Ultrasonographic Evaluation of Diaphragm Thickness During Mechanical Ventilation in Intensive Care Patients

Ultrasound for measurement of skeletal muscle mass quantity and muscle composition/architecture in critically ill patients: A scoping review on studies' aims, methods, and findings

AIMS

This scoping review aimed to identify, explore, and map the objectives, methodological aspects, and results of studies that used ultrasound (US) to assess skeletal muscle (SM) in critically ill patients.

METHODS

A scoping review was conducted according to the Joanna Briggs Institute's methodology. All studies that evaluated SM parameters from the US in patients admitted to the intensive care unit (ICU) were considered eligible. We categorized muscle thickness and cross-sectional area as parameters for assessing SM quantity, while echogenicity, fascicle length, and pennation angle analysis were used to evaluate muscle "quality" (composition/architecture). A literature search was conducted using four databases for articles published until December 2022. Independent reviewers selected the studies and extracted data. Descriptive statistics were calculated to present the results.

RESULTS

A total of 107 studies were included, the majority of which were prospective cohort studies (59.8 %) conducted in general ICUs (49.5 %). The most frequent objective of the studies was to evaluate SM quantity depletion during the ICU stay (25.2 %), followed by determining whether a specific intervention would modify SM (21.5 %). Most studies performed serial SM evaluations (76.1 %). The rectus femoris muscle thickness was evaluated in most studies (67.9 %), followed by the rectus femoris cross-sectional area (54.3 %) and the vastus intermedius muscle thickness (40.2 %). The studies demonstrated the feasibility and reproducibility of US for SM evaluation, especially related to quantitative parameters. Most studies (70.3 %) reported significant SM quantity depletion during hospitalization. However, the accuracy of the US in measuring SM varied across the studies.

CONCLUSIONS

The lack of detailed description and standardization in the protocols adopted by the studies included in this scoping review precludes the translation of the evidence related to US for SM assessment into clinical practice.

Effects of multimodal exercise program on postural balance in patients with chronic obstructive pulmonary disease: study protocol for a randomized controlled trial

BACKGROUND

Evidence has shown that patients with chronic obstructive pulmonary disease present significant deficits in the control of postural balance when compared to healthy subjects. In view of this, it is pertinent to investigate the effects of different therapeutic strategies used alone or in association with pulmonary rehabilitation with the potential to improve postural balance and other outcomes with clinical significance in patients with chronic obstructive pulmonary disease. This study will investigate the effects of an 8-week (short-term) multimodal exercise program [inspiratory muscle training (IMT) plus neuromuscular electrical stimulation (NMES)] on postural balance in patients with chronic obstructive pulmonary disease enrolled in a pulmonary rehabilitation program compared to individualized addition of IMT or NMES to pulmonary rehabilitation or standard pulmonary rehabilitation.

METHODS

This is a randomized, single-blind, 4-parallel-group trial. Forty patients with chronic obstructive pulmonary disease will be included prospectively to this study during a pulmonary rehabilitation program. Patients will be randomly assigned to one of four groups: multimodal exercise program (IMT + NMES + pulmonary rehabilitation group) or (IMT + pulmonary rehabilitation group) or (NMES + pulmonary rehabilitation group) or standard pulmonary rehabilitation group. Patients will receive two sessions per week for 8 weeks. The primary outcome will be static postural balance and secondary outcomes will include as follows: static and dynamic postural balance, fear of falling, muscle strength and endurance (peripheral and respiratory), functional capacity, health-related quality of life, muscle architecture (quadriceps femoris and diaphragm), and laboratory biomarkers.

DISCUSSION

This randomized clinical trial will investigate the effects of adding of short-term multimodal exercise program, in addition to pulmonary rehabilitation program, in postural balance in patients with chronic obstructive pulmonary disease enrolled in a pulmonary rehabilitation. Furthermore, this randomized control trial will enable important directions regarding the effectiveness of short-term intervention as part of the need to expand the focus of pulmonary rehabilitation to include balance management in chronic obstructive pulmonary disease patients which will be generated.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04387318. Registered on May 13, 2020.

Temporary phrenic nerve stimulated patients: What is the role of ultrasound examination?

