Lung-protective ventilation worsens ventilator-induced diaphragm atrophy and weakness

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

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

CONCLUSION

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

WHAT IS KNOWN

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

WHAT IS NEW

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

Optimizing perioperative lung protection strategies for reducing postoperative respiratory complications in pediatric patients: a narrative review

Background and Objective

Despite significant advancements in the safe delivery of anesthesia and improvements in surgical techniques, postoperative respiratory complications (PRCs) remain a serious concern. PRCs can lead to increased length of hospital stay, worsened patient outcomes, and higher hospital and postoperative costs. Perioperative lung injury and PRCs are more common in children than in adults owing to children's unique physiology and anatomical characteristics. Studies have shown that lung-protective ventilation (LPV) strategies can improve lung function and minimize the risk of PRCs in adults. However, individualized LPV in children remains underexplored. This narrative review provides an overview of the various perioperative pulmonary protection strategies and their effect on pediatric PRCs.

Methods

We searched PubMed for articles published from 2000 to 2024, setting our inclusion criteria to include studies that involved pediatric patients, addressed LPV strategies, and reported data on PRCs. Non-English language studies, case reports, editorials, conference abstracts, and non-full text published literatures were excluded. We utilized the following keyword strategy: (((lung protective ventilation) OR (PEEP)) OR (recruitment maneuver)) OR (low tidal volume) AND (2000:2024[pdat])) AND (pediatric) filters. In total, 1,106 articles were retrieved, with only 23 being deemed relevant to the review. Data extraction and analysis were conducted by two independent researchers to ensure accuracy and consistency. We conducted descriptive statistical analysis for quantitative data and thematic analysis for qualitative data.

Key Content and Findings

The key content are an overview of risk factors for PRCs in children including the patients themselves, anesthesia, and surgery, as well as the effectiveness of LPV strategies in pediatric surgery, including low tidal volume (TV), positive end-expiratory pressure (PEEP), ultrasound-guided pulmonary recruitment maneuver (RM), low fraction of inspired oxygen (FiO2), pressure-controlled ventilation (PCV), as well as fluids, pain, and high-flow nasal cannula (HFNC). We found that age, mechanical ventilation with general anesthesia, and thoracic surgery increased the risk of PRCs in children. The application of LPV strategies in pediatric surgery had positive effect, including low TV combined with titrated PEEP, age- and physiologically appropriate FiO2, ultrasound-guided RM, target directed fluid infusion, adequate analgesia, and the use of HFNC in special circumstances. However, we also found that the application of LPV has certain potential risks and therefore needs to be implemented according to the patient's actual age and physical condition.

Conclusions

Perioperative LPV strategies show potential benefits in reducing lung injury and PRCs in pediatric patients. These strategies, including low TV, appropriate individualized PEEP, lung RM, and avoidance of high FiO2, appear to be effective methods for protecting lung function in pediatric patients. Additionally, perioperative fluid management and effective pain control are crucial for lung protection. The emerging use of HFNC therapy shows promise, but further research is needed to fully understand its benefits.

The Hemodynamic Changes Induced by Lung Recruitment Maneuver to Predict Fluid Responsiveness in Children during One Lung Ventilation-A Prospective Observational Study

BACKGROUND

The prediction of fluid responsiveness in critical patients helps clinicians in decision making to avoid either under- or overloading of fluid. This study was designed to determine whether lung recruitment maneuver (LRM) would have an effect on the predictability of fluid responsiveness by the changes of hemodynamic parameters in pediatric patients who were receiving lung-protective ventilation and one-lung ventilation (OLV).

METHODS

A total of 34 children, aged 1-6 years old, scheduled for heart surgeries via right thoracotomy were enrolled. Patients were anesthetized and OLV with lung-protection ventilation settings was established, and then, positioned on left lateral decubitus. LRM and volume expansion (VE) were performed in sequence. Heart rate (HR), systolic arterial pressure (SAP), mean arterial pressure (MAP) diastolic arterial pressure (DAP), stroke volume (SV), stroke volume variation (SVV), and pulse pressure variation (PPV) were recorded via an A-line based monitor system at the following time points: before and after LRM (T1 and T2) and before and after VE (T3 and T4). An increase in stroke volume (SV) or mean arterial pressure (MAP) of ≥10% following fluid loading identified fluid responders. The predictability of fluid responsiveness by the changes of SV (ΔSVLRM) and MAP (ΔMAPLRM) after LRM and VE were statistically evaluated by receiver operating characteristic curves [area under the curves (AUC)].

