Comparison of Lung Ultrasound-based Weaning Indices with Rapid Shallow Breathing Index: Are They Helpful?

Diaphragm ultrasound in patients with prolonged weaning from mechanical ventilation

Background

Several publications have examined diaphragmatic ultrasound using two-dimensional (2D) parameters in the context of weaning from mechanical ventilation (MV) and extubation. However, the studied cohorts had rather short duration of ventilation. Examinations on patients with prolonged weaning after long-term ventilation were missing. It was the aim of this study to assess of the diaphragm and peripheral musculature of patients undergoing prolonged weaning creating a chronological sequence of ultrasonic parameters during the course of weaning.

Methods

This study was carried out as a monocentric, prospective observational cross-sectional study. Patients in prolonged weaning who were transferred to a specialized weaning unit were eligible for inclusion if they were ventilated invasively by means of an endotracheal tube or tracheal cannula and if their expected treatment period was at least 5 days. Diaphragmatic function and one representative peripheral muscle were examined in 50 patients between March 2020 and April 2021. The 2D sonographic parameters of diaphragm and diaphragmatic function consisted of diaphragmatic thickness (Tdi) at the end of inspiration and expiration, the fractional thickening (FT) and the diaphragmatic excursion. Additionally, the M. quadriceps femoris was sonographically assessed at two locations. The difference of measurements between the first and the last measuring timepoint were examined using the Wilcoxon signed-rank test. For a longer chronological sequence, the Friedman's rank sum test with subsequent Wilcoxon-Nemenyi-McDonald-Thompson test for multiple comparisons was carried out.

Results

Fifty patients with prolonged weaning were included. The median duration of MV before transfer to the weaning unit was 11.5 [interquartile range (IQR) 10] days. Forty-one patients could be assessed over the full course of weaning, with 38 successfully weaned. Within these 41 patients, the sonographic parameters of the diaphragm slightly increased over the course of weaning indicating an increase in thickness and mobility. Especially parameters which represented an active movement reached statistical significance, i.e., inspiratory Tdi when assessed under spontaneous breathing [begin 3.41 (0.99) vs. end 3.43 (1.31) mm; P=0.01] and diaphragmatic excursion [begin 0.7 (0.8) vs. end 0.9 (0.6) cm; P=0.01]. The presence of positive end-expiratory pressure (PEEP) and pressure support did not influence the sonographic parameters significantly. The M. quadriceps femoris, in contrast, decreased slightly but constantly over the time [lower third: begin 1.36 (0.48) vs. end 1.28 (0.36) cm; P=0.054].

Conclusions

The present study is the first one to longitudinally analyse diaphragmatic ultrasound in patients with prolonged weaning. Sonographic assessment showed that Tdi and excursion increased over the course of prolonged weaning, while the diameter of a representative peripheral muscle decreased. However, the changes are rather small, and data show a wide dispersion. To allow a potential, standardized use of diaphragm ultrasound for diagnostic decision support in prolonged weaning, further studies in this specific patient group are required.

Accuracy of respiratory muscle assessments to predict weaning outcomes: a systematic review and comparative meta-analysis

BACKGROUND

Several bedside assessments are used to evaluate respiratory muscle function and to predict weaning from mechanical ventilation in patients on the intensive care unit. It remains unclear which assessments perform best in predicting weaning success. The primary aim of this systematic review and meta-analysis was to summarize and compare the accuracy of the following assessments to predict weaning success: maximal inspiratory (PImax) and expiratory pressures, diaphragm thickening fraction and excursion (DTF and DE), end-expiratory (Tdiee) and end-inspiratory (Tdiei) diaphragm thickness, airway occlusion pressure (P0.1), electrical activity of respiratory muscles, and volitional and non-volitional assessments of transdiaphragmatic and airway opening pressures.