BACKGROUND

Prolonged mechanical ventilation caused by ventilator-induced diaphragm dysfunction (VIDD) is a serious problem in critically ill patients. Identification of patients who will have difficulty weaning from ventilation along with attempts to reduce total time on mechanical ventilation is some of the aims of intensive care medicine.

OBSERVATIONS

This article briefly summarizes current options for temporary phrenic nerve stimulation therapy in an effort to keep the diaphragm active as direct prevention and treatment of ventilator-associated diaphragmatic dysfunction in patients on mechanical ventilation. The results of feasibility studies using different approaches are promising but so far, the clinical relevance is low. One important question is which tool would reliably identify early signs of diaphragmatic dysfunction and also be useful in guiding therapy. The authors present a brief overview of the current options considering the advantages and disadvantages of the available examination modalities. Despite the fact that current data point out some limitations of ultrasound examination, we believe that it still has a unique position in the bedside examination of critically ill patients on mechanical ventilation.

CONCLUSION

Temporary phrenic nerve stimulation, regardless of the specific approach used, has the potential to directly treat or reverse VIDD, and ultrasound examination plays an important role in the comprehensive care of critically ill patients.

Ultrasonography Comparison of Diaphragm Morphological Structure and Function in Young and Middle-Aged Subjects with and without Non-Specific Chronic Low Back Pain: A Case-Control Study

Background

It is reported that impaired postural control in patients with non-specific chronic low back pain (NCLBP) was associated with "core" trunk muscle incoordination. However, as the diaphragm is an important component of the "core" deep trunk muscle group, we still know little about the potential relationship between diaphragm dysfunction and NCLBP.

Objectives

This case-control study is intended to investigate the changes of diaphragm morphological structure and function in young and middle-aged subjects with and without NCLBP by ultrasound evaluation and its possible validity in predicating the occurrence of NCLBP.

Methods

31 subjects with NCLBP (NCLBP group) and 32 matched healthy controls (HC group) were enrolled in this study. The diaphragm thickness at the end of inspiration (T ^ins) or expiration (T ^exp) during deep breathing was measured through B-mode ultrasound, and the diaphragm excursion (T ^exc) was estimated at deep breathing through M-mode ultrasound. The diaphragm thickness change rate (T ^rate) was calculated by the formula: T ^rate=(T ^ins - T ^exp)/T ^exp × 100%.

Results

Compared with the HC group, the NCLBP group had a significant smaller degree of T^ins (t = -3.90, P < 0.001), T ^exp (Z = -2.79, P=0.005), and T ^rate (t = -2.03, P=0.047). However, there was no statistical difference in T ^exc between the two groups (t = -1.42, P=0.161). The binary logistic regression analysis indicated that T ^rate (OR = 16.038, P=0.014) and T ^exp (OR = 7.714, P=0.004) were potential risk factors for the occurrence of NCLBP.

Conclusions

The diaphragm morphological structure and function were changed in young and middle-aged subjects with NCLBP, while the diaphragm thickness change rate (T ^rate) and diaphragm thickness at the end of expiration (T ^exp) may be conductive to the occurrence of NCLBP. Furthermore, these findings may suggest that abnormal diaphragm reeducation is necessary for the rehabilitation of patients with NCLBP.

Robot-assisted early mobilization of intensive care patients: a feasibility study protocol

Background

Early mobilization positively influences the outcome of critically ill patients, yet in clinical practice, the implementation is sometimes challenging. In this study, an adaptive robotic assistance system will be used for early mobilization in intensive care units. The study aims to evaluate the experience of the mobilizing professionals and the general feasibility of implementing robotic assistance for mobilization in intensive care as well as the effects on patient outcomes as a secondary outcome.

Methods

The study is single-centric, prospective, and interventional and follows a longitudinal study design. To evaluate the feasibility of robotic-assisted early mobilization, the number of patients included, the number of performed VEM (very early mobilization) sessions, and the number and type of adverse events will be collected. The behavior and experience of mobilizing professionals will be evaluated using standardized observations (n > 90) and episodic interviews (n > 36) before implementation, shortly after, and in routine. Patient outcomes such as duration of mechanical ventilation, loss of muscle mass, and physical activity will be measured and compared with a historical patient population. Approximately 30 patients will be included.

