Role of Transthoracic Lung Ultrasonography in the Diagnosis of Pulmonary Embolism: A Systematic Review and Meta-Analysis

The Diagnostic Role of Lung Ultrasound and Contrast-Enhanced Ultrasound in Pulmonary Embolism

The diagnosis of pulmonary embolism (PE) relies essentially on a probabilistic approach that requires careful clinical assessments, targeted laboratory tests, and the use of appropriate imaging tools. Nowadays, the diagnostic gold standard is computed tomographic pulmonary angiography. Lung ultrasound (LUS) can play a role in the diagnosis of PE mainly by allowing the visualization of peripheral lung infarctions. Hypoechoic, pleural-based parenchymal consolidation is the most typical and common finding of pulmonary infarction. More than 85% of infarct lesions are wedge-shaped, extending to the pleural surface and are localized to where the patient complains of pleuritic chest pain. Contrast-enhanced ultrasound can be performed in addition to basic ultrasound examination to ascertain nonvascularization of the consolidation, thus confirming that the lesion is an infarct. The aim of this narrative review is to summarize the latest evidence on the application of LUS to the diagnosis of PE, focusing purely on thoracic/lung signs.

Retrospective analysis of the diagnostic accuracy of lung ultrasound for pulmonary embolism in patients with and without pleuritic chest pain

Background

Lung ultrasound (LUS) has a role in the diagnosis of pulmonary embolism (PE) mainly based on the visualization of pulmonary infarctions. However, examining the whole chest to detect small peripheral infarctions by LUS may be challenging. Pleuritic pain, a frequent presenting symptom in patients with PE, is usually localized in a restricted chest area identified by the patient itself. Our hypothesis is that sensitivity of LUS for PE in patients with pleuritic chest pain may be higher due to the possibility of focusing the examination in the painful area. We combined data from three prospective studies on LUS in patients suspected of PE and extracted data regarding patients with and without pleuritic pain at presentation to compare the performances of LUS.

Results

Out of 872 patients suspected of PE, 217 (24.9%) presented with pleuritic pain and 279 patients (32%) were diagnosed with PE. Pooled sensitivity of LUS for PE in patients with and without pleuritic chest pain was 81.5% (95% CI 70–90.1%) and 49.5% (95% CI 42.7–56.4%) (p < 0.001), respectively. Specificity of LUS was similar in the two groups, respectively 95.4% (95% CI 90.7–98.1%) and 94.8% (95% CI 92.3–97.7%) (p = 0.86). In patients with pleuritic pain, a diagnostic strategy combining Wells score with LUS performed better both in terms of sensitivity (93%, 95% CI 80.9–98.5% vs 90.7%, 95% CI 77.9–97.4%) and negative predictive value (96.2%, 95% CI 89.6–98.7% vs 93.3%, 95% CI 84.4–97.3%). Efficiency of Wells score + LUS outperformed the conventional strategy based on Wells score + d-dimer (56.7%, 95% CI 48.5–65% vs 42.5%, 95% CI 34.3–51.2%, p = 0.02).

Conclusions

In a population of patients suspected of PE, LUS showed better sensitivity for the diagnosis of PE when applied to the subgroup with pleuritic chest pain. In these patients, a diagnostic strategy based on Wells score and LUS performed better to exclude PE than the conventional strategy combining Wells score and d-dimer.

Point-of-care ultrasound for critically-ill patients: A mini-review of key diagnostic features and protocols

Point-of-care ultrasonography (POCUS) for managing critically ill patients is increasingly performed by intensivists or emergency physicians. Results of needs surveys among intensivists reveal emphasis on basic cardiac, lung and abdominal ultrasound, which are the commonest POCUS modalities in the intensive care unit. We therefore aim to describe the key diagnostic features of basic cardiac, lung and abdominal ultrasound as practised by intensivists or emergency physicians in terms of accuracy (sensitivity, specificity), clinical utility and limitations. We also aim to explore POCUS protocols that integrate basic cardiac, lung and abdominal ultrasound, and highlight areas for future research.

