Ultrasonographic Evaluation of Liver/Spleen Movements and Extubation Outcome

Establishment of a prediction model for extubation failure risk in ICU patients using bedside ultrasound technology

BACKGROUND

Mechanical ventilation (MV) is crucial for managing critically ill patients; however, extubation failure, associated with adverse outcomes, continues to pose a significant challenge.

OBJECTIVE

The purpose of this prospective observational study was to develop and validate a predictive numerical model utilizing bedside ultrasound to forecast extubation outcomes in ICU patients.

METHODS

We enrolled 300 patients undergoing MV, from whom clinical variables, biomarkers, and ultrasound parameters were collected. Patients were randomly assigned to two groups at a 6:4 ratio: the derivation cohort (n = 180) and the validation cohort (n = 120). A nomogram prediction model was developed using significant predictors identified through multivariate analysis and its performance was assessed and validated by evaluating its discrimination, calibration, and clinical utility.

RESULTS

A total of 300 patients (mean age 72 years; 57.3 % male) were included, with an extubation failure rate of 26.7 %. The model, including diaphragm thickening fraction (OR: 0.890, P = 0.009), modified lung ultrasound score (OR: 1.371, P < 0.001), peak relaxation velocity (OR: 1.515, P = 0.015), and APACHE II (OR: 1.181, P = 0.006), demonstrated substantial discriminative capability, as indicated by an area under the receiver operating characteristic curve (AUC) of 0.886 (95 % CI: 0.830-0.942) for the derivation cohort and 0.846 (95 % CI: 0.827-0.945) for the validation cohort. Hosmer-Lemeshow tests yielded P-values of 0.224 and 0.212 for the derivation and validation cohorts.

CONCLUSIONS

We have established a risk prediction model for extubation failure in mechanically ventilated ICU patients. This risk model base on bedside ultrasound parameters provides valuable insights for identifying high-risk patients and preventing extubation failure.

Assessment of Diaphragmatic Dysfunction in Mechanically Ventilated Patients with Ultrasonography

INTRODUCTION

The reliability of the diaphragm thickening fraction in predicting weaning failure in mechanically ventilated patients in the intensive care unit (ICU), as well as the relationship between the patients' diaphragmatic inspiratory excursion and diaphragmatic thickness.

MATERIALS AND METHODS

Fifty mechanically ventilated patients participated in this hospital-based cross-sectional prospective study in a tertiary care teaching hospital. Patients who had been on a mechanical ventilator for at least 7 days and whose legal guardian was willing to provide consent were also included in the research. People with hemodynamic instability and those whose legal guardians were reluctant to comply were excluded.

RESULTS

Using diaphragmatic thickening fraction as a diagnostic criterion, the weaning failure group consisted of 24 patients, out of which we predicted diaphragmatic dysfunction (DD) in 19 patients. The weaning success group consisted of 26 patients, of which we predicted no DD in 21 patients. Weaning success or failure was predicted by diaphragmatic thickening fraction with a sensitivity of 79.16% and a specificity of 80.76%, diaphragm excursion with a sensitivity of 70.8% and an 80.7%, and diaphragmatic thickness with a sensitivity of 66.66% and a specificity of 73.91%, respectively.

CONCLUSION

Diagnosing DD in mechanically ventilated, figuring out if extubation would be effective or not, monitoring respiratory effort, and assessing atrophy in ICU patients, ultrasonography may be an effective and accurate technique for mechanical ventilation patients, and it provides a convenient, noninvasive, affordable, and secure way to assess DD.

Operator independent continuous ultrasound monitoring of diaphragm excursion predicts successful weaning from mechanical ventilation: a prospective observational study

BACKGROUND

In mechanically ventilated patients, diaphragm ultrasound can identify diaphragm weakness and predict weaning failure. We evaluated whether a novel operator-independent ultrasound-based medical device allowing continuous monitoring of the diaphragm (CUSdi) could reliably (1) measure diaphragm excursion (EXdi) and peak contraction velocity (PCVdi), (2) predict weaning outcome, and (3) approximate transdiaphragmatic pressure (Pdi).

METHODS

In 49 mechanically ventilated patients, CUSdi was recorded during a 30-min spontaneous breathing trial (SBT), and EXdi and PCVdi were measured. In subgroups of patients, standard ultrasound measurement of EXdi and PCVdi was performed (n = 36), and Pdi derived parameters (peak and pressure time product, n = 30) were measured simultaneously.

RESULTS

The agreement bias between standard ultrasound and CUSdi for EXdi was 0.1 cm (95% confidence interval -0.7-0.9 cm). The regression of Passing-Bablok indicated a lack of systematic difference between EXdi measured with standard ultrasound and CUSdi, which were positively correlated (Rho = 0.84, p < 0.001). Weaning failure was observed in 54% of patients. One, two and three minutes after the onset of the SBT, EXdi was higher in the weaning success group than in the failure group. Two minutes after the onset of the SBT, an EXdi < 1.1 cm predicted weaning failure with a sensitivity of 0.83, a specificity of 0.68, a positive predictive value of 0.76, and a negative predictive value of 0.24. There was a weak correlation between EXdi and both peak Pdi (r = 0.22, 95% confidence interval 0.15 - 0.28) and pressure time product (r = 0.13, 95% confidence interval 0.06 - 0.20). Similar results were observed with PCVdi.

CONCLUSIONS

Operator-independent continuous diaphragm monitoring quantifies EXdi reliably and can predict weaning failure with an identified cut-off value of 1.1 cm. Trial registration clinicaltrial.gov, NCT04008875 (submitted 12 April 2019, posted 5 July 2019) and NCT03896048 (submitted 27 March 2019, posted 29 March 2019).

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.

Temporal evolution of diaphragm thickness and diaphragm excursion among subjects hospitalized with COVID-19: A prospective observational study

BACKGROUND

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has an affinity for the angiotensin-converting enzyme 2 (ACE2) receptors, which are present abundantly on the diaphragm. This study aims to describe temporal changes in diaphragmatic thickness and excursion using ultrasonography in subjects with acute COVID-19.

METHODS

This prospective observational study included adults hospitalized with COVID-19 in the past 48 hours. The diaphragm thickness at end-expiration (DTE), diaphragm thickening fraction (DTF), and diaphragm excursion during tidal breathing (DE) and maximal inspiration (DEmax) were measured using ultrasonography daily for 5 days. The changes in DTE, DTF, DE, and Demax from day 1 to day 5 were assessed.