METHODS

Medline (via Pubmed), EMBASE, Web of Science, Cochrane Library and CINAHL were comprehensively searched from inception to 04/05/2023. Studies including adult mechanically ventilated patients reporting data on predictive accuracy were included. Hierarchical summary receiver operating characteristic (HSROC) models were used to estimate the SROC curves of each assessment method. Meta-regression was used to compare SROC curves. Sensitivity analyses were conducted by excluding studies with high risk of bias, as assessed with QUADAS-2. Direct comparisons were performed using studies comparing each pair of assessments within the same sample of patients.

RESULTS

Ninety-four studies were identified of which 88 studies (n = 6296) reporting on either PImax, DTF, DE, Tdiee, Tdiei and P0.1 were included in the meta-analyses. The sensitivity to predict weaning success was 63% (95% CI 47-77%) for PImax, 75% (95% CI 67-82%) for DE, 77% (95% CI 61-87%) for DTF, 74% (95% CI 40-93%) for P0.1, 69% (95% CI 13-97%) for Tdiei, 37% (95% CI 13-70%) for Tdiee, at fixed 80% specificity. Accuracy of DE and DTF to predict weaning success was significantly higher when compared to PImax (p = 0.04 and p < 0.01, respectively). Sensitivity and direct comparisons analyses showed that the accuracy of DTF to predict weaning success was significantly higher when compared to DE (p < 0.01).

CONCLUSIONS

DTF and DE are superior to PImax and DTF seems to have the highest accuracy among all included respiratory muscle assessments for predicting weaning success. Further studies aiming at identifying the optimal threshold of DTF to predict weaning success are warranted.

TRIAL REGISTRATION

PROSPERO CRD42020209295, October 15, 2020.

Prediction of Successful Spontaneous Breathing Trial and Extubation of Trachea by Lung Ultrasound in Mechanically Ventilated Patients in Intensive Care Unit

Introduction

Spontaneous breathing trial (SBT) is always successful in mechanically ventilated patients. This study was conducted to assess the prediction of successful SBT and extubation of trachea by bedside lung ultrasound in mechanically ventilated patients.

Methodology

This was a prospective observational study for 1 year conducted at a tertiary teaching hospital ICU on 102 patients with age more than 18 years and who were mechanically ventilated for more than 24 hours. Bedside lung ultrasound was used to assess the lung ultrasound score (LUS) and lung profiles in patients who clinically met the criteria for SBT. The LUS at the beginning of SBT and 30 minutes after SBT were used to predict the successful SBT and tracheal extubation.

Result

Spontaneous breathing trial and tracheal extubation were successful in 73 (71.6%) and 57 (55.8%) of the patients. The AUC for lung ultrasound in predicting successful SBT at the beginning and 30 minutes of SBT were 0.781 (CI 95% 0.674-0.888, p < 0.001) and 0.841 (CI 95% 0.742-0.941, p < 0.001) with a cut-off value of 17.5 and 19.5, respectively. Similarly, AUC for LUS in relation to tracheal extubation was 0.786 (CI 95% 0.694-0.879, p < 0.001) and 0.841(CI 95% 0.756-0.925, p < 0.001) at 0 and 30 minutes. About 57.5% of the patients with A profiles tolerated successful SBT while 48.3% of the patients having C profile had failed SBT (p < 0.001). COPD, lung ultrasound, higher SOFA score, and longer duration of mechanical ventilation had a statistically significant negative correlation with successful SBT.

Conclusion

Lower LUS and A profiles lung ultrasound are associated with more successful weaning and tracheal extubation in mechanically ventilated patients.

How to cite this article

Rajbanshi LK, Bajracharya A, Devkota D. Prediction of Successful Spontaneous Breathing Trial and Extubation of Trachea by Lung Ultrasound in Mechanically Ventilated Patients in Intensive Care Unit. Indian J Crit Care Med 2023;27(7):482-487.