Discussion

The study will provide information about patient outcomes, feasibility, and the experience of mobilizing professionals. It will show whether robotic systems can increase the early mobilization frequency of critically ill patients. Within ICU structures, early mobilization as therapy could become more of a focus. Effects on the mobilizing professionals such as increased motivation, physical relief, or stress will be evaluated. In addition, this study will focus on whether current structures allow following the recommendation of mobilizing patients twice a day for at least 20 min.

Trial registration

ClinicalTrials.gov, NCT05071248. Date: 2021/10/21

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.

Phrenic nerve stimulation prevents diaphragm atrophy in patients with respiratory failure on mechanical ventilation

BACKGROUND

Diaphragm atrophy and dysfunction is a major problem among critically ill patients on mechanical ventilation. Ventilator-induced diaphragmatic dysfunction is thought to play a major role, resulting in a failure of weaning. Stimulation of the phrenic nerves and resulting diaphragm contraction could potentially prevent or treat this atrophy. The subject of this study is to determine the effectiveness of diaphragm stimulation in preventing atrophy by measuring changes in its thickness.

METHODS

A total of 12 patients in the intervention group and 10 patients in the control group were enrolled. Diaphragm thickness was measured by ultrasound in both groups at the beginning of study enrollment (hour 0), after 24 hours, and at study completion (hour 48). The obtained data were then statistically analyzed and both groups were compared.

RESULTS

The results showed that the baseline diaphragm thickness in the interventional group was (1.98 ± 0.52) mm and after 48 hours of phrenic nerve stimulation increased to (2.20 ± 0.45) mm (p=0.001). The baseline diaphragm thickness of (2.00 ± 0.33) mm decreased in the control group after 48 hours of mechanical ventilation to (1.72 ± 0.20) mm (p<0.001).

CONCLUSIONS

Our study demonstrates that induced contraction of the diaphragm by pacing the phrenic nerve not only reduces the rate of its atrophy during mechanical ventilation but also leads to an increase in its thickness - the main determinant of the muscle strength required for spontaneous ventilation and successful ventilator weaning.

TRIAL REGISTRATION

The study was registered with ClinicalTrials.gov (18/06/2018, NCT03559933, https://clinicaltrials.gov/ct2/show/NCT03559933 ).

Ultrasonographic evaluation of diaphragm thickness and excursion in patients with cervical spinal cord injury

Objective: To evaluate the diaphragm thickness and excursion in patients with cervical spinal cord injury and reliability of diaphragmatic ultrasonography.Design: A Pilot Case-Control Study.Setting: China Rehabilitation Research Center (CRRC) /Beijing BO AI Hospital.Participants: Sixty participants with cervical spinal cord injury and sixty control participants were eligible for inclusion in this study.Interventions: Ultrasonographic evaluation of the diaphragm.Outcome Measures: All demographic data were evaluated. Diaphragm thickness, thickening ratio, and diaphragm excursions were assessed at the end of quiet tidal breathing and maximal inspiration. The reliability of inter- and intra-ultrasonography operators were evaluated.Results: Diaphragm thickness was significantly higher in patients with cervical spinal cord injury than the control group (P < 0.001). Diaphragmatic excursion of the right hemidiaphragm was significantly greater in patients with cervical spinal cord injury than the control group (P < 0.001) at the end of quiet tidal breathing. No difference was found in diaphragmatic excursion between two groups (P = 0.32) at the end of maximal inspiration. No significant difference was shown between two groups in thickening ratio. Intraclass correlation coefficients of inter-and intra-ultrasonography operators for the thickness and excursions of the diaphragm were greater than 0.93.Conclusion: Compared with the control group the diaphragm in patients with cervical spinal cord injury is hypertrophied and the diaphragm excursion is greater. Ultrasound is a highly reliable tool for the evaluation of diaphragm thickness and excursion in patients with cervical spinal cord injury.Trial Registration: This trail was registered in Chinese Clinical Trial Registry (NO. ChiCTR-ROC-17010973).

Initial Assessment of the Percutaneous Electrical Phrenic Nerve Stimulation System in Patients on Mechanical Ventilation

Supplemental Digital Content is available in the text.

Maintaining diaphragm work using electrical stimulation during mechanical ventilation has been proposed to attenuate ventilator-induced diaphragm dysfunction. This study assessed the safety and feasibility of temporary percutaneous electrical phrenic nerve stimulation on user-specified inspiratory breaths while on mechanical ventilation.

