein Synthesis in Diaphragm Muscle

Mechanical ventilation (MV) is a clinical tool that provides respiratory support to patients unable to maintain adequate alveolar ventilation on their own. Although MV is often a life-saving intervention in critically ill patients, an undesired side-effect of prolonged MV is the rapid occurrence of diaphragmatic atrophy due to accelerated proteolysis and depressed protein synthesis. Investigations into the mechanism(s) responsible for MV-induced diaphragmatic atrophy reveal that activation of the calcium-activated protease, calpain, plays a key role in accelerating proteolysis in diaphragm muscle fibers. Moreover, active calpain has been reported to block signaling events that promote protein synthesis (i.e., inhibition of mammalian target of rapamycin (mTOR) activation). While this finding suggests that active calpain can depress muscle protein synthesis, this postulate has not been experimentally verified. Therefore, we tested the hypothesis that active calpain plays a key role in the MV-induced depression of both anabolic signaling events and protein synthesis in the diaphragm muscle. MV-induced activation of calpain in diaphragm muscle fibers was prevented by transgene overexpression of calpastatin, an endogenous inhibitor of calpain. Our findings indicate that overexpression of calpastatin averts MV-induced activation of calpain in diaphragm fibers and rescues the MV-induced depression of protein synthesis in the diaphragm muscle. Surprisingly, deterrence of calpain activation did not impede the MV-induced inhibition of key anabolic signaling events including mTOR activation. However, blockade of calpain activation prevented the calpain-induced cleavage of glutaminyl-tRNA synthetase in diaphragm fibers; this finding is potentially important because aminoacyl-tRNA synthetases play a central role in protein synthesis. Regardless of the mechanism(s) responsible for calpain’s depression of protein synthesis, these results provide the first evidence that active calpain plays an important role in promoting the MV-induced depression of protein synthesis within diaphragm fibers.

High-Intensity Inspiratory Muscle Training Improves Scalene and Sternocleidomastoid Muscle Oxygenation Parameters in Patients With Weaning Difficulties: A Randomized Controlled Trial

Background

Critically ill patients who have difficulties weaning from the mechanical ventilator are prone to develop respiratory muscle weakness. Inspiratory muscle training (IMT) can improve respiratory muscle strength. Whether IMT can improve scalene and sternocleidomastoid muscle oxygenation parameters is unknown.

Aim

To compare changes in muscle oxygenation parameters of scalene and sternocleidomastoid inspiratory muscles during a standardized task between patients with weaning difficulties who received either high-intensity IMT (intervention) or sham low-intensity IMT (control).

Method

Forty-one patients performed daily IMT sessions (4 sets, 6–10 breaths) until weaning success or for 28 consecutive days. The training load was progressively adjusted in the intervention group (n = 22) to the highest tolerable load, whilst the control group (n = 19) kept training at 10% of their baseline maximal inspiratory pressure (PImax). Breathing characteristics (i.e., work and power of breathing, PoB), respiratory muscle function [i.e., PImax and forced vital capacity (FVC)] were measured during a standardized loaded breathing task against a load of 30% of baseline PImax before and after the IMT period. In addition, during the same loaded breathing task, absolute mean and nadir changes from baseline in local scalene and sternocleidomastoid muscle oxygen saturation index (Δ%StiO2) (an index of oxygen extraction) and nadir Δ%StiO2 normalized for the PoB were measured by near-infrared spectroscopy.