Update on Lean Body Mass Diagnostic Assessment in Critical Illness

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

Nivolumab-induced Diaphragm Dysfunction: A Case Report

Nivolumab is increasingly used in the treatment of melanoma. However, its use is associated with potentially severe side effects and every organ system can be affected. A case is presented where nivolumab therapy resulted in severe diaphragm dysfunction. With nivolumab's increased use, these types of complications may become more common and every clinician should be alerted to its potential presence when a patient on nivolumab treatment presents with dyspnea. Ultrasound is a readily available method to assess for diaphragm dysfunction.

How to cite this article

Schouwenburg JJ. Nivolumab-induced Diaphragm Dysfunction: A Case Report. Indian J Crit Care Med 2023;27(2):147-148.

Methodological and Clinimetric Evaluation of Inspiratory Respiratory Muscle Ultrasound in the Critical Care Setting: A Systematic Review and Meta-Analysis

OBJECTIVE

Significant variations exist in the use of respiratory muscle ultrasound in intensive care with no society-level consensus on the optimal methodology. This systematic review aims to evaluate, synthesize, and compare the clinimetric properties of different image acquisition and analysis methodologies.

DATA SOURCES

Systematic search of five databases up to November 24, 2021.

STUDY SELECTION

Studies were included if they enrolled at least 50 adult ICU patients, reported respiratory muscle (diaphragm or intercostal) ultrasound measuring either echotexture, muscle thickness, thickening fraction, or excursion, and evaluated at least one clinimetric property. Two independent reviewers assessed titles, abstracts, and full text against eligibility.

DATA EXTRACTION

Study demographics, ultrasound methodologies, and clinimetric data.

DATA SYNTHESIS

Sixty studies, including 5,025 patients, were included with 39 studies contributing to meta-analyses. Most commonly measured was diaphragm thickness (DT) or diaphragm thickening fraction (DTF) using a linear transducer in B-mode, or diaphragm excursion (DE) using a curvilinear transducer in M-mode. There are significant variations in imaging methodology and acquisition across all studies. Inter- and intrarater measurement reliabilities were generally excellent, with the highest reliability reported for DT (ICC, 0.98; 95% CI, 0.94-0.99). Pooled data demonstrated acceptable to excellent accuracy for DT, DTF, and DE to predicting weaning outcome after 48 to 72 hours postextubation (DTF AUC, 0.79; 95% CI, 0.73-0.85). DT imaging was responsive to change over time. Only three eligible studies were available for intercostal muscles. Intercostal thickening fraction was shown to have excellent accuracy of predicting weaning outcome after 48-hour postextubation (AUC, 0.84; 95% CI, 0.78-0.91).

CONCLUSIONS

Diaphragm muscle ultrasound is reliable, valid, and responsive in ICU patients, but significant variation exists in the imaging acquisition and analysis methodologies. Future work should focus on developing standardized protocols for ultrasound imaging and consider further research into the role of intercostal muscle imaging.

Author\'s Response to Diaphragm Evaluation and Lung Ultrasound Score during Weaning

How to cite this article: Amara V, Chaudhuri S. Author's Response to Diaphragm Evaluation and Lung Ultrasound Score during Weaning. Indian J Crit Care Med 2022;26(9):1056–1057.

The role of diaphragmatic thickness measurement in weaning prediction and its comparison with rapid shallow breathing index: a single-center experience

