Sepsis Is Associated with a Preferential Diaphragmatic Atrophy

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Early urea-to-creatinine ratio to predict rapid muscle loss in critically ill patients with sepsis: a single-center retrospective observational study

BACKGROUND

Patients with sepsis in the intensive care unit (ICU) often experience rapid muscle loss. The urea-to-creatinine ratio (UCR) is thought to reflect muscle breakdown (creatinine) and catabolism (urea) and is commonly used to assess nutritional and metabolic status. This study aimed to investigate whether changes in UCR (ΔUCR) can predict the development of rapid muscle loss in patients with sepsis.

METHODS

This retrospective observational study was conducted in a university ICU between 2014 and 2021, involving adult patients (≥ 18 years) diagnosed with sepsis. The primary outcome was the incidence of rapid muscle loss during ICU hospitalization. Changes in the cross-sectional muscle area at the third lumbar vertebra (L3SMA) were measured using CT images to evaluate muscle loss. Rapid muscle loss was defined as a change in ΔL3SMA greater than 2% per day. Multivariable logistic regression was used to examine the association between UCR or ΔUCR and rapid muscle loss. The area under the receiver operating characteristic curve (AUC) was calculated to assess the predictive performance of UCR or ΔUCR for rapid muscle loss.

RESULTS

Of the 482 patients, 141 (29.2%) experienced rapid muscle loss during their ICU stay. Multivariable logistic regression analysis revealed that ΔUCR was significantly associated with an increased risk of rapid muscle loss, with an odds ratio (OR) of 1.02 [95% CI: 1.01, 1.02]. The AUC for ΔUCR in predicting rapid muscle loss was 0.76 [95% CI: 0.68-0.83], with a threshold value of 19.4 µmol urea/µmol creatinine for ΔUCR.

CONCLUSION

The results demonstrate that ΔUCR is independently associated with rapid muscle loss in patients with sepsis and the AUC of the ROC curve for the ability of ΔUCR to predict rapid muscle loss was 0.76. Though additional prospective data are needed, our results suggest that ΔUCR may be useful in the early identification of critically ill patients with sepsis at risk of rapid muscle loss.

Time course of plasma urea and urinary urea excretion in patients with a prolonged ICU stay

Whereas urinary creatinine excretion (UCE) is an established marker of muscle mass, both in critically ill and non-critically ill patients, analysis of urinary urea excretion (UUE) may allow estimation of proteolysis that is associated with critical illness. We evaluated the time courses of plasma urea and creatinine as well UUE and UCE in critically ill patients with a prolonged ICU stay. Our goal was to evaluate changes in plasma urea and creatinine in conjunction with their urinary excretion, to get a better understanding of urea handling in ICU patients. From 2002 to 2021, plasma urea and creatinine, UUE and UCE were determined in routinely obtained 24 h urine samples between ICU admission and day 30, in adult patients with an ICU-stay ≥ 28d. Urea-to-creatinine ratios in plasma and urine were calculated. Patients with stage 3 acute kidney injury (AKI) were excluded. Analyses were performed separately for females and males and for patients with and without acute renal failure to account for respectively differences in muscle mass and impaired renal function. Of 47,120 patients, who were admitted to the ICU between 2002 and 2021, 638 patients met the inclusion criteria. During the first 10 days mean ± SD plasma urea increased from 9.7 ± 6.0 mmol/L at ICU admission to 12.4 ± 7.9 mmol/L (P < 0.001) on day 11 and decreased afterwards with a rate of 0.1 mmol/l/d. UUE peaked at 590 ± 317 mmol/day on day 13 whereas UCE peaked already on day 4. Males had higher plasma urea, plasma creatinine, UUE and UCE than females. Plasma and urinary urea-to-creatinine ratio (UCR) stabilized after day 7, with a gradual increase in plasma UCR and urinary UCR between day 7 and day 30. Similar courses, although less pronounced, were seen in patients without AKI. The course of urea in critically ill patients is characterized by an initial rise of both plasma urea and urinary urea excretion, presumably due to increased catabolism of endogenous and exogenous protein in the first week of ICU admission. Subsequently, UUE and UCE declined steadily in a rate that was comparable to the known loss of muscle mass during ICU admission of approximately 1%/day.

A short duration of mechanical ventilation alters redox status in the diaphragm and aggravates inflammation in septic mice

BACKGROUND

Mechanical ventilation (MV) is a life support method used to treat patients with respiratory failure. High tidal volumes during MV can cause ventilator-induced lung injury (VILI), but also affect other organs, such as the diaphragm (Dia) causing ventilator-induced diaphragmatic dysfunction (VIDD). VIDD is often associated with a complicated course on MV. Sepsis can induce inflammation and oxidative stress, contributing to the impairment of the Dia and worsening of the prognosis. This study evaluated the additive or synergistic effects of a short course of mechanical ventilation on Dia in healthy and septic adult mice.

METHODS

32 adult male C57BL/6 mice were randomly into four groups: Control (CG), non-ventilated animals instilled with saline solution (PBS1x); Lipopolysaccharide (LPS), non-ventilated animals instilled with PBS solution containing lipopolysaccharide; Mechanical Ventilation (MV) for 1 h, ventilated animals instilled with PBS solution; and Mechanical Ventilation and LPS (MV+LPS), ventilated animals instilled with PBS solution containing LPS. At the end of the experimental protocol, the animals were euthanized, then blood and diaphragm tissue samples were collected.

RESULTS

Evaluation of leukocyte/blood parameters and diaphragm muscle showed that MV, LPS and the combination of both were able to increase neutrophil count, creatine kinase, inflammatory mediators and oxidative stress in all groups compared to the control. MV and sepsis combined had additive effects on inflammation and lipid peroxidation.

CONCLUSIONS

A short course of Mechanical ventilation promotes inflammation and oxidative stress and, its combination with sepsis further increases local and systemic inflammation.

Ability of parasternal intercostal muscle thickening fraction to predict reintubation in surgical patients with sepsis

OBJECTIVES

We aimed to evaluate the ability of the parasternal intercostal (PIC) thickening fraction during spontaneous breathing trial (SBT) to predict the need for reintubation within 48 h after extubation in surgical patients with sepsis.

METHODS

This prospective observational study included adult patients with sepsis who were mechanically ventilated and indicated for SBT. Ultrasound measurements of the PIC thickening fraction and diaphragmatic excursion (DE) were recorded 15 min after the start of the SBT. After extubation, the patients were followed up for 48 h for the need for reintubation. The study outcomes were the ability of the PIC thickening fraction (primary outcome) and DE to predict reintubation within 48 h of extubation using area under receiver characteristic curve (AUC) analysis. The accuracy of the model including the findings of right PIC thickening fraction and right DE was also assessed using the current study cut-off values. Multivariate analysis was performed to identify independent risk factors for reintubation.

RESULTS

We analyzed data from 49 patients who underwent successful SBT, and 10/49 (20%) required reintubation. The AUCs (95% confidence interval [CI]) for the ability of right and left side PIC thickening fraction to predict reintubation were 0.97 (0.88-1.00) and 0.96 (0.86-1.00), respectively; at a cutoff value of 6.5-8.3%, the PIC thickening fraction had a negative predictive value of 100%. The AUCs for the PIC thickening fraction and DE were comparable; and both measures were independent risk factors for reintubation. The AUC (95% CI) of the model including the right PIC thickening fraction > 6.5% and right DE ≤ 18 mm to predict reintubation was 0.99 (0.92-1.00), with a positive predictive value of 100% when both sonographic findings are positive and negative predictive value of 100% when both sonographic findings are negative.

CONCLUSIONS

Among surgical patients with sepsis, PIC thickening fraction evaluated during the SBT is an independent risk factor for reintubation. The PIC thickening fraction has an excellent predictive value for reintubation. A PIC thickening fraction of ≤ 6.5-8.3% can exclude reintubation, with a negative predictive value of 100%. Furthermore, a combination of high PIC and low DE can also indicate a high risk of reintubation. However, larger studies that include different populations are required to replicate our findings and validate the cutoff values.