Lung Ultrasound Imaging: A Primer for Echocardiographers

Lung ultrasound (LUS) has gained considerable acceptance in emergency and critical care medicine but is yet to be fully implemented in cardiology. Standard imaging protocols for LUS in acute care settings have allowed the rapid and accurate diagnosis of dyspnea, respiratory failure, and shock. LUS is greatly additive to echocardiography and is superior to auscultation and chest radiography, particularly when the diagnosis of acute decompensated heart failure is in question. In this review, the authors describe LUS techniques, interpretation, and clinical applications, with the goal of informing cardiologists on the imaging modality. Additionally, the authors review LUS findings associated with various disease states most relevant to cardiac care. Although there is extensive literature on LUS in the acute care setting, there is a dearth of reviews directly focused for practicing cardiologists. Current evidence demonstrates that this modality is an important adjunct to echocardiography, providing valuable clinical information at the bedside.

Lung ultrasound in the emergency department - a valuable tool in the management of patients presenting with respiratory symptoms during the SARS-CoV-2 pandemic

BACKGROUND

Typical lung ultrasound (LUS) findings in patients with a COVID-19 infection were reported early on. During the global SARS-CoV-2 pandemic, LUS was propagated as a useful instrument in triage and monitoring. We evaluated LUS as a rapid diagnostic triage tool for the management of patients with suspected COVID-19 in the emergency department (ED).

METHODS

The study retrospectively enrolled patients with suspected COVID-19, who were admitted from 1st April to 25th of April 2020 to the ED of a tertiary care center in Germany. During clinical work-up, patients underwent LUS and polymerase chain reaction (PCR) testing for SARS-CoV-2. The recorded ultrasound findings were analyzed and judged regarding typical signs of viral pneumonia, blinded for clinical information of the patients. The results were compared with PCR test and chest computed tomography (CT).

RESULTS

2236 patients were treated in the ED during the study period. 203 were tested for SARS-CoV-2 using PCR, 135 (66.5%) underwent LUS and 39 (28.9%) of the patients were examined by chest CT scan. 39 (28.9%) of the 135 patients were tested positive for SARS-CoV-2 with PCR. In 52 (38.5%) COVID-19 was suspected from the finding of the LUS, resulting in a sensitivity of 76.9% and a specificity of 77.1% compared with PCR results. The negative predictive value reached 89.2%. The findings of the LUS had - compared to a positive chest CT scan for COVID-19 - a sensitivity of 70.6% and a specificity of 72.7%.

CONCLUSIONS

LUS is a rapid and useful triage tool in the work-up of patients with suspected COVID-19 infection during a pandemic scenario. Still, the results of the LUS depend on the physician's experience and skills.

Impact of Bedside Combined Cardiopulmonary Ultrasound on Etiological Diagnosis and Treatment of Acute Respiratory Failure in Critically Ill Patients

AIMS AND OBJECTIVES

To prospectively evaluate the impact of cardiopulmonary ultrasound (CPUS) on etiological diagnosis and treatment of critically ill acute respiratory failure (ARF) patients.

DESIGN

This is a prospective observational study conducted in a general intensive care unit (ICU) of a tertiary care center in India. Patients over 18 years old with presence of one of the objective criteria of ARF. Patients either consecutively admitted for ARF to ICU or already admitted to ICU for a different reason but later developed ARF during their hospital stay. Written informed consent in local language was obtained from next of kin.

INTERVENTIONS

All included patients underwent bedside CPUS including lung ultrasound (US) and transthoracic echocardiography plus targeted venous US by single investigator, blinded to clinical data. The US diagnosis of ARF etiology was shared with treating intensivist. Initial clinical diagnosis (ICD) and treatment plan (made before US) of each patient were compared with post-US clinical diagnosis and treatment plan. The changes in diagnosis and treatment up to 24 hours post-US were considered as impact of US.

RESULTS

Mean age of 108 included patients was 45.7 ± 20.4 years (standard deviation). The ICD was correct in 67.5% (73/108) cases, whereas the combined CPUS yielded correct etiological diagnosis in 88% (95/108) cases. Among the 108 included patients, etiological diagnosis of ARF was altered after CPUS in 40 (37%) patients, which included "diagnosis changed" in 18 (17%) and "diagnosis added" in 22 (20%). Treatment plan was changed in 39 (36%) patients after CPUS, which included surgical interventions in 17 (16%), changes in medical therapy in 12 (11%), and changes in ventilation strategy in 4 (3.5%) patients.