Background: Acute respiratory failure (ARF) is commonly managed with invasive mechanical ventilation (IMV). The majority of the time that a patient spends on IMV is in the process of weaning. Prediction of the weaning outcome is of paramount importance, as untimely/delayed extubation is associated with a high risk of mortality. Diaphragmatic ultrasonography is a promising tool in the intensive care unit, and its utility in predicting the success of weaning remains understudied.Methods: In this prospective-observational study, we recruited 54 ARF patients on IMV, along with 50 healthy controls. During a spontaneous breathing trial, all subjects underwent diaphragmatic ultrasonography along with a rapid shallow breathing index (RSBI) assessment.Results: The mean age was 41.8±17.0 and 37.6±10.5 years among the cases and control group, respectively. Demographic variables were broadly similar in the two groups. The most common cause of ARF was obstructive airway disease. The average duration of IMV was 5.41±2.81 days. Out of 54 subjects, 45 were successfully weaned, while nine patients failed weaning. Age, body mass index, and severity of disease were similar in the successful and failed weaning patients. The sensitivity in predicting successful weaning of percent change in diaphragmatic thickness (Δtdi%) >29.71% was high (93.33%), while specificity was 66.67%. The sensitivity and specificity of mean diaphragmatic thickness (tdi) end-expiratory >0.178 cm was 60.00% and 77.78%, respectively. RSBI at 1 minute of <93.75 had an equally high sensitivity (93.33%) but a lower specificity (22.22%). Similar results were also found for RSBI measured at 5 minutes.Conclusions: During the weaning assessment, the purpose is to minimize both premature as well as delayed extubation. We found that diaphragmatic ultrasonography, in particular Δtdi%, is better than RSBI in predicting weaning outcomes.

Diaphragmatic ultrasound in weaning ventilated patients: a reliable predictor?

Timely weaning of mechanical ventilation is clinically difficult, as both early and late discontinuations are associated with adverse events impeding the patient's favorable course in the critical care unit. Many parameters aid in judging whether the patient is going to be safely extubated; however, some remain deficient. We herein describe diaphragmatic ultrasound as a new modality for this purpose, detailing diaphragm excursion and thickness as means of it.

Utility of the One-time HACOR Score as a Predictor of Weaning Failure from Mechanical Ventilation: A Prospective Observational Study

Aim

To determine the utility of the HACOR score in predicting weaning failure in resource-limited settings.

Objectives

The primary objective was to determine a cut-off value of the HACOR score, sensitivity, and specificity to predict failed weaning. The secondary objective was to determine which out of five components of the score was significantly different between the successful weaning and the failed weaning groups.

Introduction

Most weaning indices are either inaccurate or are dependent on complex ventilatory parameters, which are difficult to measure in resource-limited settings. This study aimed to determine the utility of the HACOR score consisting of heart rate, acidosis, consciousness level, oxygenation, and respiratory rate as a predictor of weaning in the intensive care unit.

Materials and methods

It was a prospective observational study on 120 patients between 18 and 90 years. The HACOR score was evaluated at 30 minutes of spontaneous breathing trial (SBT). The total duration of SBT was 120 minutes.

Results

Out of 120 patients, 83 (69.2%) had successful weaning, whereas 37 (30.8%) had weaning failure. The median and interquartile range (IQR) of the HACOR score in the successful weaning group was 2 (0–3) and 6 (5–8) in the failed weaning group (p-value <0.001). There was a significant difference in each of the five components of the HACOR score between the successful and failed weaning groups (p <0.05). HACOR score ≥5 predicted failed weaning, sensitivity 83.8%, specificity 96.4%, area under the curve (AUC) 0.950, and 95% confidence interval (CI) [0.907–0.993], p <0.001. Multivariable logistic regression analysis showed that HACOR score ≥5 is an independent predictor of weaning failure [p <0.001, 95% CI (1.9–4.2), adjusted odds ratio 2.82].

Conclusion

A HACOR score ≥5 is an excellent predictor of weaning failure. This score may be useful as a weaning strategy in the intensive care unit.

How to cite this article

Chaudhuri S, Gupta N, Adhikari SD, Todur P, Maddani SS, Rao S. Utility of the One-time HACOR Score as a Predictor of Weaning Failure from Mechanical Ventilation: A Prospective Observational Study. Indian J Crit Care Med 2022;26(8):900–905.

Ethical approval

Prior to the commencement of the study, Institutional Ethics Committee permission was obtained (IEC: 197/2021) and Clinical Trial Registry of India (CTRI) registration was done before recruitment (CTRI/2021/07/035139). We obtained written informed consent from the legally authorized representative prior to recruiting patients for the study.