Protective role of pretreatment with Anisodamine against sepsis-induced diaphragm atrophy via inhibiting JAK2/STAT3 pathway

There is an increasing tendency for sepsis patients to suffer from diaphragm atrophy as well as mortality. Therefore, reducing diaphragm atrophy could benefit sepsis patients' prognoses. Studies have shown that Anisodamine (Anis) can exert antioxidant effects when blows occur. However, the role of Anisodamine in diaphragm atrophy in sepsis patients has not been reported. Therefore, this study investigated the antioxidant effect of Anisodamine in sepsis-induced diaphragm atrophy and its mechanism. We used cecal ligation aspiration (CLP) to establish a mouse septic mode and stimulated the C2C12 myotube model with lipopolysaccharide (LPS). After treatment with Anisodamine, we measured the mice's bodyweight, diaphragm weight, fiber cross-sectional area and the diameter of C2C12 myotubes. The malondialdehyde (MDA) levels in the diaphragm were detected using the oxidative stress kit. The expression of MuRF1, Atrogin1 and JAK2/STAT3 signaling pathway components in the diaphragm and C2C12 myotubes was measured by RT-qPCR and Western blot. The mean fluorescence intensity of ROS in C2C12 myotubes was measured by flow cytometry. Meanwhile, we also measured the levels of Drp1 and Cytochrome C (Cyt-C) in vivo and in vitro by Western blot. Our study revealed that Anisodamine alleviated the reduction in diaphragmatic mass and the loss of diaphragmatic fiber cross-sectional area and attenuated the atrophy of the C2C12 myotubes by inhibiting the expression of E3 ubiquitin ligases. In addition, we observed that Anisodamine inhibited the JAK2/STAT3 signaling pathway and protects mitochondrial function. In conclusion, Anisodamine alleviates sepsis-induced diaphragm atrophy, and the mechanism may be related to inhibiting the JAK2/STAT3 signaling pathway.

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.

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.

Change in diaphragmatic morphology in single-lung transplant recipients: a computed tomographic study

Introduction: The influence of lung disease on the diaphragm has been poorly studied. The study aimed to evaluate the diaphragm morphology (height and thickness) in single-lung transplantation (SLTx), using computed tomography (CT), by assessing the evolution of the hemidiaphragm of the transplanted and the native side. Methods: Patients who underwent single lung transplantation in our center (Marseille, France) between January 2009 and January 2022 were retrospectively included. Thoracic or abdominal CT scans performed before and the closest to and at least 3 months after the surgery were used to measure the diaphragm crus thickness and the diaphragm dome height. Results: 31 patients mainly transplanted for emphysema or pulmonary fibrosis were included. We demonstrated a significant increase in diaphragm crus thickness on the side of the transplanted lung, with an estimated difference of + 1.25 mm, p = <0.001, at the level of the celiac artery, and + 0.90 mm, p < 0.001, at the level of the L1 vertebra while no significant difference was observed on the side of the native lung. We showed a significant reduction in the diaphragm height after SLTx on the transplanted side (-1.20 cm, p = 0.05), while no change on the native side (+0.02 cm, p = 0.88). Conclusion: After a SLTx, diaphragmatic morphology significantly changed on the transplanted lung, while remaining altered on the native lung. These results highlights that an impaired lung may have a negative impact on its diaphragm. Replacement with a healthy lung can promote the recovery of the diaphragm to its anatomical morphology, reinforcing the close relationship between these two organs.

Ultrasonographic evaluation of the diaphragm in critically ill patients to predict invasive mechanical ventilation

BACKGROUND

Diaphragm dysfunction is common in critically ill patients and associated with poorer outcomes. The function of the diaphragm can be evaluated at the bedside by measuring diaphragmatic excursion using ultrasonography. In this study, we investigated the ability of right-sided diaphragmatic excursion (RDE) to predict the need for invasive mechanical ventilation (IMV).

METHODS

Critically ill patients aged 18 years and older who presented to our emergency department between May 20, 2021 and May 19, 2022 and underwent measurement of RDE within 10 min of arrival were enrolled in this prospective study. The ability of RDE to predict the need for IMV was assessed by multivariable logistic regression and analysis of the area under the receiver-operating characteristic curve (AUROC).

RESULTS

A total of 314 patients were enrolled in the study; 113 (35.9%) of these patients required IMV. An increase of RDE value per each 0.1 cm was identified to be an independent predictor of IMV (adjusted odds ratio 0.08, 95% confidence interval [CI] 0.04-0.17, p < 0.001; AUROC 0.850, 95% CI 0.807-0.894). The RDE cutoff value was 1.2 cm (sensitivity 82.3%, 95% CI 74.0-88.8; specificity 78.1%, 95% CI 71.7-83.6). Time on a ventilator was significantly longer when the RDE was ≤ 1.2 cm (13 days [interquartile range 5, 27] versus 5 days [interquartile range 3, 8], p = 0.006).

CONCLUSIONS

In this study, RDE had a good ability to predict the need for IMV in critically ill patients. The optimal RDE cutoff value was 1.2 cm. Its benefit in patient management requires further investigation.

Computed tomography reveals hypertrophic remodelling of the diaphragm in cystic fibrosis but not in COPD

Background

Computed tomography (CT) is increasingly used for assessing skeletal muscle characteristics. In cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD), reduced limb muscle mass predicts poor clinical outcomes. However, the degree to which quantity or quality of respiratory and nonrespiratory muscles is affected by these diseases remains controversial.

Methods

Thoracic CT images of 29 CF, 21 COPD and 20 normal spirometry control subjects were analysed to measure indices of muscle quantity (volume or cross-sectional area) and quality (radiodensity) in respiratory (diaphragm, abdominal) and nonrespiratory (pectoralis, lumbar paraspinal) muscles. Multivariable linear regression assessed relationships of CT measurements with body mass index (BMI), forced expiratory volume in 1 s (FEV1) % pred, inflammation and infection biomarkers, nutritional status and CF genotype.

Results

Diaphragm volume in CF was significantly higher than in COPD (by 154%) or controls (by 140%). Abdominal muscle area in CF was also greater than in COPD (by 130%). Nonrespiratory muscles in COPD had more low radiodensity muscle (marker of lipid content) compared to CF and controls. In CF but not COPD, higher BMI and FEV1 % pred were independently associated with higher diaphragm and/or abdominal muscle quantity indices. Serum creatinine also predicted respiratory and nonrespiratory muscle quantity in CF, whereas other biomarkers including genotype correlated poorly with muscle CT parameters.

Conclusions

Our data suggest that the CF diaphragm undergoes hypertrophic remodelling, whereas in COPD the nonrespiratory muscles show altered muscle quality consistent with greater lipid content. Thoracic CT can thus identify distinctive respiratory and nonrespiratory muscle remodelling signatures associated with different chronic lung diseases.

Diaphragm Dysfunction and ICU-Acquired Weakness in Septic Shock Patients with or without Mechanical Ventilation: A Pilot Prospective Observational Study

Sepsis is a risk factor for diaphragm dysfunction and ICU-acquired weakness (ICU-AW); however, the impact of mechanical ventilation (MV) on these relationships has not been thoroughly investigated. This study aimed to compare the incidence of diaphragm dysfunction and ICU-AW in patients with septic shock, with and without MV. We conducted a single-center prospective observational study that included consecutive patients diagnosed with septic shock admitted to the ICU between March 2021 and February 2022. Ultrasound measurements of diaphragm thickness and manual measurements of limb muscle strength were repeated after ICU admission. The incidences of diaphragm dysfunction and ICU-AW, as well as their associations with clinical outcomes, were compared between patients with MV and without MV (non-MV). Twenty-four patients (11 in the MV group and 13 in the non-MV group) were analyzed. At the final measurements in the MV group, eight patients (72.7%) had diaphragm dysfunction, and six patients (54.5%) had ICU-AW. In the non-MV group, 10 patients (76.9%) had diaphragm dysfunction, and three (23.1%) had ICU-AW. No association was found between diaphragm dysfunction and clinical outcomes. Patients with ICU-AW in the MV group had longer ICU and hospital stays. Among patients with septic shock, the incidence of diaphragm dysfunction was higher than that of ICU-AW, irrespective of the use of MV. Further studies are warranted to examine the association between diaphragm dysfunction and clinical outcomes.