RESULTS

This study included 64 adults (62.5% male) with a mean (SD) age of 50.2 (17.5) years. A majority (91%) of the participants had mild or moderate illness. The median (IQR) DTE, DTF (%), DE and Demax on day 1 were 2.2 (1.9, 3.0) mm, 21.5% (14.2, 31.0), 19.2 (16.5, 24.0) mm, and 26.7 (22.0, 30.2) mm, respectively. On day 5, there was a significant reduction in the DTE (p=0.002) with a median (IQR) percentage change of -15.7% (-21.0, 0.0). The DTF significantly increased on day 5 with a median (IQR) percentage change of 25.0% (-19.2, 98.4), p=0.03. There was no significant change in DE and Demax from day 1 to day 5, with a median (IQR) percentage change of 3.6% (-5.2, 15) and 0% (-6.7, 5.9), respectively.

CONCLUSIONS

Non-intubated patients with COVID-19 exhibited a temporal decline in diaphragm thickness with increase in thickening fraction over 5 days of hospital admission. Further research is warranted to assess the impact of COVID-19 pneumonia on diaphragmatic function.

The effects of external diaphragmatic pacing on diaphragm function and weaning outcomes of critically ill patients with mechanical ventilation: a prospective randomized study

BACKGROUND

Diaphragmatic pacing can improve diaphragm function, which is beneficial for the prognosis of patients treated with prolonged mechanical ventilation (MV). While most previous studies have focused on the role of implanted diaphragm pacing (IDP), our study is the first to examine the effects of external diaphragmatic pacing (EDP) in mechanically ventilated patients. Specifically, the effect of EDP on diaphragm function, the success rate of weaning, the duration of MV (DMV), and the intensive care unit (ICU) length of stay (ILOS) were assessed.

METHODS

From September 2019 to December 2020, a total of 51 mechanically ventilated patients in the ICU of the Sun Yat-sen Memorial Hospital, Sun Yat-sen University were enrolled and randomly divided into an EDP group of 27 patients and a control group of 24 patients. The control group received routine treatment, and the EDP group received EDP treatment in addition to routine treatment. The diaphragm excursion (DE), diaphragm thickening fraction (DTF), DMV, ILOS, and average survival time were recorded to evaluate efficacy.

RESULTS

Patients treated with EDP had increased DE [exp(B) =1.86, 95% CI: 1.39 to 2.50, P<0.001] and DTF [exp(B) =1.35, 95% CI: 1.05 to 1.76, P=0.022], shortened weaning time (P=0.026) and prolonged average survival time (P<0.001) compared to patients who did not receive EDP therapy. Especially in cases with difficult weaning, the improvement of DE and DTF in the EDP treatment group was more obvious than that in the control group (P=0.013 and P=0.032). Moreover, the DTF upon attempted spontaneous breathing trial (SBT) was negatively correlated with the fraction of inspired oxygen (FiO2) [r=-0.54; 95% confidence interval (CI): -0.77 to -0.19; P=0.004], the arterial partial pressure of oxygen (PaO2) (r=-0.58; 95% CI: -0.79 to -0.25; P=0.001), the PaO2/FiO2 ratio (r=-0.52; 95% CI: -0.75 to -0.16; P=0.006), and the serum lactate concentration (Lac) (r=-0.39; 95% CI: -0.68 to 0.003; P=0.046).

CONCLUSIONS

EDP treatment can effectively reduce the DMV and prolong the average survival time of mechanically ventilated patients.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR1900024096.

Diaphragmatic ultrasonography-based rapid shallow breathing index for predicting weaning outcome during a pressure support ventilation spontaneous breathing trial

Background

The optimum timing to wean is crucial to avoid negative outcomes for mechanically ventilated patients. The rapid shallow breathing index (RSBI), a widely used weaning index, has limitations in predicting weaning outcomes. By replacing the tidal volume of the RSBI with diaphragmatic excursion (DE) and diaphragm thickening fraction (DTF) assessed by ultrasonography, we calculated two weaning indices, the diaphragmatic excursion rapid shallow breathing index (DE-RSBI, respiratory rate [RR]/DE) and the diaphragm thickening fraction rapid shallow breathing index (DTF-RSBI, RR/DTF). The aim of this study was to evaluate the predictive values of DTF-RSBI, DE-RSBI and traditional RSBI in weaning failure.

Methods

This prospective observational study included patients undergoing mechanical ventilation (MV) for > 48 h and who were readied for weaning. During a pressure support ventilation (PSV) spontaneous breathing trial (SBT), right hemidiaphragmatic excursion and DTF were measured by bedside ultrasonography as well as RSBI. Weaning failure was defined as: (1) failing the SBT and (2) SBT success but inability to maintain spontaneous breathing for more than 48 h without noninvasive or invasive ventilation. A receiver operator characteristic (ROC) curve was used for analyzing the diagnostic accuracy of RSBI, DE-RSBI, and DTF-RSBI.

Results

Of the 110 patients studied, 37 patients (33.6%) failed weaning. The area under the ROC (AUROC) curves for RSBI, DE-RSBI, and DTF-RSBI for predicting failed weaning were 0.639, 0.813, and 0.859, respectively. The AUROC curves for DE-RSBI and DTF-RSBI were significantly higher than for RSBI (P = 0.004 and P < 0.001, respectively). The best cut-off values for predicting failed weaning were RSBI > 51.2 breaths/min/L, DE-RSBI > 1.38 breaths/min/mm, and DTF-RSBI > 78.1 breaths/min/%.

Conclusions

In this study, two weaning indices determined by bedside ultrasonography, the DE-RSBI (RR/DE) and DTF-RSBI (RR/DTF), were shown to be more accurate than the traditional RSBI (RR/VT) in predicting weaning outcome during a PSV SBT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-02133-5.

The weaning from mechanical ventilation: a comprehensive ultrasound approach

PURPOSE OF REVIEW

Due to heart, lung and diaphragm interactions during weaning from mechanical ventilation, an ultrasound integrated approach may be useful in the detection of dysfunctions potentially leading to weaning failure. In this review, we will summarize the most recent advances concerning the ultrasound applications relevant to the weaning from mechanical ventilation.

RECENT FINDINGS

The role of ultrasonographic examination of heart, lung and diaphragm has been deeply investigated over the years. Most recent findings concern the ability of lung ultrasound in detecting weaning induced pulmonary edema during spontaneous breathing trial. Furthermore, in patients at high risk of cardiac impairments, global and anterolateral lung ultrasound scores have been correlated with weaning and extubation failure, whereas echocardiographic indexes were not. For diaphragmatic ultrasound evaluation, new indexes have been proposed for the evaluation of diaphragm performance during weaning, but further studies are needed to validate these results.

SUMMARY

The present review summarizes the potential role of ultrasonography in the weaning process. A multimodal integrated approach allows the clinician to comprehend the pathophysiological processes of weaning failure.

