Thoracic Ultrasound: Technique, Applications, and Interpretation

Lung, Pleura, and Diaphragm Point-of-Care Ultrasound

Thoracic Ultrasonography involves the ultrasonographic examination of the lungs, pleura, and diaphragm. This provides a plethora of clinical information during the point of care assessment of patients. The air filled lungs create consistent artifacts and careful examination and understanding of these artefactual signs can provide useful information on underlying clinicopathologic states. This review aims to provide a review of the ultrasound signs and features that can be seen in horacic ultrasonography and summarize the clinical evidence to support its use.

PLUS-IS-LESS project: Procalcitonin and Lung UltraSonography-based antibiotherapy in patients with Lower rESpiratory tract infection in Swiss Emergency Departments: study protocol for a pragmatic stepped-wedge cluster-randomized trial

BACKGROUND

Lower respiratory tract infections (LRTIs) are among the most frequent infections and a significant contributor to inappropriate antibiotic prescription. Currently, no single diagnostic tool can reliably identify bacterial pneumonia. We thus evaluate a multimodal approach based on a clinical score, lung ultrasound (LUS), and the inflammatory biomarker, procalcitonin (PCT) to guide prescription of antibiotics. LUS outperforms chest X-ray in the identification of pneumonia, while PCT is known to be elevated in bacterial and/or severe infections. We propose a trial to test their synergistic potential in reducing antibiotic prescription while preserving patient safety in emergency departments (ED).

METHODS

The PLUS-IS-LESS study is a pragmatic, stepped-wedge cluster-randomized, clinical trial conducted in 10 Swiss EDs. It assesses the PLUS algorithm, which combines a clinical prediction score, LUS, PCT, and a clinical severity score to guide antibiotics among adults with LRTIs, compared with usual care. The co-primary endpoints are the proportion of patients prescribed antibiotics and the proportion of patients with clinical failure by day 28. Secondary endpoints include measurement of change in quality of life, length of hospital stay, antibiotic-related side effects, barriers and facilitators to the implementation of the algorithm, cost-effectiveness of the intervention, and identification of patterns of pneumonia in LUS using machine learning.

DISCUSSION

The PLUS algorithm aims to optimize prescription of antibiotics through improved diagnostic performance and maximization of physician adherence, while ensuring safety. It is based on previously validated tests and does therefore not expose participants to unforeseeable risks. Cluster randomization prevents cross-contamination between study groups, as physicians are not exposed to the intervention during or before the control period. The stepped-wedge implementation of the intervention allows effect calculation from both between- and within-cluster comparisons, which enhances statistical power and allows smaller sample size than a parallel cluster design. Moreover, it enables the training of all centers for the intervention, simplifying implementation if the results prove successful. The PLUS algorithm has the potential to improve the identification of LRTIs that would benefit from antibiotics. When scaled, the expected reduction in the proportion of antibiotics prescribed has the potential to not only decrease side effects and costs but also mitigate antibiotic resistance.

TRIAL REGISTRATION

This study was registered on July 19, 2022, on the ClinicalTrials.gov registry using reference number: NCT05463406.

TRIAL STATUS

Recruitment started on December 5, 2022, and will be completed on November 3, 2024. Current protocol version is version 3.0, dated April 3, 2023.

Lung Ultrasound Artifacts Interpreted as Pathology Footprints

Background: The original observation that lung ultrasound provides information regarding the physical state of the organ, rather than the anatomical details related to the disease, has reinforced the idea that the observed acoustic signs represent artifacts. However, the definition of artifact does not appear adequate since pulmonary ultrasound signs have shown valuable diagnostic accuracy, which has been usefully exploited by physicians in numerous pathologies. Method: A specific method has been used over the years to analyze lung ultrasound data and to convert artefactual information into anatomical information. Results: A physical explanation of the genesis of the acoustic signs is provided, and the relationship between their visual characteristics and the surface histopathology of the lung is illustrated. Two important sources of potential signal alteration are also highlighted. Conclusions: The acoustic signs are generated by acoustic traps that progressively release previously trapped energy. Consequently, the acoustic signs highlight the presence of acoustic traps and quantitatively describe their distribution on the lung surface; they are not artifacts, but pathology footprints and anatomical information. Moreover, the impact of the dynamic focusing algorithms and the impact of different probes on the visual aspect of the acoustic signs should not be neglected.