Results

At post measures, only the intervention group improved mean PoB compared to pre measures (Pre: 0.42 ± 0.33 watts, Post: 0.63 ± 0.51watts, p-value &lt; 0.01). At post measures, both groups significantly improved nadir scalene muscles StiO2% normalized for the mean PoB (ΔStiOnadir%/watt) compared to pre measurements and the improvement was not significant different between groups (p-value = 0.40). However, at post measures, nadir sternocleidomastoid muscle StiO2% normalized for the mean PoB (ΔStiOnadir%/watt) was significantly greater improved in the intervention group (mean difference: +18.4, 95%CI: −1.4; 38.1) compared to the control group (mean difference: +3.7, 95%CI: −18.7; 26.0, between group p-value &lt; 0.01). Both groups significantly improved PImax (Intervention: +15 ± 13 cmH2O p-value &lt; 0.01, Control: +13 ± 15 cmH2O p-value &lt; 0.01). FVC only significantly improved in the intervention group (+0.33 ± 0.31 L p &lt; 0.01) report also change in control group.

Conclusion

This exploratory study suggests that high-intensity IMT induces greater improvements in scalene and sternocleidomastoid muscle oxygenation parameters attributed for oxygen delivery, utilization and oxygen saturation index compared to low-intensity IMT in patients with weaning difficulties.

The Effect of Clusters of Double Triggering and Ineffective Efforts in Critically Ill Patients

OBJECTIVES

To characterize clusters of double triggering and ineffective inspiratory efforts throughout mechanical ventilation and investigate their associations with mortality and duration of ICU stay and mechanical ventilation.

DESIGN

Registry-based, real-world study.

BACKGROUND

Asynchronies during invasive mechanical ventilation can occur as isolated events or in clusters and might be related to clinical outcomes.

SUBJECTS

Adults requiring mechanical ventilation greater than 24 hours for whom greater than or equal to 70% of ventilator waveforms were available.

INTERVENTIONS

We identified clusters of double triggering and ineffective inspiratory efforts and determined their power and duration. We used Fine-Gray's competing risk model to analyze their effects on mortality and generalized linear models to analyze their effects on duration of mechanical ventilation and ICU stay.

MEASUREMENTS AND MAIN RESULTS

We analyzed 58,625,796 breaths from 180 patients. All patients had clusters (mean/d, 8.2 [5.4-10.6]; mean power, 54.5 [29.6-111.4]; mean duration, 20.3 min [12.2-34.9 min]). Clusters were less frequent during the first 48 hours (5.5 [2.5-10] vs 7.6 [4.4-9.9] in the remaining period [p = 0.027]). Total number of clusters/d was positively associated with the probability of being discharged alive considering the total period of mechanical ventilation (p = 0.001). Power and duration were similar in the two periods. Power was associated with the probability of being discharged dead (p = 0.03), longer mechanical ventilation (p < 0.001), and longer ICU stay (p = 0.035); cluster duration was associated with longer ICU stay (p = 0.027).

CONCLUSIONS

Clusters of double triggering and ineffective inspiratory efforts are common. Although higher numbers of clusters might indicate better chances of survival, clusters with greater power and duration indicate a risk of worse clinical outcomes.

Improving molecular and histopathology in diaphragm muscle of the double transgenic ACTA1-MCM/FLExDUX4 mouse model of FSHD with systemic antisense therapy

Facioscapulohumeral muscular dystrophy (FSHD) is a rare muscle dystrophy causing muscle weakness initially in the face, shoulders and upper arms, and extended to lower body muscles as the disease progresses. Respiratory restriction in FSHD is increasingly reported to be more common and severe than previously thought, with the involvement of diaphragm weakness in pulmonary insufficiency being under debate. As aberrant expression of the double homeobox 4 (DUX4) gene is the prime cause of FSHD, we and others have developed numerous strategies and reported promising results on downregulating DUX4 expression in both cellular and animal models of FSHD. However, the effect of DUX4 and anti-DUX4 approaches on diaphragm muscle has not been elucidated. Here we show that toxic DUX4 expression causes pathology that affects the diaphragm of ACTA1-MCM/FLExDUX4 mouse model of FSHD at both molecular and histological levels. Of importance, a systemic antisense treatment that suppresses DUX4 and target genes expression by 50% significantly improves muscle regeneration and muscle fibrosis, and prevents modification in myofiber type composition, supporting its development as a treatment for FSHD.

