Publications by authors named "Rasmus Aagaard"

17 Publications

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Remote Real-Time Ultrasound Supervision via Commercially Available and Low-Cost Tele-Ultrasound: a Mixed Methods Study of the Practical Feasibility and Users' Acceptability in an Emergency Department.

J Digit Imaging 2019 10;32(5):841-848

Emergency Department, Regional Hospital West Jutland, Herning, Denmark.

Minor emergency departments (ED) struggle to access sufficient expertise to supervise learners of lung and cardiac point-of-care ultrasound (POCUS). Using tele-ultrasound (tele-US) for remote supervision may remedy this situation. We aimed to evaluate the feasibility of real-time supervision via tele-US when applied to an everyday ED clinic. We conducted a mixed methods study that assessed practical feasibility, determined performance, and explored users' acceptability of supervision via tele-US. Technical performance was assessed quantitatively by the ratio in mean gray value between images on site and as received by the supervisor, and by after-compression frame rate. Qualitatively, 12 exploratory semi-structured interviews were conducted with exposed junior doctors and supervisors. Remote supervision via tele-US was performed with 10 junior doctors scanning 45 included patients. During performance assessment, neither alternating internet connection nor software significantly changed the mean gray value ratio. The lowest median frame rate of 4.6 (interquartile range [IQR]: 3.1-5.0) was found by using a 4G internet connection; the highest of 28.5 (IQR: 28.5-29.0) was found with alternative computer and local area network internet connection. In interviews, supervisors stressed the importance of preserving frame rate, and junior doctors emphasized a need for shared ultrasound terminology. In the qualitative analysis, setup mobility, accessibility, and time consumption were emphasized as being of key importance for future clinical implementations. Remote supervision via a commercially available and low-cost tele-US setup is operational for both junior doctors and supervisors when applied to lung and cardiac POCUS scans of hospitalized patients.
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http://dx.doi.org/10.1007/s10278-018-0157-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6737136PMC
October 2019

Remote real-time supervision via tele-ultrasound in focused cardiac ultrasound: A single-blinded cluster randomized controlled trial.

Acta Anaesthesiol Scand 2019 03 17;63(3):403-409. Epub 2018 Oct 17.

Research Center for Emergency Medicine, Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark.

Background: Supervision via tele-ultrasound presents a remedy for lacking on-site supervision in focused cardiac ultrasound, but knowledge of its impact is largely absent. We aimed to investigate tele-supervised physicians' cine-loop quality compared to that of non-supervised physicians and compared to that of experts.

Methods: We conducted a single-blinded cluster randomized controlled trial in an emergency department in western Denmark. Physicians with basic ultrasound competence scanned admitted patients twice. The first scan was non-supervised, and the second was non-supervised (control) or tele-supervised (intervention). Finally, experts in focused cardiac ultrasound scanned the same patient. Two blinded observers graded cine-loops recorded from all scans on a 1-5 scale. The outcome was the mean summarized scan gradings compared with a linear mixed-effects model.

Results: In each group, 10 physicians scanned 44 patients. From the mean summarized gradings, on a scale from 4 to 20, the second non-supervised scan grading was 10.9 (95% CI 10.2-11.7), whereas the tele-supervised grading was 12.6 (95% CI: 11.8-13.3). From the first to the second scan, tele-supervised physicians moved 9% (1.09; 95% CI: 1.00-1.19; P = 0.041) closer to the experts' quality than the non-supervised physicians.

Conclusion: Tele-supervised physicians performed scans of better quality than non-supervised physicians. The present study supports the use of tele-supervision for physicians with basic focused ultrasound competence in a setting where on-site supervision is unavailable.
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http://dx.doi.org/10.1111/aas.13276DOI Listing
March 2019

A low end-tidal CO/arterial CO ratio during cardiopulmonary resuscitation suggests pulmonary embolism.

Resuscitation 2018 12 12;133:137-140. Epub 2018 Oct 12.

Department of Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark.

Introduction: Identifying reversible causes of cardiac arrest is challenging. The diagnosis of pulmonary embolism is often missed. Pulmonary embolism increases alveolar dead space resulting in low end-tidal CO (EtCO) relative to arterial CO (PaCO) tension. Thus, a low EtCO/PaCO ratio during resuscitation may be a sign of pulmonary embolism.