RESULTS

SVs in all patients were significantly decreased after LRM (p < 0.01) and then, increased and returned to baseline after VE (p < 0.01). In total, 16 out of 34 patients who were fluid responders had significantly lower SV after LRM compared to that in fluid non-responders. The area under the receiver operating characteristic curves for ΔSVLRM was 0.828 (95% confidence interval [CI], 0.660 to 0.935; p < 0.001) and it indicated that ΔSVLRM was able to predict the fluid responsiveness of pediatric patients. MAPs in all patients were also decreased significantly after LRM, and 12 of them fell into the category of fluid responders after VE. Statistically, ΔMAPLRM did not predict fluid responsiveness when LRM was considered as an influential factor (p = 0.07).

CONCLUSIONS

ΔSVLRM, but not ΔMAPLRM, showed great reliability in the prediction of the fluid responsiveness following VE in children during one-lung ventilation with lung-protective settings.

TRIAL REGISTRATION

ChiCTR2300070690.

Electrical stimulation mitigates muscle degradation shift in gene expressions during 12-h mechanical ventilation

Ventilator-induced diaphragm dysfunction (VIDD), a dysfunction of the diaphragm muscle caused by prolonged mechanical ventilation (MV), is an important factor that hinders successful weaning from ventilation. We evaluated the effects of electrical stimulation of the diaphragm muscle (pulsed current with off-time intervals) on genetic changes during 12 h of MV (E-V12). Rats were divided into four groups: control, 12-h MV, sham operation, and E-V12 groups. Transcriptome analysis using an RNA microarray revealed that 12-h MV caused upregulation of genes promoting muscle atrophy and downregulation of genes facilitating muscle synthesis, suggesting that 12-h MV is a reasonable method for establishing a VIDD rat model. Of the genes upregulated by 12-h MV, 18 genes were not affected by the sham operation but were downregulated by E-V12. These included genes related to catabolic processes, inflammatory cytokines, and skeletal muscle homeostasis. Of the genes downregulated by 12-h MV, 6 genes were not affected by the sham operation but were upregulated by E-V12. These included genes related to oxygen transport and mitochondrial respiration. These results suggested that 12-h MV shifted gene expression in the diaphragm muscle toward muscle degradation and that electrical stimulation counteracted this shift by suppressing catabolic processes and increasing mitochondrial respiration.

PEEP application during mechanical ventilation contributes to fibrosis in the diaphragm

BACKGROUND

Positive end-expiratory airway pressure (PEEP) is a potent component of management for patients receiving mechanical ventilation (MV). However, PEEP may cause the development of diaphragm remodeling, making it difficult for patients to be weaned from MV. The current study aimed to explore the role of PEEP in VIDD.

METHODS

Eighteen adult male New Zealand rabbits were divided into three groups at random: nonventilated animals (the CON group), animals with volume-assist/control mode without/ with PEEP 8 cmH₂O (the MV group/ the MV + PEEP group) for 48 h with mechanical ventilation. Ventilator parameters and diaphragm were collected during the experiment for further analysis.

RESULTS

There was no difference among the three groups in arterial blood gas and the diaphragmatic excursion during the experiment. The tidal volume, respiratory rate and minute ventilation were similar in MV + PEEP group and MV group. Airway peak pressure in MV + PEEP group was significantly higher than that in MV group (p < 0.001), and mechanical power was significantly higher (p < 0.001). RNA-seq showed that genes associated with fibrosis were enriched in the MV + PEEP group. This results were further confirmed on mRNA expression. As shown by Masson's trichrome staining, there was more collagen fiber in the MV + PEEP group than that in the MV group (p = 0.001). Sirius red staining showed more positive staining of total collagen fibers and type I/III fibers in the MV + PEEP group (p = 0.001; p = 0.001). The western blot results also showed upregulation of collagen types 1A1, III, 6A1 and 6A2 in the MV + PEEP group compared to the MV group (p < 0.001, all). Moreover, the positive immunofluorescence of COL III in the MV + PEEP group was more intense (p = 0.003). Furthermore, the expression of TGF-β1, one of the most potent fibrogenic factors, was upregulated at both the mRNA and protein levels in the MV + PEEP group (mRNA: p = 0.03; protein: p = 0.04).

