Beyond Ventilator-induced Diaphragm Dysfunction: New Evidence for Critical Illness-associated Diaphragm Weakness

Transvenous phrenic nerve stimulation reduces diaphragm injury during controlled mechanical ventilation in a preclinical model of ARDS

Patients with acute respiratory distress syndrome (ARDS) require periods of deep sedation and mechanical ventilation, leading to diaphragm dysfunction. Our study seeks to determine whether the combination of temporary transvenous diaphragm neurostimulation (TTDN) and mechanical ventilation changes the degree of diaphragm injury and cytokines concentration in a preclinical ARDS model. Moderate ARDS was induced in pigs using oleic acid, followed by ventilation for 12 h post-injury with volume-control at 8 mL/kg, positive end-expiratory pressure (PEEP) 5 cmH2O, respiratory rate and [Formula: see text] set to achieve normal arterial blood gases. Two groups received TTDN: every second breath (MV + TTDN50%, n = 6) or every breath (MV + TTDN100%, n = 6). One group received ventilation only (MV, n = 6). Full-thickness diaphragm and quadricep muscle biopsies were taken at study end. Samples were fixed and stained with hematoxylin and eosin and a point-counting technique was applied to calculate abnormal muscle area fraction. Cytokine concentrations were measured in homogenized tissue using porcine-specific enzyme-linked immunosorbent assay (ELISA) and compared with serum samples. Percentage of abnormal diaphragm tissue was different between MV [8.1% (6.0-8.8)] versus MV + TTDN50% [3.4% (2.1-4.8)], P = 0.010 and MV versus MV + TTDN100% [3.1% (2.5-4.0)], P = 0.005. Percentage of abnormal quadriceps tissue was not different between groups. Cytokine concentration patterns in diaphragm samples were different between all groups (P < 0.001) and the interaction between TTDN application and resultant cytokine concentration pattern was significant (P = 0.025). TTDN, delivered in synchrony with mechanical ventilation, mitigated diaphragm injury, as evidenced by less abnormal tissue in the diaphragm samples, in pigs with oleic acid-induced ARDS and is an exciting tool for lung and diaphragm-protective ventilation.NEW & NOTEWORTHY This study adds to our understanding of applying transvenous diaphragm neurostimulation synchronously with mechanical ventilation by examining its effects on diaphragm muscle injury and cytokine concentration patterns in pigs with acute respiratory distress syndrome (ARDS). We observed that using this therapy for 12 h post lung injury mitigated ventilator-induced diaphragm injury and changed the pattern of cytokine concentration measured in diaphragm tissue. These findings suggest that transvenous diaphragm neurostimulation is an exciting tool for lung and diaphragm protective ventilation.

The ratio of parasternal intercostal muscle-thickening fraction-to-diaphragm thickening fraction for predicting weaning failure

BACKGROUND

Diaphragm dysfunction is associated with weaning outcomes in mechanical ventilation patients, in the case of diaphragm dysfunction, the accessory respiratory muscles would be recruited. The main purpose of this study is to explore the performance of parasternal intercostal muscle thickening fraction in relation to diaphragmatic thickening fraction ratio (TFic1/TFdi2) for predicting weaning outcomes, and compare its accuracy with D-RSBI in predicting weaning failure.

MATERIALS AND METHODS

We prospectively enrolled consecutive patients from 7/2022-5/2023. We measured TFic, TFdi, and diaphragmatic excursion (DE3) by ultrasound and calculated the TFic/TFdi ratio and diaphragmatic rapid shallow breathing index (D-RSBI4). Receiver-operator characteristic (ROC5) curves evaluated the accuracy of the TFic/TFdi ratio and D-RSBI in predicting weaning failure.

RESULTS

161 were included in the final analysis, 114 patients (70.8%) were successfully weaned from mechanical ventilation. The TFic/TFdi ratio (AUROC = 0.887 (95% CI: 0.821-0.953)) was superior to the D-RSBI (AUROC = 0.875 (95% CI: 0.807-0.944)) for predicting weaning failure.

CONCLUSIONS

The TFic/TFdi ratio predicted weaning failure with high accuracy and outperformed the D-RSBI.