Serial ultrasonographic monitoring of diaphragmatic and mid-upper arm muscle thickness in mechanically ventilated respiratory patients: A single-center observational study

INTRODUCTION

Muscle monitoring during mechanical ventilation (MV) is gaining great interest nowadays; however, a proper monitoring tool is not well-established yet.

OBJECTIVES

To assess the role of ultrasound in muscle monitoring during MV in respiratory patients.

METHODS

Eligible 68 mechanically ventilated patients were consecutively enrolled. Serial ultrasound measurements of diaphragmatic thickness at the end of inspiration (Tdi) and mid-upper arm (MUA) muscle thickness were recorded every other day till weaning. Before discharge, functional status score (FSS) was assessed.

RESULTS

Tdi decreased in 72.1%, did not change in 13.2% and increased in 14.7% of the patients. MUA muscle thickness decreased in 47.17% and did not change in others. Significant correlation between Tdi and MUA muscle thickness change was found (r = 0.404, P = 0.001); however, MUA muscle thickness change could not predict Tdi change (B = 0.067, P = 0.059). Diaphragmatic and MUA thickness change showed significant negative correlation with ICU stay (r = -0.260, -0.647, P = 0.032, <0.001) and MV duration (r = -0.335, -0.596, P = 0.005, <0.001), respectively. Weaning failure was significantly higher among patients with decreased Tdi (64.28%) and FSS was significantly lower in those with decreased MUA muscle thickness. US measurements of Tdi and MUA muscle thickness showed excellent intra-observer (ICC = 0.996, 0.999, P < 0.001) and inter-observer agreement (ICC = 0.992, 0.998, P < 0.001), respectively.

CONCLUSION

Sonographic muscle monitoring during MV is promising. Changes in the diaphragmatic thickness during MV are common and weakly related to those of peripheral muscles. Early decreased muscle thickness heralds poor weaning and functional outcome.

Health status can predict diaphragmatic muscle thickness in COPD: pilot study

Abstract Introduction: Among the systemic implications of chronic obstructive pulmonary disease (COPD) there are changes in the diaphragm and impact on health status. However, there are few studies on the possible relationship between these variables, and whether health status could predict diaphragmatic muscle thickness (DMT). Objective: To investigate whether there is a relationship between DMT and the prognostic mortality index Body Mass-Index, Airway Obstruction, Dyspnea and Exercise Capacity (BODE), dyspnea and health status, and to investigate whether health status can predict DMT in patients with COPD entering a pulmonary rehabilitation program. Methods: This is a pilot study with a cross-sectional design. Diaphragmatic muscle thickness was evaluated using ultrasound; health status through the COPD Assessment Test (CAT); the sensation of dyspnea by the modified Medical Research Council scale; and mortality, using the BODE index. Results: The sample consisted of 13 patients (68.69 ± 9.3 years) classified as having moderate to severe COPD. There was a strong and inverse correlation between diaphragmatic muscle thickness and health status (r = -0.735; p = 0.004). Simple regression analysis demonstrated that health status influenced diaphragmatic muscle thickness (β = -0.002; IC 95% - 0.004 to -0.001; p = 0.004), explaining 49% of the variance. However, no correlations were observed between diaphragmatic muscle thickness with dyspnea (r = 0.005; p = 0.985) or with the BODE mortality index (r = -0.219; p = 0.472). Conclusion: This pilot study demonstrated a strong inverse correlation between health status and DMT. In addition, health status was able to predict DMT in patients with COPD.

Sonographically Measured Improvement in Diaphragmatic Mobility and Outcomes Among Patients Requiring Prolonged Weaning from the Ventilator

Background:

The need of prolonged weaning from the ventilator is a well-known predictor of an unfavorable patients` outcome. Diaphragmatic dysfunction is a serious problem for these patients. We wanted to determine the survival in patients who were already intubated for more than 4 weeks before they were admitted to our weaning unit. In this prospective study, we wanted to investigate if the diaphragmatic function could improve or was related to survival over an 18 months follow up period.