Diaphragm Ultrasound in Cardiac Surgery: State of the Art

In cardiac surgery, patients are at risk of phrenic nerve injury, which leads to diaphragm dysfunction and acute respiratory failure. Diaphragm dysfunction (DD) is relatively frequent in cardiac surgery and particularly affects patients after coronary artery bypass graft. The onset of DD affects patients’ prognosis in term of weaning from mechanical ventilation and hospital length of stay. The authors present a narrative review about diaphragm physiology, techniques used to assess diaphragm function, and the clinical application of diaphragm ultrasound in patients undergoing cardiac surgery.

Ultrasound assessment of the diaphragm during the first days of mechanical ventilation compared to spontaneous respiration: a comparative study

INTRODUCTION

In critically ill patients, the diaphragm is subject to several aggressions mainly those induced by mechanical ventilation (MV). Currently, diaphragmatic ultrasound has become the most useful bedside for the clinician to evaluate diaphragm contractility.

AIM

  To examine the effects of MV on the diaphragm contractility during the first days of ventilation.

METHODS

Two groups of subjects were studied: a study group (n=30) of adults receiving MV versus a control group (n=30) of volunteers on spontaneous ventilation (SV). Using an ultrasound device, we compared the diaphragmatic thickening fraction (DTF). Secondly, we analysed the relationship between DTF and weaning.

RESULTS

comparatively to SV group, patients of MV group have a higher end expiratory diameter (EED) (2.09 ± 0.6 vs. 1.76 ± 0.32 mm, p=0.01) and a lower DTF (39.9 ± 12.5%  vs.  49.0 ± 20.5%, p=0.043). Fourteen among the 30 ventilated patients successfully weaned. No significant correlation was shown between DTF and weaning duration (Rho= - 0.464, p=0.09). A DTF value > 33% was near to be significantly associated with weaning success (OR=2; 95% CI= [1.07-3.7], p=0.05) with a sensitivity at 85.7%.

CONCLUSIONS

diaphragmatic contractility was altered from the first days of MV. A DTF value >32,7% was associated to the weaning success and that may be useful to predict successful weaning with sensitivity at 85.7%.

Ultrasound diaphragmatic manual and semi-automated motion measurements: Application in simulated and in vivo data of critically ill subjects

BACKGROUND AND OBJECTIVE

Ultrasound diaphragmatic muscle motion characteristics may provide useful information about normal or abnormal diaphragmatic function and indicate diaphragmatic weakness, or paralysis. In the present work we propose and evaluate an integrated semi-automated analysis system for the quantitative analysis of ultrasonic motion from ultrasound diaphragmatic videos.

METHODS

The proposed system was evaluated in simulated videos and in 13 patients, four of whom patients were mechanically ventilated. The major steps of the methodology were as follows: video normalization, despeckle filtering, generation of an M-Mode image, snakes segmentation, and motion measurements.

RESULTS

The following manual (-/) vs semi-automated (/-), (median±IQR) measurements, which are routinely carried out by the experts, for assessing the severity of the disease, were computed. For the simulated videos the diaphragmatic excursion was 1.80±0.00 cm / 1.76±0.03 cm. For all the real ultrasound videos investigated in this study the following measurements were computed: (i) diaphragmatic excursion: 0.84±0.15 cm / 0.83±0.14 cm, (ii) inspiration time (T_insp): 0.71±0.18 sec / 0.70±0.15 sec, (iii) total breathing time for one cycle (T_tot): 1.71±0.37 sec / 1.67±0.37 sec, (iv) diaphragmatic curve slope: 1.29±0.36 cm/sec / 1.27±0.36 cm/sec, and (v) relaxation rate (RR): 0.82±0.17 cm/sec / 0.82±0.18 cm/sec.

CONCLUSIONS

Manual and semi-automated measurements were very close with non-statistical significant differences and strong correlations between them. It is anticipated that the proposed system might be useful in the clinical practice in the assessment and follow up of patients with diaphragmatic weakness or paralysis and aid in the separation of normal and abnormal diaphragmatic motion. Further validation and additional experimentation in a larger sample of videos and different patient groups is required.

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.

The Utility of Diaphragm Ultrasound in Reducing Time to Extubation

Purpose

Prediction of optimal timing for extubation of mechanically ventilated patients is challenging. Ultrasound measures of diaphragm thickness or diaphragm dome excursion have been used to aid in predicting extubation success or failure. The aim of this study was to determine if incorporating results of diaphragm ultrasound into usual ICU care would shorten the time to extubation.

Methods

We performed a prospective, randomized, controlled study at three Brown University teaching hospitals. Included subjects underwent block randomization to either usual care (Control) or usual care enhanced with ultrasound measurements of the diaphragm (Intervention). The primary outcome was the time to extubation after ultrasound, and the secondary outcome was the total days on the ventilator. Only intensivists in the Intervention group would have the ultrasound information on the likelihood of successful extubation available to incorporate with traditional clinical and physiologic measures to determine the timing of extubation.

Results

A total of 32 subjects were studied; 15 were randomized into the Control group and 17 into the Intervention group. The time from ultrasound to extubation was significantly reduced in the Intervention group compared to the Control group in patients with a ∆tdi% ≥ 30% (4.8 ± 8.4 vs 35.0 ± 41.0 h, p = 0.04). The time from ultrasound to extubation was shorter in subjects with a normally functioning diaphragm (∆tdi% ≥ 30%) compared to those with diaphragm dysfunction (∆tdi% < 30%) (23.2 ± 35.2 vs 57.3 ± 52.0 h p = 0.046). When combining the Intervention and Control groups, a value of ∆tdi% ≥ 30% for extubation success at 24 h provided a sensitivity, specificity, PPV and NPV of 90.9%, 86.7%, 90.9%, and 86.7%, respectively.

Conclusions

Diaphragm ultrasound evaluation of ∆tdi% aids in reducing time to extubation.

Mechanical ventilation weaning issues can be counted on the fingers of just one hand: part 1

Although mechanical ventilation may be a patient’s vital ally during acute illness, it can quickly transform into an enemy during chronic conditions. The weaning process is the fundamental phase that enables the resumption of physiological respiratory function; however, it is also associated with a number of life-threatening complications, and a large percentage of critically ill patients never achieve airway device removal or require the resumption of mechanical ventilation just a few days post-weaning. Indeed, the weaning process is, at present, more of an art than a science. As such, there is urgent need for novel contributions from the scientific literature to abate the growing rates of morbidity and mortality associated with weaning failure. The physician attempting to wean a patient must integrate clinical parameters and common-sense criteria. Numerous studies have striven to identify single predictive factors of weaning failure and sought to standardize the weaning process, but the results are characterized by remarkable heterogeneity. Despite the lack of benchmarks, it is clear that the analysis of respiratory function must include a detailed overview of the five situations described below rather than a single aspect. The purpose of this two-part review is to provide a comprehensive description of these situations to clarify the “arena” physicians are entering when weaning critically ill patients from mechanical ventilation.