Reference values of diaphragmatic dimensions in healthy children aged 0-8 years

Diaphragmatic thickness (Tdi) and diaphragm thickening fraction (dTF) are widely used parameters in ultrasound studies of the diaphragm in mechanically ventilated children, but normal values for healthy children are scarce. We determined reference values of Tdi and dTF using ultrasound in healthy children aged 0-8 years old and assessed their reproducibility. In a prospective, observational cohort, Tdi and dTF were measured on ultrasound images across four age groups comprising at least 30 children per group: group 1 (0-6 months), group 2 (7 months-1 year), group 3 (2-4 years) and group 4 (5-8 years). Ultrasound images of 137 healthy children were included. Mean Tdi at inspiration was 2.07 (SD 0.40), 2.09 (SD 0.40), 1.69 (SD 0.30) and 1.72 (SD 0.30) mm for groups 1, 2, 3 and 4, respectively. Mean Tdi at expiration was 1.64 (SD 0.30), 1.67 (SD 0.30), 1.38 (SD 0.20) and 1.42 (SD 0.20) mm for groups 1, 2, 3 and 4, respectively. Mean Tdi at inspiration and mean Tdi at expiration for groups 1 and 2 were significantly greater than those for groups 3 and 4 (both p < 0.001). Mean dTF was 25.4% (SD 10.4), 25.2% (SD 8.3), 22.8% (SD 10.9) and 21.3% (SD 7.1) for group 1, 2, 3 and 4, respectively. The intraclass correlation coefficients (ICC) representing the level of inter-rater reliability between two examiners performing the ultrasounds was 0.996 (95% CI 0.982-0.999). ICC of the inter-rater reliability between the raters in 11 paired assessments was 0.989 (95% CI 0.973-0.995).   Conclusion: Ultrasound measurements of Tdi and dTF were highly reproducible in healthy children aged 0-8 years.    Trial registration: ClinicalTrials.gov identifier (NCT number): NCT04589910. What is Known: • Diaphragmatic thickness and diaphragm thickening fraction are widely used parameters in ultrasound studies of the diaphragm in mechanically ventilated children, but normal values for healthy children to compare these with are scarce. What is New: • We determined normal values of diaphragmatic thickness and diaphragm thickening fraction using ultrasound in 137 healthy children aged 0-8 years old. The diaphragmatic thickness of infants up to 1 year old was significantly greater than that of children from 2 to 8 years old. Diaphragmatic thickness decreased with an increase in body surface area. These normal values in healthy children can be used to assess changes in respiratory muscle thickness in mechanically ventilated children.

SPECKLE TRACKING QUANTIFICATION PARASTERNAL INTERCOSTAL MUSCLE LONGITUDINAL STRAIN TO PREDICT WEANING OUTCOMES: A MULTICENTRIC OBSERVATIONAL STUDY

ABSTRACT

Background: The purpose of this study was to determine the feasibility, reliability, and reproducibility of parasternal intercostal muscle longitudinal strain (LSim) quantification by speckle tracking and the value of maximal LSim to predict weaning outcomes. Methods: This study was divided into three phases. Phases 1 and 2 comprehended prospective observational programs to evaluate the feasibility, reliability, and repeatability of speckle tracking to assess LSim in healthy subjects and mechanically ventilated patients. Phase 3 was a multicenter retrospective study to evaluate the value of maximal LSim, intercostal muscle thickening fraction (TFim), diaphragmatic thickening fraction, diaphragmatic excursion, and rapid shallow breathing index to predict weaning outcomes. Results: A total of 25 healthy subjects and 20 mechanically ventilated patients were enrolled in phases 1 and 2, respectively. Maximal LSim was easily accessible, and the intraoperator reliability and interoperator reliability were excellent in eupnea, deep breathing, and mechanical ventilation. The intraclass correlation coefficient ranged from 0.85 to 0.96. Moreover, 83 patients were included in phase 3. The areas under the receiver operating characteristic curve of maximal LSim, TFim, diaphragmatic thickening fraction, diaphragmatic excursion, and rapid shallow breathing index were 0.91, 0.79, 0.71, 0.70, and 0.78 for the prediction of successful weaning, respectively. The best cutoff values of LSim and TFim were >-6% (sensitivity, 100%; specificity, 64.71%) and <7.6% (sensitivity, 100%; specificity, 50.98%), respectively. Conclusions: The quantification of LSim by speckle tracking was easily achievable in healthy subjects and mechanically ventilated patients and presented a higher predictive value for weaning success compared with conventional weaning parameters. Trial registration no. ChiCTR2100049817.

Respiratory and peripheral muscular ultrasound characteristics in ICU COVID 19 ARDS patients

PURPOSE

Severe cases of coronavirus disease 2019 develop ARDS requiring admission to the ICU. This study aimed to investigate the ultrasound characteristics of respiratory and peripheral muscles of patients affected by COVID19 who require mechanical ventilation.

MATERIALS AND METHODS

This is a prospective observational study. We performed muscle ultrasound at the admission of ICU in 32 intubated patients with ARDS COVID19. The ultrasound was comprehensive of thickness and echogenicity of both parasternal intercostal and diaphragm muscles, and cross-sectional area and echogenicity of the rectus femoris.

RESULTS

Patients who survived showed a significantly lower echogenicity score as compared with those who did not survive for both parasternal intercostal muscles. Similarly, the diaphragmatic echogenicity was significantly different between alive or dead patients. There was a significant correlation between right parasternal intercostal or diaphragm echogenicity and the cumulative fluid balance and urine protein output. Similar results were detected for rectus femoris echogenicity.

