The sound of air: point-of-care lung ultrasound in perioperative medicine

The Promise of Artificial Intelligence-Assisted Point-of-Care Ultrasonography in Perioperative Care

The role of point-of-care ultrasonography in the perioperative setting has expanded rapidly over recent years. Revolutionizing this technology further is integrating artificial intelligence to assist clinicians in optimizing images, identifying anomalies, performing automated measurements and calculations, and facilitating diagnoses. Artificial intelligence can increase point-of-care ultrasonography efficiency and accuracy, making it an even more valuable point-of-care tool. Given this topic's importance and ever-changing landscape, this review discusses the latest trends to serve as an introduction and update in this area.

Lung Ultrasound Signs: The Beginning. Part 3-An Accademia di Ecografia Toracica Comprehensive Review on Ultrasonographic Signs and Real Needs

Over the last 20 years, scientific literature and interest on chest/lung ultrasound (LUS) have exponentially increased. Interpreting mixed-anatomical and artifactual-pictures determined the need of a proposal of a new nomenclature of artifacts and signs to simplify learning, spread, and implementation of this technique. The aim of this review is to collect and analyze different signs and artifacts reported in the history of chest ultrasound regarding normal lung, pleural pathologies, and lung consolidations. By reviewing the possible physical and anatomical interpretation of these artifacts and signs reported in the literature, this work aims to present the AdET (Accademia di Ecografia Toracica) proposal of nomenclature and to bring order between published studies.

Lung ultrasound score in dogs and cats: A reliability study

BACKGROUND

Lung ultrasound (LUS) is a noninvasive tool for examining respiratory distress patients. The lung ultrasound score (LUSS) can be used to quantify and monitor lung aeration loss with good reliability.

HYPOTHESIS/OBJECTIVES

Assess the reliability of a new LUSS among raters with different levels of experience and determine how well the same raters agree on identifying patterns of LUS abnormalities.

ANIMALS

Forty LUS examinations of dogs and cats and 320 videos were reviewed from a digital database.

METHODS

Retrospective reliability study with post hoc analysis. Protocolized LUS were randomly selected; intrarater and interrater reliability of the LUSS and pattern recognition agreement among 4 raters with different levels of experience in LUS were tested.

RESULTS

The intrarater intraclass correlation coefficient (ICC) single measurement, absolute agreement, and 2-way mixed effects model was 0.967 for the high-experience rater (H-Exp), 0.963 and 0.952 for the medium-experience raters (M-Exp-1; M-Exp-2), and 0.950 for the low-experience rater (L-Exp). The interrater ICC average measurement, absolute agreement, and 2-way random effects model among the observers was 0.980. The Fleiss' kappa (k) values showed almost perfect agreement (k = 1) among raters in identifying pleural effusion and translobar tissue-like pattern, strong agreement for A-lines (k = 0.881) and B-lines (k = 0.806), moderate agreement (k = 0.693) for subpleural loss of aeration, and weak agreement (k = 0.474) for irregularities of the pleural line.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results indicate excellent intra- and interrater reliability for LUS scoring and pattern identification, providing a foundation for the use of the LUSS in emergency medicine and intensive care.

A New Global Definition of Acute Respiratory Distress Syndrome

Background: Since publication of the 2012 Berlin definition of acute respiratory distress syndrome (ARDS), several developments have supported the need for an expansion of the definition, including the use of high-flow nasal oxygen, the expansion of the use of pulse oximetry in place of arterial blood gases, the use of ultrasound for chest imaging, and the need for applicability in resource-limited settings. Methods: A consensus conference of 32 critical care ARDS experts was convened, had six virtual meetings (June 2021 to March 2022), and subsequently obtained input from members of several critical care societies. The goal was to develop a definition that would 1) identify patients with the currently accepted conceptual framework for ARDS, 2) facilitate rapid ARDS diagnosis for clinical care and research, 3) be applicable in resource-limited settings, 4) be useful for testing specific therapies, and 5) be practical for communication to patients and caregivers. Results: The committee made four main recommendations: 1) include high-flow nasal oxygen with a minimum flow rate of ⩾30 L/min; 2) use PaO2:FiO2 ⩽ 300 mm Hg or oxygen saturation as measured by pulse oximetry SpO2:FiO2 ⩽ 315 (if oxygen saturation as measured by pulse oximetry is ⩽97%) to identify hypoxemia; 3) retain bilateral opacities for imaging criteria but add ultrasound as an imaging modality, especially in resource-limited areas; and 4) in resource-limited settings, do not require positive end-expiratory pressure, oxygen flow rate, or specific respiratory support devices. Conclusions: We propose a new global definition of ARDS that builds on the Berlin definition. The recommendations also identify areas for future research, including the need for prospective assessments of the feasibility, reliability, and prognostic validity of the proposed global definition.