Ultrasonography for predicting a difficult laryngoscopy. Getting closer

Our objective was to evaluate the usefulness of five ultrasound measurements to predict a difficult laryngoscopy (DL). Prospective observational study. 50 patients underwent scheduled surgery under general anesthesia with orotracheal intubation with classical laryngoscopy at the University Hospital of Jaén (Spain). Sociodemographic variables, classic preintubation screening tests and ultrasound measurements of the neck soft tissue from skin to hyoid (DSH), epiglottis (DSE) and glottis (DSG) were obtained, as well as two measurements derived from the above: DSH + DSE and DSE - DSG. The relationship between a DL and ultrasound measurements was evaluated using t student test. The ROC Curve was used to establish the diagnostic accuracy of ultrasound measurements to discriminate a DL and logistic regression was used to establish a cut-off point. Multivariate analysis was performed to assess the impact of these measures in clinical practice. Patients with DL showed greater thickness of DSE (2.9 ± 0.46 cm vs 2.32 ± 0.54 cm; p = 0.001), DSH + DSE (4.25 ± 0.45 cm vs 3.62 ± 0.77 cm; p = 0.001) and DSE - DSG (1.83 ± 0.54 cm vs 1.24 ± 0.46 cm; p = 0.001) than those with an easy laryngoscopy. DSE and DSE - DSG had the highest diagnostic accuracy for DL with an area under the ROC curve of 0.79 [95%IC 0.66-0.92] and 0.82 [95%IC 0.68-0.96], respectively. It was established that DSE ≥ 3 cm, could predict a DL with a positive predictive value (PPV) of 69.23% [95%CI 40.3-98.2], and DSE - DSG ≥ 1.9 cm would do so with a PPV of 78.57% [95%CI 53.31-100%]. The multivariate analysis endorsed that DSE and DSE - DSG combined with classic tests (the Modified Mallampati score, the thyromental distance and the upper lip bite test) improved the preoperative detection of a DL. The inclusion of DSE and DSE - DSG in a multivariate model with classic parameters may offer the anesthesiologist better information for detecting a DL preoperatively.

Respiratory muscle ultrasonography: methodology, basic and advanced principles and clinical applications in ICU and ED patients-a narrative review

Respiratory muscle ultrasound is used to evaluate the anatomy and function of the respiratory muscle pump. It is a safe, repeatable, accurate, and non-invasive bedside technique that can be successfully applied in different settings, including general intensive care and the emergency department. Mastery of this technique allows the intensivist to rapidly diagnose and assess respiratory muscle dysfunction in critically ill patients and in patients with unexplained dyspnea. Furthermore, it can be used to assess patient-ventilator interaction and weaning failure in critically ill patients. This paper provides an overview of the basic and advanced principles underlying respiratory muscle ultrasound with an emphasis on the diaphragm. We review different ultrasound techniques useful for monitoring of the respiratory muscle pump and possible therapeutic consequences. Ideally, respiratory muscle ultrasound is used in conjunction with other components of critical care ultrasound to obtain a comprehensive evaluation of the critically ill patient. We propose the ABCDE-ultrasound approach, a systematic ultrasound evaluation of the heart, lungs and respiratory muscle pump, in patients with weaning failure.

Possibilities of ultrasound research of the diaphragm

The ultrasound method is a non-invasive and safe diagnostic method. Ultrasound examination (ultrasound) of the diaphragm allows you to conduct a direct study of its structure and function. Using stationary and portable ultrasound scanners, the study of the diaphragm can be carried out in specialized laboratories, in outpatient departments, in various departments of the clinic, including in intensive care units, in patients in different clinical conditions. Ultrasound of the diaphragm can be implemented on devices of different technical levels. Despite the fact that at present the diaphragm ultrasound method is not standardized, nevertheless, it provides clinically important information for solving various clinical studies, including when conducting dynamic observation.

Pulmonary Ultrasound: A New Era in Critical Care Medicine

Pulmonary ultrasonography is a complementary study that is easy to perform at the patient bedside with no need to transfer the patient to special areas. The technique provides information with high sensitivity and specificity for different pathologies. Pulmonary ultrasonography is a very important diagnostic tool in the assessment of lung, pleural, and chest wall diseases. Pulmonary ultrasound provides low-cost analysis, easy real-time reproduction, and safety, all of which have made it a beneficial tool in the diagnostic arsenal available to medical personnel. The purpose of this review was to describe the usefulness of pulmonary ultrasound in critical areas.

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.

Clinical Application of Modified Burns Wean Assessment Program Scores at First Spontaneous Breathing Trial in Weaning Patients from Mechanical Ventilation

Background:

The purpose of this study was to evaluate the clinical application of modified Burns Wean Assessment Program (m-BWAP) scoring at first spontaneous breathing trial (SBT) as a predictor of successful liberation from mechanical ventilation (MV) in patients with endotracheal intubation.

Methods:

Patients requiring MV for more than 72 hours and undergoing more than one SBT in a medical intensive care unit (ICU) were prospectively enrolled over a 3-year period. The m-BWAP score at first SBT was obtained by a critical care nursing practitioner.

Results:

A total of 103 subjects were included in this study. Their median age was 69 years (range, 22 to 87 years) and 72 subjects (69.9%) were male. The median duration from admission to first SBT was 5 days (range, 3 to 26 days), and the rate of final successful liberation from MV was 84.5% (n=87). In the total group of patients, the successful liberation from MV group at first SBT (n=65) had significantly higher m-BWAP scores than did the unsuccessful group (median, 60; range, 43 to 80 vs. median, 53; range, 33 to 70; P<0.001). Also, the area under the m-BWAP curve for predicting successful liberation of MV was 0.748 (95% confidence interval, 0.650 to 0.847), while the cutoff value based on Youden’s index was 53 (sensitivity, 76%; specificity, 64%).

Conclusions:

The present data show that the m-BWAP score represents a good predictor of weaning success in patients with an endotracheal tube in place at first SBT.

Diaphragmatic parameters by ultrasonography for predicting weaning outcomes

Background

Diaphragmatic dysfunction remains the main cause of weaning difficulty or failure. Ultrasonographic measurement of diaphragmatic function can be used to predict the outcomes of weaning from mechanical ventilation. Our primary objective was to investigate the performance of various sonographic parameters of diaphragmatic function for predicting the success of weaning from mechanical ventilation.