CONCLUSIONS

We demonstrated that PEEP application for 48 h in mechanically ventilated rabbits will cause collagen deposition and fibrosis in the diaphragm. Moreover, activation of the TGF-β1 signaling pathway and myofibroblast differentiation may be the potential mechanism of this diaphragmatic fibrosis. These findings might provide novel therapeutic targets for PEEP application-induced diaphragm dysfunction.

IL-6 Deficiency Attenuates Skeletal Muscle Atrophy by Inhibiting Mitochondrial ROS Production through the Upregulation of PGC-1α in Septic Mice

Current evidences indicate that both inflammation and oxidative stress contribute to the pathogenesis of sepsis-associated skeletal muscle atrophy. However, the interaction between inflammation and oxidative stress has not been completely understood in sepsis-associated skeletal muscle atrophy. Here in the present study, a murine model of sepsis has been established by cecal ligation and puncture (CLP) with wild-type and interleukin- (IL-) 6 knockout (KO) mice. Our results suggested that IL-6 KO largely attenuated skeletal muscle atrophy as reflected by reduced protein degradation, increased cross-sectional area (CSA) of myofibers, and improved muscle contractile function (all $P<0.05$ ). In addition, we observed that IL-6 KO promoted the expression of peroxisome proliferator-activated receptor γ coactivator–1alpha (PGC–1α) and inhibited CLP-induced mitochondrial reactive oxygen species (ROS) production in skeletal muscles (all $P<0.05$ ). However, the knockdown of PGC–1α abolished the protective effects of IL-6 KO in CLP-induced skeletal muscle atrophy and reversed the changes in mitochondrial ROS production (all $P<0.05$ ). Ex vivo experiments found that exogenous IL-6 inhibited PGC–1α expression, promoted mitochondrial ROS production, and induced proteolysis in C2C12 cells (all $P<0.05$ ). Together, these results suggested that IL-6 deficiency attenuated skeletal muscle atrophy by inhibiting mitochondrial ROS production through the upregulation of PGC–1α expression in septic mice.

Effect of Lung Protective Ventilation Combined With Flurbiprofen Axetil on Immune Function During Thoracoscopic Radical Resection of Lung Cancer

The decreased immune function of patients with lung cancer has always been the focus of clinical attention. However, the stress response caused by surgery, anesthesia and pain will further reduce the body's immune function and affect the prognosis of patients to a certain extent. It was found that both protective ventilation and flurbiprofen ester pretreatment could reduce the immunosuppression caused by stress response. In this study, 120 lung cancer patients treated with video-assisted thoracoscopic radical resection were divided into group A, group B, group C and group D, which were treated with conventional mechanical ventilation, lung protective ventilation, conventional mechanical ventilation + flurbiprofen axetil and lung protective ventilation + flurbiprofen axetil, respectively. The results showed that the levels of CD3+, CD4+, CD4/CD8+, and NK in groups A, B, and C were lower than T0 on T1, T2, and T3, while those indicators in group D were lower than T0 on T1 and T2 (P < 0.05). The above indicators in group D were higher than those in the other three groups on T1, T2, and T3 (P < 0.05). The above indicators were statistically significant compared with those in group A and group C, group B and group D, and group A and group B at T1, T2, and T3 (P < 0.05). The comparisons of CD3+, CD4+, CD4/CD8+, and NK among the four groups within different time groups, and the repeated - measures analysis of variance (repeated - measures ANOVA) showed that there were interactions among time, group, and between groups × within groups (P < 0.05). It was confirmed that lung protective ventilation combined with flurbiprofen axetil could alleviate the immunosuppression of patients undergoing thoracoscopic radical lung cancer, providing a new idea for clinical treatment.

Mechanosensitive cation channel Piezo1 contributes to ventilator-induced lung injury by activating RhoA/ROCK1 in rats

Background

Mechanical ventilation can induce or aggravate lung injury, which is termed ventilator-induced lung injury (VILI). Piezo1 is a key element of the mechanotransduction process and can transduce mechanical signals into biological signals by mediating Ca²⁺ influx, which in turn regulates cytoskeletal remodeling and stress alterations. We hypothesized that it plays an important role in the occurrence of VILI, and investigated the underlying mechanisms.

