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      The Area method: a new method for ultrasound assessment of diaphragmatic movement

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          Abstract

          Background

          Ultrasound can be used to assess diaphragm movement. Existing methods focus on movement at a single point at the hemidiaphragm and may not consider the anatomic and functional complexity. We aimed to develop an ultrasound method, the Area method, to assess movement of the entire hemidiaphragm dome and to compare it with existing methods to evaluate accuracy, inter-rater agreement, and feasibility.

          Methods

          Movement of the diaphragm was evaluated by ultrasonography in 19 healthy subjects and correlated with simultaneously performed spirometry. Two existing methods, the M-mode excursion at the posterior part of diaphragm and the B-mode at the top of the diaphragm, were compared with the Area method. Two independent raters reviewed film clips to analyze inter-rater agreement. Feasibility was tested by novice ultrasound operators.

          Results

          Correlation with expired lung volume was higher with the Area method, 0.88 (95% CI 0.81–0.95), p < 0.001, and with the M-mode measurement, 0.84 (95% CI 0.75–0.92), p < 0.001, than with the B-mode measurement, 0.71 (95% CI 0.59–0.83), p < 0.001. Inter-rater agreement was highest with the Area method, 0.9, p < 0.001, and M-mode measurement 0.9, p < 0.001, and lower with the B-mode measurement, 0.8, p < 0.001. The M-mode measurement could be done in only 20% at the left side. The Area method could be performed in all participants at both hemidiaphragms, and novice operators found it easy to perform.

          Conclusion

          A new method to evaluate diaphragm movement is introduced. Accuracy and inter-rater agreement are high. The Area method is equally feasible at both hemidiaphragms in contrast to existing methods. However, additional studies should include more participants, different types of pulmonary diseases, and investigate the role of patient position to validate the Area method fully.

          Electronic supplementary material

          The online version of this article (10.1186/s13089-018-0092-5) contains supplementary material, which is available to authorized users.

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          Most cited references12

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          Diaphragmatic motion studied by m-mode ultrasonography: methods, reproducibility, and normal values.

          Although diaphragmatic motion is readily studied by ultrasonography, the procedure remains poorly codified. The aim of this prospective study was to determine the reference values for diaphragmatic motion as recorded by M-mode ultrasonography. Two hundred ten healthy adult subjects (150 men, 60 women) were investigated. Both sides of the posterior diaphragm were identified, and M-mode was used to display the movement of the anatomical structures. Examinations were performed during quiet breathing, voluntary sniffing, and deep breathing. Diaphragmatic excursions were measured from the M-mode sonographic images. In addition, the reproducibility (inter- and intra-observer) was assessed. Right and left diaphragmatic motions were successfully assessed during quiet breathing in all subjects. During voluntary sniffing, the measurement was always possible on the right side, and in 208 of 210 volunteers, on the left side. During deep breathing, an obscuration of the diaphragm by the descending lung was noted in subjects with marked diaphragmatic excursion. Consequently, right diaphragmatic excursion could be measured in 195 of 210 subjects, and left diaphragmatic excursion in only 45 subjects. Finally, normal values of both diaphragmatic excursions were determined. Since the excursions were larger in men than in women, the gender should be taken into account. The lower limit values were close to 0.9 cm for women and 1 cm for men during quiet breathing, 1.6 cm for women and 1.8 cm for men during voluntary sniffing, and 3.7 cm for women and 4.7 cm for men during deep breathing. We demonstrated that M-mode ultrasonography is a reproducible method for assessing hemidiaphragmatic movement.
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            Diaphragm ultrasonography to estimate the work of breathing during non-invasive ventilation.