Evaluation of Abdominal Expiratory Muscle Thickness Pattern, Diaphragmatic Excursion, and Lung Ultrasound Score in Critically Ill Patients and Their Association with Weaning Patterns: A Prospective Observational Study

Introduction

The expiratory muscles are an indispensable component of respiratory function in critically ill patients, yet is often overlooked. We evaluated the association of abdominal expiratory muscles thickness pattern with weaning.

Materials and methods

This was a single-center, prospective observational study done on 81 adult mechanically ventilated patients who underwent the weaning process.

Results

Sixteen patients had simple weaning and 65 patients had either difficult or prolonged weaning. The mean and standard deviation (SD) of the thickness of expiratory abdominal muscles—rectus abdominis (RA), internal oblique (IO), external oblique (EO), and transversus abdominis (TA) were significantly more in patients with simple weaning than those with difficult or prolonged weaning. The receiver operating curve (ROC) of expiratory muscles showed RA, IO, EO, TA cut-offs 0.638, 0.492, 0.315, and 0.253 cm, respectively, to predict simple weaning. The pattern of expiratory muscle thickness RA > IO > EO > TA was maintained in both simple and difficult/prolonged weaning groups (p = 0.362). The ROC of diaphragmatic excursion (DE) for predicting simple weaning had cut-off 1.79 cm. The lung ultrasound score (LUS) was 5.75 ± 3.32 in the simple weaning group, compared to 9.71 ± 5.18 in the difficult/prolonged weaning group (p = 0.005).

Conclusion

Abdominal expiratory muscles were significantly thicker in patients with simple weaning compared to those with difficult or prolonged weaning. The pattern of expiratory muscle thickness followed the pattern of RA > IO > EO > TA in both simple weaning and difficult or prolonged weaning groups. DE >1.79 cm predicted simple weaning and LUS was significantly lesser in patients with simple weaning (CTRI/2020/11/028895).

How to cite this article

Amara V, Vishwas P, Maddani SS, Natarajan S, Chaudhuri S. Evaluation of Abdominal Expiratory Muscle Thickness Pattern, Diaphragmatic Excursion, and Lung Ultrasound Score in Critically Ill Patients and Their Association with Weaning Patterns: A Prospective Observational Study. Indian J Crit Care Med 2022;26(3):307–313.

Ultrasound Protocols to Assess Skeletal and Diaphragmatic Muscle in People Who Are Critically Ill: A Systematic Review

This study aims to review published studies that use protocols and ultrasound measurements to evaluate skeletal and diaphragmatic muscles in patients who are critically ill. We searched for references on databases through September 2020 and included in our systematic review studies that used muscular ultrasound to assess skeletal or diaphragm muscles in patients who are critically ill. Seventy-six studies were included, 32 (1720 patients) using skeletal-muscle ultrasound and 44 (2946 patients) using diaphragmatic-muscle ultrasound, with a total of 4666 patients. The population is predominantly adult men. As for designs, most studies (n = 62) were cohort studies. B-mode B was dominant in the evaluations. Medium-to-high frequency bands were used in the analysis of peripheral muscles and medium-to-low frequency bands for diaphragmatic muscles. Evaluation of the echogenicity, muscle thickness and pennation angle of the muscle was also reported. These variables are important in the composition of the diagnosis of muscle loss. Studies demonstrate great variability in their protocols, and sparse description of the important variables that can directly interfere with the quality and validity of these measures. Therefore, a document is needed that standardizes these parameters for ultrasound assessment in patients who are critically ill.