Methods

We prospectively enrolled 68 adult patients requiring mechanical ventilation who were admitted to the intensive care unit from June 2013 to November 2013. The diaphragmatic inspiratory excursion, time to peak inspiratory amplitude of the diaphragm (TPIA_dia), diaphragmatic thickness (DT), DT difference (DTD), and diaphragm thickening fraction (TFdi) were determined by bedside ultrasonography performed at the end of a spontaneous breathing trial. A receiver operating characteristic curve was used for analysis.

Results

In total, 62 patients were analyzed. The mean TPIA_dia was significantly higher in the weaning success group (right, 1.27 ± 0.38 s; left, 1.14 ± 0.37 s) than in the weaning failure group (right, 0.97 ± 0.43 s; left, 0.85 ± 0.39 s) (P <  0.05). The sensitivity, specificity, positive predictive value, and negative predictive value of a TPIA_dia of > 0.8 s in predicting weaning success were 92, 46, 89, and 56%, respectively. The diaphragmatic inspiratory excursion, DTD, and TFdi were associated with reintubation within 48 h. The P values were 0.047, 0.021, and 0.028, and the areas under the receiver operating characteristic curve were 0.716, 0.805, and 0.784, respectively.

Conclusion

Among diaphragmatic parameters, TPIA_dia exhibits good performance in predicting the success of weaning from mechanical ventilation. This study demonstrated a trend toward successful use of TPIA_dia rather than diaphragmatic inspiratory excursion as a predictor of weaning from mechanical ventilation.

Electronic supplementary material

The online version of this article (10.1186/s12890-018-0739-9) contains supplementary material, which is available to authorized users.

Respiratory and Peripheral Muscle Assessment in the Intensive Care Unit

Atrophy and weakness of the respiratory and peripheral muscles is a common problem in the intensive care unit (ICU). It is difficult to diagnose, particularly in the early stages of critical disease. Consequently, many cases are detected only in advanced stages, for example, when difficulties in mechanical ventilation weaning are encountered. The aim of this review is to describe the main tools that are currently available for evaluation of peripheral and respiratory muscles in the ICU. Techniques of varying complexity and specificity are discussed, and particular emphasis is placed on those with greater relevance in daily clinical practice, such as ultrasound.

Avoiding Respiratory and Peripheral Muscle Injury During Mechanical Ventilation: Diaphragm-Protective Ventilation and Early Mobilization

Both limb muscle weakness and respiratory muscle weakness are exceedingly common in critically ill patients. Respiratory muscle weakness prolongs ventilator dependence, predisposing to nosocomial complications and death. Limb muscle weakness persists for months after discharge from intensive care and results in poor long-term functional status and quality of life. Major mechanisms of muscle injury include critical illness polymyoneuropathy, sepsis, pharmacologic exposures, metabolic derangements, and excessive muscle loading and unloading. The diaphragm may become weak because of excessive unloading (leading to atrophy) or because of excessive loading (either concentric or eccentric) owing to insufficient ventilator assistance.

Body Position Affects Ultrasonographic Measurement of Diaphragm Contractility

PURPOSE

(1) Determine whether ultrasonography can detect differences in diaphragm contractility between body positions. (2) Perform reliability analysis of diaphragm thickness measurements in each test condition.

METHODS

We used a repeated-measures experimental design with 45 healthy adults where 3 B-mode ultrasound images were collected at peak-inspiration and end-expiration in supine, sitting, and standing. Mean diaphragm thickening fractions were calculated for each test position. Statistical significance was tested using 1-way repeated-measures analysis of variance with planned comparisons. For reliability analysis, the intraclass correlation coefficient (3, 3) was calculated.

RESULTS

Mean diaphragm thickening fraction increased from 60.2% (95% confidence interval [CI] 53.0%, 67.9%) in supine, to 96.5% (95% CI 83.2%, 109.9%) while seated and to 173.8% (95% CI 150.5%, 197.1%) while standing. Body position was a significant factor overall (P < .001), as were comparisons between each individual position (P < .001). Intraobserver reliability was excellent (>0.93) for all body positions tested.

CONCLUSIONS

Ultrasound imaging detected positional differences in diaphragm contractility. The effect of gravitational loading on diaphragm length-tension, and body position-mediated changes in intra-abdominal pressure may explain the differences found. Future research should address methodological concerns and apply this method to patients participating in early mobilization programs in the intensive care unit.

Predictive factors of weaning from mechanical ventilation and extubation outcome: A systematic review

PURPOSE

To identify, describe and discuss the parameters used to predict weaning from mechanical ventilation and extubation outcomes.

METHODS

Systematic review of scientific articles using four electronic databases: PubMed, Embase, PEDro and Cochrane Library. Search terms included "weaning", "extubation", "withdrawal" and "discontinuation", combined with "mechanical ventilation" and "predictive factors", "predictive parameters" and "predictors for success". In this study, we included original articles that presented predictive factors for weaning or extubation outcomes in adult patients and not restricted to a single disease. Articles not written in English were excluded.

RESULTS

A total of 43 articles were included, with a total of 7929 patients and 56 different parameters related to weaning and extubation outcomes. Rapid Shallow Breathing Index (RSBI) was the most common predictor, discussed in 15 studies (2159 patients), followed by Age and Maximum Inspiratory Pressure in seven studies. The other 53 parameters were found in less than six studies.

CONCLUSION

There are several parameters used to predict weaning and extubation outcomes. RSBI was the most frequently studied and seems to be an important measurement tool in deciding whether to wean/extubate a patient. Furthermore, the results demonstrated that weaning and extubation should be guided by several parameters, and not only to respiratory ones.

[Ultrasound guided airway access]

Ultrasound has increasingly growing applications in anesthesia. This procedure has proven to be a novel, non-invasive and simple technique for the upper airway management, proving to be a useful tool, not only in the operating room but also in the intensive care unit and emergency department. Indeed, over the years mounting evidence has showed an increasing role of ultrasound in airway management. In this review, the authors will discuss the importance of ultrasound in the airway preoperative assessment as a way of detecting signs of difficult intubation or to define the type and/or size of the endotracheal tube as well as to help airway procedures such as endotracheal intubation, cricothyrotomy, percutaneous tracheal intubation, retrograde intubation as well as the criteria for extubation.

Prediction of extubation failure in Intensive Care Unit: systematic review of parameters investigated

INTRODUCTION

Extubation failure (EF) refers to the inability to maintain spontaneous breathing after removal of endotracheal tube. The aim of this review is to identify the best parameter to predict EF in adult intensive care patients.