Methods: Post hoc analysis of data from two porcine studies comparing ultrasonographic measurements of right ventricular diameter during resuscitation from cardiac arrest of different causes. Pigs were grouped according to cause of arrest (pulmonary embolism, hypovolemia, primary arrhythmia, hypoxia, or hyperkalaemia) and EtCO/PaCO ratios were compared.

Results: Data from 54 pigs were analysed. EtCO levels at the third rhythm analysis were significantly lower when cardiac arrest was caused by pulmonary embolism than by primary arrhythmia, hypoxia and hyperkalaemia, but there was no significant difference between pulmonary embolism and hypovolemia. In contrast, PaCO levels were higher in cardiac arrest caused by pulmonary embolism than in the other causes of cardiac arrest. Consequently, the EtCO/PaCO ratio was lower in pulmonary embolism 0.2 (95%CI 0.1-0.4), than in hypovolaemia 0.5 (95%CI 0.3-0.6), primary arrhythmia 0.7 (95%CI 0.7-0.8), hypoxia 0.5 (95%CI 0.4-0.6), and hyperkalaemia 0.6 (95%CI 0.6-0.7).

Conclusion: A low EtCO/PaCO ratio during cardiopulmonary resuscitation suggests pulmonary embolism.
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http://dx.doi.org/10.1016/j.resuscitation.2018.10.008DOI Listing
December 2018

Reply letter to focused ultrasound during advanced life support as a part of a structured approach to the resuscitation of PEA.

Resuscitation 2018 08 9;129:e5. Epub 2018 Jun 9.

Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark; Research & Development, Prehospital Emergency Medical Services, Central Denmark Region, Olof Palmes Allé 34,1(st)floor, 8200 Aarhus N, Denmark.

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http://dx.doi.org/10.1016/j.resuscitation.2018.06.010DOI Listing
August 2018

Point-of-Care Ultrasound in the Periarrest Setting-Lessons Learned: A Case Report.

A A Pract 2018 May;10(9):246-249

From the Department of Anesthesiology and Intensive Care, Aarhus University Hospital, Aarhus N, Denmark.

Point-of-care ultrasound may elucidate reversible causes of cardiac arrest, and its use is supported by international guidelines in the periarrest setting. We present a case in which the treatment of cardiac arrest caused tension pneumothoraces and cardiac tamponade by pneumopericardium. Both pneumothorax and tamponade were expected to be identified with ultrasound, but were not. Subcutaneous emphysema precluded the diagnosis of pneumothorax. Cardiac imaging was false negative for tamponade, because the latter was caused by air and not fluid. Diagnoses are not to be excluded with inconclusive point-of-care ultrasound examinations, which should prompt further clinical evaluation and imaging.
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http://dx.doi.org/10.1213/XAA.0000000000000678DOI Listing
May 2018

In a bed or on the floor? - The effect of realistic hospital resuscitation training: A randomised controlled trial.

Am J Emerg Med 2018 Jul 13;36(7):1236-1241. Epub 2017 Dec 13.

Research Center for Emergency Medicine, Aarhus University Hospital, Nørrebrogade 44, Building 1B, 8000 Aarhus C, Denmark; Department of Internal Medicine and Clinical Research Unit, Randers Regional Hospital, Skovlyvej 15, 8930 Randers NE, Denmark; Department of Clinical Medicine, Aarhus University, Palle Juul-Jensens Blvd. 99, 8200 Aarhus N, Denmark. Electronic address:

Introduction: In-hospital cardiac arrest has a poor prognosis and often occurs in patients lying in a hospital bed. A bed mattress is a soft compressible surface that may decrease cardiopulmonary resuscitation (CPR) quality. Often hospital CPR training is performed with a manikin on the floor.

Aim: To study CPR quality following realistic CPR training with a manikin in a bed compared with one on the floor.

Methods: We conducted a randomised controlled study. Healthcare professionals were randomised to CPR training with a manikin in a hospital bed or one on the floor. Data on CPR quality was collected from manikins. The primary outcome measure was chest compression depth.

Results: In total, 108 healthcare professionals (age: 40years, female: 94%) were included. The mean chest compression depth was 39mm (standard deviation (SD): 10), for the bed group compared with 38mm (SD: 9) for the floor group, p=0.49. A post hoc analysis showed that regardless of the training method, the participants who optimised their working position by jumping onto the bed or lowering the bed had a median chest compression depth of 39mm (25th-75th percentiles: 33-45) compared with 29mm (25th-75th percentiles: 23-41) for participants who did neither, p=0.04.