Methods:

84 patients were included when they were able to breathe at least 10 minutes over a t-piece and sit upright for at least 5 minutes. The diaphragmatic function was estimated sonographically using the up and downward movement of the lung silhouette. Sonographic follow-ups were performed for over 18 months. The survival rate, outcome and changes in diaphragm mobility were investigated.

Results:

a) Survival: 49 patients (58%) survived the 18 months follow up period - 30 had a good outcome; 19 needed assistance. b) Survival in relation to diaphragm mobility: If diaphragmatic mobility improved ≥ 15.5 mm on the left side, the probability of survival was 94% with a probability of 76% to have a satisfying outcome.

Conclusion:

Survival and outcome of prolonged weaning were significantly better when sonographically measured the mobility of left hemidiaphragm improved.

Is rectus abdominis thickness associated with survival among patients with liver cirrhosis? A prospective cohort study

BACKGROUND

Sarcopenia may affect patients with liver cirrhosis and worsen disease outcomes.

OBJECTIVES

To evaluate ultrasound-measured psoas major (PM) and rectus abdominis (RA) thickness for predicting survival among patients with liver cirrhosis.

DESIGN AND SETTING

Prospective cohort study in a tertiary-level hospital.

METHODS

61 patients with liver cirrhosis were prospectively included during a 15-month period and followed up for at least six months. Cirrhosis was classified using the Child-Pugh score. Sarcopenia was assessed using surrogate parameters: handgrip strength (HGS), mid-arm muscle circumference (MAMC) and SGA (subjective global assessment). We used ultrasound to measure RA and PM thickness at admission.

RESULTS

There were 41 men. The patients' mean age was 58.03 ± 10.8 years. 26.22% of them were Child-Pugh A, 45.9% B and 27.86% C. The patients were followed up for 11.9 ± 5.63 months. RA thickness correlated moderately with MAMC (r = 0. 596; P < 0.0001) and HGS (r = 0.515; P < 0.0001) and decreased with increasing SGA class (A, 10.6 ± 2.8 mm; B, 8.3 ± 1.9 mm; C, 6.5 ± 1.9 mm; P < 0.0001). Survival at six months was independently predicted by using the model for end-stage liver disease-serum sodium score (odds ratio, OR 1.305; 95% OR confidence interval 1.083-1.572; P = 0.005). Survival during follow-up was independently predicted by RA thickness (hazard ratio, HR 0.701; 95% HR confidence interval 0.533-0.922; P = 0.011) and ascites (HR 1.876; 95% HR confidence interval 1.078-3.267; P = 0.026). PM thickness did not have any predictive value.

CONCLUSIONS

As a surrogate marker of sarcopenia, RA thickness may predict survival among patients with liver cirrhosis.

Assessment of peripheral muscle thickness and architecture in healthy volunteers using hand-held ultrasound devices; a comparison study with standard ultrasound

BACKGROUND

Pocket-sized ultrasound devices are increasingly used in a variety of clinical situations, and perform well against standard ultrasound machines. We sought to investigate if a pocket-sized ultrasound device can assess muscle thickness and architecture in healthy volunteers.

METHODS

Healthy male volunteers (n = 21) across a range of ages were recruited to the study. Laying supine, ultrasound images were taken from the right anterior and lateral thigh. Thickness of the rectus femoris (RFMT), vastus intermedius (VIMT), and the two combined (anterior thigh, AMT) were measured, along with thickness of vastus lateralis (VLMT), pennation angle (VLPA) and derived fascicle length (VLFL). These scans were performed initially using a pocket-sized ultrasound (VScan) and then using a standard device (Telemed Echoblaster 128).

RESULTS

In all six variables, there was no significant difference between the two sets of measurements. Intra-class correlation co-efficients (ICC) for VLMT, VLPA, and AMT were all excellent (0.93, 0.89, 0.90 respectively) with the derived value of VLFL having an ICC of 0.84. All ICC values were statistically significant. Regression analysis demonstrated no evidence of proportional bias in any of the measured or derived variables.

CONCLUSION

A pocket-sized ultrasound device gives similar measurements of lower limb muscle thickness and architecture as a standard device in healthy volunteers.