EVIDENCE ACQUISITION

We searched for publications in PubMed (2000-2016). Studies of patients intubated and mechanically ventilated for more than 24 hours were included and divided in groups basing on the extubation method. 2x2 tables were performed to evaluate the sensitivity, specificity and the predictive values only for those parameters investigated in more than three studies. Studies were divided in groups, basing on time required to define EF (<24 hours, <72 or >72 hours), and EF percentage was calculated for each group.

EVIDENCE SYNTHESIS

On 443 potentially studies, 26 were included. Rapid Shallow Breathing Index (RSBI) and cough strength parameters were found in more than three studies. RSBI or cough strength parameter showed a sensitivity of 20-88.8% or 55.5-85.2%, a specificity of 68.5-94.8% or 24-49%, a positive predictive value (PPV) of 39.5-66.6% or 24-49% and a negative predictive value of 98-82% or 89.5-96.4%, respectively. EF rate was 12.5%, 15.3% and 22% in patients evaluated within 24 hours, 72 hours and over 72 hours, respectively.

CONCLUSIONS

This review shows that all parameters used to predict EF have a low PPV. Therefore, the limitation of use of such predictive tests may prolong unnecessarily the intubation and increase the unfavorable outcome. A prospective study involving all variables could be useful to predict the EF in ICU.

The impact of heart, lung and diaphragmatic ultrasound on prediction of failed extubation from mechanical ventilation in critically ill patients: a prospective observational pilot study

Background

Failed extubation from mechanical ventilation in critically ill patients is multifactorial, complex and not well understood. We aimed to identify whether combined transthoracic echocardiography, lung and diaphragmatic ultrasound can predict extubation failure in critically ill patients.

Results

Fifty-three participants who were intubated > 48 h and deemed by the treating intensivist ready for extubation underwent a 60-min pre-extubation weaning trial (pressure support ≤ 10 cmH₂O and positive end expiratory pressure 5 cmH₂O). Prior to extubation, data collected included ultrasound assessment of left ventricular ejection fraction, left atrial area, early diastolic trans-mitral flow velocity wave (E), early diastolic trans-mitral flow velocity wave/late diastolic trans-mitral flow velocity wave (E/A), early diastolic trans-mitral flow velocity wave/early diastolic mitral annulus velocity (E/E′), interatrial septal motion, lung loss of aeration score and diaphragm movement. At the end of the weaning trial, the rapid shallow breathing index and serum B-type natriuretic peptide concentration were measured. Success and failure of weaning was assessed by defined criteria. Decision to extubate was at the discretion of the treating intensivist. Failure of extubation was defined as re-intubation, non-invasive ventilation or death within 48 h after extubation. Of 53 extubated participants, 11 failed extubation. Failed extubation was associated with diabetes, ischaemic heart disease, higher E/E′ (OR 1.27, 95% CI 1.05–1.54), left atrial area (OR 1.14, CI 1.02–1.28), fixed rightward curvature of the interatrial septum (OR 12.95, CI 2.73–61.41), and higher loss of aeration score of anterior and lateral regions of the lungs (OR 1.41, CI 1.01–1.82).

Conclusions

Failed extubation in mechanically ventilated patients is more prevalent if markers of left ventricular diastolic dysfunction and loss of lung aeration are present.

Point of care diaphragm ultrasound in infants with bronchiolitis: A prospective study

BACKGROUND

Bronchiolitis is the most common reason for hospitalization of children worldwide. Many scoring systems have been developed to quantify respiratory distress and predict outcome, but none of them have been validated. We hypothesized that the ultrasound evaluation of the diaphragm could quantify respiratory distress and therefore we correlated the ultrasound diaphragm parameters with outcome.

METHODS

Prospective study of infants with bronchiolitis (1-12 months) evaluated in a pediatric emergency department. Ultrasonography examinations of the diaphragm was performed (diaphragm excursion [DE], inspiratory excursion [IS], inspiratory/expiratory relationship [I/E], and thickness at end-expiration [TEE] and at end-inspiration [TEI]; thickening fraction [TF]).

RESULTS

We evaluated 61 infants, 50.8 % males. Mean TF was 47% (IQR 28.6-64.7), mean I/E 0.47 (± 0.15), mean DE 10.39 ± 4 mm. There was a linear correlation between TF and oxygen saturation at first evaluation (P = 0.006, r = 0.392). All children with lower values of TF required HFNC and one of them required CPAP. A higher IS was associated with the future need of respiratory support during admission (P = 0.007). IS correlated with the hours of oxygen delivery needed (P = 0.032, r = 0.422). TEI (t = 3.701, P = 0.002) was found to be main predictor of hours of oxygen delivery needed.

CONCLUSION

This study described ultrasound diaphragmatic values of previously healthy infants with bronchiolitis. DE, IS, and TEI correlated with outcome. If confirmed in larger studies, bedside ultrasound semiology of the diaphragm can be a new objective tool for the evaluation and outcome prediction of infants with bronchiolitis.

Diaphragm function and weaning from mechanical ventilation: an ultrasound and phrenic nerve stimulation clinical study

Background

Diaphragm dysfunction is defined by a value of twitch tracheal pressure in response to magnetic phrenic stimulation (twitch pressure) amounting to less than 11 cmH₂O. This study assessed whether this threshold or a lower one would predict accurately weaning failure from mechanical ventilation. Twitch pressure was compared to ultrasound measurement of diaphragm function.

Methods

In patients undergoing a first spontaneous breathing trial, diaphragm function was evaluated by twitch pressure and by diaphragm ultrasound (thickening fraction). Receiver operating characteristics curves were computed to determine the best thresholds predicting failure of spontaneous breathing trial.

Results

Seventy-six patients were evaluated, 48 (63%) succeeded and 28 (37%) failed the spontaneous breathing trial. The optimal thresholds of twitch pressure and thickening fraction to predict failure of the spontaneous breathing trial were, respectively, 7.2 cmH₂O and 25.8%, respectively. The receiver operating characteristics curves were 0.80 (95% CI 0.70–0.89) for twitch pressure and 0.82 (95% CI 0.73–0.93) for thickening fraction. Both receiver operating characteristics curves were similar (p = 0.83). A twitch pressure value lower than 11 cmH₂O (the traditional cutoff for diaphragm dysfunction) predicted failure of the spontaneous breathing trial with a sensitivity of 89% (95% CI 72–98%) and a specificity of 45% (95% CI 30–60%).

Conclusions

Failure of spontaneous breathing trial can be predicted with a lower value of twitch pressure than the value defining diaphragm dysfunction. Twitch pressure and thickening fraction had similar strong performance in the prediction of failure of the spontaneous breathing trial.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0401-y) contains supplementary material, which is available to authorized users.