CONCLUSION

This study demonstrates that use of combined US approach as an initial test in ARF, improves diagnostic accuracy for identification of underlying etiology, and frequently changes clinical diagnosis and/or treatment.

HOW TO CITE THIS ARTICLE

Barman B, Parihar A, Kohli N, Agarwal A, Dwivedi DK, Kumari G. Impact of Bedside Combined Cardiopulmonary Ultrasound on Etiological Diagnosis and Treatment of Acute Respiratory Failure in Critically Ill Patients. Indian J Crit Care Med 2020;24(11):1062-1070.

Recommendations for Lung Ultrasound in Internal Medicine

A growing amount of evidence prompts us to update the first version of recommendations for lung ultrasound in internal medicine (POLLUS-IM) that was published in 2018. The recommendations were established in several stages, consisting of: literature review, assessment of literature data quality (with the application of QUADAS, QUADAS-2 and GRADE criteria) and expert evaluation carried out consistently with the modified Delphi method (three rounds of on-line discussions, followed by a secret ballot by the panel of experts after each completed discussion). Publications to be analyzed were selected from the following databases: Pubmed, Medline, OVID, and Embase. New reports published as of October 2019 were added to the existing POLLUS-IM database used for the original publication of 2018. Altogether, 528 publications were systematically reviewed, including 253 new reports published between September 2017 and October 2019. The new recommendations concern the following conditions and issues: pneumonia, heart failure, monitoring dialyzed patients' hydration status, assessment of pleural effusion, pulmonary embolism and diaphragm function assessment. POLLUS-IM 2020 recommendations were established primarily for clinicians who utilize lung ultrasound in their everyday clinical work.

Evaluation of the Diagnostic Value of Bedside Transthoracic Ultrasonography (TTUS) and Lower Extremity Three-Points Compression Duplex in the Diagnosis of the Pulmonary Embolism

Background:

The present study aimed at evaluating the diagnostic value of lung transthoracic ultrasonography (TTUS) and lower extremity sonography versus computed tomography pulmonary angiography (CTPA) in the diagnosis of pulmonary embolus (PE).

Materials and Methods:

This study was performed on 104 patients with clinically suspected PE. CTPA and D-dimer was performed on all patients. Wells’ deep vein thrombosis criteria (WDVTC) was evaluated and recorded at the patient’s admission. Finally, the results of adding venous and lung sonography scores to the WDVTC with and without the results of D-dimer test were analyzed for predicting the diagnosis of PE.

Results:

There were 104 patients clinically suspected of having a PE and enrolled in the study. A PE was confirmed in 37.5% of this cohort. WDVTC had a sensitivity and specificity of 94.87% and 80.00%, respectively, to predict PE. When adding D-dimer to the WDVTC for patients unlikely to have a PE (WDVTC≤4), the sensitivity and specificity of positive D-dimer in diagnosis of PE were 94.87% and 56.92%, respectively ( P < .001).

Conclusion:

According to these study results, the modification of the WDVTC along with the results of lung TTUS and lower extremity venous sonogram significantly increase the diagnostic power for PE.

Transthoracic parametric Doppler for bedside diagnosis of pulmonary embolism: A pilot study

Transthoracic parametric Doppler (TPD), unlike conventional ultrasonography, measures signals originating from movements of pulmonary blood vessel walls. In this pilot study, we tested TPD in 15 patients diagnosed with pulmonary embolism on computed tomography pulmonary angiography. Results were mapped to the upper, middle, and lower thirds of the right lung. In the lower third, TPD yielded 100% specificity and positive predictive value for acute pulmonary embolism. If validated in a larger series, this rapid bedside technique might obviate the need for computed tomography in specific cases. This could be advantageous in patients who are unstable, in intensive care, or have allergies to iodinated contrast material.