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.

Diaphragm function in patients with sepsis and septic shock: A longitudinal ultrasound study

BACKGROUND

Previous literature on the determinants of diaphragm dysfunction in septic patients is limited. The goal of this study is to assess diaphragm dysfunction in terms of its prevalence and its potential associated factors in septic intensive care unit (ICU) patients.

METHODS

This prospective and observational study was conducted between June 2015 and July 2019. Ultrasound measures of diaphragm thickness were performed daily on septic patients. The primary outcome was the prevalence of diaphragm dysfunction at baseline and during the ICU stay. The secondary outcome was the diaphragm thickness. Possible associated factors were prospectively recorded.

RESULTS

Fifty patients were enrolled in the study. The prevalence of diaphragm dysfunction was 58%. No diaphragm atrophy was found during the ICU stay. Diaphragm dysfunction was associated with the alteration of consciousness, intra-abdominal sepsis, hypnotics and opioids, and mechanical ventilation. Administration of hypnotics, opioids, and steroids was associated with a decreased diaphragm thickening fraction. Diaphragm dysfunction had no impact on patient outcomes.

CONCLUSIONS

Our data reveal a high prevalence of diaphragm dysfunction in septic patients at the onset of sepsis. Administration of hypnotics, opioids, and steroids was associated with the alteration of diaphragm function as well as intra-abdominal sepsis.

Early passive orthostatic training prevents diaphragm atrophy and dysfunction in intensive care unit patients on mechanical ventilation: A retrospective case‒control study

BACKGROUND

Intensive care unit (ICU) patients on mechanical ventilation (MV), who are always bedridden, easily develop diaphragm atrophy and dysfunction. However, few studies have assessed diaphragmatic thickness and functional changes after early passive orthostatic training.

OBJECTIVES

This is the first study to investigate the efficacy of early passive orthostatic training in preventing diaphragm atrophy and dysfunction in ICU patients on MV.

METHODS

In this randomized retrospective case‒control study, 81 ICU patients on MV for 8 days or longer were enrolled. Forty-four patients received early passive orthostatic training initiated within 72 h of MV initiation (training group), and 37 patients did not receive training (no-training group). The protocol was performed for seven days, once a day for 30 min. The primary outcomes were diaphragmatic thickness and diaphragm contractile fraction (TFdi). The ventilatory parameters were secondary outcomes.

RESULTS

This study included 81 (45 male) ICU patients on MV [(mean ± SD) age = (60.63 ± 7.88) years]. The training group had a larger diaphragmatic thickness at end-expiration (Tdi_,ee) and a smaller magnitude of decrease in Tdi_,ee and TFdi (p = 0.001, 0.029, and <0.001, respectively) than the no-training group after 7 days of training. The mean arterial pressure, fraction of inspired oxygen, and white blood cell levels were decreased in the training group compared with the no-training group (p = 0.003, 0.001, and 0.026, respectively), but lactic acid levels decreased slightly in the training group with no significant difference (p = 0.708).

CONCLUSIONS

Early passive orthostatic training is suitable to ameliorate diaphragm atrophy and dysfunction in ICU patients on MV.

The rate and assessment of muscle wasting during critical illness: a systematic review and meta-analysis

BACKGROUND

Patients with critical illness can lose more than 15% of muscle mass in one week, and this can have long-term detrimental effects. However, there is currently no synthesis of the data of intensive care unit (ICU) muscle wasting studies, so the true mean rate of muscle loss across all studies is unknown. The aim of this project was therefore to systematically synthetise data on the rate of muscle loss and to identify the methods used to measure muscle size and to synthetise data on the prevalence of ICU-acquired weakness in critically ill patients.

METHODS

We conducted a systematic literature search of MEDLINE, PubMed, AMED, BNI, CINAHL, and EMCARE until January 2022 (International Prospective Register of Systematic Reviews [PROSPERO] registration: CRD420222989540. We included studies with at least 20 adult critically ill patients where the investigators measured a muscle mass-related variable at two time points during the ICU stay. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and assessed the study quality using the Newcastle-Ottawa Scale.

RESULTS

Fifty-two studies that included 3251 patients fulfilled the selection criteria. These studies investigated the rate of muscle wasting in 1773 (55%) patients and assessed ICU-acquired muscle weakness in 1478 (45%) patients. The methods used to assess muscle mass were ultrasound in 85% (n = 28/33) of the studies and computed tomography in the rest 15% (n = 5/33). During the first week of critical illness, patients lost every day -1.75% (95% CI -2.05, -1.45) of their rectus femoris thickness or -2.10% (95% CI -3.17, -1.02) of rectus femoris cross-sectional area. The overall prevalence of ICU-acquired weakness was 48% (95% CI 39%, 56%).

CONCLUSION

On average, critically ill patients lose nearly 2% of skeletal muscle per day during the first week of ICU admission.

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.

Validity of Diaphragm Volume Measurements Using Three-Dimensional Computed Tomography

Objectives

The aim of this study was to measure the diaphragm volume using three-dimensional computed tomography (3D-CT) and verify its validity.

Design

This was a retrospective study of existing samples.

Methods

Participants comprised five male patients, aged 65-70 years, who underwent preoperative chest CT (with a slice thickness of 0.5 mm) before coronary artery bypass surgery. The diaphragm was selectively extracted using a workstation to reconstruct a stereoscopic image, and the total muscle volume was measured. To confirm the accuracy and reproducibility of diaphragm muscle volume measurements on CT, all cases were measured three times by two observers, and intraclass correlation coefficients (ICCs) and interobserver correlations were determined.

Results

Observers #1 and #2 reported an average diaphragm volume of 256.7±33 cm3 and 259.3±36 cm3, respectively. The ICC analyses yielded Cronbach's alphas of 0.992 and 0.981 from both observers, and the interobserver correlation was 0.991. The ICC of a single measurement and the average measurement was 0.984 (95% confidence interval: 0.998-0.884) and 0.992 (95% confidence interval: 0.999-0.939), respectively.

Conclusions

To our knowledge, this study is the first to standardize the method for measuring the total diaphragm volume and examine the reproducibility and validity of the new method. The diaphragm could be selectively extracted and reconstructed. Measurement of the total diaphragm muscle volume using a workstation to reconstruct a stereoscopic image is feasible and highly reproducible. This technique can be reliably employed to evaluate diaphragm volume, thickness, and morphology.

Peripheral and respiratory muscle impairment during murine acute lung injury

Acute respiratory distress syndrome is associated with skeletal muscle compromise, which decreases survival and impairs functional capacity. A comparative analysis of peripheral and respiratory muscles' atrophy and dysfunction in acute lung injury (ALI) has not been performed. We aimed to evaluate diaphragmatic and peripheral muscle mass and contractility in an ALI animal model. ALI was induced in C57BL/6 mice by intratracheal lipopolysaccharides instillation. Muscle mass and in vitro contractility were evaluated at different time points in hindlimb soleus (slow-twitch) and extensor digitorum longus (EDL, fast-twitch), as well as in the main respiratory muscle diaphragm. Myogenic precursor satellite cell-specific transcription factor Pax7 expression was determined by Western blot. Lung injury was associated with atrophy of the three studied muscles, although it was more pronounced and persistent in the diaphragm. Specific contractility was reduced during lung injury in EDL muscle but restored by the time lung injury has resolved. Specific force was not affected in soleus and diaphragm. A persistent increase in Pax7 expression was detected in diaphragm and EDL muscles after induction of ALI, but not in soleus muscle. Different peripheral and respiratory skeletal muscles are distinctly affected during the course of ALI. Each of the studied muscles presented a unique pattern in terms of atrophy development, contractile dysfunction and Pax7 expression.