Sonographic Aeration Scoring Indicates Disease Severity in Critically Ill Patients with COVID-19

AIMS AND METHODS

We evaluated an ultrasound score from 0 to 32 points in eight pulmonary regions to monitor critically ill COVID-19 patients. The score was correlated to surrogate parameters of disease severity, i.e., the oxygenation index, respiratory support, mortality, plasma interleukin-6, and WHO and ARDS classifications.

RESULTS

A total of 27 patients were repeatedly examined, and 71 examinations were evaluated. Patients with severe COVID-19 scored higher (median 17) than those with moderate disease (median 11, p < 0.01). The score did not differentiate between stages of ARDS as defined by the Berlin criteria (p = 0.1) but could discern ARDS according to the revised ESICM definition (p = 0.002). Non-survivors had higher ultrasound scores than survivors (median 18.5 vs. 14, p = 0.04). The score correlated to the oxygenation index (ρ = -0.56, p = 0.03), and changes in the score between examinations correlated to changes in oxygenation (ρ = -0.41, p = 0.16). The correlation between the score and interleukin-6 was ρ = 0.35 (p < 0.001). The interrater reliability for the score was ICC = 0.87 (p < 0.001).

CONCLUSIONS

The ultrasound score is a reliable tool that might help monitor disease severity and may help stratify the risk of mortality.

Vertical Artifacts as Lung Ultrasound Signs: Trick or Trap? Part 2- An Accademia di Ecografia Toracica Position Paper on B-Lines and Sonographic Interstitial Syndrome

Although during the last few years the lung ultrasound (LUS) technique has progressed substantially, several artifacts, which are currently observed in clinical practice, still need a solid explanation of the physical phenomena involved in their origin. This is particularly true for vertical artifacts, conventionally known as B-lines, and for their use in clinical practice. A wider consensus and a deeper understanding of the nature of these artifactual phenomena will lead to a better classification and a shared nomenclature, and, ultimately, result in a more objective correlation between anatomo-pathological data and clinical scenarios. The objective of this review is to collect and document the different signs and artifacts described in the history of chest ultrasound, with a particular focus on vertical artifacts (B-lines) and sonographic interstitial syndrome (SIS). By reviewing the possible physical and anatomical interpretation of the signs and artifacts proposed in the literature, this work also aims to bring order to the available studies and to present the AdET (Accademia di Ecografia Toracica) viewpoint in terms of nomenclature and clinical approach to the SIS.

Point-of-care ultrasound use in emergencies: what every anaesthetist should know

Point-of-care ultrasound has been embraced by anaesthetists as an invaluable tool for rapid diagnosis of haemodynamic instability, to ensure procedural safety and monitor response to treatments. Increasingly available, affordable and portable, with emerging evidence of improved patient outcomes, point-of-care ultrasound has become a valuable tool in the emergency setting. This state-of-the-art review describes the feasibility of point-of-care ultrasound practice, training and maintenance of competence. It also describes the many uses of point-of-care ultrasound for the anaesthetist and describes the most salient point-of-care ultrasound views for anaesthetic emergencies including: undifferentiated shock; hypoxemia; and trauma. Procedural safety is also discussed in addition to relevant important governance aspects. Cardiac function should be assessed using the parasternal long axis, parasternal short basal/mid-papillary/apical, apical four chamber and subcostal four chamber views, and should include a visual estimation of global left ventricular ejection fraction. Other cardiovascular conditions that can be identified using point-of-care ultrasound include: pericardial effusion; cardiac tamponade; and pulmonary embolism. Pulmonary emergency conditions that can be diagnosed using point-of-care ultrasound include pneumothorax; pleural effusion; and interstitial syndrome. The extended focused assessment with sonography for trauma examination may of value in patients who are hypotensive in order to identify intra-abdominal haemorrhage, pneumothoraces and haemothoraces.

