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      Association Between Arterial Oxygen Saturation and Lung Ultrasound B-Lines After Competitive Deep Breath-Hold Diving

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          Abstract

          Breath-hold diving (freediving) is an underwater sport that is associated with elevated hydrostatic pressure, which has a compressive effect on the lungs that can lead to the development of pulmonary edema. Pulmonary edema reduces oxygen uptake and thereby the recovery from the hypoxia developed during freediving, and increases the risk of hypoxic syncope. We aimed to examine the efficacy of SpO 2, via pulse-oximetry, as a tool to detect pulmonary edema by comparing it to lung ultrasound B-line measurements after deep diving. SpO 2 and B-lines were collected in 40 freedivers participating in an international deep freediving competition. SpO 2 was measured within 17 ± 6 min and lung B-lines using ultrasound within 44 ± 15 min after surfacing. A specific symptoms questionnaire was used during SpO 2 measurements. We found a negative correlation between B-line score and minimum SpO 2 ( r s = −0.491; p = 0.002) and mean SpO 2 ( r s = −0.335; p = 0.046). B-line scores were positively correlated with depth ( r s = 0.408; p = 0.013), confirming that extra-vascular lung water is increased with deeper dives. Compared to dives that were asymptomatic, symptomatic dives had a 27% greater B-line score, and both a lower mean and minimum SpO 2 (all p < 0.05). Indeed, a minimum SpO 2 ≤ 95% after a deep dive has a positive predictive value of 29% and a negative predictive value of 100% regarding symptoms. We concluded that elevated B-line scores are associated with reduced SpO 2 after dives, suggesting that SpO 2 via pulse oximetry could be a useful screening tool to detect increased extra-vascular lung water. The practical application is not to diagnose pulmonary edema based on SpO 2 – as pulse oximetry is inexact – rather, to utilize it as a tool to determine which divers require further evaluation before returning to deep freediving.

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          International evidence-based recommendations for point-of-care lung ultrasound.

          The purpose of this study is to provide evidence-based and expert consensus recommendations for lung ultrasound with focus on emergency and critical care settings. A multidisciplinary panel of 28 experts from eight countries was involved. Literature was reviewed from January 1966 to June 2011. Consensus members searched multiple databases including Pubmed, Medline, OVID, Embase, and others. The process used to develop these evidence-based recommendations involved two phases: determining the level of quality of evidence and developing the recommendation. The quality of evidence is assessed by the grading of recommendation, assessment, development, and evaluation (GRADE) method. However, the GRADE system does not enforce a specific method on how the panel should reach decisions during the consensus process. Our methodology committee decided to utilize the RAND appropriateness method for panel judgment and decisions/consensus. Seventy-three proposed statements were examined and discussed in three conferences held in Bologna, Pisa, and Rome. Each conference included two rounds of face-to-face modified Delphi technique. Anonymous panel voting followed each round. The panel did not reach an agreement and therefore did not adopt any recommendations for six statements. Weak/conditional recommendations were made for 2 statements, and strong recommendations were made for the remaining 65 statements. The statements were then recategorized and grouped to their current format. Internal and external peer-review processes took place before submission of the recommendations. Updates will occur at least every 4 years or whenever significant major changes in evidence appear. This document reflects the overall results of the first consensus conference on "point-of-care" lung ultrasound. Statements were discussed and elaborated by experts who published the vast majority of papers on clinical use of lung ultrasound in the last 20 years. Recommendations were produced to guide implementation, development, and standardization of lung ultrasound in all relevant settings.
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            Lung ultrasound in the critically ill