Severe but reversible impaired diaphragm function in septic mechanically ventilated patients

Background

Whether sepsis-associated diaphragm dysfunction may improve despite the exposure of mechanical ventilation in critically ill patients is unclear. This study aims at describing the diaphragm function time course of septic and non-septic mechanically ventilated patients.

Methods

Secondary analysis of two prospective observational studies of mechanically ventilated patients in whom diaphragm function was assessed twice: within the 24 h after intubation and when patients were switched to pressure support mode, by measuring the endotracheal pressure in response to bilateral anterior magnetic phrenic nerve stimulation (Ptr,stim). Change in diaphragm function was expressed as the difference between Ptr,stim measured under pressure support mode and Ptr,stim measured within the 24 h after intubation. Sepsis was defined according to the Sepsis-3 international guidelines upon inclusion. In a sub-group of patients, the right hemidiaphragm thickness was measured by ultrasound.

Results

Ninety-two patients were enrolled in the study. Sepsis upon intubation was present in 51 (55%) patients. In septic patients, primary reason for ventilation was acute respiratory failure related to pneumonia (37/51; 73%). In non-septic patients, main reasons for ventilation were acute respiratory failure not related to pneumonia (16/41; 39%), coma (13/41; 32%) and cardiac arrest (6/41; 15%). Ptr,stim within 24 h after intubation was lower in septic patients as compared to non-septic patients: 6.3 (4.9–8.7) cmH₂O vs. 9.8 (7.0–14.2) cmH₂O (p = 0.004), respectively. The median (interquartile) duration of mechanical ventilation between first and second diaphragm evaluation was 4 (2–6) days in septic patients and 3 (2–4) days in non-septic patients (p = 0.073). Between first and second measurements, the change in Ptr,stim was + 19% (− 13–61) in septic patients and − 7% (− 40–12) in non-septic patients (p = 0.005). In the sub-group of patients with ultrasound measurements, end-expiratory diaphragm thickness decreased in both, septic and non-septic patients. The 28-day mortality was higher in patients with decrease or no change in diaphragm function.

Conclusion

Septic patients were associated with a more severe but reversible impaired diaphragm function as compared to non-septic patients. Increase in diaphragm function was associated with a better survival.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01005-9.

Sepsis and the muscle tissue. A narrative review

Sepsis and septic shock are considered major factors in the development of myopathy in critically ill patients, which is correlated with increased morbidity rates and ICU length of stay. The underlying pathophysiology is complex, involving mitochondrial dysfunction, increased protein breakdown and muscle inexcitability. Sepsis induced myopathy is characterized by several electrophysiological and histopathological abnormalities of the muscle, also has clinical consequences such as flaccid weakness and failure to wean from ventilator. In order to reach definite diagnosis, clinical assessment, electrophysiological studies and muscle biopsy must be performed, which can be challenging in daily practice. Ultrasonography as a screening tool can be a promising alternative, especially in the ICU setting. Sepsis and mechanical ventilation have additive effects leading to diaphragm dysfunction thus complicating the patient's clinical course and recovery. Here, we summarize the effects of the septic syndrome on the muscle tissue based on the existing literature.

Diaphragm Morphology Assessed by Computed Tomography in Chronic Obstructive Pulmonary Disease

Rationale: Chronic obstructive pulmonary disease (COPD) is associated with abnormal skeletal muscle morphology and function. Objectives: To test the hypothesis that in vivo diaphragm muscle morphology assessed by computed tomography (CT) imaging would be associated with COPD severity, exacerbations, health status, and exercise capacity. Methods: The COPD Morphometry Study is a cross-sectional study that enrolled a clinical sample of smokers with COPD. Spirometry was performed and COPD severity was defined according to guidelines. Three-dimensional left hemidiaphragm morphology was segmented from contiguous axial CT images acquired at maximal inspiration, yielding quantitative measures of diaphragm CT density in Hounsfield units, dome height, and muscle volume. Exacerbations prompting pharmacotherapy or hospitalization in the preceding 12 months and St. George's Respiratory Questionnaire for COPD were assessed. Incremental symptom-limited cycle ergometry quantified peak oxygen uptake ([Formula: see text]o_2Peak). Associations were adjusted for age, sex, body height, body mass index, and smoking status. Results: Among 65 smokers with COPD (75% male; [mean ± standard deviation (SD)] 56 ± 26 pack-years; forced expiratory volume in 1 second [FEV₁] percentage predicted 55 ± 23%), mean diaphragm CT density was 3.1 ± 10 Hounsfield units, dome height was 5.2 ± 1.3 cm, and muscle volume was 57 ± 24 cm³. A 1-SD decrement in the diaphragm CT density was associated with 8.3% lower FEV₁, 3.27-fold higher odds of exacerbation history, 9.7-point higher score on the St. George's Respiratory Questionnaire for COPD, and 2.5 ml/kg/min lower [Formula: see text]o_2Peak. A 1-SD decrement in dome height was associated with 11% lower FEV₁ and 1.3 ml/kg/min lower [Formula: see text]o_2Peak. There were no associations with diaphragm volume observed. Conclusions: CT-assessed diaphragm morphology was associated with COPD severity, exacerbations, impaired health status, and exercise intolerance. The mechanisms and functional impact of lower diaphragm CT density merit investigation.

Shear Wave Elastography, A New Tool for Diaphragmatic Qualitative Assessment. A Translational Study

RATIONALE

Prolonged mechanical ventilation (MV) is often associated either with a decrease (known atrophy) or an increase (supposed injury) in diaphragmatic thickness. Shear wave elastography is a non-invasive technique that measures shear modulus, a surrogate of tissue stiffness and mechanical properties.

OBJECTIVES

To describe changes in shear modulus (SM) during the ICU stay and the relationship with alterations in muscle thickness. To perform a comprehensive ultrasound-based characterization of histological and force production changes occurring in the diaphragm.

METHODS

Translational study using critically ill patients and mechanically ventilated piglets. Serial ultrasound examination of the diaphragm collecting thickness and SM was performed in both patients and piglets. Transdiaphragmatic pressure and diaphragmatic biopsies were collected in piglets.

MEASUREMENTS AND MAIN RESULTS

We enrolled 102 patients, 88 of whom were invasively mechanically ventilated. At baseline, SM was 14.3+/-4.3 kPa and diaphragm end-expiratory thickness was 2.0+/-0.5 mm. Decrease or increase by more than 10% from baseline was reported in 86% of the patients for thickness and in 92% of the patients for shear modulus. An increase in diaphragmatic thickness during the stay was associated with a decrease in SM (β=-9.34±4.41; p=0.03) after multivariable analysis. In the piglet sample, a decrease in SM over 3 days of MV was associated with loss of force production, slow and fast fiber atrophy and increased lipid droplets accumulation.

CONCLUSIONS

Increases in diaphragm thickness during critical illness is associated with decreased tissue stiffness as demonstrated by shear wave ultrasound elastography, consistent with the development of muscle injury and weakness.

Energetic dysfunction in sepsis: a narrative review

Background

Growing evidence associates organ dysfunction(s) with impaired metabolism in sepsis. Recent research has increased our understanding of the role of substrate utilization and mitochondrial dysfunction in the pathophysiology of sepsis-related organ dysfunction. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Main text

Sepsis is characterized by systemic and organ-specific changes in metabolism. Alterations of oxygen consumption, increased levels of circulating substrates, impaired glucose and lipid oxidation, and mitochondrial dysfunction are all associated with organ dysfunction and poor outcomes in both animal models and patients. The pathophysiological relevance of bioenergetics and metabolism in the specific examples of sepsis-related immunodeficiency, cerebral dysfunction, cardiomyopathy, acute kidney injury and diaphragmatic failure is also described.