Circulating Skeletal Troponin During Weaning From Mechanical Ventilation and Their Association to Diaphragmatic Function: A Pilot Study

Background: Patients with acute respiratory failure (ARF) may need mechanical ventilation (MV), which can lead to diaphragmatic dysfunction and muscle wasting, thus making difficult the weaning from the ventilator. Currently, there are no biomarkers specific for respiratory muscle and their function can only be assessed trough ultrasound or other invasive methods. Previously, the fast and slow isoform of the skeletal troponin I (fsTnI and ssTnI, respectively) have shown to be specific markers of muscle damage in healthy volunteers. We aimed therefore at describing the trend of skeletal troponin in mixed population of ICU patients undergoing weaning from mechanical ventilation and compared the value of fsTnI and ssTnI with diaphragmatic ultrasound derived parameters.

Methods: In this prospective observational study we enrolled consecutive patients recovering from acute hypoxemic respiratory failure (AHRF) within 24 h from the start of weaning. Every day an arterial blood sample was collected to measure fsTnI, ssTnI, and global markers of muscle damage, such as ALT, AST, and CPK. Moreover, thickening fraction (TF) and diaphragmatic displacement (DE) were assessed by diaphragmatic ultrasound. The trend of fsTnI and ssTnI was evaluated during the first 3 days of weaning.

Results: We enrolled 62 consecutive patients in the study, with a mean age of 67 ± 13 years and 43 of them (69%) were male. We did not find significant variations in the ssTnI trend (p = 0.623), but fsTnI significantly decreased over time by 30% from Day 1 to Day 2 and by 20% from Day 2 to Day 3 (p < 0.05). There was a significant interaction effect between baseline ssTnI and DE [F₍₂₎ = 4.396, p = 0.015], with high basal levels of ssTnI being associated to a higher decrease in DE. On the contrary, the high basal levels of fsTnI at day 1 were characterized by significant higher DE at each time point.

Conclusions: Skeletal muscle proteins have a distinctive pattern of variation during weaning from mechanical ventilation. At day 1, a high basal value of ssTnI were associated to a higher decrease over time of diaphragmatic function while high values of fsTnI were associated to a higher displacement at each time point.

A research update: Significance of cytokine storm and diaphragm in COVID-19

Emerging research on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) shows that it is spreading to multiple organs in addition to the respiratory system. Though the SARS-CoV2 enters the human body by binding to ACE2 receptors on pulmonary alveolar cells, recent studies indicate that it is spreading to the central nervous system, cardiac and skeletal muscles leading to various pathological conditions in these organs. In particular, the effects of SARS-CoV-2 on triggering the cytokine storm and its consequential effects on skeletal muscles has generated a lot of discussion. The effects of this virus on muscular function especially in susceptible elderly populations is still being explored. However, its effects on diaphragm, a respiratory muscle which plays an important role in determining lung capacity are not completely explored. Currently, as new evidence on using lung ultrasounds to confirm COVID-19 diagnosis is gaining traction, it is necessary to explore the role of diaphragm in treating COVID-19 patients. This article will review the effects of cytokine storm triggered by the SARS-CoV-2 and its resultant effects on skeletal muscle with a specific focus on the diaphragm in order to identify knowledge gaps in effectively treating COVID-19 patients, especially those who are on a mechanical ventilator.

Ultrasound assessment of ventilator-induced diaphragmatic dysfunction in mechanically ventilated pediatric patients

INTRODUCTION

Ultrasonography has recently emerged as a promising technique that can rapidly estimate diaphragm function, especially during the weaning period. The aims of this study were to describe the evolution of diaphragmatic morphology and functional measurements by ultrasound in ventilated children.

MATERIAL AND METHODS

This was a prospective, observational, single-center study. All the children admitted to our Pediatric Intensive Care Unit requiring mechanical ventilation for more than 48 h were included. Diaphragmatic thickness and the thickening fraction were assessed by ultrasound.