Methods

High tidal volume mechanical ventilation and high magnitude cyclic stretch were performed on Sprague–Dawley rats, and A549 and human pulmonary microvascular endothelial cells, respectively, to establish VILI models. Immunohistochemical staining, flow cytometry, histological examination, enzyme-linked immunosorbent assay, western blotting, quantitative real-time polymerase chain reaction and survival curves were used to assess the effect of Piezo1 on induction of lung injury, as well as the signaling pathways involved.

Results

We observed that Piezo1 expression increased in the lungs after high tidal volume mechanical ventilation and in cyclic stretch-treated cells. Mechanistically, we observed the enhanced expression of RhoA/ROCK1 in both cyclic stretch and Yoda1-treated cells, while the deficiency or inhibition of Piezo1 dramatically antagonized RhoA/ROCK1 expression. Furthermore, blockade of RhoA/ROCK1 signaling using an inhibitor did not affect Piezo1 expression. GSMTx4 was used to inhibit Piezo1, which alleviated VILI-induced pathologic changes, water content and protein leakage in the lungs, and the induction of systemic inflammatory mediators, and improved the 7-day mortality rate in the model rats.

Conclusions

These findings indicate that Piezo1 affects the development and progression of VILI through promotion of RhoA/ROCK1 signaling.

Altered expression of microRNAs in the rat diaphragm in a model of ventilator-induced diaphragm dysfunction after controlled mechanical ventilation

BACKGROUND

Ventilator-induced diaphragm dysfunction (VIDD) is a common complication of life support by mechanical ventilation observed in critical patients in clinical practice and may predispose patients to severe complications such as ventilator-associated pneumonia or ventilator discontinuation failure. To date, the alterations in microRNA (miRNA) expression in the rat diaphragm in a VIDD model have not been elucidated. This study was designed to identify these alterations in expression.

RESULTS

Adult male Wistar rats received conventional controlled mechanical ventilation (CMV) or breathed spontaneously for 12 h. Then, their diaphragm tissues were collected for RNA extraction. The miRNA expression alterations in diaphragm tissue were investigated by high-throughput microRNA-sequencing (miRNA-seq). For targeted mRNA functional analysis, gene ontology (GO) analyses and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were subsequently conducted. qRT-PCR validation and luciferase reporter assays were performed. We successfully constructed a model of ventilator-induced diaphragm dysfunction and identified 38 significantly differentially expressed (DE) miRNAs, among which 22 miRNAs were upregulated and 16 were downregulated. GO analyses identified functional genes, and KEGG pathway analyses revealed the signaling pathways that were most highly correlated, which were the MAPK pathway, FoxO pathway and Autophagy-animal. Luciferase reporter assays showed that STAT3 was a direct target of both miR-92a-1-5p and miR-874-3p and that Trim63 was a direct target of miR-3571.

CONCLUSIONS

The current research supplied novel perspectives on miRNAs in the diaphragm, which may not only be implicated in diaphragm dysfunction pathogenesis but could also be considered as therapeutic targets in diaphragm dysfunction.

Effect of different levels of PEEP on mortality in ICU patients without acute respiratory distress syndrome: systematic review and meta-analysis with trial sequential analysis

OBJECTIVE

To determine whether higher positive end- expiratory pressure (PEEP) could provide a survival advantage for patients without acute respiratory distress syndrome (ARDS) compared with lower PEEP.

METHODS

Eligible studies were identified through searches of Embase, Cochrane Library, Web of Science, Medline, and Wanfang database from inception up to 1 June 2021. Trial sequential analysis (TSA) was used in this meta-analysis.

DATA SYNTHESIS

Twenty-seven randomized controlled trials (RCTs) were identified for further evaluation. Higher and lower PEEP arms included 1330 patients and 1650 patients, respectively. A mean level of 9.6±3.4 cmH₂O was applied in the higher PEEP groups and 1.9±2.6 cmH₂O was used in the lower PEEP groups. Higher PEEP, compared with lower PEEP, was not associated with reduction of all-cause mortality (RR 1.03; 95% CI 0.91-1.18; P =0.627), and 28-day mortality (RR 1.07 ; 95% CI 0.92-1.24; P =0.365). In terms of risk of ARDS (RR 0.43; 95% CI 0.24-0.78; P =0.005), duration of intensive care unit (MD -1.04; 95%CI-1.36 to -0.73; P < 0.00001), and oxygenation (MD 40.30; 95%CI 0.94 to 79.65; P = 0.045), higher PEEP was superior to lower PEEP. Besides, the pooled analysis showed no significant differences between groups both in the duration of mechanical ventilation (MD 0.00; 95%CI-0.13 to 0.13; P = 0.996) and hospital stay (MD -0.66; 95%CI-1.94 to 0.61; P = 0.309). More importantly, lower PEEP did not increase the risk of pneumonia, atelectasis, barotrauma, hypoxemia, or hypotension among patients compared with higher PEEP. The TSA analysis showed that the results of all-cause mortality and 28-day mortality might be false-negative results.