XperCT facilitates sharp recanalization for the treatment of chronic thoracic venous occlusive disease in hemodialysis patients

OBJECTIVE

Our objective was to evaluate the feasibility of XperCT combined fluoroscopy to guide sharp recanalization for the treatment of chronic thoracic venous occlusive disease in hemodialysis patients.

METHODS

The records of hemodialysis patients with chronic thoracic venous occlusive disease who received endovascular sharp recanalization after conventional techniques failed were retrospectively reviewed. The sharp devices used for recanalization included the stiff end of a guidewire, Chiba biopsy needle, RUPS-100 set, and transseptal needle. The needle was advanced toward a target placed at the opposite end of the occlusion and was guided by fluoroscopy and/or XperCT. While the guidewire crossed the occlusion, endovascular procedures such as percutaneous angioplasty were performed for the treatment of the occlusion.

RESULTS

The analysis included 32 sharp thoracic vein recanalization procedures in 29 patients. Two attempts in one patient failed, and in one patient the first attempt failed but the second attempt was successful. In one patient, two separate successful procedures were performed, and the other 26 procedures in 26 patients were successful. The overall technical success rate of sharp recanalization was 90%. The mean number of puncture attempts in the combined group was less than that of the fluoroscopy-guided alone group (2 vs 5, p < 0.05). The success rate of sharp recanalization in the combined group was higher (100% vs 86%), and the recanalization time (28.5 min vs 36 min, p > 0.05) was no different. There was no statistical difference in procedure-related complications between the groups.

CONCLUSION

XperCT can facilitate sharp recanalization for the treatment of chronic thoracic venous occlusive disease in hemodialysis patients.

Comparison of thoracic ultrasonography and thoracic radiography between healthy adult horses and horses with bacterial pneumonia using a novel, objective ultrasonographic scoring system

Background

Thoracic ultrasonography (TUS) is widely used in equine practice but comparison to radiography is limited in horses.

Objectives

To validate a novel, objective scoring system for TUS in adult horses and to compare ultrasonographic and radiographic findings.

Animals

13 healthy horses and 9 with confirmed bacterial pneumonia

Methods

Prospective study in which TUS and radiography were performed on healthy horses and those with bacterial pneumonia confirmed by clinical signs and results of transtracheal wash analysis. Ultrasonography was scored utilizing a novel scoring system evaluating number of comet tail lesions, the presence or absence of pleural effusion and/or pulmonary consolidation in each intercostal space. Eighteen horses had thoracic radiographs taken that were scored by a board-certified radiologist utilizing a previously described system. Total scores were recorded and compared between control and diseased patients.

Results/Findings

Ultrasonographic scores were significantly higher in the diseased group (median= 126) than in the control group (median = 20, p = 0.01). Receiver operating characteristics (ROC) analysis identified a sensitivity of 66.7% (95% CI 0.417–1) and specificity of 92.3% (95% CI 0.462–1) for the ability of ultrasonography to identify bacterial pneumonia utilizing a TUS score cutoff of 37.

Conclusions and clinical importance

TUS had moderate sensitivity and high specificity for identification of bacterial pneumonia in adult horses. TUS appears to be an acceptable stand-alone imaging modality for diagnosis of bacterial pneumonia in horses when radiography is not practical.

Point-of-care lung ultrasonography for early identification of mild COVID-19: a prospective cohort of outpatients in a Swiss screening center

OBJECTIVES

Early identification of SARS-CoV-2 infection is important to guide quarantine and reduce transmission. This study evaluates the diagnostic performance of lung ultrasound (LUS), an affordable, consumable-free point-of-care tool, for COVID-19 screening.

DESIGN, SETTING AND PARTICIPANTS

This prospective observational cohort included adults presenting with cough and/or dyspnoea at a SARS-CoV-2 screening centre of Lausanne University Hospital between 31 March and 8 May 2020.

INTERVENTIONS

Investigators recorded standardised LUS images and videos in 10 lung zones per patient. Two blinded independent experts reviewed LUS recording and classified abnormal findings according to prespecified criteria to investigate their predictive value to diagnose SARS-CoV-2 infection according to PCR on nasopharyngeal swabs (COVID-19 positive vs COVID-19 negative).

PRIMARY AND SECONDARY OUTCOME MEASURES

We finally combined LUS and clinical findings to derive a multivariate logistic regression diagnostic score.