Ultrasonography of Diaphragm Can Predict Pulmonary Function in Spinal Cord Injury Patients: A Pilot Case-Control Study

BACKGROUND Ultrasonography of the diaphragm is an under-utilized instrument in cervical spinal cord injury patients. We conducted a pilot study to first compare the difference of diaphragm thickness and the excursion between patients with cervical spinal cord injury and healthy volunteers, and second to correlate diaphragmic ultrasonography and pulmonary function in cervical spinal cord injury patients. MATERIAL AND METHODS Thirty patients with C4-C5 cervical spinal cord injury of more than 1 year and thirty healthy volunteers were included in this study. All demographic data were evaluated. All participants underwent diaphragmic ultrasonography evaluation and pulmonary function test. Diaphragm thickness of both sides and diaphragm excursions of the right hemi-diaphragm were obtained at the end of quiet tidal breathing and maximal inspiration. We compared diaphragmatic thickness and excursions, and we analyzed the relationship between diaphragmatic ultrasonography and pulmonary function. RESULTS All spinal cord injury patients had restrictive pulmonary dysfunction compared to the control group of healthy volunteers. Diaphragm thickness on both sides was significantly increased in spinal cord injury patients. Diaphragmatic excursion in spinal cord injury patients was increased on the right hemi-diaphragm during tidal breathing. However, the right hemi-diaphragmatic excursion was no difference in both groups during maximal inspiration. Right hemi-diaphragmatic excursion during deep breathing correlated positively with expiratory volume in 1 second (P<0.01) and forced vital capacity (P<0.01). Right hemi-diaphragm thickness at end of maximum inspiration correlated positively with expiratory volume in 1 second (P<0.01) and forced vital capacity (P<0.01). Left hemi-diaphragm thickness at end of maximum inspiration correlated positively with expiratory volume in 1 second (P<0.01) and forced vital capacity (P<0.01). CONCLUSIONS Diaphragm thickness and motion of the cervical spinal cord injury patients were different from controls. Pulmonary function was impaired in spinal cord injury patients. Ultrasonography of the diaphragm as a non-invasive method that is correlated with pulmonary function.

Diaphragmatic ultrasonography for predicting ventilator weaning: A meta-analysis

BACKGROUND

Weaning failure is common in mechanically ventilated patients. Whether ultrasound can predict weaning outcome remains controversial. This meta-analysis was performed to assess the accuracy of diaphragmatic ultrasonography for predicting reintubation within 48 hours of extubation.

METHODS

Literature search was performed in PubMed, Embase, and Cochrane Library to identify all the relevant papers, published in English up to July 16, 2017. Eligible studies were included if data were in adequate details to rebuild 2 × 2 contingency tables. Methodological quality of the included studies was evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) in Review Manager 5.3. The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) curve were pooled using the fixed or random effects model, meanwhile, the heterogeneity was evaluated using Cochran Q test and I statistics in Meta-DiSc 1.4. Publication bias was assessed using Deeks funnel plot in Stata 12.0.

RESULTS

Thirteen studies with 742 subjects were included in this meta-analysis. The pooled sensitivities for diaphragm excursion (DE) and diaphragm thickness fraction (DTF) were 0.786 and 0.893, and the pooled specificities were 0.711 and 0.796, respectively. The area under curve (AUC) for DE and DTF were 0.8590 and 0.8381. The DORs for DE and DTF were 10.623 and 32.521. No publication bias was observed among these studies.

CONCLUSIONS

Diaphragmatic ultrasonography is a promising tool for predicting reintubation within 48 hours of extubation. However, due to heterogeneities among the included studies, large-scale studies are warranted to confirm our findings.

Progressive Diaphragm Atrophy in Pediatric Acute Respiratory Failure

OBJECTIVES

Diaphragm atrophy is associated with delayed weaning from mechanical ventilation and increased mortality in critically ill adults. We sought to test for the presence of diaphragm atrophy in children with acute respiratory failure.

DESIGN

Prospective, observational study.

SETTING

Single-center tertiary noncardiac PICU in a children's hospital.

PATIENTS

Invasively ventilated children with acute respiratory failure.