Speckle tracking ultrasonography as a new tool to assess diaphragmatic function: a feasibility study

A reliable method of measuring diaphragmatic function at the bedside is still lacking. Widely used two-dimensional (2D) ultrasonographic measurements, such as diaphragm excursion, diaphragm thickness, and fractional thickening (FT) have failed to show clear correlations with diaphragmatic function. A reason for this is that 2D ultrasonographic measurements, like FT, are merely able to measure the deformation of muscular diaphragmatic tissue in the transverse direction, while longitudinal measurements in the direction of contracting muscle fibres are not possible. Speckle tracking ultrasonography, which is widely used in cardiac imaging, overcomes this disadvantage and allows observations of movement in the direction of the contracting muscle fibres, approximating muscle deformation and the deformation velocity. Several studies have evaluated speckle tracking as a promising method to assess diaphragm contractility in healthy subjects. This technical note demonstrates the feasibility of speckle tracking ultrasonography of the diaphragm in a group of 20 patients after an aortocoronary bypass graft procedure. The results presented herein suggest that speckle tracking ultrasonography is able to depict alterations in diaphragmatic function after surgery better than 2D ultrasonographic measurements.

Correlation of Oxygenation and Radiographic Assessment of Lung Edema (RALE) Score to Lung Ultrasound Score (LUS) in Acute Respiratory Distress Syndrome (ARDS) Patients in the Intensive Care Unit

Background

Lung ultrasound score (LUS) as well as radiographic assessment of lung edema (RALE) score as calculated from chest radiography (CXR) have been applied to assess Acute Respiratory Distress Syndrome (ARDS) severity. CXRs, which are frequently performed in ARDS patients, pose a greater risk of radiation exposure to patients and health care staff.

Aims and objectives

The aim of the study was to evaluate if LUS had a better correlation to oxygenation (PaO₂/FiO₂) compared with the RALE score in ARDS patients. We also aimed to analyse if there was a correlation between RALE score and LUS. We wanted to determine the LUS and RALE score cut-off, which could predict a prolonged length of intensive care unit (ICU) stay (≥10 days) and survival.

Methods

Thirty-seven patients aged above 18 years with ARDS as per Berlin definition and admitted to the ICU were included in the study. It was a retrospective study done over a period of 11 months. On the day of admission to ICU, the global and basal LUS, global and basal RALE score, and PaO₂ /FiO₂ were recorded. Outcome and days of ICU stay were noted.

Results

Global LUS score and PaO₂/FiO₂ showed the best negative correlation (r = –0.491), which was significant (p = 0.002), followed by global RALE score and PaO₂/FiO₂ (r = –0.422, p = 0.009). Basal LUS and PaO₂/FiO₂ also had moderate negative correlation (r = –0.334, p = 0.043) followed by basal RALE score and PaO₂/FiO₂ (r = –0.34, p = 0.039). Global RALE score and global LUS did not show a significant correlation. Similarly, there was no significant correlation between basal RALE score and basal LUS. Global and basal LUS as well as global and basal RALE score were not beneficial in predicting either a prolonged length of ICU stay or survival as the area under curve was low.

Conclusion

In ARDS patients, global LUS had the best correlation to oxygenation (PaO₂/FiO₂), followed by global RALE score. Basal LUS and basal RALE score also had moderate correlation to oxygenation. However, there was no significant correlation between global LUS and global RALE score as well as between basal LUS and basal RALE score. Global and basal LUS as well as global and basal RALE scores were not able to predict a prolonged ICU stay or survival in ARDS patients.

Diagnostic accuracy of diaphragm ultrasound to predict weaning outcome: A systematic review and meta-analysis

BACKGROUND

The accuracy of diaphragm ultrasound for predicting weaning outcome is still debated, despite the publication of numerous studies evaluating this issue.

OBJECTIVE

The aim of this systematic review and meta-analysis was to assess the diagnostic accuracy of diaphragm ultrasound for predicting weaning failure in critically ill patients.