RESULTS

From June to December 2018, 47 patients (median age 3 months; interquartile range, 1-17) underwent 164 ultrasonographic evaluations. The median duration of mechanical ventilation was 168 h (interquartile range, 96-196). At the initial measurement, the thickness at end-inspiration was 2.2 mm (interquartile range, 1.8-2.5) and the thickness at end-expiration was 1.8 mm (interquartile range, 1.5-2.0) with a median decrease in thickness of -14% (interquartile range, -33% to -3%) and a -2% daily atrophy rate (interquartile range, -4.2% to 0%). Diaphragmatic atrophy was observed in 30/47 cases. Children who had been exposed to neuromuscular blockade infusion (n = 31) had a significantly lower mean thickness [-22% (interquartile range, -34% to -13%) vs. -6% (interquartile range, -12% to 0%); p = 0.009] and increased daily atrophy rate [-2.2% (interquartile range, -4.6 to 0%) vs. -1.4% (interquartile range, -2.6 to 0%); p = 0.049] compared to unexposed children. The decrease in thickness was significantly less in children ventilated for at least 12 hours with pressure support before extubation compared with those with shorter periods of spontaneous respiratory effort [-9.5% (interquartile range, -21 to 0%) vs. -26% (interquartile range, -37 to -12%); p = 0.011].

CONCLUSIONS

Point-of-care diaphragmatic ultrasound can detect diaphragmatic atrophy in mechanically ventilated children. Diaphragmatic atrophy was strongly associated with the use of mechanical ventilation and neuromuscular blockade. Diaphragmatic thickness also tended to decrease less in the pre-extubation stage with pressure support. We found no correlation between progressive diaphragm thinning, extubation failure, or an increased need for non-invasive ventilation post extubation.

Prolonged mechanical ventilation increases diaphragm arteriole circumferential stretch without changes in stress/stretch: Implications for the pathogenesis of ventilator-induced diaphragm dysfunction

INTRODUCTION

Prolonged mechanical ventilation (MV; ≥6 h) results in large, time-dependent reductions in diaphragmatic blood flow and shear stress. We tested the hypothesis that MV would impair the structural and material properties (ie, increased stress/stretch relation and/or circumferential stretch) of first-order arterioles (1A) from the medial costal diaphragm.

METHODS

Shear stress was estimated from isolated arterioles and prior blood flow data from the diaphragm during spontaneous breathing (SB) and prolonged MV (6 h MV). Thereafter, female Sprague-Dawley rats (~5 months) were randomly divided into two groups, SB (n = 6) and 6 h MV (n = 6). Following SB and 6 h MV, 1A medial costal diaphragm arterioles were isolated, cannulated, and subjected to stepwise (0-140 cmH2 O) increases in intraluminal pressure in calcium-free Ringer's solution. Inner diameter and wall thickness were measured at each pressure step and used to calculate wall:lumen ratio, Cauchy-stress, and circumferential stretch.

RESULTS

Compared to SB, there was a ~90% reduction in arteriolar shear stress with prolonged MV (9 ± 2 vs 78 ± 20 dynes/cm2 ; p ≤ .05). In the unloaded condition (0 cmH2 O), the arteriolar intraluminal diameter was reduced (37 ± 8 vs 79 ± 13 μm) and wall:lumen ratio was increased (120 ± 18 vs 46 ± 10%) compared to SB (p ≤ .05). There were no differences in the passive diameter responses or the circumferential stress/stretch relationship between groups (p > .05), but at each pressure step, circumferential stretch was increased with 6 h MV vs SB (p ≤ .05).

CONCLUSION

During prolonged MV, medial costal diaphragm arteriolar shear stress is severely diminished. Despite no change in the material behavior (stress/stretch), prolonged MV resulted in altered structural and mechanical properties (ie, elevated circumferential stretch) of medial costal diaphragm arterioles. This provides important novel mechanistic insights into the impaired diaphragm blood flow capacity and vascular dysfunction following prolonged MV.