MEASUREMENTS AND MAIN RESULTS

Diaphragm thickness at end-expiration and end-inspiration were serially measured by ultrasound in 56 patients (median age, 17 mo; interquartile range, 5.5-52), first within 36 hours of intubation and last preceding extubation. The median duration of mechanical ventilation was 140 hours (interquartile range, 83-201). At initial measurement, thickness at end-expiration was 2.0 mm (interquartile range, 1.8-2.5) and thickness at end-inspiration was 2.5 mm (interquartile range, 2-2.8). The change in thickness at end-expiration during mechanical ventilation between first and last measurement was -13.8% (interquartile range, -27.4% to 0%), with a -3.4% daily atrophy rate (interquartile range, -5.6 to 0%). Thickening fraction = ([thickness at end-inspiration - thickness at end-expiration]/thickness at end-inspiration) throughout the course of mechanical ventilation was linearly correlated with spontaneous breathing fraction (beta coefficient, 9.4; 95% CI, 4.2-14.7; p = 0.001). For children with a period of spontaneous breathing fraction less than 0.5 during mechanical ventilation, those with exposure to a continuous neuromuscular blockade infusion (n = 15) had a significantly larger decrease in thickness at end-expiration compared with children with low spontaneous breathing fraction who were not exposed to a neuromuscular blockade infusion (n = 18) (-16.4%, [interquartile range, -28.4% to -7.0%] vs -7.3%; [interquartile range, -10.9% to -0%]; p = 0.036).

CONCLUSIONS

Diaphragm atrophy is present in children on mechanical ventilation for acute respiratory failure. Diaphragm contractility, measured as thickening fraction, is strongly correlated with spontaneous breathing fraction. The combination of exposure to neuromuscular blockade infusion with low overall spontaneous breathing fraction is associated with a greater degree of atrophy.

Respiratory failure because of neuromuscular disease

PURPOSE OF REVIEW

Understanding the mechanisms and abnormalities of respiratory function in neuromuscular disease is critical to supporting the patient and maintaining ventilation in the face of acute or chronic progressive impairment.

RECENT FINDINGS

Retrospective clinical studies reviewing the care of patients with Guillain-Barré syndrome and myasthenia have shown a disturbingly high mortality following step-down from intensive care. This implies high dependency and rehabilitation management is failing despite evidence that delayed improvement can occur with long-term care. A variety of mechanisms of phrenic nerve impairment have been recognized with newer investigation techniques, including EMG and ultrasound. Specific treatment for progressive neuromuscular and muscle disease has been increasingly possible particularly for the treatment of myasthenia, metabolic myopathies, and Duchenne muscular dystrophy. For those conditions without specific treatment, it has been increasingly possible to support ventilation in the domiciliary setting with newer techniques of noninvasive ventilation and better airway clearance. There remained several areas of vigorous debates, including the role for tracheostomy care and the place of respiratory muscle training and phrenic nerve/diaphragm pacing.

SUMMARY

Recent studies and systematic reviews have defined criteria for anticipating, recognizing, and managing ventilatory failure because of acute neuromuscular disease. The care of patients requiring long-term noninvasive ventilatory support for chronic disorders has also evolved. This has resulted in significantly improved survival for patients requiring domiciliary ventilatory support.

Reproducibility of diaphragm thickness measurements by ultrasonography in patients on mechanical ventilation

AIM

To prospectively evaluate the reproducibility of diaphragm thickness measurement by ultrasonography at the bedside by critical care physicians in patients on invasive mechanical ventilation.

METHODS

In a prospective observational study of 64 invasively ventilated patients, diaphragmatic thickness measurement was taken by 2 different observers at the same site. Three measurements were taken by each observer and averaged. The intraobserver and interobserver variability was assessed by estimation of intraclass correlation coefficient. The limits of agreement were plotted as the difference between two observations against the average of the two observations in Bland and Altman analysis.

RESULTS

The mean diaphragm thickness at the functional residual capacity was 2.29 ± 0.4 mm and the lower limit of the normal, i.e., the 5^th percentile was 1.7 mm (95%CI: 1.6-1.8). The intraclass correlation coefficient for intraobserver variability was 0.986 (95%CI: 0.979-0.991) with a P value of < 0.001. The intraclass correlation coefficient for interobserver variability was 0.987 (95%CI: 0.949-0.997) with a P value of < 0.001. In Bland and Altman analysis, both intraobserver and interobserver measurements showed high limits of agreement.

CONCLUSION

Our study demonstrates that the measurement of diaphragm thickness by ultrasound can be accurately performed by critical care physicians with high degree of reproducibility in patients on mechanical ventilation.