Conclusion: There was no significant difference in chest compression depth between healthcare professionals who trained CPR on a manikin in a hospital bed compared with one on the floor. Chest compression depth was too shallow in both groups. Irrespective of the training method, participants who optimised their working position performed deeper chest compressions.
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http://dx.doi.org/10.1016/j.ajem.2017.12.029DOI Listing
July 2018

Timing of focused cardiac ultrasound during advanced life support - A prospective clinical study.

Resuscitation 2018 03 12;124:126-131. Epub 2017 Dec 12.

Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark; Research & Development, Prehospital Emergency Medical Services, Central Denmark Region, Olof Palmes Allé 34, 1st Floor, 8200 Aarhus N, Denmark.

Introduction: Focused cardiac ultrasound can potentially identify reversible causes of cardiac arrest during advanced life support (ALS), but data on the timing of image acquisition are lacking. This study aimed to compare the quality of images obtained during rhythm analysis, bag-mask ventilations, and chest compressions.

Methods: Adult patients in cardiac arrest were prospectively included during 23 months at a Danish community hospital. Physicians who had completed basic ultrasound training performed subcostal focused cardiac ultrasound during rhythm analysis, bag-mask ventilations, and chest compressions. Image quality was categorised as either useful for interpretation or not. Two echocardiography experts rated images useful for interpretation if all the following characteristics could be determined: 1) right ventricle larger than left ventricle, 2) pericardial fluid, and 3) collapsing ventricles.

Results: Images were obtained from 60 of 114 patients undergoing ALS. A higher proportion of the images obtained during rhythm analysis and bag-mask ventilations were useful for interpretation when compared with chest compressions (rhythm analysis vs chest compressions: OR 2.2 (95%CI 1.3-3.8), P = 0.005; bag mask ventilations vs chest compressions: OR 2.0 (95%CI 1.1-3.7), P = 0.03). There was no difference between images obtained during rhythm analysis and bag-mask ventilations (OR 1.1 (95%CI 0.6-2.0), P = 0.74).

Conclusion: The quality of focused cardiac ultrasound images obtained during rhythm analysis and bag-mask ventilations was superior to that of images obtained during chest compressions. There was no difference in the quality of images obtained during rhythm analysis and bag-mask ventilations. Bag-mask ventilations may constitute an overlooked opportunity for image acquisition during ALS.
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http://dx.doi.org/10.1016/j.resuscitation.2017.12.012DOI Listing
March 2018

The Right Ventricle Is Dilated During Resuscitation From Cardiac Arrest Caused by Hypovolemia: A Porcine Ultrasound Study.

Crit Care Med 2017 Sep;45(9):e963-e970

1Research Center for Emergency Medicine, Aarhus University Hospital, Denmark. 2Department of Anesthesiology, Randers Regional Hospital, Denmark. 3Department of Anesthesiology and Intensive Care Medicine, Aarhus University Hospital, Denmark. 4Research & Development, Prehospital Emergency Medical Services, Central Denmark Region, Denmark. 5Department of Internal Medicine, Randers Regional Hospital, Denmark.

Objectives: Dilation of the right ventricle during cardiac arrest and resuscitation may be inherent to cardiac arrest rather than being associated with certain causes of arrest such as pulmonary embolism. This study aimed to compare right ventricle diameter during resuscitation from cardiac arrest caused by hypovolemia, hyperkalemia, or primary arrhythmia (i.e., ventricular fibrillation).

Design: Thirty pigs were anesthetized and then randomized to cardiac arrest induced by three diffrent methods. Seven minutes of untreated arrest was followed by resuscitation. Cardiac ultrasonographic images were obtained during induction of cardiac arrest, untreated cardiac arrest, and resuscitation. The right ventricle diameter was measured. Primary endpoint was the right ventricular diameter at the third rhythm analysis.

Setting: University hospital animal laboratory.

Subjects: Female crossbred Landrace/Yorkshire/Duroc pigs (27-32 kg).

Interventions: Pigs were randomly assigned to cardiac arrest caused by either hypovolemia, hyperkalemia, or primary arrhythmia.

Measurements And Main Results: At the third rhythm analysis during resuscitation, the right ventricle diameter was 32 mm (95% CI, 29-35) in the hypovolemia group, 29 mm (95% CI, 26-32) in the hyperkalemia group, and 25 mm (95% CI, 22-28) in the primary arrhythmia group. This was larger than baseline for all groups (p = 0.03). When comparing groups at the third rhythm analysis, the right ventricle was larger for hypovolemia than for primary arrhythmia (p < 0.001).