Conclusions

Recent understandings in substrate utilization and mitochondrial dysfunction may pave the way for new diagnostic and therapeutic approaches. These findings could help physicians to identify distinct subgroups of sepsis and to develop personalized treatment strategies. Implications for their use as bioenergetic targets to identify metabolism- and mitochondria-targeted treatments need to be evaluated in future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00893-7.

Dynamic inhomogeneity of aeration along the vertical axis of the lung may predict weaning failure regardless of diaphragm dysfunction

PURPOSE

This study aimed to investigate dynamic changes of lung aeration during a spontaneous breathing trial (SBT) in patients with diaphragm dysfunction (DD) and to predict weaning failure using electrical impedance tomography (EIT).

MATERIALS AND METHODS

We enrolled 40 adult patients who received mechanical ventilation over 48 h and were eligible for SBT with a T-piece. All patients were screened for DD using ultrasonography before SBT. EIT data, including global inhomogeneity index (an off-site parameter), and temporal skew of aeration (TSA) (an on-site parameter) were collected.

RESULTS

Sixteen (40%) patients had DD. During SBT, the tidal impedance variation decreased by 32% from baseline in patients with DD and by 14% in those without DD (p = 0.001). The global inhomogeneity index in the SBT failure group (n = 9) was 0.92 (median), and that of the SBT success group was 0.65 (p = 0.004). The TSA along the vertical axis of the lung was 12.0% and 2.0%, respectively (p = 0.001). With a vertical TSA cutoff of ≥4.35%, SBT failure was predicted with a sensitivity of 88.9% and specificity of 96.9% (area under the curve: 0.955).

CONCLUSION

Dynamic inhomogeneity of aeration along the vertical axis of the lung as assessed using TSA predicts SBT failure regardless of DD.

TRIAL REGISTRATION

This trial was retrospectively registered at cris.nih.go.kr (identifier: KCT003567; release date February 27, 2019).

Muscle atrophy in critically ill patients : a review of its cause, evaluation, and prevention

Critically ill patients exhibit prominent muscle atrophy, which occurs rapidly after ICU admission and leads to poor clinical outcomes. The extent of atrophy differs among muscles as follows: upper limb: 0.7%-2.4% per day, lower limb: 1.2%-3.0% per day, and diaphragm 1.1%-10.9% per day. This atrophy is caused by numerous risk factors such as inflammation, immobilization, nutrition, hyperglycemia, medication, and mechanical ventilation. Muscle atrophy should be monitored noninvasively by ultrasound at the bedside. Ultrasound can assess muscle mass in most patients, although physical assessment is limited to almost half of all critically ill patients due to impaired consciousness. Important strategies to prevent muscle atrophy are physical therapy and electrical muscular stimulation. Electrical muscular stimulation is especially effective for patients with limited physical therapy. Regarding diaphragm atrophy, mechanical ventilation should be adjusted to maintain spontaneous breathing and titrate inspiratory pressure. However, the sufficient timing and amount of nutritional intervention remain unclear. Further investigation is necessary to prevent muscle atrophy and improve long-term outcomes. J. Med. Invest. 67 : 1-10, February, 2020.

Evaluation of the effect of high protein supply on diaphragm atrophy in critically ill patients receiving prolonged mechanical ventilation

BACKGROUND

Our aim was to evaluate the effect of high protein to the target of 2.0 g/kg/d on diaphragm atrophy and clinical prognosis of patients receiving prolonged mechanical ventilation (MV).

METHODS

This prospective, randomized, controlled, single-center study included 41 patients who were treated with ≥7 days' MV. The patients were randomly divided into a standard nutrition treatment (SNT) group and intensive nutrition treatment (INT) group, followed by evaluation of computer tomography-analyzed diaphragm volume, the level of butyrylcholinesterase (BChE) as a muscle mass indicator, and respiratory mechanics indices weekly to observe and compare the differences between the groups.

RESULTS

In the INT group, the actual protein (1.70 ± 0.21 vs 1.06 ± 0.21 g/kg/d, P < .001) and calorie intake (33.46 ± 2.78 vs 25.75 ± 4.81 kcal/kg/d, P < .001) were significantly different from those of the SNT group. Compared with the SNT group, the INT group's diaphragm atrophy improved in the fourth and fifth weeks (all P < .05). The BChE after the third week was higher (all P < .05). No significant differences in respiratory mechanical indices and clinical outcomes were found in the surviving patients between the groups.

CONCLUSION

INT improved the diaphragm atrophy and muscle mass of critically ill patients receiving prolonged MV. There was no evidence that increasing protein to the target amount of 2.0 g/kg/d is related to improvement in clinical prognosis for patients receiving prolonged MV.

Late Ventilator-Induced Diaphragmatic Dysfunction After Extubation

OBJECTIVES

Mechanical ventilation is associated with primary diaphragmatic dysfunction, also termed ventilator-induced diaphragmatic dysfunction. Studies evaluating diaphragmatic function recovery after extubation are lacking. We evaluated early and late recoveries from ventilator-induced diaphragmatic dysfunction in a mouse model.

DESIGN

Experimental randomized study.

SETTING

Research laboratory.

SUBJECTS

C57/BL6 mice.

INTERVENTIONS

Six groups of C57/BL6 mice. Mice were ventilated for 6 hours and then euthanatized immediately (n = 18), or 1 (n = 18) or 10 days after extubation with (n = 5) and without S107 (n = 16) treatment. Mice euthanatized immediately after 6 hours of anesthesia (n = 15) or after 6 hours of anesthesia and 10 days of recovery (n = 5) served as controls.

MEASUREMENTS AND MAIN RESULTS

For each group, diaphragm force production, posttranslational modification of ryanodine receptor, oxidative stress, proteolysis, and cross-sectional areas were evaluated. After 6 hours of mechanical ventilation, diaphragm force production was decreased by 25-30%, restored to the control levels 1 day after extubation, and secondarily decreased by 20% 10 days after extubation compared with controls. Ryanodine receptor was protein kinase A-hyperphosphorylated, S-nitrosylated, oxidized, and depleted of its stabilizing subunit calstabin-1 6 hours after the onset of the mechanical ventilation, 1 and 10 days after extubation. Post extubation treatment with S107, a Rycal drug that stabilizes the ryanodine complex, did reverse the loss of diaphragmatic force associated with mechanical ventilation. Total protein oxidation was restored to the control levels 1 day after extubation. Markers of proteolysis including calpain 1 and calpain 2 remained activated 10 days after extubation without significant changes in cross-sectional areas.

CONCLUSIONS

We report that mechanical ventilation is associated with a late diaphragmatic dysfunction related to a structural alteration of the ryanodine complex that is reversed with the S107 treatment.

Mitochondrial Dysfunction Is a Common Denominator Linking Skeletal Muscle Wasting Due to Disease, Aging, and Prolonged Inactivity

Skeletal muscle is the most abundant tissue in the body and is required for numerous vital functions, including breathing and locomotion. Notably, deterioration of skeletal muscle mass is also highly correlated to mortality in patients suffering from chronic diseases (e.g., cancer). Numerous conditions can promote skeletal muscle wasting, including several chronic diseases, cancer chemotherapy, aging, and prolonged inactivity. Although the mechanisms responsible for this loss of muscle mass is multifactorial, mitochondrial dysfunction is predicted to be a major contributor to muscle wasting in various conditions. This systematic review will highlight the biochemical pathways that have been shown to link mitochondrial dysfunction to skeletal muscle wasting. Importantly, we will discuss the experimental evidence that connects mitochondrial dysfunction to muscle wasting in specific diseases (i.e., cancer and sepsis), aging, cancer chemotherapy, and prolonged muscle inactivity (e.g., limb immobilization). Finally, in hopes of stimulating future research, we conclude with a discussion of important future directions for research in the field of muscle wasting.