Lung Ultrasound and Electrical Impedance Tomography During Ventilator-Induced Lung Injury

OBJECTIVES

Lung damage during mechanical ventilation involves lung volume and alveolar water content, and lung ultrasound (LUS) and electrical impedance tomography changes are related to these variables. We investigated whether these techniques may detect any signal modification during the development of ventilator-induced lung injury (VILI).

DESIGN

Experimental animal study.

SETTING

Experimental Department of a University Hospital.

SUBJECTS

Forty-two female pigs (24.2 ± 2.0 kg).

INTERVENTIONS

The animals were randomized into three groups (n = 14): high tidal volume (TV) (mean TV, 803.0 ± 121.7 mL), high respiratory rate (RR) (mean RR, 40.3 ± 1.1 beats/min), and high positive-end-expiratory pressure (PEEP) (mean PEEP, 24.0 ± 1.1 cm H2O). The study lasted 48 hours. At baseline and at 30 minutes, and subsequently every 6 hours, we recorded extravascular lung water, end-expiratory lung volume, lung strain, respiratory mechanics, hemodynamics, and gas exchange. At the same time-point, end-expiratory impedance was recorded relatively to the baseline. LUS was assessed every 12 hours in 12 fields, each scoring from 0 (presence of A-lines) to 3 (consolidation).

MEASUREMENTS AND MAIN RESULTS

In a multiple regression model, the ratio between extravascular lung water and end-expiratory lung volume was significantly associated with the LUS total score (p < 0.002; adjusted R2, 0.21). The variables independently associated with the end-expiratory difference in lung impedance were lung strain (p < 0.001; adjusted R2, 0.18) and extravascular lung water (p < 0.001; adjusted R2, 0.11).

CONCLUSIONS

Data suggest as follows. First, what determines the LUS score is the ratio between water and gas and not water alone. Therefore, caution is needed when an improvement of LUS score follows a variation of the lung gas content, as after a PEEP increase. Second, what determines the end-expiratory difference in lung impedance is the strain level that may disrupt the intercellular junction, therefore altering lung impedance. In addition, the increase in extravascular lung water during VILI development contributed to the observed decrease in impedance.

Diagnostic ultrasound imaging of the lung: A simulation approach based on propagation and reverberation in the human body

Although ultrasound cannot penetrate a tissue/air interface, it images the lung with high diagnostic accuracy. Lung ultrasound imaging relies on the interpretation of "artifacts," which arise from the complex reverberation physics occurring at the lung surface but appear deep inside the lung. This physics is more complex and less understood than conventional B-mode imaging in which the signal directly reflected by the target is used to generate an image. Here, to establish a more direct relationship between the underlying acoustics and lung imaging, simulations are used. The simulations model ultrasound propagation and reverberation in the human abdomen and at the tissue/air interfaces of the lung in a way that allows for direct measurements of acoustic pressure inside the human body and various anatomical structures, something that is not feasible clinically or experimentally. It is shown that the B-mode images beamformed from these acoustical simulations reproduce primary clinical features that are used in diagnostic lung imaging, i.e., A-lines and B-lines, with a clear relationship to known underlying anatomical structures. Both the oblique and parasagittal views are successfully modeled with the latter producing the characteristic "bat sign," arising from the ribs and intercostal part of the pleura. These simulations also establish a quantitative link between the percentage of fluid in exudative regions and the appearance of B-lines, suggesting that the B-mode may be used as a quantitative imaging modality.

The Role of Lung Ultrasound Before and During the COVID-19 Pandemic: A review article

Lung ultrasound [LUS] has evolved considerably over the last years. The aim of the current review is to conduct a systematic review reported from a number of studies to show the usefulness of [LUS] and point of care ultrasound for diagnosing COVID-19. A systematic search of electronic data was conducted including the national library of medicine, and the national institute of medicine, PubMed Central [PMC] to identify the articles depended on [LUS] to monitor COVID-19. This review highlights the ultrasound findings reported in articles before the pandemic [11], clinical articles before COVID-19 [14], review studies during the pandemic [27], clinical cases during the pandemic [5] and other varying aims articles. The reviewed studies revealed that ultrasound findings can be used to help in the detection and staging of the disease. The common patterns observed included irregular and thickened A-lines, multiple B-lines ranging from focal to diffuse interstitial consolidation, and pleural effusion. Sub-plural consolidation is found to be associated with the progression of the disease and its complications. Pneumothorax was not recorded for COVID-19 patients. Further improvement in the diagnostic performance of [LUS] for COVID-19 patients can be achieved by using elastography, contrast-enhanced ultrasound, and power Doppler imaging.

