Replacement Fibrosis in the Diaphragm of Mechanically Ventilated Critically Ill Patients

Diagnostic accuracy of rapid shallow breathing index based on diaphragm ultrasound predicting successful weaning from mechanical ventilation: A systematic review and meta-analysis

OBJECTIVES

This meta-analysis aimed to evaluate the effectiveness of the rapid shallow breathing index based on diaphragm ultrasound, specifically the diaphragmatic excursion-rapid shallow breathing index (DE-RSBI) and the diaphragmatic thickness fraction- rapid shallow breathing index (DTF-RSBI), in predicting successful weaning from mechanical ventilation.

METHOD

Two researchers independently searched four databases, PubMed, Embase, Cochrane Library and Web of Science, from their inception until 2 November 2024, and conducted literature screening and data extraction. The QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) was employed to evaluate the methodological quality of the included studies. Data analyses were performed using Stata 15 and Meta-Disc 1.4 software.

RESULTS

Fifteen studies (1,519 patients) were included in the meta-analysis. For the DE-RSBI, the pooled sensitivity was 0.89 (95% CI [0.84-0.93]), the pooled specificity was 0.85 (95% CI [0.79-0.90]), and the area under the curve (AUC) for the summary receiver operator characteristic (SROC) curve was 0.93 (95% CI [0.90-0.95]). For the DTF-RSBI, the pooled sensitivity was 0.85 (95% CI [0.56-0.96]), the pooled specificity was 0.81 (95% CI [0.66-0.90]), and the AUC was 0.88 (95% CI [0.85-0.90]).

CONCLUSION

Both DE-RSBI and DTF-RSBI demonstrate strong diagnostic accuracy in predicting successful weaning from mechanical ventilation. Given the apparent heterogeneity among the studies, we anticipate more large-sample, multi-center, and high-quality clinical studies in the future.

IMPLICATIONS FOR CLINICAL PRACTICE

DE-RSBI and DTF-RSBI are simple, non-invasive and objective evaluation indicators, and both can be utilized to predict a patient's capacity to successfully withdraw from mechanical ventilation. This meta-analysis comprehensively evaluated the value of these two tools in predicting successful extubation, aiming to provide clinicians with a strong decision-making basis to improve the success rate of extubation.

Single-nucleus transcriptomic profiling of the diaphragm during mechanical ventilation

Mechanical ventilation contributes to diaphragm atrophy and muscle weakness, which is referred to as ventilator-induced diaphragmatic dysfunction (VIDD). The pathogenesis of VIDD has not been fully understood until recently. The aim of this study was to investigate the effects of 24 h of mechanical ventilation on fibro-adipogenic progenitor (FAP) proliferation, endothelial-mesenchymal transition (EndMT), and immune cell infiltration driving diaphragm fibrosis in a rabbit model. The rabbits were anaesthetized and randomly divided into two groups (n = 3 each group): a control group and an experimental group. Diaphragm nuclei for sequencing were prepared by dissociating and filtering muscle tissue. 10X Genomics Platform for single-nucleus RNA sequencing (snRNA-seq) was used to profile the cells. Normalization and clustering were performed by Seurat, and clusters were manually annotated as different cell types. In this study, we performed differentially expressed genes (DEGs) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, pseudotime analysis and high dimensional weighted gene coexpression network analysis (hdWGCNA) to identify the key genes and signaling pathways related to the pathogenesis of VIDD. We further performed quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting to verify the results of snRNA-seq. The snRNA-seq results showed that acute postmechanical ventilation diaphragm cell changes included an increase in the proportion of fibroblasts and a decrease in the proportion of myofibres. The DEGs, KEGG, hdWGCNA and pseudotime analyses demonstrated that fibro-adipogenic progenitor (FAP) proliferation, endothelial-mesenchymal transition (EndMT) and immune cell infiltration are the three main processes involved in early stage of fibrosis development, among which Pdgfd, Sema3a, Cxcr2, are the corresponding regulatory genes. Glycolysis and the gene Pfkfb3 are also important metabolic factors for fibrosis formation. Negr1 and Mef2c are involved in phrenic nerve ending loss and diaphragm fibre atrophy. The qRT-PCR data showed that the mRNA levels of the genes Pdgfd, Cxcr2, Pfkfb3 and Negr1 were significantly greater in the experimental group than in the control group (P < 0.01), and the expression levels of Sema3a and Mef2c were significantly lower (P < 0.01). Despite limitations, including the lack of functional evaluations to confirm ventilator-induced diaphragm dysfunction (VIDD) and the absence of data validating diaphragm unloading during ventilation, our findings suggest that FAP proliferation and immune cell infiltration may play a role in the early stage of driving diaphragm fibrosis during mechanical ventilation. However, future studies are needed to confirm these findings and investigate the potential mechanisms underlying them.