DESIGN AND DATA SOURCES

MEDLINE, Science direct, Cochrane Library, EMBASE and CENTRAL were searched. Two investigators independently selected studies that met the inclusion criteria, and three extracted data and performed a bias analysis using the Quality Assessment of Diagnostic Accuracy Studies-2 instrument. A bivariate model was used to estimate the pooled results for sensitivity, specificity and diagnostic odds ratio. Sources of heterogeneity were explored, and subgroup analyses were performed.

RESULTS

Twenty-eight studies were included in the systematic review, from which 16 studies (816 patients in total) were included in the meta-analysis. The pooled sensitivity, specificity and area under the summary receiver operator characteristic curve were 0.70 (95% CI 0.57-0.80), 0.84 (95% CI 0.73-0.91), and 0.82 (95% Cl 0.78-0.85) for diaphragm thickening fraction, respectively, and 0.71 (95% CI 0.61-0.79), 0.80 (95% CI 0.73-0.86), and 0.82 (95% Cl 0.79-0.86) for diaphragm excursion, respectively. There was substantial heterogeneity among the studies. Meta-regression highlighted significant effects of prevalence of extubation failure, cut-off and risk of bias in flow and timing of the study on diaphragm ultrasound accuracy. By excluding outlier and influential studies, sensitivity was lower and specificity higher for diaphragm thickening fraction.

CONCLUSION

The specificity of diaphragm ultrasound for predicting the risk of extubation failure in critically ill patients was moderate-to-high. However, sensitivity was low because weaning is also affected by non-diaphragm-related factors. Further research in subgroups of critically ill patients applying a homogeneous definition of weaning and uniformly conducted measure is needed to assess the accuracy of diaphragm ultrasound.

CLINICAL TRIAL REGISTRATION

Registered on http://www.crd.york.ac.uk/PROSPERO as CRD42017058028. Tweetable abstract: Diaphragm ultrasound predicts extubation failure with high specificity. Absence of diaphragm dysfunction does not imply no risk of extubation failure.

Use of Ultrasound to Determine Changes in Diaphragm Mechanics During A Spontaneous Breathing Trial

OBJECTIVE

Assess change in ultrasound measures of diaphragm mechanics over the course of a 30-minute spontaneous breathing trial (SBT).

DESIGN

Prospective observational study.

SETTING

Single intensive care unit (Logan Hospital, Queensland, Australia), patients recruited from August 2016 to April 2018.

PARTICIPANTS

Eligible patients were over the age of 18 years, ventilated for >24 hours, and planned to undergo an SBT. In total, 129 patients were screened.

MAIN OUTCOME MEASURES

Ultrasound measures taken at 5 and 30 minutes during SBT: diaphragmatic excursion (DE), diaphragmatic thickening fraction (DTF), and diaphragmatic contraction speed (DCS). Diaphragmatic rapid shallow breathing index (DRSBI) was calculated using DE/respiratory rate. The presence of diaphragmatic dysfunction (DD) was also determined using DTF < 30%, DE < 11 mm, or DRSBI > 1.6.

RESULTS

Eighteen patients had ultrasound measures during an SBT. Four were unable to have DTF visualized. There was no significant change in DTF (n = 14, 32.41 ± 32.21 vs 23.19 ± 17.42, P = .33) or DE (n = 18, 1.72 ± 0.63 vs 1.66 ± 0.59, P = .63) over time. Diaphragmatic contraction speed increased over time (n = 18, 2.21 ± 1.25 vs 2.67 ± 1.61, P = .007). Diaphragmatic rapid shallow breathing index worsened over time (n = 18, 1.65 ± 1.02 vs 2.08 ± 1.51, P = .03). There was no significant change in the presence of DD. Diaphragmatic dysfunction by DTF 8/14 versus 10/14, by DE 4/18 versus 3/18, and by DRSBI 7/18 versus 9/18. No patients failed SBT and one patient failed extubation.

CONCLUSIONS

Diaphragmatic mechanics may change over the course of an SBT. Further research is required to determine the clinical implications of these changes and the optimal timing of diaphragmatic ultrasound to predict weaning outcome. Diaphragmatic ultrasound may be less feasible than the published data suggest.