Ultrasound versus Computed Tomography Assessment of Focal Lung Aeration in Invasively Ventilated ICU Patients

It is unknown whether and to what extent the penetration depth of lung ultrasound (LUS) influences the accuracy of LUS findings. The current study evaluated and compared the LUS aeration score and two frequently used B-line scores with focal lung aeration assessed by chest computed tomography (CT) at different levels of depth in invasively ventilated intensive care unit (ICU) patients. In this prospective observational study, patients with a clinical indication for chest CT underwent a 12-region LUS examination shortly before CT scanning. LUS images were compared with corresponding regions on the chest CT scan at different subpleural depths. For each LUS image, the LUS aeration score was calculated. LUS images with B-lines were scored as the number of separately spaced B-lines (B-line count score) and the percentage of the screen covered by B-lines divided by 10 (B-line percentage score). The fixed-effect correlation coefficient (β) was presented per 100 Hounsfield units. A total of 40 patients were included, and 372 regions were analyzed. The best association between the LUS aeration score and CT was found at a subpleural depth of 5 cm for all LUS patterns (β = 0.30, p < 0.001), 1 cm for A- and B1-patterns (β = 0.10, p < 0.001), 6 cm for B1- and B2-patterns (β = 0.11, p < 0.001) and 4 cm for B2- and C-patterns (β = 0.07, p = 0.001). The B-line percentage score was associated with CT (β = 0.46, p = 0.001), while the B-line count score was not (β = 0.07, p = 0.305). In conclusion, the subpleural penetration depth of ultrasound increased with decreased aeration reflected by the LUS pattern. The LUS aeration score and the B-line percentage score accurately reflect lung aeration in ICU patients, but should be interpreted while accounting for the subpleural penetration depth of ultrasound.

Ultrasound: The New Stethoscope (Point-of-Care Ultrasound)

Advances in technology have led to more user-friendly ultrasound devices that allow for easy incorporation into daily perioperative practice, with the anesthesiologist serving as the sonographer. With appropriate knowledge and training, bedside ultrasound examinations can be used to better diagnose pathology and guide perioperative strategies. Cardiac ultrasound examination was the initial emphasis in anesthesiology, with now expansion into lung and gastric ultrasound imaging. In this review, the indications, procedural description, and clinical findings for lung and gastric ultrasound examinations are discussed to demonstrate its importance and build confidence in the user.

The role of lung ultrasound in COVID-19 disease

This statement summarises basic settings in lung ultrasonography and best practice recommendations for lung ultrasonography in COVID-19, representing the agreed consensus of experts from the Ultrasound Subcommittee of the European Society of Radiology (ESR). Standard lung settings and artefacts in lung ultrasonography are explained for education and training, equipment settings, documentation and self-protection.

Clinical Impact of Vertical Artifacts Changing with Frequency in Lung Ultrasound

Background: This study concerns the application of lung ultrasound (LUS) for the evaluation of the significance of vertical artifact changes with frequency and pleural line abnormalities in differentiating pulmonary edema from pulmonary fibrosis. Study Design and Methods: The study was designed as a diagnostic test. Having qualified patients for the study, an ultrasound examination was performed, consistent with a predetermined protocol, and employing convex and linear transducers. We investigated the possibility of B-line artifact conversion depending on the set frequency (2 MHz and 6 MHz), and examined pleural line abnormalities. Results: The study group comprised 32 patients with interstitial lung disease (ILD) (and fibrosis) and 30 patients with pulmonary edema. In total, 1941 cineloops were obtained from both groups and analyzed. The employment of both types of transducers (linear and convex) was most effective (specificity 91%, specificity 97%, positive predictive value (PPV) 97%, negative predictive value (NPV) 91%, LR(+) 27,19, LR(−) 0.097, area under curve (AUC) = 0.936, p = 7 × 10⁻⁶). Interpretation: The best accuracy in differentiating the etiology of B-line artifacts was obtained with the use of both types of transducers (linear and convex), complemented with the observation of the conversion of B-line artifacts to Z-line.