Conclusions: The right ventricle was dilated during resuscitation from cardiac arrest caused by hypovolemia, hyperkalemia, and primary arrhythmia. These findings indicate that right ventricle dilation may be inherent to cardiac arrest, rather than being associated with certain causes of arrest. This contradicts a widespread clinical assumption that in hypovolemic cardiac arrest, the ventricles are collapsed rather than dilated.
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http://dx.doi.org/10.1097/CCM.0000000000002464DOI Listing
September 2017

Detection of Pulmonary Embolism During Cardiac Arrest-Ultrasonographic Findings Should Be Interpreted With Caution.

Crit Care Med 2017 Jul;45(7):e695-e702

1Research Center for Emergency Medicine, Aarhus University Hospital, Aarhus, Denmark.2Department of Anesthesiology, Randers Regional Hospital, Randers, Denmark.3Department of Cardiology, Aarhus University Hospital, Skejby, Aarhus, Denmark.4Research and Development, Prehospital Emergency Medical Services, Central Denmark Region, Denmark.5Department of Anesthesiology and Intensive Care Medicine, Aarhus University Hospital, Aarhus, Denmark.6Department of Internal Medicine, Randers Regional Hospital, Randers, Denmark.

Objectives: The aim of this study was to test the hypothesis that the right ventricle is more dilated during resuscitation from cardiac arrest caused by pulmonary embolism, compared with hypoxia and primary arrhythmia.

Design: Twenty-four pigs were anesthetized and cardiac arrest was induced using three different methods. Pigs were resuscitated after 7 minutes of untreated cardiac arrest. Ultrasonographic images were obtained and the right ventricular diameter was measured.

Setting: University hospital animal laboratory.

Subjects: Female crossbred Landrace/Yorkshire/Duroc pigs (27-32 kg).

Interventions: Pigs were randomly assigned to cardiac arrest induced by pulmonary embolism, hypoxia, or primary arrhythmia.

Measurements And Main Results: There was no difference at baseline. During induction of cardiac arrest, the right ventricle dilated in all groups (p < 0.01 for all). The primary endpoint was right ventricle diameter at the third rhythm analysis: 32 mm (95% CI, 29-36) for pulmonary embolism which was significantly larger than both hypoxia: 23 mm (95% CI, 20-27) and primary arrhythmia: 25 mm (95% CI, 22-28)-the absolute difference was 7-9 mm. Physicians with basic training in focused cardiac ultrasonography were able to detect a difference in right ventricle diameter of approximately 10 mm with a sensitivity of 79% (95% CI, 64-94) and a specificity of 68% (95% CI, 56-80).

Conclusions: The right ventricle was more dilated during resuscitation when cardiac arrest was caused by pulmonary embolism compared with hypoxia and primary arrhythmia. However, the right ventricle was dilated, irrespective of the cause of arrest, and diagnostic accuracy by physicians with basic training in focused cardiac ultrasonography was modest. These findings challenge the paradigm that right ventricular dilatation on ultrasound during cardiopulmonary resuscitation is particularly associated with pulmonary embolism.
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http://dx.doi.org/10.1097/CCM.0000000000002334DOI Listing
July 2017

Clinical experience and skills of physicians in hospital cardiac arrest teams in Denmark: a nationwide study.

Open Access Emerg Med 2017 7;9:37-41. Epub 2017 Mar 7.

Department of Internal Medicine; Research Center for Emergency Medicine, Aarhus University Hospital; Institute of Clinical Medicine, Aarhus University, Aarhus.

Background: The quality of in-hospital resuscitation is poor and may be affected by the clinical experience and cardiopulmonary resuscitation (CPR) training. This study aimed to investigate the clinical experience, self-perceived skills, CPR training and knowledge of the guidelines on when to abandon resuscitation among physicians of cardiac arrest teams.

Methods: We performed a nationwide cross-sectional study in Denmark. Telephone interviews were conducted with physicians in the cardiac arrest teams in public somatic hospitals using a structured questionnaire.