[Usefulness of diaphragmatic ultrasound in predicting extubation success]

OBJECTIVE

To evaluate the diagnostic accuracy of diaphragmatic ultrasound in predicting extubation success.

DESIGN

A diagnostic accuracy study was carried out.

SCOPE

Intensive Care Unit of an Academic hospital in the city of Bogotá (Colombia).

PATIENTS OR PARTICIPANTS

A consecutive sample of patients >18 years of age subjected to invasive mechanical ventilation for >48h.

INTERVENTIONS

Diaphragmatic ultrasound evaluation at the end of spontaneous ventilation testing.

MAIN VARIABLES OF INTEREST

Diaphragmatic excursion (DE, cm), inspiration time (TPIA_dia, s), diaphragm contraction speed (DE/TPIA_dia, cm/s) and total time (Ttot, s) were evaluated, together with thickening fraction (TF_di, %).

RESULTS

A total of 84 patients were included, 79.8% (n=67) with successful extubation and 20.2% (n=17) with failed extubation. The variable with the best discriminatory capacity in predicting extubation success was diaphragm contraction speed, with AUC-ROC 0.70 (p=0.008).

CONCLUSIONS

Diaphragm contraction speed exhibited acceptable discriminatory capacity. Ultrasound could be part of a multifactorial approach in the extubation process.

The spontaneous breathing trial is of low predictive value regarding spontaneous breathing ability in subjects with prolonged, unsuccessful weaning

Background

The spontaneous breathing trial (SBT) is a well-established diagnostic test for predicting extubation failure in intubated intensive care unit (ICU) patients. However, the SBT has not been evaluated in a specific cohort of tracheostomized patients in whom weaning is prolonged and ultimately unsuccessful.

Objective

The aim of the trial was to investigate the relevance of SBT failure criteria in chronic respiratory failure subjects undergoing long-term invasive home mechanical ventilation following tracheostomy and weaning failure.

Methods

Measurement of all established failure criteria including pneumotachygraphical assessment of the rapid shallow breathing index (RSBI) took place during an SBT. The decision to continue spontaneous breathing was based on failure criteria as well as the subjective willingness of the patient.

Results

Fifteen subjects with a median age of 58 years (interquartile range [IQR] 44–74) were studied; 10 with COPD, 4 with neuromuscular diseases and 1 with both. Twelve subjects met the SBT failure criteria within 30 min, but one third of these subjects were still able to continue with spontaneous breathing. In contrast, 3 subjects could not be weaned despite the SBT being successful. An increased RSBI was the most frequently observed SBT failure criterion (57% of all SBT). However, the SBT varied substantially in individual subjects who were able to sustain spontaneous breathing, despite having reached the cut-off for SBT failure.

Conclusion

The SBT was of low predictive value regarding spontaneous breathing ability in chronic respiratory failure subjects with prolonged, unsuccessful weaning.

A narrative review of diaphragm ultrasound to predict weaning from mechanical ventilation: where are we and where are we heading?

Background

The use of ultrasound to visualize the diaphragm is well established. Over the last 15 years, certain indices of diaphragm function, namely diaphragm thickness, thickening fraction and excursion have been established for mechanically ventilated patients to track changes in diaphragm size and function over time, to assess and diagnose diaphragmatic dysfunction, and to evaluate if these indices can predict successful liberation from mechanical ventilation. In the last 2 years, three meta-analyses and a systematic review have assessed the usability of diaphragmatic ultrasound to predict successful weaning. Since then, further data have been published on the topic.

Conclusions

The aim of this narrative review is to briefly describe the common methods of diaphragmatic function assessment using ultrasound techniques, before summarizing the major points raised by the recent reviews. A narrative summary of the most recent data will be presented, before concluding with a brief discussion of future research directions in this field.