[Use of lung and pleural ultrasonography in emergency and intensive care medicine]

Bedside lung ultrasound (LUS) in emergency rooms and intensive care units can serve as a tool to diagnose common lung pathologies, monitor their course and guide clinical management. LUS requires only a few minutes and is a useful extension of the physical examination. Fractures of the ribs as well as the sternum are seen well on ultrasound. Minute pleural fluids (effusion, hemtothorax) are detectable. LUS is able to detect the sound of lung water and thus to differentiate a cardiogenic pulmonary edema from chronic obstructive lung disease. Inflammatory lung diseases such as pleuritis and pneumonia are better seen than on chest X‑ray. LUS should replace chest X‑ray in the diagnosis of ambulant acquired pneumonia. In ventilator-associated pneumonia and atelectasis, LUS measures the presence of lung consolidation as well as dynamic changes und reventilation. A heart-lung-vessel integrated triple ultrasonography according to clinical findings can help with the diagnosis of pulmonary embolism and should be a necessary weapon for the physicians, especially in emergency departments.

Imaging the Injured Lung: Mechanisms of Action and Clinical Use

Acute respiratory distress syndrome (ARDS) consists of acute hypoxemic respiratory failure characterized by massive and heterogeneously distributed loss of lung aeration caused by diffuse inflammation and edema present in interstitial and alveolar spaces. It is defined by consensus criteria, which include diffuse infiltrates on chest imaging-either plain radiography or computed tomography. This review will summarize how imaging sciences can inform modern respiratory management of ARDS and continue to increase the understanding of the acutely injured lung. This review also describes newer imaging methodologies that are likely to inform future clinical decision-making and potentially improve outcome. For each imaging modality, this review systematically describes the underlying principles, technology involved, measurements obtained, insights gained by the technique, emerging approaches, limitations, and future developments. Finally, integrated approaches are considered whereby multimodal imaging may impact management of ARDS.

Diagnostic chest ultrasound for acute respiratory failure

Acute respiratory failure (ARF) is a common life-threatening medical condition, with multiple underlying aetiologies. Diagnostic chest ultrasound provides accurate diagnosis of conditions that commonly cause ARF, and may improve overall diagnostic accuracy in critical care settings as compared to standard diagnostic approaches. Respiratory physicians are becoming increasingly familiar with ultrasound as a part of routine clinical practice, although the majority of data to date has focused on the emergency and intensive care settings. This review will examine the evidence for the use of diagnostic chest ultrasound, focusing on different levels of imaging efficacy; specifically ultrasound test attributes, impacts on clinician behaviour and impact on health outcomes. The evidence behind use of multi-modality ultrasound examinations in ARF will be reviewed. It is hoped that readers will become familiar with the advantages and potential issues with chest ultrasound, as well as evidence gaps in the field.

Polish recommendations for lung ultrasound in internal medicine (POLLUS-IM)

The aim of this study was to establish recommendations for the use of lung ultrasound in internal medicine, based on reliable data and expert opinions. Methods: The bibliography from the databases (Pubmed, Medline, OVID, Embase) has been fully reviewed up to August 2017. Members of the expert group assessed the credibility of the literature data. Then, in three rounds, a discussion was held on individual recommendations (in accordance with the Delphi procedure) followed by secret voting. Thirty-eight recommendations for the use of lung ultrasound in internal medicine were established as well as discussed and subjected to secret voting in three rounds. The first 31 recommendations concerned the use of ultrasound in the diagnosis of the following conditions: pneumothorax, pulmonary consolidation, pneumonia, atelectasis, pulmonary embolism, malignant neoplastic lesions, interstitial lung lesions, cardiogenic pulmonary edema, interstitial lung diseases with fibrosis, dyspnea, pleural pain and acute cough. Furthermore, seven additional statements were made regarding the technical conditions of lung ultrasound examination and the need for training in the basics of lung ultrasound in a group of doctors during their specialization programs and medical students. The panel of experts established a consensus on all 38 recommendations.

Is a linear probe helpful in diagnosing diseases of pulmonary interstitial spaces?

In a lung ultrasound examination, interstitial lung lesions are visible as numerous B-line artifacts, and are best recorded with the use of a convex probe. Interstitial lung lesions may result from many conditions, including cardiogenic pulmonary oedema, non-cardiogenic pulmonary oedema, or interstitial lung disease. Hence difficulties in the differential diagnostics of the above clinical conditions. This article presents cases of patients suffering from interstitial lung lesions discovered in the course of lung ultrasound examination. The patients were examined with a 3.5–5.0 MHz convex probe and a 7.0–11.0 MHz linear probe. Ultrasound images have been analysed, and differences in the imaging with both probes in patients with interstitial lung lesions have been detailed. The use of a linear probe in patients with interstitial lung lesions (discovered with a convex or a micro-convex probe) provides additional information on the source of the origin of the lesions.