Impact of limb weakness on extubation failure after planned extubation in medical patients

BACKGROUND AND OBJECTIVE

Limb muscle weakness is associated with difficult weaning. However, there are limited data on extubation failure. The objective of this cohort study was to evaluate the association between limb muscle weakness according to the Medical Research Council (MRC) scale and extubation failure rates among patients in a medical intensive care unit (ICU).

METHODS

All consecutive medical ICU patients who were mechanically ventilated for more than 24 h and who were weaned according to protocol were prospectively registered, and limb muscle weakness was assessed using the MRC scale on the day of planned extubation. Association of limb muscle weakness with extubation failure within 48 h following planned extubation was evaluated with logistic regression analysis.

RESULTS

Over the study period, 377 consecutive patients underwent planned extubation through a standardized weaning process. Extubation failure occurred in 106 (28.1%) patients. Median scores on the MRC scale for four limbs were lower in patients with extubation failure (14, interquartile range (IQR) 12-16) than in patients without extubation failure (16, IQR 12-18; P = 0.024). In addition, extubation failure rates decreased significantly with increasing quartiles of MRC scores (P for trend <0.001). In multivariable analysis, MRC scores ≤10 points were independently associated with extubation failure within 48 h (adjusted OR 2.131, 95% CI: 1.071-4.240, P = 0.031).

CONCLUSION

Limb muscle weakness assessed on the day of extubation was found to be independently associated with higher extubation failure rates within 48 h following planned extubation in medical patients.

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.

Serial Diaphragm Ultrasonography to Predict Successful Discontinuation of Mechanical Ventilation

INTRODUCTION

Diaphragm excursion and contraction velocity measured using ultrasonography have been used to assess diaphragm function. We aimed to evaluate the performance of diaphragm ultrasonography during weaning from mechanical ventilation (MV).

METHODS

Diaphragm ultrasonography was performed on 73 mechanically ventilated patients who were being considered for extubation on three separate occasions: (1) on assist control mode (A/C) during consistent patient triggered ventilation, (2) following 30 min during a spontaneous breathing trial (SBT), (3) 4-24 h following extubation. Right hemidiaphragm excursion and contraction velocity were measured on A/C, during SBT, and following extubation. These measurements were correlated with the outcome of extubation.

RESULTS

Twenty patients failed extubation: 6 of whom required re-intubation and 14 of whom required non-invasive ventilatory support. During SBT, the mean diaphragm excursions were 1.7 ± 0.82 cm in the group who failed extubation compared to 2.1 ± 0.9 cm in the group who were successfully extubated (p = 0.06). To predict successful extubation, a decrease in diaphragm excursion of < 16.4% between A/C and SBT had a sensitivity of 84.9% and a specificity of 65%. The area under curve (AUC) for receiver operative characteristics for above cut-off was 0.75. Diaphragm contraction velocity performed poorly in predicting weaning outcome.

CONCLUSIONS

Diaphragm excursion measured during SBT is an imperfect predictor of the outcome of extubation. Maintenance of diaphragm excursion between A/C and SBT has good performance characteristics by AUC analysis. Diaphragm contraction velocity has poor ability to predict outcome of extubation.

Point-of-care ultrasound (POCUS) of the upper airway

Airway management is a critical skill in the practice of several medical specialities including anesthesia, emergency medicine, and critical care. Over the years mounting evidence has showed an increasing role of ultrasound (US) in airway management. The objective of this narrative review is to provide an overview of the indications for point-of-care ultrasound (POCUS) of the upper airway. The use of US to guide and assist clinical airway management has potential benefits for both provider and patient. Ultrasound can be utilized to determine airway size and predict the appropriate diameter of single-lumen endotracheal tubes (ETTs), double-lumen ETTs, and tracheostomy tubes. Ultrasonography can differentiate tracheal, esophageal, and endobronchial intubation. Ultrasonography of the neck can accurately localize the cricothyroid membrane for emergency airway access and similarly identify tracheal rings for US-guided tracheostomy. In addition, US can identify vocal cord dysfunction and pathology before induction of anesthesia. A rapidly growing body of evidence showing ultrasonography used in conjunction with hands-on management of the airway may benefit patient care. Increasing awareness and use of POCUS for many indications have resulted in technologic advancements and increased accessibility and portability. Upper airway POCUS has the potential to become the first-line non-invasive adjunct assessment tool in airway management.

Diaphragm Excursion-Time Index: A New Parameter Using Ultrasonography to Predict Extubation Outcome

BACKGROUND

The diaphragmatic response to increased mechanical load following withdrawal of mechanical ventilation is critical in determining the outcome of extubation. Using ultrasonography, we aimed to evaluate the performance of the excursion-time (E-T) index-a product of diaphragm excursion and inspiratory time, to predict the outcome of extubation.

METHODS

Right hemidiaphragm excursion, inspiratory time, and E-T index were measured by ultrasonography during mechanical ventilation: (1) on assist-control (A/C) mode during consistent patient-triggered ventilation, (2) following 30 min during a spontaneous breathing trial (SBT), and (3) between 4 and 24 h following extubation. These measurements were correlated with the outcome of extubation. Patients in the "failure" group required reintubation or noninvasive ventilation within 48 h of extubation.

RESULTS

Of the 73 patients studied, 20 patients failed extubation. During SBT, diaphragm excursion was 1.65 ± 0.82 and 2.1 ± 0.9 cm (P = .06), inspiratory time was 0.89 ± 0.30 and 1.11 ± 0.39 s (P = .03), and the E-T index was 1.64 ± 1.19 and 2.42 ± 1.55 cm-s (P < .03) in the "failure" and "success" groups, respectively. The mean change in E-T index between A/C and SBT was -3.9 ± 57.8% in the failure group and 59.4 ± 74.6% in the success group (P < .01). A decrease in diaphragmatic E-T index less than 3.8% between A/C and SBT had a sensitivity of 79.2% and a specificity of 75%, to predict successful extubation.

CONCLUSIONS

Diaphragm E-T index measured during SBT may help predict the outcome of extubation. Maintenance or increase in diaphragm E-T index between A/C and SBT increases the likelihood of successful extubation.

Different effects of cardiac and diaphragm function assessed by ultrasound on extubation outcomes in difficult-to-wean patients: a cohort study

Background

Ultrasound is a convenient tool to evaluate cardiac and diaphragm function. The ratio (E/Ea) of mitral Doppler inflow velocity to annular tissue Doppler wave velocity by transthoracic echocardiography (TTE) and diaphragmatic excursion (DE) by diaphragm ultrasound have been confirmed in predicting extubation outcomes independently, however their different roles in the weaning process have not been determined until now.