Ultrasound and non-ultrasound imaging techniques in the assessment of diaphragmatic dysfunction

Diaphragm muscle dysfunction is increasingly recognized as an important element of several diseases including neuromuscular disease, chronic obstructive pulmonary disease and diaphragm dysfunction in critically ill patients. Functional evaluation of the diaphragm is challenging. Use of volitional maneuvers to test the diaphragm can be limited by patient effort. Non-volitional tests such as those using neuromuscular stimulation are technically complex, since the muscle itself is relatively inaccessible. As such, there is a growing interest in using imaging techniques to characterize diaphragm muscle dysfunction. Selecting the appropriate imaging technique for a given clinical scenario is a critical step in the evaluation of patients suspected of having diaphragm dysfunction. In this review, we aim to present a detailed analysis of evidence for the use of ultrasound and non-ultrasound imaging techniques in the assessment of diaphragm dysfunction. We highlight the utility of the qualitative information gathered by ultrasound imaging as a means to assess integrity, excursion, thickness, and thickening of the diaphragm. In contrast, quantitative ultrasound analysis of the diaphragm is marred by inherent limitations of this technique, and we provide a detailed examination of these limitations. We evaluate non-ultrasound imaging modalities that apply static techniques (chest radiograph, computerized tomography and magnetic resonance imaging), used to assess muscle position, shape and dimension. We also evaluate non-ultrasound imaging modalities that apply dynamic imaging (fluoroscopy and dynamic magnetic resonance imaging) to assess diaphragm motion. Finally, we critically review the application of each of these techniques in the clinical setting when diaphragm dysfunction is suspected.

SARS-CoV-2/Renin-Angiotensin System: Deciphering the Clues for a Couple with Potentially Harmful Effects on Skeletal Muscle

Severe acute respiratory syndrome coronavirus (SARS-CoV-2) has produced significant health emergencies worldwide, resulting in the declaration by the World Health Organization of the coronavirus disease 2019 (COVID-19) pandemic. Acute respiratory syndrome seems to be the most common manifestation of COVID-19. A high proportion of patients require intensive care unit admission and mechanical ventilation (MV) to survive. It has been well established that angiotensin-converting enzyme type 2 (ACE2) is the primary cellular receptor for SARS-CoV-2. ACE2 belongs to the renin–angiotensin system (RAS), composed of several peptides, such as angiotensin II (Ang II) and angiotensin (1-7) (Ang-(1-7)). Both peptides regulate muscle mass and function. It has been described that SARS-CoV-2 infection, by direct and indirect mechanisms, affects a broad range of organ systems. In the skeletal muscle, through unbalanced RAS activity, SARS-CoV-2 could induce severe consequences such as loss of muscle mass, strength, and physical function, which will delay and interfere with the recovery process of patients with COVID-19. This article discusses the relationship between RAS, SARS-CoV-2, skeletal muscle, and the potentially harmful consequences for skeletal muscle in patients currently infected with and recovering from COVID-19.

Diaphragm-protective mechanical ventilation

PURPOSE OF REVIEW

Diaphragm dysfunction is common in mechanically ventilated patients and predisposes them to prolonged ventilator dependence and poor clinical outcomes. Mechanical ventilation is a major cause of diaphragm dysfunction in these patients, raising the possibility that diaphragm dysfunction might be prevented if mechanical ventilation can be optimized to avoid diaphragm injury - a concept referred to as diaphragm-protective ventilation. This review surveys the evidence supporting the concept of diaphragm-protective ventilation and introduces potential routes and challenges to pursuing this strategy.

RECENT FINDINGS

Mechanical ventilation can cause diaphragm injury (myotrauma) by a variety of mechanisms. An understanding of these various mechanisms raises the possibility of a new approach to ventilatory management, a diaphragm-protective ventilation strategy. Deranged inspiratory effort is the main mediator of diaphragmatic myotrauma; titrating ventilation to maintain an optimal level of inspiratory effort may help to limit diaphragm dysfunction and accelerate liberation of mechanical ventilation.

SUMMARY

Mechanical ventilation can cause diaphragm injury and weakness. A novel diaphragm-protective ventilation strategy, avoiding the harmful effects of both excessive and insufficient inspiratory effort, has the potential to substantially improve outcomes for patients.

Association of Low Baseline Diaphragm Muscle Mass With Prolonged Mechanical Ventilation and Mortality Among Critically Ill Adults

IMPORTANCE

Low diaphragm muscle mass at the outset of mechanical ventilation may predispose critically ill patients to poor clinical outcomes.

OBJECTIVE

To determine whether lower baseline diaphragm thickness (Tdi) is associated with delayed liberation from mechanical ventilation and complications of acute respiratory failure (reintubation, tracheostomy, prolonged ventilation >14 days, or death in the hospital).

DESIGN, SETTING, AND PARTICIPANTS

Secondary analysis (July 2018 to June 2019) of a prospective cohort study (data collected May 2013 to January 2016). Participants were 193 critically ill adult patients receiving invasive mechanical ventilation at 3 intensive care units in Toronto, Ontario, Canada.

EXPOSURES

Diaphragm thickness was measured by ultrasonography within 36 hours of intubation and then daily. Patients were classified as having low or high diaphragm muscle mass according to the median baseline Tdi.

MAIN OUTCOMES AND MEASURES

The primary outcome was time to liberation from ventilation accounting for the competing risk of death and adjusting for age, body mass index, severity of illness, sepsis, change in Tdi during ventilation, baseline comorbidity, and study center. Secondary outcomes included in-hospital death and complications of acute respiratory failure.

RESULTS

A total of 193 patients were available for analysis; the mean (SD) age was 60 (15) years, 73 (38%) were female, and the median (interquartile range) Sequential Organ Failure Assessment score was 10 (8-13). Median (interquartile range) baseline Tdi was 2.3 (2.0-2.7) mm. In the primary prespecified analysis, baseline Tdi of 2.3 mm or less was associated with delayed liberation from mechanical ventilation (adjusted hazard ratio for liberation, 0.51; 95% CI, 0.36-0.74). Lower baseline Tdi was associated a higher risk of complications of acute respiratory failure (adjusted odds ratio, 1.77; 95% CI, 1.20-2.61 per 0.5-mm decrement) and prolonged weaning (adjusted odds ratio, 2.30; 95% CI, 1.42-3.74). Lower baseline Tdi was also associated with a higher risk of in-hospital death (adjusted odds ratio, 1.47; 95% CI, 1.00-2.16 per 0.5-mm decrement), particularly after discharge from the intensive care unit (adjusted odds ratio, 2.68; 95% CI, 1.35-5.32 per 0.5-mm decrement).

CONCLUSIONS AND RELEVANCE

In this study, low baseline diaphragm muscle mass in critically ill patients was associated with prolonged mechanical ventilation, complications of acute respiratory failure, and an increased risk of death in the hospital.

Atrophy of Diaphragm and Pectoral Muscles in Critically Ill Patients

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

Muscle atrophy is common in the critically ill, and diaphragm atrophy occurs during mechanical ventilation. It is not known whether wasting of diaphragm and nondiaphragm muscle is related.

WHAT THIS ARTICLE TELLS US THAT IS NEW

Ultrasound was used for serial assessment of diaphragm and pectoral muscle in 97 critically ill patients. Diaphragm and pectoral atrophy occurred in 48% and 29%, respectively, and was associated with septic shock (diaphragm) and steroid use (pectoral); atrophy of the two muscle types appears unrelated.

BACKGROUND

Muscle atrophy occurs early during critical illnesses. Although diffuse, this atrophy may specifically affect the diaphragm under artificial inactivity accompanying invasive mechanical ventilation. The primary objective of this study was to highlight diaphragm atrophy during the first 5 days of critical illness. Monitoring of pectoral thickness (a nonpostural muscle with mainly phasic function) served as a control.

METHODS

Diaphragm and pectoral thicknesses were measured by ultrasound within the first 24 h of admission in 97 critically ill patients, including 62 on mechanical ventilation. Thirty-five patients were reexamined at day 5.