The efficacy of bedside chest ultrasound: from accuracy to outcomes

For many respiratory physicians, point-of-care chest ultrasound is now an integral part of clinical practice. The diagnostic accuracy of ultrasound to detect abnormalities of the pleura, the lung parenchyma and the thoracic musculoskeletal system is well described. However, the efficacy of a test extends beyond just diagnostic accuracy. The true value of a test depends on the degree to which diagnostic accuracy efficacy influences decision-making efficacy, and the subsequent extent to which this impacts health outcome efficacy. We therefore reviewed the demonstrable levels of test efficacy for bedside ultrasound of the pleura, lung parenchyma and thoracic musculoskeletal system.For bedside ultrasound of the pleura, there is evidence supporting diagnostic accuracy efficacy, decision-making efficacy and health outcome efficacy, predominantly in guiding pleural interventions. For the lung parenchyma, chest ultrasound has an impact on diagnostic accuracy and decision-making for patients presenting with acute respiratory failure or breathlessness, but there are no data as yet on actual health outcomes. For ultrasound of the thoracic musculoskeletal system, there is robust evidence only for diagnostic accuracy efficacy.We therefore outline avenues to further validate bedside chest ultrasound beyond diagnostic accuracy, with an emphasis on confirming enhanced health outcomes.

Evaluation of the Diagnostic Role of Bedside Lung Ultrasonography in Patients with Suspected Pulmonary Embolism in the Emergency Department

Background:

Despite the existence of detailed consensus guidelines, challenges remain regarding efficient, appropriate, and safe imaging methods for the diagnosis of suspected pulmonary embolism.

Aims:

To investigate the role of the wedge sign, B-lines, and pleural effusion seen on bedside lung ultrasound in the diagnosis of pulmonary embolism.

Study Design:

Diagnostic accuracy study.

Methods:

During the first evaluation of patients with suspected pulmonary embolism, bedside lung ultrasound was performed, and the B-lines, wedge sign, and pleural effusion were investigated. Computed tomography angiography was used as a confirmatory test and was compared with the lung ultrasound findings.

Results:

Pulmonary embolism was detected in 38 (38%) patients. In the comparison of bedside lung ultrasound results, statistically significant differences were found between the groups in terms of the B-lines and wedge sign (p=0.005 and p<0.001, respectively). There were no significant differences in terms of effusion (p=0.234). Comparison of these findings with computed tomography angiography of the chest showed weak negative correlations between the groups in terms of B-lines (r=-0297) and a moderately positive correlation in terms of the wedge sign (r=0.523). The sensitivity, specificity, and positive and negative predictive values of lung ultrasound findings alone were low. In the logistic regression analysis, the wedge sign (p<0.01, OR=69.45, 95% CI=6.94-695.17) and B-line (p=0.033, OR=1.96, 95% CI=0.41-8.40) were found to be effective in the diagnosis of pulmonary embolism.

Conclusion:

Although the role of lung ultrasound has been increasing in the management of critically ill patients, its value is limited and cannot replace the gold standard tests in the diagnosis of pulmonary embolism.

Thoracic Ultrasound: What Non-radiologists Need to Know

Purpose of review

The aim of this review is to provide the theoretical and practical knowledge essential for non-radiologists to develop the skills necessary to apply thoracic ultrasound as an extension of clinical assessment and intervention.

Recent findings

Issues relating to training and competence are discussed and a library of thoracic ultrasound videos is provided to illustrate artefacts, pleural, parenchymal and pneumothorax pathology as well as important pitfalls to consider. Novel and future diagnostic applications of thoracic ultrasound in the setting of acute cardiorespiratory pathology including consolidation, acute interstitial syndromes and pulmonary embolism are explored.

Summary

Thoracic ultrasound requires an understanding of imaging artefact specific to lung and pleura and a working knowledge of machine knobology for image optimisation and interpretation. Ultrasound is a valuable tool for the practicing chest clinician providing diagnostic information for the assessment of pleural and parenchymal disease and increased safety and cost effectiveness of thoracic interventions.

Electronic supplementary material

The online version of this article (doi:10.1007/s13665-017-0164-1) contains supplementary material, which is available to authorized users.