RESULTS

Of 134 included patients, 23% (n=30/134) were COVID-19 positive and 77% (n=103/134) were COVID-19 negative; 85%, (n=114/134) cases were previously healthy healthcare workers presenting within 2-5 days of symptom onset (IQR). Abnormal LUS findings were significantly more frequent in COVID-19 positive compared with COVID-19 negative (45% vs 26%, p=0.045) and mostly consisted of focal pathologic B lines. Combining clinical findings in a multivariate logistic regression score had an area under the receiver operating curve of 80.3% to detect COVID-19, and slightly improved to 84.5% with the addition of LUS features.

CONCLUSIONS

COVID-19-positive patients are significantly more likely to have lung pathology by LUS. However, LUS has an insufficient sensitivity and is not an appropriate screening tool in outpatients. LUS only adds little value to clinical features alone.

Operative Use of Thoracic Ultrasound in Respiratory Medicine: A Clinical Study

For over 15 years, thoracic ultrasound has been applied in the evaluation of numerous lung diseases, demonstrating a variable diagnostic predictive power compared to traditional imaging techniques such as chest radiography and CT. However, in unselected pulmonary patients, there are no rigorous scientific demonstrations of the complementarity of thoracic ultrasound with traditional and standardized imaging techniques that use radiation. In this study 101 unselected pulmonary patients were evaluated blindly with ultrasound chest examinations during their hospital stay. Other instrumental examinations, carried out during hospitalization, were standard chest radiography, computed tomography (CT), and, when needed, radioisotopic investigation and cardiac catheterization. The operator who performed the ultrasound examinations was unaware of the anamnestic and clinical data of the patients. Diffuse fibrosing disease was detected with a sensitivity, specificity and diagnostic accuracy of 100%, 95% and 97%, respectively. In pleural effusions, ultrasound showed a sensitivity, specificity and diagnostic accuracy of 100%. In consolidations, the sensitivity, specificity and diagnostic accuracy were 83%, 98% and 93%, respectively. Low values of sensitivity were recorded for surface nodulations of less than one centimeter. Isolated subpleural ground glass densities were identified as White Lung with a sensitivity of 72% and a specificity of 86%. Only the associations Diffuse ultrasound findings/Definitive fibrosing disease, Ultrasound Consolidation/Definitive consolidation and non-diffuse ultrasound artefactual features/Definitive vascular pathology (pulmonary hypertension, embolism) were statistically significant with adjusted residuals of 7.9, 7 and 4.1, respectively. The obtained results show how chest ultrasound is an effective complementary diagnostic tool for the pulmonologist. When performed, as a complement to the patient’s physical examination, it can restrict the diagnostic hypothesis in the case of pleural effusion, consolidation and diffuse fibrosing disease of the lung.

Ultrasound for Pleural Disease. Beyond a Pocket of Pleural Fluid

The evolution of pleural disease imaging modalities through the years has helped the scientific community understand and treat various disease states. Ultrasound (US) has been an image modality that has reigned superior to those used in the past such as chest X-ray and computed tomographic scan in terms of cost effectiveness, portability, and reduction in unwarranted radiation exposure to patients. Here we provide a succinct review of US use in pleural disease including imaging techniques, identifying safe pleural space for access, and predicting pleural fluid volume and etiology along with specificities regarding trapped lung identification and pleural mass biopsy. We believe bedside chest US is an adjunct to the physical exam adding superior diagnostic abilities. Further research is warranted in more specific aspects of sonographic use such as in fibrinolytic therapy management, evaluation for trapped lung, and the utility of specific modes like the color flow Doppler.

Lung ultrasonography for risk stratification in patients with COVID-19: a prospective observational cohort study

Background

Point-of-care lung ultrasound (LUS) is a promising pragmatic risk stratification tool in COVID-19. This study describes and compares LUS characteristics between patients with different clinical outcomes

Methods

Prospective observational study of PCR-confirmed COVID-19 adults with symptoms of lower respiratory tract infection in the emergency department (ED) of Lausanne University Hospital. A trained physician recorded LUS images using a standardized protocol. Two experts reviewed images blinded to patient outcome. We describe and compare early LUS findings (acquired within 24hours of presentation to the ED) between patient groups based on their outcome at 7 days after inclusion: 1) outpatients, 2) hospitalised and 3) intubated/death. Normalized LUS score was used to discriminate between groups

Results

Between March 6 and April 3 2020, we included 80 patients (17 outpatients, 42 hospitalized and 21 intubated/dead). 73 patients (91%) had abnormal LUS (70% outpatients, 95% hospitalised and 100% intubated/death; p=0.003). The proportion of involved zones was lower in outpatients compared with other groups (median 30% [IQR 0-40%], 44% [31-70%] and 70% [50-88%], p<0.001). Predominant abnormal patterns were bilateral and multifocal spread thickening of the pleura with pleural line irregularities (70%), confluent B lines (60%) and pathologic B lines (50%). Posterior inferior zones were more often affected. Median normalized LUS score had a good level of discrimination between outpatients and others with area under the ROC of 0.80 (95% CI 0.68-0.92)