RESULTS

Baseline median (interquartile) values of diaphragm and pectoral thicknesses at day 1 were 2.4 (2.0, 2.9) and 5.9 (4.7, 7.2) mm, respectively (n = 97). Higher values of diaphragm thickness at baseline were positively associated with male sex, chronic obstructive pulmonary disease, and diabetes. Diaphragm and pectoral atrophies (defined as a decrease of 10% or more between day 1 and day 5) were detected in 48% (17 of 35) and 29% (10 of 34) respectively, and were uncorrelated with each other. Diaphragm atrophy was significantly more frequent in patients with septic shock and in those with mechanical ventilation, as compared with their respective counterparts (71% [10 of 14] vs. 33% [7 of 21], P = 0.027 and 71% [17 of 28] vs. 0% [0 of 7], P = 0.004, respectively), whereas pectoral atrophy was more common in patients treated with steroids as compared with their counterparts (58% [7 of 12] vs. 14% [3 of 22], P = 0.006). A statistically significant association between diaphragm atrophy and outcome was not found. Pectoral atrophy seemed associated with less successful weaning from mechanical ventilation at day 14 (12% [1 of 8] vs. 58% [11 of 19], P = 0.043).

CONCLUSIONS

Ultrasound enables identification of specific early diaphragm atrophy that affects the majority of mechanically ventilated patients and septic shock patients. Diaphragm atrophy and pectoral muscle atrophy seem to be two unrelated processes.

Measuring diaphragm movement and respiratory frequency using a novel ultrasound device in healthy volunteers

PURPOSE

To evaluate the ability of a novel ultrasound (US) device, DiaMon, to monitor diaphragm movement via its proxy liver movement, and compare it with the respired flow measured with a flowmeter, in awake and healthy volunteers. We wanted to (1) establish the optimal anatomical position for attaching the DiaMon device to the abdominal wall, and (2) evaluate the accuracy of continuous monitoring of respiratory frequency.

METHODS

Thirty healthy subjects were recruited. The DiaMon probe was applied subcostally in four different positions with the subjects in five different postures. The subjects breathed tidal volumes into a spirometer for 30-60 s with the DiaMon recording simultaneously.

RESULTS

The device detected a readable signal in 83-100% of the position/posture-combinations. The technical correlation between the two signals was highest in the anterior axillary-supine position (mean ± SD: 0.95 ± 0.03), followed by paramidline-supine (0.90 ± 0.09) and midclavicular-supine (0.89 ± 0.12). The frequency measurements yielded a mean difference of 0.03 (95% limits of agreement - 0.11, 0.16) breaths per minute in the anterior axillary-supine position.

CONCLUSION

The DiaMon device is able to detect liver movement in most subjects, and it measures breathing frequency accurately.

Ventilator-induced diaphragm dysfunction: translational mechanisms lead to therapeutical alternatives in the critically ill

Mechanical ventilation [MV] is a life-saving technique delivered to critically ill patients incapable of adequately ventilating and/or oxygenating due to respiratory or other disease processes. This necessarily invasive support however could potentially result in important iatrogenic complications. Even brief periods of MV may result in diaphragm weakness [i.e., ventilator-induced diaphragm dysfunction [VIDD]], which may be associated with difficulty weaning from the ventilator as well as mortality. This suggests that VIDD could potentially have a major impact on clinical practice through worse clinical outcomes and healthcare resource use. Recent translational investigations have identified that VIDD is mainly characterized by alterations resulting in a major decline of diaphragmatic contractile force together with atrophy of diaphragm muscle fibers. However, the signaling mechanisms responsible for VIDD have not been fully established. In this paper, we summarize the current understanding of the pathophysiological pathways underlying VIDD and highlight the diagnostic approach, as well as novel and experimental therapeutic options.

Alterations in diaphragmatic function assessed by ultrasonography in mechanically ventilated patients with sepsis

PURPOSE

To assess alteration of diaphragmatic function by ultrasonography in a population of mechanically ventilated patients with or without sepsis.

METHODS

We performed a prospective, 6-month, single-center, observational cohort study. Mechanically ventilated septic and nonseptic patients were studied within 24 hours following intubation and before the moment of ventilator liberation. Diaphragm thickness and contractile activity (quantified by diaphragmatic thickening fraction, DTF) were measured by ultrasonography at the zone of apposition. Intraobserver and interobserver reproducibility were measured.

RESULTS

Fifty-two critically ill patients were included, 28 with sepsis and 24 without sepsis. Upon initiation of ventilation, DTF was lower in septic than that in nonseptic patients (P = 0.03). No difference was observed between septic and nonseptic patients for diaphragm thickness. Mean 188 ± 111 hours after the first measurement, both diaphragm thickness and DTF decreased significantly compared with first measurements in septic and nonseptic patients, all P < 0.001. Diaphragm thickness decreased by 9.1 ± 10.7% in nonseptic and by 16.0 ± 13.5% in septic patients, P = 0.049. DTF decreased by 15.2 ± 21.3% in nonseptic and by 30.7 ± 22.0% in septic patients, P = 0.013.

CONCLUSIONS

Mechanically ventilated patients with sepsis were associated with an earlier and more severe diaphragm dysfunction compared with patients without sepsis.

Neuregulin-1β attenuates sepsis-induced diaphragm atrophy by activating the PI3K/Akt signaling pathway

The aim of this study was to investigate the protective effects of neuregulin-1β (NRG-1β) on sepsis-induced diaphragm atrophy and the possible underlying mechanisms. Sprague-Dawley rats were randomly divided into sham, sepsis and NRG groups. Sepsis was induced by cecal ligation and puncture (CLP). In the NRG group, rats received tail vein injections of NRG-1β (10 μg/kg) every 12 h for 72 h after CLP. At 3 days after surgery, diaphragm contractile forces were measured by determining the force-frequency curve and muscle fiber areas by hematoxylin-eosin staining. Moreover, the NRG-1 expression level in the diaphragm was detected by Western blotting. Furthermore, the proteins in the PI3K/Akt signaling pathway and its downstream Akt-mTOR and Akt-FOXO axes were detected by Western blotting analysis. In L6 myotubes treated with lipopolysaccharide (LPS) and NRG-1β, PI3K/Akt signaling pathway-related protein expression was further determined using the PI3K inhibitor LY294002. Exogenous NRG-1β could compensate for sepsis-induced diminished NRG-1 in the diaphragm and attenuate the reduction in diaphragm contractile forces and muscle fiber areas during sepsis. Moreover, NRG-1β treatment could activate the PI3K/Akt signaling pathway in the diaphragm during sepsis. The inhibition of p70S6K and 4E-BP1 on the Akt-mTOR axis and the increased expression of Murf1 on the Akt-FOXO axis were reversed after NRG-1 treatment. In addition, NRG-1β could activate the PI3K/Akt signaling pathway in L6 myotubes treated with LPS, while the PI3K inhibitor LY294002 blocked the effects of NRG-1β. NRG-1 expression in the diaphragm was reduced during sepsis, and exogenously administered recombinant human NRG-1β could attenuate sepsis-induced diaphragm atrophy by activating the PI3K/Akt signaling pathway.

Temporary transvenous diaphragm pacing vs. standard of care for weaning from mechanical ventilation: study protocol for a randomized trial

BACKGROUND

Mechanical ventilation (MV) is a life-saving technology that restores or assists breathing. Like any treatment, MV has side effects. In some patients it can cause diaphragmatic atrophy, injury, and dysfunction (ventilator-induced diaphragmatic dysfunction, VIDD). Accumulating evidence suggests that VIDD makes weaning from MV difficult, which involves increased morbidity and mortality.