CONCLUSIONS

Our results suggest that a lower PEEP ventilation strategy was non-inferior to a higher PEEP ventilation strategy in ICU patients without ARDS, with no increased risk of all-cause mortality and 28-day mortality. Further high-quality RCTs should be performed to confirm these findings.

Transcriptome profiling of the diaphragm in a controlled mechanical ventilation model reveals key genes involved in ventilator-induced diaphragmatic dysfunction

BACKGROUND

Ventilator-induced diaphragmatic dysfunction (VIDD) is associated with weaning difficulties, intensive care unit hospitalization (ICU), infant mortality, and poor long-term clinical outcomes. The expression patterns of long noncoding RNAs (lncRNAs) and mRNAs in the diaphragm in a rat controlled mechanical ventilation (CMV) model, however, remain to be investigated.

RESULTS

The diaphragms of five male Wistar rats in a CMV group and five control Wistar rats were used to explore lncRNA and mRNA expression profiles by RNA-sequencing (RNA-seq). Muscle force measurements and immunofluorescence (IF) staining were used to verify the successful establishment of the CMV model. A total of 906 differentially expressed (DE) lncRNAs and 2,139 DE mRNAs were found in the CMV group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to determine the biological functions or pathways of these DE mRNAs. Our results revealed that these DE mRNAs were related mainly related to complement and coagulation cascades, the PPAR signaling pathway, cholesterol metabolism, cytokine-cytokine receptor interaction, and the AMPK signaling pathway. Some DE lncRNAs and DE mRNAs determined by RNA-seq were validated by quantitative real-time polymerase chain reaction (qRT-PCR), which exhibited trends similar to those observed by RNA-sEq. Co-expression network analysis indicated that three selected muscle atrophy-related mRNAs (Myog, Trim63, and Fbxo32) were coexpressed with relatively newly discovered DE lncRNAs.

CONCLUSIONS

This study provides a novel perspective on the molecular mechanism of DE lncRNAs and mRNAs in a CMV model, and indicates that the inflammatory signaling pathway and lipid metabolism may play important roles in the pathophysiological mechanism and progression of VIDD.

Effect of controlled ventilation during assist-control ventilation on diaphragm thickness : a post hoc analysis of an observational study

Background : Since diaphragm passivity induces oxidative stress that leads to rapid atrophy of diaphragm, we investigated the effect of controlled ventilation on diaphragm thickness during assist-control ventilation (ACV). Methods : Previously, we measured end-expiratory diaphragm thickness (Tdiee) of patients mechanically ventilated for more than 48 hours on days 1, 3, 5 and 7 after the start of ventilation. We retrospectively investigated the proportion of controlled ventilation during the initial 48-hour ACV (CV48%). Patients were classified according to CV48% : Low group, less than 25% ; High group, higher than 25%. Results : Of 56 patients under pressure-control ACV, Tdiee increased more than 10% in 6 patients (11%), unchanged in 8 patients (14%) and decreased more than 10% in 42 patients (75%). During the first week of ventilation, Tdiee decreased in both groups : Low (difference, -7.4% ; 95% confidence interval [CI], -10.1% to -4.6% ; p < 0.001) and High group (difference, -5.2% ; 95% CI, -8.5% to -2.0% ; p = 0.049). Maximum Tdiee variation from baseline did not differ between Low (-15.8% ; interquartile range [IQR], -22.3 to -1.5) and High group (-16.7% ; IQR, -22.6 to -11.1, p = 0.676). Conclusions : During ACV, maximum variation in Tdiee was not associated with proportion of controlled ventilation higher than 25%. J. Med. Invest. 67 : 332-337, August, 2020.