Conclusions

Systematic LUS has potential as a reliable, cheap and easy-to-use triage tool for the early risk stratification in COVID-19 patients presenting in EDs

The emerging role of lung ultrasound in COVID-19 pneumonia

In the last decades lung ultrasound (LUS) has become of crucial importance in the evaluation and monitoring of a widely range of pulmonary diseases. One of the major benefits which favours this examination, is that this is a non-invasive, low-cost and radiation-free imaging modality which allows repeated imaging. LUS plays an important role in a wide range of pathologies, including cardiogenic oedema, acute respiratory distress syndrome and fibrosis. Specific LUS findings have proved useful and predictive of acute respiratory distress syndrome which is of particular relevance in the suspicion and monitoring of patients with lung disease. Furthermore, several studies have confirmed the role of LUS in the screening of interstitial lung diseases in connective tissue diseases. Given these data, LUS will likely play an important role in the management of COVID-19 patients from identification of specific abnormalities corresponding to definite pneumonia phases and CT scans findings. In addition, LUS could allow reduction in the exposure of health-care workers to potential infection. Herein, we provide a summary on emerging role of lung ultrasound in COVID-19 pneumonia.

Physical Mechanisms Providing Clinical Information From Ultrasound Lung Images: Hypotheses and Early Confirmations

In standard B mode imaging, a set of ultrasound pulses is used to reconstruct a 2-D image even though some of the assumptions needed to do this are not fully satisfied. For this reason, ultrasound medical images show numerous artifacts which physicians recognize and evaluate as part of their diagnosis since even one artifact can provide clinical information. Understanding the physical mechanisms at the basis of the formation of an artifact is important to identify the physiopathological state of the biological medium which generated the artifact. Ultrasound lung images are a significant example of this challenge since everything that is represented beyond the thickness of the chest wall ( ≈ 2 cm) is artifactual information. A convincing physical explanation of the genesis of important ultrasound lung artifacts does not exist yet. Physicians simply base their diagnosis on a correlation observed over the years between the manifestation of some artifacts and the occurrence of particular lung pathologies. In this article, a plausible genesis of some important lung artifacts is suggested.

Procalcitonin and lung ultrasonography point-of-care testing to decide on antibiotic prescription in patients with lower respiratory tract infection in primary care: protocol of a pragmatic cluster randomized trial

Background

A minority of patients presenting with lower respiratory tract infection (LRTI) to their general practitioner (GP) have community-acquired pneumonia (CAP) and require antibiotic therapy. Identifying them is challenging, because of overlapping symptomatology and low diagnostic performance of chest X-ray.

Procalcitonin (PCT) can be safely used to decide on antibiotic prescription in patients with LRTI. Lung ultrasound (LUS) is effective in detecting lung consolidation in pneumonia and might compensate for the lack of specificity of PCT.

We hypothesize that combining PCT and LUS, available as point-of care tests (POCT), might reduce antibiotic prescription in LRTIs without impacting patient safety in the primary care setting.

Methods

This is a three-arm pragmatic cluster randomized controlled clinical trial. GPs are randomized either to PCT and LUS-guided antibiotic therapy or to PCT only-guided therapy or to usual care. Consecutive adult patients with an acute cough due to a respiratory infection will be screened and included if they present a clinical pneumonia as defined by European guidelines. Exclusion criteria are previous antibiotics for the current episode, working diagnosis of sinusitis, severe underlying lung disease, severe immunosuppression, hospital admission, pregnancy, inability to provide informed consent and unavailability of the GP. Patients will fill in a 28 day-symptom diary and will be contacted by phone on days 7 and 28. The primary outcome is the proportion of patients prescribed any antibiotic up to day 28. Secondary outcomes include clinical failure by day 7 (death, admission to hospital, absence of amelioration or worsening of relevant symptoms) and by day 28, duration of restricted daily activities, episode duration as defined by symptom score, number of medical visits, number of days with side effects due to antibiotics and a composite outcome combining death, admission to hospital and complications due to LRTI by day 28. An evaluation of the cost-effectiveness and of processes in the clinic using a mixed qualitative and quantitative approach will also be conducted.