            Lung ultrasound is a basic application of critical ultrasound, defined as a loop associating urgent diagnoses with immediate therapeutic decisions. It requires the mastery of ten signs: the bat sign (pleural line), lung sliding (yielding seashore sign), the A-line (horizontal artifact), the quad sign, and sinusoid sign indicating pleural effusion, the fractal, and tissue-like sign indicating lung consolidation, the B-line, and lung rockets indicating interstitial syndrome, abolished lung sliding with the stratosphere sign suggesting pneumothorax, and the lung point indicating pneumothorax. Two more signs, the lung pulse and the dynamic air bronchogram, are used to distinguish atelectasis from pneumonia. All of these disorders were assessed using CT as the “gold standard” with sensitivity and specificity ranging from 90% to 100%, allowing ultrasound to be considered as a reasonable bedside “gold standard” in the critically ill. The BLUE-protocol is a fast protocol (<3 minutes), which allows diagnosis of acute respiratory failure. It includes a venous analysis done in appropriate cases. Pulmonary edema, pulmonary embolism, pneumonia, chronic obstructive pulmonary disease, asthma, and pneumothorax yield specific profiles. Pulmonary edema, e.g., yields anterior lung rockets associated with lung sliding, making the “B-profile.” The FALLS-protocol adapts the BLUE-protocol to acute circulatory failure. It makes sequential search for obstructive, cardiogenic, hypovolemic, and distributive shock using simple real-time echocardiography (right ventricle dilatation, pericardial effusion), then lung ultrasound for assessing a direct parameter of clinical volemia: the apparition of B-lines, schematically, is considered as the endpoint for fluid therapy. Other aims of lung ultrasound are decreasing medical irradiation: the LUCIFLR program (most CTs in ARDS or trauma can be postponed), a use in traumatology, intensive care unit, neonates (the signs are the same than in adults), many disciplines (pulmonology, cardiology…), austere countries, and a help in any procedure (thoracentesis). A 1992, cost-effective gray-scale unit, without Doppler, and a microconvex probe are efficient. Lung ultrasound is a holistic discipline for many reasons (e.g., one probe, perfect for the lung, is able to scan the whole-body). Its integration can provide a new definition of priorities. The BLUE-protocol and FALLS-protocol allow simplification of expert echocardiography, a clear advantage when correct cardiac windows are missing.
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              Usefulness of ultrasound lung comets as a nonradiologic sign of extravascular lung water.

              The "comet-tail" is an ultrasound sign detectable with ultrasound chest instruments; this sign consists of multiple comet-tails fanning out from the lung surface. They originate from water-thickened interlobular septa and would be ideal for nonradiologic bedside assessment of extravascular lung water. To assess the feasibility and value of ultrasonic comet signs, we studied 121 consecutive hospitalized patients (43 women and 78 men; aged 67 +/- 12 years) admitted to our combined cardiology-pneumology department (including cardiac intensive care unit); the study was conducted with commercially available echocardiographic systems including a portable unit. Transducer frequencies (range 2.5 to 3.5 MHz) were used. In each patient, the right and left chest was scanned by examining predefined locations in multiple intercostal spaces. Examiners blinded to clinical diagnoses noted the presence and numbers of lung comets at each examining site. A patient lung comet score was obtained by summing the number of comets in each of the scanning spaces. Within a few minutes, patients underwent chest x-ray, with specific assessment of extravascular lung water score by 2 pneumologist-radiologists blinded to clinical and echo findings. The chest ultrasound scan was obtained in all patients (feasibility 100%). The imaging time per examination was always <3 minutes. There was a linear correlation between echocardiographic comet score and radiologic lung water score (r = 0.78, p <0.01). Intrapatient variations (n = 15) showed an even stronger correlation between changes in echocardiographic lung comet and radiologic lung water scores (r = 0.89; p <0.01). In 121 consecutive hospitalized patients, we found a linear correlation between echocardiographic comet scores and radiologic extravascular lung water scores. Thus, the comet-tail is a simple, non-time-consuming, and reasonably accurate chest ultrasound sign of extravascular lung water that can be obtained at bedside (also with portable echocardiographic equipment) and is not restricted by cardiac acoustic window limitations.
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                Author and article information

                Contributors
                Journal
                Front Physiol
                Front Physiol
                Front. Physiol.
                Frontiers in Physiology
                Frontiers Media S.A.
                1664-042X
                04 August 2021
                2021
                : 12
                : 711798
                Affiliations
                [1] 1Centre for Heart, Lung & Vascular Health, University of British Columbia , Okanagan, BC, Canada
                [2] 2Environmental Physiology Group, Department of Health Sciences, Mid Sweden University , Östersund, Sweden
                [3] 3Department of Nursing Science, Mid Sweden University , Sundsvall, Sweden
                [4] 4Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University , Östersund, Sweden
                Author notes

                Edited by: François Billaut, Laval University, Canada

                Reviewed by: Danilo Cialoni, Dan Europe Foundation, Italy; Lars Eichhorn, University Hospital Bonn, Germany

                *Correspondence: Alexander Patrician, amdpatrician@ 123456gmail.com

                These authors share first authorship

                This article was submitted to Environmental, Aviation and Space Physiology, a section of the journal Frontiers in Physiology

                Article
                10.3389/fphys.2021.711798
                8371971
                34421654
                13abcf66-604a-4d3c-bae0-56313b9c33e7
                Copyright © 2021 Patrician, Pernett, Lodin-Sundström and Schagatay.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 19 May 2021
                : 12 July 2021
                Page count
                Figures: 4, Tables: 1, Equations: 0, References: 68, Pages: 9, Words: 0
                Categories
                Physiology
                Original Research

                Anatomy & Physiology
                hypoxia,apnea,hypoxic syncope,blackout,pulmonary edema,barotrauma,injury,extreme environment

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