            Ultrasonography allows the direct observation of the diaphragm. Its thickness variation measured in the zone of apposition has been previously used to diagnose diaphragm paralysis. We assessed the feasibility and accuracy of this method to assess diaphragmatic function and its contribution to respiratory workload in critically ill patients under non-invasive ventilation. This was a preliminary physiological study in the intensive care unit of a university hospital. Twelve patients requiring planned non-invasive ventilation after extubation were studied while spontaneously breathing and during non-invasive ventilation at three levels of pressure support (5, 10 and 15 cmH(2)O). Diaphragm thickness was measured in the zone of apposition during tidal ventilation and the thickening fraction (TF) was calculated as (thickness at inspiration - thickness at expiration)/thickness at expiration. Diaphragmatic pressure-time product per breath (PTP(di)) was measured from oesophageal and gastric pressure recordings. PTP(di) and TF both decreased as the level of pressure support increased. A significant correlation was found between PTP(di) and TF (ρ = 0.74, p < 0.001). The overall reproducibility of TF assessment was good but the coefficient of repeatability reached 18% for inter-observer reproducibility. Ultrasonographic assessment of the diaphragm TF is a non-invasive method that may prove useful in evaluating diaphragmatic function and its contribution to respiratory workload in intensive care unit patients.
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              Diaphragm ultrasound as indicator of respiratory effort in critically ill patients undergoing assisted mechanical ventilation: a pilot clinical study

              Introduction Pressure-support ventilation, is widely used in critically ill patients; however, the relative contribution of patient’s effort during assisted breathing is difficult to measure in clinical conditions. Aim of the present study was to evaluate the performance of ultrasonographic indices of diaphragm contractile activity (respiratory excursion and thickening) in comparison to traditional indices of inspiratory muscle effort during assisted mechanical ventilation. Method Consecutive patients admitted to the ICU after major elective surgery who met criteria for a spontaneous breathing trial with pressure support ventilation were enrolled. Patients with airflow obstruction or after thoracic/gastric/esophageal surgery were excluded. Variable levels of inspiratory muscle effort were achieved by delivery of different levels of ventilatory assistance by random application of pressure support (0, 5 and 15 cmH2O). The right hemidiaphragm was evaluated by B- and M-mode ultrasonography to record respiratory excursion and thickening. Airway, gastric and oesophageal pressures, and airflow were recorded to calculate indices of respiratory effort (diaphragm and esophageal pressure–time product). Results 25 patients were enrolled. With increasing levels of pressure support, parallel reductions were found between diaphragm thickening and both diaphragm and esophageal pressure–time product (respectively, R = 0.701, p < 0.001 and R = 0.801, p < 0.001) during tidal breathing. No correlation was found between either diaphragm or esophageal pressure–time product and diaphragm excursion (respectively, R = −0.081, p = 0.506 and R = 0.003, p = 0.981), nor was diaphragm excursion correlated to diaphragm thickening (R = 0.093, p = 0.450) during tidal breathing. Conclusions In patients undergoing in assisted mechanical ventilation, diaphragm thickening is a reliable indicator of respiratory effort, whereas diaphragm excursion should not be used to quantitatively assess diaphragm contractile activity. Electronic supplementary material The online version of this article (doi:10.1186/s13054-015-0894-9) contains supplementary material, which is available to authorized users.
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                Author and article information

                Contributors
                soeska@gmail.com , soeska@rm.dk
                andeotte@rm.dk
                christian.b.laursen@rsyd.dk
                Journal
                Crit Ultrasound J
                Crit Ultrasound J
                Critical Ultrasound Journal
                Springer Milan (Milan )
                2036-3176
                2036-7902
                27 June 2018
                27 June 2018
                2018
                : 10
                : 15
                Affiliations
                [1 ]ISNI 0000 0004 0512 597X, GRID grid.154185.c, Department of Respiratory Diseases and Allergy, , Aarhus University Hospital, ; Nørrebrogade 44, 8000 Aarhus C, Denmark
                [2 ]ISNI 0000 0004 0512 5013, GRID grid.7143.1, Department of Respiratory Medicine, , Odense University Hospital, ; Odense, Denmark
                [3 ]ISNI 0000 0001 0728 0170, GRID grid.10825.3e, Department of Clinical Research, , University of Southern Denmark, ; Odense, Denmark
                Article
                92
                10.1186/s13089-018-0092-5
                6019663
                29946769
                1aba06b0-fc13-40a1-9bee-cd2bb0000436
                © The Author(s) 2018

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

                History
                : 5 December 2017
                : 2 May 2018
                Categories
                Original Article
                Custom metadata
                © The Author(s) 2018

                Radiology & Imaging
                Radiology & Imaging

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