Discussion

Our intervention targets only patients with clinically suspected CAP who have a higher pretest probability of definite pneumonia. The intervention will not substitute clinical assessment but completes it by introducing new easy-to-perform tests.

Trial registration

The study was registered on the 19th of June 2017 on the clinicaltrials.gov registry using reference number; NCT03191071.

Electronic supplementary material

The online version of this article (10.1186/s12890-019-0898-3) contains supplementary material, which is available to authorized users.

Effectiveness of Bedside Lung Ultrasound for Clinical Follow-Up of Primary Spontaneous Pneumothorax Patients Treated With Tube Thoracostomy

Primary spontaneous pneumothorax (PSP) is a common cause of presentation to emergency departments and subsequent hospitalization. Patients with large PSP are treated with tube thoracostomy (TT) and followed up with x-rays. In this study, we investigated the efficiency of bedside ultrasound and compared it with x-ray imaging for the clinical follow-up of PSP patients treated with TT.This is a prospective observational study. After ethical committee approval and written informed consent were obtained, patients who were treated with TT because of PSP were screened. In the follow-up of these patients, a bedside lung ultrasound (BLUS) was performed before every chest x-ray by an emergency physician experienced in performing BLUSs. The performance of BLUSs in detecting free air in the pleural cavity was compared statistically with that of x-rays.Sixty-two patients were enrolled in the study. In total, 166 BLUSs and x-rays were compared. The sensitivity of BLUS was 95.65% (85.20-99.50), specificity was 100% (79.40-100.00), positive predictive value was 100% (92-100), negative predictive value was 88.90% (65.30-98.60), and the area under the curve was 0.99 (0.974-1.000; P = 0.001) for detecting air in the pleural cavity. These results showed that there was no statistically significant difference between BLUS and x-ray methods for detecting air in the pleural cavity.Our study revealed that BLUS can be safely used for the follow-up of PSP patients treated with TT to determine if air is present in the pleural cavity. Further studies are needed.

The role of ultrasound lung artifacts in the diagnosis of respiratory diseases

INTRODUCTION

Thoracic ultrasound is employed for the diagnosis of many thoracic diseases and is an accepted detection tool of pleural effusions, atelectasis, pneumothorax, and pneumonia. However, the use of ultrasound for the evaluation of parenchymal lung disease, when the organ is still aerated, is a relatively new application. Areas covered: The diagnosis of a normal lung and the differentiation between a normally aerated lung and a lung with interstitial pathology is based on the interpretation of ultrasound artifacts universally known as A and B-Lines. Even though the practical role of lung ultrasound artifacts is accepted by many clinicians, their physical basis and the correlations between these signs and the causal pathology is not known in depth. Expert commentary: In this review, we discuss the meaning of A- and B-Lines in the diagnostic ultrasound imaging of the lung and the acoustic properties of the pleural plane which are at the basis of their generation.

Visual assessment versus computer-assisted gray scale analysis in the ultrasound evaluation of neonatal respiratory status

Background and aim

Lung ultrasound has been used to describe common respiratory diseases both by visual and computer-assisted gray scale analysis. In the present paper, we compare both methods in assessing neonatal respiratory status keeping two oxygenation indexes as standards.

Patients and methods

Neonates admitted to the NICU for respiratory distress were enrolled. Two neonatologists not attending the patients performed a lung scan, built a single frame database and rated the images with a standardized score. The same dataset was processed using the gray scale analysis implemented with textural features and machine learning analysis. Both the oxygenation ratio (PaO2/FiO2) and the alveolar arterial oxygen gradient (A-a) were kept as reference standards.

Results

Seventy-five neonates with different respiratory status were enrolled in the study and a dataset of 600 ultrasound frames was built. Visual assessment of respiratory status correlated significantly with PaO2/FiO2 (r = -0.55; p<0.0001) and the A-a (r = 0.59; p<0.0001) with a strong interobserver agreement (K = 0.91). A significant correlation was also found between both oxygenation indexes and the gray scale analysis of lung ultrasound scans using regions of interest corresponding to 50K (r = -0.42; p<0.002 for PaO2/FiO2; r = 0.46 p<0.001 for A-a) and 100K (r = -0.35 p<0.01 for PaO2/FiO2; r = 0.58 p<0.0001 for A-a) pixels regions of interest.

Conclusions

A semi quantitative estimate of the degree of neonatal respiratory distress was demonstrated both by a validated scoring system and by computer assisted analysis of the ultrasound scan. This data may help to implement point of care ultrasound diagnostics in the NICU.