American Society of Regional Anesthesia and Pain Medicine expert panel recommendations on point-of-care ultrasound education and training for regional anesthesiologists and pain physicians-part II: recommendations

Point-of-care ultrasound (POCUS) is a critical skill for all regional anesthesiologists and pain physicians to help diagnose relevant complications related to routine practice and guide perioperative management. In an effort to inform the regional anesthesia and pain community as well as address a need for structured education and training, the American Society of Regional Anesthesia and Pain Medicine Society (ASRA) commissioned this narrative review to provide recommendations for POCUS. The recommendations were written by content and educational experts and were approved by the guidelines committee and the Board of Directors of the ASRA. In part II of this two-part series, learning goals and objectives were identified and outlined for achieving competency in the use of POCUS, specifically, airway ultrasound, lung ultrasound, gastric ultrasound, the focus assessment with sonography for trauma exam, and focused cardiac ultrasound, in the perioperative and chronic pain setting. It also discusses barriers to POCUS education and training and proposes a list of educational resources. For each POCUS section, learning goals and specific skills were presented in the Indication, Acquisition, Interpretation, and Medical decision-making framework.

American Society of Regional Anesthesia and Pain Medicine expert panel recommendations on point-of-care ultrasound education and training for regional anesthesiologists and pain physicians-part I: clinical indications

Point-of-care ultrasound (POCUS) is a critical skill for all regional anesthesiologists and pain physicians to help diagnose relevant complications related to routine practice and guide perioperative management. In an effort to inform the regional anesthesia and pain community as well as address a need for structured education and training, the American Society of Regional Anesthesia and Pain Medicine (ASRA) commissioned this narrative review to provide recommendations for POCUS. The guidelines were written by content and educational experts and approved by the Guidelines Committee and the Board of Directors of the ASRA. In part I of this two-part series, clinical indications for POCUS in the perioperative and chronic pain setting are described. The clinical review addresses airway ultrasound, lung ultrasound, gastric ultrasound, the focus assessment with sonography for trauma examination and focused cardiac ultrasound for the regional anesthesiologist and pain physician. It also provides foundational knowledge regarding ultrasound physics, discusses the impact of handheld devices and finally, offers insight into the role of POCUS in the pediatric population.

Ultrasound assessment of pulmonary fibroproliferative changes in severe COVID-19: a quantitative correlation study with histopathological findings

PURPOSE

This study was designed to evaluate the usefulness of lung ultrasound (LUS) imaging to characterize the progression and severity of lung damage in cases of COVID-19.

METHODS

We employed a set of combined ultrasound parameters and histopathological images obtained simultaneously in 28 patients (15 women, 0.6-83 years) with fatal COVID-19 submitted to minimally invasive autopsies, with different times of disease evolution from initial symptoms to death (3-37 days, median 18 days). For each patient, we analysed eight post-mortem LUS parameters and the proportion of three histological patterns (normal lung, exudative diffuse alveolar damage [DAD] and fibroproliferative DAD) in eight different lung regions. The relationship between histopathological and post-mortem ultrasonographic findings was assessed using various statistical approaches.

RESULTS

Statistically significant positive correlations were observed between fibroproliferative DAD and peripheral consolidation (coefficient 0.43, p = 0.02) and pulmonary consolidation (coefficient 0.51, p = 0.005). A model combining age, time of evolution, sex and ultrasound score predicted reasonably well (r = 0.66) the proportion of pulmonary parenchyma with fibroproliferative DAD.

CONCLUSION

The present study adds information to previous studies related to the use of LUS as a tool to assess the severity of acute pulmonary damage. We provide a histological background that supports the concept that LUS can be used to characterize the progression and severity of lung damage in severe COVID-19.

Point-of-Care Ultrasound in Acute Care Nephrology

The use of point-of-care ultrasound (POCUS) is rapidly increasing in nephrology. It provides the opportunity to obtain complementary information that is more accurate than the classic physical examination. One can quickly follow the physical examination with a systematic POCUS evaluation of the kidneys, ureter bladder, inferior vena cava, heart, and lungs, which can provide diagnostic information and an accurate assessment of the patient's hemodynamics and volume status. Moreover, because it is safe and relatively easy to perform, it can be performed in a repeated manner as often as necessary so that the physician can reassess the patient's hemodynamics and volume status and adjust their therapy accordingly, permitting a more personalized approach to patient care (rather than blindly following protocols), especially to patients in acute care nephrology. Despite these advantages, nephrologists have been slow to adopt this diagnostic modality, perhaps because of lack of expertise. This review will provide an overview of the most commonly used POCUS examinations performed by nephrologists in the acute care setting. Its aim is to spark interest in in POCUS and to lay the foundation for readers to pursue more advanced training so that POCUS becomes a readily available tool in your diagnostic arsenal.