METHODS AND ANALYSIS

This paper describes the protocol of a randomized, controlled, open-label, multicenter trial that is designed to investigate the safety and effectiveness of a novel therapy, temporary transvenous diaphragm pacing (TTVDP), to improve weaning from MV in up to 88 mechanically ventilated adult patients who have failed at least two spontaneous breathing trials over at least 7 days. Patients will be randomized (1:1) to TTVDP (treatment) or standard of care (control) groups. The primary efficacy endpoint is time to successful extubation with no reintubation within 48 h. Secondary endpoints include maximal inspiratory pressure and ultrasound-measured changes in diaphragm thickness and diaphragm thickening fraction over time. In addition, observational data will be collected and analyzed, including 30-day mortality and time to discharge from the intensive care unit and from the hospital. The hypothesis to be tested postulates that more TTVDP patients than control patients will be successfully weaned from MV within the 30 days following randomization.

DISCUSSION

This study is the first large-scale clinical trial of a novel technology (TTVDP) aimed at accelerating difficult weaning from MV. The technology tested provides the first therapy directed specifically at VIDD, an important cause of delayed weaning from MV. Its results will help delineate the place of this therapeutic approach in clinical practice and help design future studies aimed at defining the indications and benefits of TTVDP.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03096639 . Registered on 30 March 2017.

Ventilator-induced diaphragm dysfunction in critical illness

IMPACT STATEMENT

Mechanical ventilation (MV) is life-saving for patients with acute respiratory failure but also causes difficult liberation of patients from ventilator due to rapid decrease of diaphragm muscle endurance and strength, which is termed ventilator-induced diaphragmatic damage (VIDD). Numerous studies have revealed that VIDD could increase extubation failure, ICU stay, ICU mortality, and healthcare expenditures. However, the mechanisms of VIDD, potentially involving a multistep process including muscle atrophy, oxidative loads, structural damage, and muscle fiber remodeling, are not fully elucidated. Further research is necessary to unravel mechanistic framework for understanding the molecular mechanisms underlying VIDD, especially mitochondrial dysfunction and increased mitochondrial oxidative stress, and develop better MV strategies, rehabilitative programs, and pharmacologic agents to translate this knowledge into clinical benefits.

Diaphragm Weakness in the Critically Ill: Basic Mechanisms Reveal Therapeutic Opportunities

The diaphragm is the primary muscle of inspiration. Its capacity to respond to the load imposed by pulmonary disease is a major determining factor both in the onset of ventilatory failure and in the ability to successfully separate patients from ventilator support. It has recently been established that a very large proportion of critically ill patients exhibit major weakness of the diaphragm, which is associated with poor clinical outcomes. The two greatest risk factors for the development of diaphragm weakness in critical illness are the use of mechanical ventilation and the presence of sepsis. Loss of force production by the diaphragm under these conditions is caused by a combination of defective contractility and reduced diaphragm muscle mass. Importantly, many of the same molecular mechanisms are implicated in the diaphragm dysfunction associated with both mechanical ventilation and sepsis. This review outlines the primary cellular mechanisms identified thus far at the nexus of diaphragm dysfunction associated with mechanical ventilation and/or sepsis, and explores the potential for treatment or prevention of diaphragm weakness in critically ill patients through therapeutic manipulation of these final common pathway targets.

Diaphragm dysfunction during weaning from mechanical ventilation: an underestimated phenomenon with clinical implications

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2018. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2018. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Critical illness-associated diaphragm weakness

Diaphragm weakness is highly prevalent in critically ill patients. It may exist prior to ICU admission and may precipitate the need for mechanical ventilation but it also frequently develops during the ICU stay. Several risk factors for diaphragm weakness have been identified; among them sepsis and mechanical ventilation play central roles. We employ the term critical illness-associated diaphragm weakness to refer to the collective effects of all mechanisms of diaphragm injury and weakness occurring in critically ill patients. Critical illness-associated diaphragm weakness is consistently associated with poor outcomes including increased ICU mortality, difficult weaning, and prolonged duration of mechanical ventilation. Bedside techniques for assessing the respiratory muscles promise to improve detection of diaphragm weakness and enable preventive or curative strategies. Inspiratory muscle training and pharmacological interventions may improve respiratory muscle function but data on clinical outcomes remain limited.

Regulation of Akt-mTOR, ubiquitin-proteasome and autophagy-lysosome pathways in locomotor and respiratory muscles during experimental sepsis in mice

Sepsis induced loss of muscle mass and function contributes to promote physical inactivity and disability in patients. In this experimental study, mice were sacrificed 1, 4, or 7 days after cecal ligation and puncture (CLP) or sham surgery. When compared with diaphragm, locomotor muscles were more prone to sepsis-induced muscle mass loss. This could be attributed to a greater activation of ubiquitin-proteasome system and an increased myostatin expression. Thus, this study strongly suggests that the contractile activity pattern of diaphragm muscle confers resistance to atrophy compared to the locomotor gastrocnemius muscle. These data also suggest that a strategy aimed at preventing the activation of catabolic pathways and preserving spontaneous activity would be of interest for the treatment of patients with sepsis-induced neuromyopathy.

Coexistence and Impact of Limb Muscle and Diaphragm Weakness at Time of Liberation from Mechanical Ventilation in Medical Intensive Care Unit Patients

RATIONALE

Intensive care unit (ICU)- and mechanical ventilation (MV)-acquired limb muscle and diaphragm dysfunction may both be associated with longer length of stay and worse outcome. Whether they are two aspects of the same entity or have a different prevalence and prognostic impact remains unclear.

OBJECTIVES

To quantify the prevalence and coexistence of these two forms of ICU-acquired weakness and their impact on outcome.

METHODS

In patients undergoing a first spontaneous breathing trial after at least 24 hours of MV, diaphragm dysfunction was evaluated using twitch tracheal pressure in response to bilateral anterior magnetic phrenic nerve stimulation (a pressure <11 cm H₂O defined dysfunction) and ultrasonography (thickening fraction [TFdi] and excursion). Limb muscle weakness was defined as a Medical Research Council (MRC) score less than 48.

MEASUREMENTS AND MAIN RESULTS

Seventy-six patients were assessed at their first spontaneous breathing trial: 63% had diaphragm dysfunction, 34% had limb muscle weakness, and 21% had both. There was a significant but weak correlation between MRC score and twitch pressure (ρ = 0.26; P = 0.03) and TFdi (ρ = 0.28; P = 0.01), respectively. Low twitch pressure (odds ratio, 0.60; 95% confidence interval, 0.45-0.79; P < 0.001) and TFdi (odds ratio, 0.84; 95% confidence interval, 0.76-0.92; P < 0.001) were independently associated with weaning failure, but the MRC score was not. Diaphragm dysfunction was associated with higher ICU and hospital mortality, and limb muscle weakness was associated with longer duration of MV and hospital stay.

CONCLUSIONS

Diaphragm dysfunction is twice as frequent as limb muscle weakness and has a direct negative impact on weaning outcome. The two types of muscle weakness have only limited overlap.

Protein Kinetics and Metabolic Effects Related to Disease States in the Intensive Care Unit

Evaluating protein kinetics in the critically ill population remains a very difficult task. Heterogeneity in the intensive care unit (ICU) population and wide spectrum of disease processes creates complexity in assessing protein kinetics. Traditionally, protein has been delivered in the context of total energy. Focus on energy delivery has recently come into question, as the importance of supplemental protein in patient outcomes has been shown in several recent trials. The ICU patient is prone to catabolism, immobilization, and impaired immunity, which is a perfect storm for massive loss of lean body tissue with a unidirectional flow of amino acids from muscle to immune tissue for immunoglobulin production, as well as liver for gluconeogenesis and acute phase protein synthesis. The understanding of protein metabolism in the ICU has been recently expanded with the discovery of how the mammalian target of rapamycin complex 1 is regulated. The concept of "anabolic resistance" and identifying the quantity of protein required to overcome this resistance is gaining support among critical care nutrition circles. It appears that a minimum of at least 1.2 g/kg/d with levels up to 2.0 g/kg/d of protein or amino acids appears safe for delivery in the ICU setting and may yield a better clinical outcome.