Suppression of Ventilation-Induced Diaphragm Fibrosis through the Phosphoinositide 3-Kinase-γ in a Murine Bleomycin-Induced Acute Lung Injury Model

Mechanical ventilation (MV), used in patients with acute lung injury (ALI), induces diaphragmatic myofiber atrophy and contractile inactivity, termed ventilator-induced diaphragm dysfunction. Phosphoinositide 3-kinase-γ (PI3K-γ) is crucial in modulating fibrogenesis during the reparative phase of ALI; however, the mechanisms regulating the interactions among MV, myofiber fibrosis, and PI3K-γ remain unclear. We hypothesized that MV with or without bleomycin treatment would increase diaphragm muscle fibrosis through the PI3K-γ pathway. Five days after receiving a single bolus of 0.075 units of bleomycin intratracheally, C57BL/6 mice were exposed to 6 or 10 mL/kg of MV for 8 h after receiving 5 mg/kg of AS605240 intraperitoneally. In wild-type mice, bleomycin exposure followed by MV 10 mL/kg prompted significant increases in disruptions of diaphragmatic myofibrillar organization, transforming growth factor-β1, oxidative loads, Masson's trichrome staining, extracellular collagen levels, positive staining of α-smooth muscle actin, PI3K-γ expression, and myonuclear apoptosis (p < 0.05). Decreased diaphragm contractility and peroxisome proliferator-activated receptor-γ coactivator-1α levels were also observed (p < 0.05). MV-augmented bleomycin-induced diaphragm fibrosis and myonuclear apoptosis were attenuated in PI3K-γ-deficient mice and through AS605240-induced inhibition of PI3K-γ activity (p < 0.05). MV-augmented diaphragm fibrosis after bleomycin-induced ALI is partially mediated by PI3K-γ. Therapy targeting PI3K-γ may ameliorate MV-associated diaphragm fibrosis.

Dyssynchronous diaphragm contractions impair diaphragm function in mechanically ventilated patients

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

Dyssynchronous diaphragm contractions may impair diaphragm function during mechanical ventilation.

TRIAL REGISTRATION

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

Hemi-diaphragm detection of chest X-ray images based on convolutional neural network and graphics

BACKGROUND

Chest X-rays (CXR) are widely used to facilitate the diagnosis and treatment of critically ill and emergency patients in clinical practice. Accurate hemi-diaphragm detection based on postero-anterior (P-A) CXR images is crucial for the diaphragm function assessment of critically ill and emergency patients to provide precision healthcare for these vulnerable populations.

OBJECTIVE

Therefore, an effective and accurate hemi-diaphragm detection method for P-A CXR images is urgently developed to assess these vulnerable populations' diaphragm function.

METHODS

Based on the above, this paper proposes an effective hemi-diaphragm detection method for P-A CXR images based on the convolutional neural network (CNN) and graphics. First, we develop a robust and standard CNN model of pathological lungs trained by human P-A CXR images of normal and abnormal cases with multiple lung diseases to extract lung fields from P-A CXR images. Second, we propose a novel localization method of the cardiophrenic angle based on the two-dimensional projection morphology of the left and right lungs by graphics for detecting the hemi-diaphragm.

RESULTS

The mean errors of the four key hemi-diaphragm points in the lung field mask images abstracted from static P-A CXR images based on five different segmentation models are 9.05, 7.19, 7.92, 7.27, and 6.73 pixels, respectively. Besides, the results also show that the mean errors of these four key hemi-diaphragm points in the lung field mask images abstracted from dynamic P-A CXR images based on these segmentation models are 5.50, 7.07, 4.43, 4.74, and 6.24 pixels,respectively.

CONCLUSION

Our proposed hemi-diaphragm detection method can effectively perform hemi-diaphragm detection and may become an effective tool to assess these vulnerable populations' diaphragm function for precision healthcare.

No association between thickening fraction of the diaphragm and extubation success in ventilated children

Introduction

In mechanically ventilated adults, thickening fraction of diaphragm (dTF) measured by ultrasound is used to predict extubation success. Whether dTF can also predict extubation success in children is unclear.

Aim

To investigate the association between dTF and extubation success in children. Second, to assess diaphragm thickness during ventilation and the correlation between dTF, diaphragm thickness (Tdi), age and body surface.

Method

Prospective observational cohort study in children aged 0-18 years old with expected invasive ventilation for >48 h. Ultrasound was performed on day 1 after intubation (baseline), day 4, day 7, day 10, at pre-extubation, and within 24 h after extubation. Primary outcome was the association between dTF pre-extubation and extubation success. Secondary outcome measures were Tdi end-inspiratory and Tdi end-expiratory and atrophy defined as <10% decrease of Tdi end-expiratory versus baseline at pre-extubation. Correlations were calculated with Spearman correlation coefficients. Inter-rater reliability was calculated with intraclass correlation (ICC).

Results

Fifty-three patients, with median age 3.0 months (IQR 0.1-66.0) and median duration of invasive ventilation of 114.0 h (IQR 55.5-193.5), were enrolled. Median dTF before extubation with Pressure Support 10 above 5 cmH₂O was 15.2% (IQR 9.7-19.3). Extubation failure occurred in six children, three of whom were re-intubated and three then received non-invasive ventilation. There was no significant association between dTF and extubation success; OR 0.33 (95% CI; 0.06-1.86). Diaphragmatic atrophy was observed in 17/53 cases, in three of extubation failure occurred. Children in the extubation failure group were younger: 2.0 months (IQR 0.81-183.0) vs. 3.0 months (IQR 0.10-48.0); p = 0.045. At baseline, pre-extubation and post-extubation there was no significant correlation between age and BSA on the one hand and dTF, Tdi- insp and Tdi-exp on the other hand. The ICC representing the level of inter-rater reliability between the two examiners performing the ultrasounds was 0.994 (95% CI 0.970-0.999). The ICC of the inter-rater reliability between the raters in 36 paired assessments was 0.983 (95% CI 0.974-0.990).

Conclusion

There was no significant association between thickening fraction of the diaphragm and extubation success in ventilated children.