Ultrasound-guided Visualization of Subglottic Secretions in Intubated Patients

Supplemental Digital Content is available in the text.

Lung Ultrasound Pattern in Healthy Infants During the First 6 Months of Life

OBJECTIVES

Lung ultrasound (LUS) has gained a primary role in the diagnosis and management of pleuropulmonary disorders in pediatric practice. However, normal and pathologic patterns are translated from adult studies and have never been specifically studied in children, particularly in infants. This was a prospective observational pilot study aiming to define the normal LUS pattern in healthy infants during the first 6 months of life.

METHODS

We recruited healthy neonates at 7 to 10 days of life, and these were followed until the sixth month of life (times: 7-10 days, 1 month, 3 months, and 6 months). We excluded neonates with a gestational age before 33 weeks and neonates with cardiac or lung abnormalities or diseases, immune deficiencies, metabolic or genetic conditions, and acute or chronic respiratory diseases. A LUS evaluation was performed by a single certified pediatrician. The chest wall was examined in 18 areas, addressing A-lines, short and long B-lines, pleural abnormalities, and subpleural consolidations.

RESULTS

Thirty-seven neonates were enrolled and followed until the sixth month of life, 27 (73%) of whom were born at term (≥37 weeks) and 10 (27%) of whom were born preterm (33-36 weeks). Most of the patients at 7 to 10 days showed multiple B-lines (long and short) with a progressive normalization toward a normal A pattern at 6 months (P < .00001; 95% confidence interval, 13.75-23.24). No infants showed subpleural consolidations or pleural abnormalities.

CONCLUSIONS

This study has implications for the interpretation of LUS during the first 6 months of life. Most healthy infants show a diffuse pattern of vertical artifacts (B-lines), and the LUS pattern tends to be similar to the physiologic pattern (A-lines) after the sixth month of life. The only pathologic LUS findings were pleural irregularities and effusion and subpleural consolidations, which have never been described in healthy infants.

Are pocket sized ultrasound devices sufficient in the evaluation of lung ultrasound patterns and aeration scoring in pulmonary ICU patients?

Lung ultrasound (LUS) is a practical diagnostic tool for several lung pathologies. Pocket sized USG devices (PSUDs) are more affordable, accessible, practical, and learning to use them is easier than standard ultrasound devices (SUDs). Their capability in image quality have been found as comparable with standard USG machines. Studies have been showing that these devices can be useful as much as SUDs in the evaluation of heart, abdomen, vascular structures, diaphragm and optic nerve. The aim of this study is to compare PSUD with a standard ultrasound devices (SUD) in the evaluation of LUS patterns such as alveolar, interstitial syndromes and lung aeration score (LAS). Study performed in an University Hospital Pulmonary ICU. All patients older than 18 years old were included in this study. The sector probe of SUD (Vivid-Q) and PSUD (Vscan) were used for investigation of A lines, interstitial (B lines), alveolar syndromes (consolidation, hepatisation, air bronchograms) and pleural effusion. 33 patients were included in the study. When PSUD was compared with SUD in terms of total B2 count, and LAS in the right, left and both lung, there was an agreement without proportional bias according to Bland Altman test. There was also good inter class correlation coefficient value as greater than 0.8 and 0.7 between two physicians in terms of counting of total B1, B2, total B lines and calculating of total LAS for SUD and PSUD respectively. PSUDs is a reliable and valid method for evaluation of LUS patterns like SUDs.

Positional Therapy and Regional Pulmonary Ventilation

BACKGROUND

Prone ventilation redistributes lung inflation along the gravitational axis; however, localized, nongravitational effects of body position are less well characterized. The authors hypothesize that positional inflation improvements follow both gravitational and nongravitational distributions. This study is a nonoverlapping reanalysis of previously published large animal data.