Nutritional screening tool for critically ill children: a systematic review

CONTEXT

Nutritional screening tools (NSTs) are used to identify patients who are at risk of nutritional status (NS) deterioration and associated clinical outcomes. Several NSTs have been developed for hospitalized children; however, none of these were specifically developed for Pediatric Intensive Care Unit (PICU) patients.

OBJECTIVE

A systematic review of studies describing the development, application, and validation of NSTs in hospitalized children was conducted to critically appraise their role in PICU patients.

DATA SOURCES

PubMed, Embase, Web of Science, Scopus, SciELO, LILACS, and Google Scholar were searched from inception to December 11, 2020.

DATA EXTRACTION

The review included 103 studies that applied NSTs at hospital admission. The NST characteristics collected included the aims, clinical setting, variables, and outcomes. The suitability of the NSTs in PICU patients was assessed based on a list of variables deemed relevant for this population.

DATA ANALYSIS

From 19 NSTs identified, 13 aimed to predict NS deterioration. Five NSTs were applied in PICU patients, but none was validated for this population. NSTs did not include clinical, NS, laboratory, or dietary variables that were deemed relevant for the PICU population.

CONCLUSION

None of the available NSTs were found to be suitable for critically ill children, so a new NST should be developed for this population. AQ6.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42020167898.

Brain-lung interactions and mechanical ventilation in patients with isolated brain injury

During the last decade, experimental and clinical studies have demonstrated that isolated acute brain injury (ABI) may cause severe dysfunction of peripheral extracranial organs and systems. Of all potential target organs and systems, the lung appears to be the most vulnerable to damage after brain injury (BI). The pathophysiology of these brain–lung interactions are complex and involve neurogenic pulmonary oedema, inflammation, neurodegeneration, neurotransmitters, immune suppression and dysfunction of the autonomic system. The systemic effects of inflammatory mediators in patients with BI create a systemic inflammatory environment that makes extracranial organs vulnerable to secondary procedures that enhance inflammation, such as mechanical ventilation (MV), surgery and infections. Indeed, previous studies have shown that in the presence of a systemic inflammatory environment, specific neurointensive care interventions—such as MV—may significantly contribute to the development of lung injury, regardless of the underlying mechanisms. Although current knowledge supports protective ventilation in patients with BI, it must be born in mind that ABI-related lung injury has distinct mechanisms that involve complex interactions between the brain and lungs. In this context, the role of extracerebral pathophysiology, especially in the lungs, has often been overlooked, as most physicians focus on intracranial injury and cerebral dysfunction. The present review aims to fill this gap by describing the pathophysiology of complications due to lung injuries in patients with a single ABI, and discusses the possible impact of MV in neurocritical care patients with normal lungs.

Mortality after Lung Transplantation for Children Bridged with Extracorporeal Membrane Oxygenation

RATIONALE

Extracorporeal membrane oxygenation (ECMO) is increasingly used to bridge waitlisted children failing conventional respiratory support to lung transplantation.

OBJECTIVES

To compare in-hospital mortality and a composite outcome of 1-year mortality or re-transplantation in children bridged with ECMO with those on mechanical ventilation (MV), and neither support.

METHODS

The United Network for Organ Sharing (UNOS) was used to analyze lung transplant recipients, aged ≤ 20 y, from January 2004 to August 2019. Recipients were categorized according to level of respiratory support at time of transplant, including ECMO, MV, or neither. Multivariable analysis was used to evaluate support type and in-hospital mortality.