Methods

We designed a cohort study to preform diaphragm ultrasound and TTE before and after the spontaneous breathing trial (SBT) in difficult-to-wean patients. Patients considered for enrollment should succeed on a SBT and have been extubated. They were followed up with the events of respiratory failure within 48 h, and divided into the respiratory failure and extubation success subgroups. Relevant risk factors predicting respiratory failure were analysed by a multivariate logistic regression model. Then, each subgroup was assessed with respect to re-intubation within 1 week, and divided into the re-intubation and non-intubation subgroups. Furthermore, relevant risk factors predicting re-intubation were also analysed in each subgroup. The area under the curve (AUC) and optimum cut-off value were identified by the receiver operating characteristic curve.

Results

Among 60 patients, 29 cases developed respiratory failure within 48 h, and 14 cases were re-intubated or died within 1 week, respectively. Multivariate logistic regression analysis showed that E/Ea (average) after SBT [odds ratio (OR) 1.450, 95% confidence intervals (CI) 1.092-1.926, P = 0.01] and left ventricular ejection fraction were associated with respiratory failure. The AUC of E/Ea (average) after SBT was 0.789, and a cut-off value ≥ 12.5 showed the highest diagnostic accuracy with a sensitivity and specificity of 72.4% and 77.4%, respectively. Furthermore, in the respiratory failure subgroup only DE (average) after SBT was associated with re-intubation (OR 0.690, CI 0.499-0.953, P = 0.024). The AUC of DE (average) after SBT was 0.805, and a cut-off value ≤ 12.6 mm showed the highest diagnostic accuracy with a sensitivity and specificity of 80% and 68.4%, respectively.

Conclusions

E/Ea (average) after SBT could help predict respiratory failure within 48 h. However, DE (average) after SBT could help predict re-intubation within 1 week in the respiratory failure subgroup.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0501-8) contains supplementary material, which is available to authorized users.

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.

The predictive value of serial changes in diaphragm function during the spontaneous breathing trial for weaning outcome: a study protocol

INTRODUCTION

There is a variety of tools being used in clinical practice for the prediction of weaning success from mechanical ventilation. However, their diagnostic performances are less than satisfactory. The purpose of this study is to investigate the value of serial changes in diaphragm function measured by ultrasound during the spontaneous breathing trial (SBT) as a weaning predictor.

METHODS AND ANALYSIS

This is a prospective observational study conducted in a 10-bed medical emergency intensive care unit (EICU) in a university-affiliated hospital. The study will be performed from November 2016 to December 2017. All patients in the EICU who are expected to have mechanical ventilation for more than 48 hours through endotracheal tube are potentially eligible for this study. Patients will be included if they fulfil the criteria for SBT. All enrolled patients will be ventilated with an Evita-4 by using volume assist control mode prior to SBT. Positive end-expiratory pressure (PEEP) will be set to 5 cmH₂O and fractional inspired oxygen (FiO₂) will be set to a value below 0.5 that guarantees oxygen saturation by pulse oximetry (SpO₂) greater than 90%. Enrolled patients will undergo SBT for 2 hours in semirecumbent position. During the SBT, the patients will breathe through the ventilator circuit by using flow triggering (2 L/min) with automatic tube compensation of 100% and 5 cmH₂O PEEP. The FiO₂ will be set to the same value as used before SBT. If the patients fail to tolerate the SBT, the trial will be discontinued immediately and the ventilation mode will be switched to that used before the trial. Patients who pass the 2-hour SBT will be extubated. Right diaphragm excursion and bilateral diaphragm thickening fraction will be measured by ultrasonography during spontaneous breathing. Images will be obtained immediately prior to the SBT, and at 5, 30, 60, 90 and 120 min after the initiation of SBT. Rapid shallow breathing index will be simultaneously calculated at the bedside by a respiratory nurse.

ETHICS AND DISSEMINATION

The study protocol is approved by the ethics committee of Sir Run Run Shaw Hospital, an affiliate of Zhejiang University, Medical College. The results will be published in a peer-reviewed journal and shared with the worldwide medical community.

TRIAL REGISTRATION NUMBER

ISRCTN42917473; Pre-results.

Ultrasound evaluation of diaphragm function in mechanically ventilated patients: comparison to phrenic stimulation and prognostic implications

RATIONALE

In intensive care unit (ICU) patients, diaphragm dysfunction is associated with adverse clinical outcomes. Ultrasound measurements of diaphragm thickness, excursion (EXdi) and thickening fraction (TFdi) are putative estimators of diaphragm function, but have never been compared with phrenic nerve stimulation. Our aim was to describe the relationship between these variables and diaphragm function evaluated using the change in endotracheal pressure after phrenic nerve stimulation (Ptr,stim), and to compare their prognostic value.

METHODS

Between November 2014 and June 2015, Ptr,stim and ultrasound variables were measured in mechanically ventilated patients <24 hours after intubation ('initiation of mechanical ventilation (MV)', under assist-control ventilation, ACV) and at the time of switch to pressure support ventilation ('switch to PSV'), and compared using Spearman's correlation and receiver operating characteristic curve analysis. Diaphragm dysfunction was defined as Ptr,stim <11 cm H₂O.

RESULTS

112 patients were included. At initiation of MV, Ptr,stim was not correlated to diaphragm thickness (p=0.28), EXdi (p=0.66) or TFdi (p=0.80). At switch to PSV, TFdi and EXdi were respectively very strongly and moderately correlated to Ptr,stim, (r=0.87, p<0.001 and 0.45, p=0.001), but diaphragm thickness was not (p=0.45). A TFdi <29% could reliably identify diaphragm dysfunction (sensitivity and specificity of 85% and 88%), but diaphragm thickness and EXdi could not. This value was associated with increased duration of ICU stay and MV, and mortality.

CONCLUSIONS

Under ACV, diaphragm thickness, EXdi and TFdi were uncorrelated to Ptr,stim. Under PSV, TFdi was strongly correlated to diaphragm strength and both were predictors of remaining length of MV and ICU and hospital death.

Ultrasound evaluation of diaphragm function and its application in critical patients, mechanical ventilation and brachial plexus block

Before diaphragm ultrasonography, assessment of diaphragm function was very difficult due to the complex nature of its exploration. The use of this new technique has shed light on diagnostic problems and treatment with an improvement in final outcomes for critically ill patients, in whom the incidence of diaphragm weakness or dysfunction has been underestimated. Better knowledge of diaphragm function enables us earlier diagnosis by quantification of diaphragm contractile activity or evaluation of functional status after delivery of plexus block anaesthesia, facilitating therapeutic decisions. It is also being used as a guide in the process of weaning from mechanical ventilation or as the safest approach for braquial plexus block. In this review we present how to perform a systematic exploration of diaphragm function and its clinical implications.