CONCLUSIONS

The early changes detected by echogenicity ultrasound suggest a potential benefit of proactive early therapies designed to preserve respiratory and peripheral muscle architecture to reduce days on MV, although what constitutes a clinically significant change in muscle echogenicity remains unknown.

Qualitative and quantitative muscle ultrasound changes in patients with COVID-19-related ARDS

OBJECTIVES

Severe forms of the novel coronavirus-19 (COVID-19) are associated with systemic inflammation and hypercatabolism. The aims of this study were to compare the time course of the size and quality of both rectus femoris and diaphragm muscles between critically ill, COVID-19 survivors and non-survivors and to explore the correlation between the change in muscles size and quality with the amount of nutritional support delivered and the cumulative fluid balance.

METHODS

This was a prospective observational study in the general intensive care unit (ICU) of a tertiary care hospital for COVID-19. The right rectus femoris cross-sectional area and the right diaphragm thickness, as well as their echo densities were assessed within 24 h from ICU admission and on day 7. We recorded anthropometric and biochemical data, respiratory mechanics and gas exchange, daily fluid balance, and the number of calories and proteins administered.

RESULTS

Twenty-eight patients were analyzed (65 ± 10 y of age; 80% men, body mass index 30 ± 7.8 kg/m²). Rectus femoris and diaphragm sizes were significantly reduced at day 7 (median = -26.1 [interquartile ratio [IQR], = -37.8 to -15.2] and -29.2% [-37.8% to -19.6%], respectively) and this reduction was significantly higher in non-survivors. Both rectus femoris and diaphragm echo density were significantly increased at day 7, with a significantly higher increase in non-survivors. The change in both rectus femoris and diaphragm size at day 7 was related to the cumulative protein deficit (R = 0.664, P < 0.001 and R = 0.640, P < 0.001, respectively), whereas the change in rectus femoris and diaphragm echo density was related to the cumulative fluid balance (R = 0.734, P < 0.001 and R = 0.646, P < 0.001, respectively).

CONCLUSIONS

Early changes in muscle size and quality seem related to the outcome of critically ill COVID-19 patients, and to be influenced by nutritional and fluid management strategies.

Current developments and future directions in respiratory physiotherapy

Respiratory physiotherapists have a key role within the integrated care continuum of patients with respiratory diseases. The current narrative review highlights the profession's diversity, summarises the current evidence and practice, and addresses future research directions in respiratory physiotherapy. Herein, we describe an overview of the areas that respiratory physiotherapists can act in the integrated care of patients with respiratory diseases based on the Harmonised Education in Respiratory Medicine for European Specialists syllabus. In addition, we highlight areas in which further evidence needs to be gathered to confirm the effectiveness of respiratory therapy techniques. Where appropriate, we made recommendations for clinical practice based on current international guidelines.

Pelvic Floor Considerations in COVID-19

BACKGROUND

Much of the research and clinical commentary on COVID-19 have been focused on respiratory function. Pelvic floor therapists understand that both respiratory dysfunction and hospitalization can have an impact on pelvic floor function. This clinical commentary provides context as to how the long-term effects of COVID-19 could affect the pelvic floor as well as some generalized treatment considerations.

DISCUSSION

The respiratory diaphragm has an impact on the ability of the pelvic floor to contract and relax in a manner that will allow for both continence and elimination. COVID-19 survivors often have disability in this muscle of respiration that can lead to implications for both overactive and underactive pelvic floor. Commonly, this population is hospitalized for long periods of time, which can have long-term consequences on both bladder and bowel functioning including, but not limited to, incontinence, urinary retention, and constipation. Pelvic floor therapists must be prepared to adjust both their evaluation and treatment methods in consideration of this novel treatment population.

CONCLUSIONS

Because of the pervasive nature of this virus, pelvic floor physical therapists should be a part of the rehabilitation team treating these patients once they have become medically stable.Video abstract with sound available at http://links.lww.com/JWHPT/A36.

Ultrasonographic assessment of parasternal intercostal muscles during mechanical ventilation

Although mechanical ventilation is a lifesaving treatment, abundant evidence indicates that its prolonged use (1 week or more) promotes respiratory muscle weakness due to both contractile dysfunction and atrophy. Along with the diaphragm, the intercostal muscles are one of the most important groups of respiratory muscles. In recent years, muscular ultrasound has become a useful bedside tool for the clinician to identify patients with respiratory muscle dysfunction related to critical illness and/or invasive mechanical ventilation. Images obtained over the course of illness can document changes in muscle dimension and can be used to estimate changes in function. Recent evidence suggests the clinical usefulness of ultrasound imaging in the assessment of intercostal muscle function. In this narrative review, we summarize the current literature on ultrasound imaging of the parasternal intercostal muscles as used to assess the extent of muscle activation and muscle weakness and its potential impact during discontinuation of mechanical ventilation. In addition, we proposed a practical flowchart based on recent evidence and experience of our group that can be applied during the weaning phase. This approach integrates multiple predictive parameters of weaning success with respiratory muscle ultrasound.