RESULTS

Of 1,014 children undergoing lung transplant, 68 (6.7%) required ECMO as a bridge-to-transplant, 144 (14.2%) MV, and 802 (79.1%) neither. Primary diagnosis in the ECMO cohort included cystic fibrosis (43%), pneumonia/ARDS (10.3%), interstitial pulmonary fibrosis (7.4%) and pulmonary hypertension (5.9%). Number of patients bridged with ECMO increased throughout the study period from none in 2004 to 16.7% in 2018. Multivariable analysis showed bridging with both ECMO (aOR = 3.57; 95% CI: 1.42, 8.97) and MV (aOR = 2.67; 95% CI: 1.26, 5.57) increased in-hospital mortality after lung transplantation. However, there was no difference in composite outcome of mortality and re-transplantation at 1-year between the three groups.

CONCLUSIONS

ECMO to bridge children to lung transplantation has increased. Despite this, ECMO is a high-risk bridge strategy for children awaiting lung transplantation. Future research should target interventions that can be focused on improving survival in these patients.

Effect of prone and supine positioning on the diaphragmatic work of breathing in convalescent preterm infants

OBJECTIVES

To compare the work of breathing in the prone and supine positions in convalescent prematurely born infants.

WORKING HYPOTHESIS

The work of breathing would be lower in the prone compared to the supine position.

STUDY DESIGN

Prospective observational cohort study.

PATIENT-SUBJECT SELECTION

Consecutive preterm infants breathing unsupported in room air with a gestational age of 28-34 weeks in a tertiary neonatal intensive care unit were studied before discharge from neonatal care.

METHODOLOGY

The diaphragmatic pressure time product (PTPdi) was used to assess the work of breathing, calculated as the integration of transdiaphragmatic pressure over the inspiratory time. The PTPdi was measured in prone, supine, and supine with 45° head-up tilt (supine-tilt) positions.

RESULTS

The mean (SD) PTPdi was lower in the prone (259 [68] cm H₂ O*s/min) compared with the supine position (320 [78] cm H₂ O*s/min, p= .005). The mean (SD) PTPdi was lower in the supine-tilt position (262 [76] cm H₂ O*s/min) compared with the supine position (p = .032). The PTPdi was not different between the prone and supine-tilt positions (p = .600). The difference in PTPdi between prone and supine was not independently associated with gestational age (standardized coefficient = 0.262, adjusted p= .335), birth weight (standardized coefficient = -0.249, adjusted p= .394) or postmenstrual age at study (standardized coefficient = -0.025, adjusted p= .902).

CONCLUSIONS

In convalescent preterm neonates, the work of breathing may be lower in the prone and supine-tilt positions, compared with supine.

Weaning from mechanical ventilation in people with neuromuscular disease: a systematic review

OBJECTIVE

This systematic review aimed in assessing the effects of different weaning protocols in people with neuromuscular disease (NMD) receiving invasive mechanical ventilation, identifying which protocol is the best and how different protocols can affect weaning outcome success, duration of weaning, intensive care unit (ICU) and hospital stay and mortality.

DESIGN

Systematic review.

DATA SOURCES

Electronic databases (MEDLINE, EMBASE, Web of Science and Scopus) were searched from January 2009 to August 2020.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised controlled trials (RCTs) and non-RCT that evaluated patients with NMD (adults and children from 5 years old) in the weaning process managed with a protocol (pressure support ventilation; synchronised intermittent mandatory ventilation; continuous positive airway pressure; 'T' piece).

PRIMARY OUTCOME

Weaning success.

SECONDARY OUTCOMES

Weaning duration, ICU stay, hospital stay, ICU mortality, complications (pneumothorax, ventilation-associated pneumonia).

DATA EXTRACTION AND SYNTHESIS

Two review authors assessed the titles and the abstracts for inclusion and reviewed the full texts independently.

RESULTS

We found no studies that fulfilled the inclusion criteria.

CONCLUSIONS

The absence of studies about different weaning protocols for patients with NMD does not allow concluding the superiority of any specific weaning protocol for patients with NMD or determining the impact of different types of protocols on other outcomes. The result of this review encourages further studies.

PROSPERO REGISTRATION NUMBER

CRD42019117393.