METHODS

Five intubated, mechanically ventilated pigs were imaged before and after lung injury by tracheal injection of hydrochloric acid (2 ml/kg). Computed tomography scans were performed at 5 and 10 cm H2O positive end-expiratory pressure (PEEP) in both prone and supine positions. All paired prone-supine images were digitally aligned to each other. Each unit of lung tissue was assigned to three clusters (K-means) according to positional changes of its density and dimensions. The regional cluster distribution was analyzed. Units of tissue displaying lung recruitment were mapped.

RESULTS

We characterized three tissue clusters on computed tomography: deflation (increased tissue density and contraction), limited response (stable density and volume), and reinflation (decreased density and expansion). The respective clusters occupied (mean ± SD including all studied conditions) 29.3 ± 12.9%, 47.6 ± 11.4%, and 23.1 ± 8.3% of total lung mass, with similar distributions before and after lung injury. Reinflation was slightly greater at higher PEEP after injury. Larger proportions of the reinflation cluster were contained in the dorsal versus ventral (86.4 ± 8.5% vs. 13.6 ± 8.5%, P < 0.001) and in the caudal versus cranial (63.4 ± 11.2% vs. 36.6 ± 11.2%, P < 0.001) regions of the lung. After injury, prone positioning recruited 64.5 ± 36.7 g of tissue (11.4 ± 6.7% of total lung mass) at lower PEEP, and 49.9 ± 12.9 g (8.9 ± 2.8% of total mass) at higher PEEP; more than 59.0% of this recruitment was caudal.

CONCLUSIONS

During mechanical ventilation, lung reinflation and recruitment by the prone positioning were primarily localized in the dorso-caudal lung. The local effects of positioning in this lung region may determine its clinical efficacy.

EDITOR’S PERSPECTIVE

[Lung ultrasonography in COVID-19 pneumonia]

BACKGROUND

Point-of-care ultrasound (POCUS) of the lung in patients with COVID-19 plays a key role in the emergency room and intensive care unit. Lung ultrasound is able to depict typical pulmonary findings of COVID-19 and is therefore suitable for diagnosis and follow-up of these patients.

CLINICAL/METHODOLOGICAL ISSUE

Lung ultrasound in COVID-19 patients in the emergency room and intensive care unit.

STANDARD RADIOLOGICAL METHODS

Computed tomography (low-dose CT) and X‑ray of the lung.

METHODOLOGICAL INNOVATIONS

Lung ultrasound in COVID-19 patients.

RECOMMENDATIONS

Lung ultrasound in patients with COVID-19 offers similar performance as CT and is superior when compared to X‑ray in evaluating pneumonia and acute respiratory distress syndrome (ARDS). Lung ultrasound plays an important role in the emergency room and intensive care unit. POCUS reduces exposure to radiation, therapy delays, and minimizes transport of high-risk patients. Differential diagnoses can also be clarified.

Lung ultrasound score to determine the effect of fraction inspired oxygen during alveolar recruitment on absorption atelectasis in laparoscopic surgery: a randomized controlled trial

Background

Although the intraoperative alveolar recruitment maneuver (RM) efficiently treats atelectasis, the effect of Fio₂ on atelectasis during RM is uncertain. We hypothesized that a high Fio₂ (1.0) during RM would lead to a higher degree of postoperative atelectasis without benefiting oxygenation when compared to low Fio₂ (0.4).

Methods

In this randomized controlled trial, patients undergoing elective laparoscopic surgery in the Trendelenburg position were allocated to low- (Fio₂ 0.4, n = 44) and high-Fio₂ (Fio₂ 1.0, n = 46) groups. RM was performed 1-min post tracheal intubation and post changes in supine and Trendelenburg positions during surgery. We set the intraoperative Fio₂ at 0.4 for both groups and calculated the modified lung ultrasound score (LUSS) to assess lung aeration after anesthesia induction and at surgery completion. The primary outcome was modified LUSS at the end of the surgery. The secondary outcomes were the intra- and postoperative Pao₂ to Fio₂ ratio and postoperative pulmonary complications.

Results

The modified LUSS before capnoperitoneum and RM (P = 0.747) were similar in both groups. However, the postoperative modified LUSS was significantly lower in the low Fio₂ group (median difference 5.0, 95% CI 3.0–7.0, P < 0.001). Postoperatively, substantial atelectasis was more common in the high-Fio₂ group (relative risk 1.77, 95% CI 1.27–2.47, P < 0.001). Intra- and postoperative Pao₂ to Fio₂ were similar with no postoperative pulmonary complications. Atelectasis occurred more frequently when RM was performed with high than with low Fio₂; oxygenation was not benefitted by a high-Fio_2.

Conclusions

In patients undergoing laparoscopic surgery in the Trendelenburg position, absorption atelectasis occurred more frequently with high rather than low Fio₂. No oxygenation benefit was observed in the high-Fio₂ group.

Trial registration

ClinicalTrials.gov, NCT03943433. Registered 7 May 2019,

Essential Image Acquisition Protocols for Thoracic Ultrasonography

Image acquisition is the technique of correct placement, holding, and manipulation of the ultrasound probe in an ultrasound examination for the purpose of answering a specific clinical question. We review the literature and discuss the image acquisition protocols used for thoracic ultrasound, explaining, where possible, the associated advantages, disadvantages, and alternatives. A better understanding of how to fine-tune image acquisition specifically for thoracic ultrasound will help physicians on all levels to standardise their practice and improve networking and collaboration. It will also lead to better-quality investigations and, potentially, new applications.

[Lung Ultrasound: new Opportunities for a Cardiologist]

This review focused on ultrasound examination of lungs, a useful complement to transthoracic echocardiography (EchoCG), which is superior to chest X-ray in the diagnostic value. The lung acoustic window always remains open and allows obtaining high-quality images in most cases. For a cardiologist, the major points of the method application are determination of pleural effusion and lung congestion. This method has a number of advantages: it is time-saving; cost-effective; portable and accessible; can be used in a real-time mode; not associated with radiation; reproducible; and highly informative. The ultrasound finding of wet lungs would indicate threatening, acute cardiac decompensation long before appearance of clinical, auscultative, and radiological signs of lung congestion. Modern EchoCG should include examination of the heart and lungs as a part of a single, integrative ultrasound examination.

Tracheal, Lung, and Diaphragmatic Applications of M-Mode Ultrasonography in Anesthesiology and Critical Care

Today, proficiency in cardiopulmonary ultrasound is considered essential for anesthesiologists and critical care physicians. Conventional 2-dimensional images, however, do not permit optimal characterization of specific conditions (eg, diaphragmatic paralysis, major atelectasis, and pneumothorax) that may have relevant clinical implications in critical care and perioperative settings. By contrast, M-mode (motion-based) ultrasonographic imaging modality offers the highest temporal resolution in ultrasonography; this modality, therefore, can provide important information in ultrasound-driven approaches performed by anesthesiologists and intensivists for diagnosis, monitoring, and procedural guidance. Despite its practicability, M-mode has been progressively abandoned in echocardiography and is often underused in lung and diaphragmatic ultrasound. This review describes contemporary applications of M-mode ultrasonography in the practice of critical care and perioperative medicine. Information presented for each clinical application includes image acquisition and interpretation, evidence-based clinical implications in critically ill and surgical patients, and main limitations. The article focuses on tracheal, lung, and diaphragmatic ultrasound. It reviews tracheal ultrasound for procedural guidance during endotracheal intubation, confirmation of correct tube placement, and detection of esophageal intubation; lung ultrasound for the confirmation of endotracheal and endobronchial (selective) intubation and for the diagnosis of pneumothorax, alveolar-interstitial syndrome (cardiogenic v noncardiogenic pulmonary edema), pulmonary consolidation (pneumonia v major atelectasis) and pleural effusion; and diaphragmatic ultrasound for the diagnosis of diaphragmatic dysfunction and prediction of extubation success.

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.

Synopsis of the point-of-care ultrasound assessment for perioperative emergencies

This module will introduce the concept of a point-of-care ultrasound (POCUS) examination for perioperative clinicians. A focused cardiac examination of ventricular filling and function is presented. An examination of the inferior vena cava is also reviewed as a tool to assess volume status. Finally, a brief examination of the lung and pleura is explored to aid the clinician in situations of patient hypoxia and difficult ventilation. Limited ultrasound cardiorespiratory examinations can be performed by non-cardiologists and non-radiologists. Information drawn from POCUS may aid in diagnosis and early rescue in perioperative care. Point-of-care ultrasound is likely to become standard of care for anesthesiologists in the same way that stethoscopy is presently.

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.