Results: In total, 93 physicians (53% male) from 45 hospitals participated in the study. Median age was 34 (interquartile range: 30-39) years. Respondents were medical students working as locum physicians (5%), physicians in training (79%) and consultants (16%), and the median postgraduate clinical experience was 48 (19-87) months. Most respondents (92%) felt confident in treating a cardiac arrest, while fewer respondents felt confident in performing intubation (41%) and focused cardiac ultrasound (39%) during cardiac arrest. Median time since last CPR training was 4 (2-10) months, and 48% had attended a European Resuscitation Council (ERC) Advanced Life Support course. The majority (84%) felt confident in terminating resuscitation; however, only 9% were able to state the ERC guidelines on when to abandon resuscitation.

Conclusion: Physicians of Danish cardiac arrest teams are often inexperienced and do not feel competent performing important clinical skills during resuscitation. Less than half have attended an ERC Advanced Life Support course, and only very few physicians know the ERC guidelines on when to abandon resuscitation.
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http://dx.doi.org/10.2147/OAEM.S124149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5349502PMC
March 2017

Use of Echocardiography in Critical Illness. Dead or Alive-Does It Matter?

Crit Care Med 2017 03;45(3):e342-e343

Research Center for Emergency Medicine, Aarhus University Hospital, Aarhus, Denmark, Clinical Research Unit, Regional Hospital of Randers, Randers, Denmark; Department of Anesthesiology and Intensive Care Medicine, Aarhus University Hospital, Aarhus, Denmark; Research Center for Emergency Medicine, Aarhus University Hospital, Aarhus, Denmark, Clinical Research Unit, Regional Hospital of Randers, Randers, Denmark, Research & Development, Prehospital Emergency Medical Services, Central Denmark Region, Aarhus, Denmark; Research Center for Emergency Medicine, Aarhus University Hospital, Aarhus, Denmark, Clinical Research Unit, Regional Hospital of Randers, Randers, Denmark, Department of Internal Medicine, Regional Hospital of Randers, Randers, Denmark.

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http://dx.doi.org/10.1097/CCM.0000000000002198DOI Listing
March 2017

Limited public ability to recognise and understand the universal sign for automated external defibrillators.

Heart 2016 05 28;102(10):770-4. Epub 2016 Jan 28.

Research Centre for Emergency Medicine, Aarhus University Hospital, Aarhus, Denmark Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark Department of Internal Medicine, Regional Hospital of Randers, Randers, Denmark.

Objective: To study if the public is able to recognise and understand the International Liaison Committee on Resuscitation (ILCOR) sign for automated external defibrillators (AEDs), and to explore how national resuscitation councils have adopted the sign.

Methods: A survey was conducted among travellers in an international airport serving 21 million passengers annually. Participants were asked to state the meaning of six international safety signs, one of which was the ILCOR AED sign. Also, all national resuscitation councils forming ILCOR were contacted to determine whether they recommend the ILCOR AED sign and the existence of national legislation regarding AED signage.

Results: In total, 493 travellers (42 nationalities) were included. Correct identification of the ILCOR AED sign was achieved by 39% (95% CI 35% to 43%). Information on AED signage was obtained from 41 of 44 (93%) national resuscitation councils; 26 councils (63%) recommended the use of the ILCOR AED sign. In two countries, the ILCOR AED sign was mandatory by law.

Conclusions: There is limited public recognition and understanding of the ILCOR AED sign. The ILCOR AED sign is not unanimously recommended by national resuscitation councils worldwide. Initiatives promoting public awareness of AEDs are warranted.
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http://dx.doi.org/10.1136/heartjnl-2015-308700DOI Listing
May 2016

Developing an emergency ultrasound app - a collaborative project between clinicians from different universities.

Scand J Trauma Resusc Emerg Med 2015 Jun 20;23:47. Epub 2015 Jun 20.

Centre for Clinical Education, Centre for HR, Capital Region of Denmark & University of Copenhagen, Copenhagen, Denmark.

Focused emergency ultrasound is rapidly evolving as a clinical skill for bedside examination by physicians at all levels of education. Ultrasound is highly operator-dependent and relevant training is essential to ensure appropriate use. When supplementing hands-on focused ultrasound courses, e-learning can increase the learning effect. We developed an emergency ultrasound app to enable onsite e-learning for trainees. In this paper, we share our experiences in the development of this app and present the final product.
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http://dx.doi.org/10.1186/s13049-015-0130-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4473832PMC
June 2015

A framework for implementation, education, research and clinical use of ultrasound in emergency departments by the Danish Society for Emergency Medicine.

Scand J Trauma Resusc Emerg Med 2014 Apr 15;22:25. Epub 2014 Apr 15.

Research Unit at the Department of Respiratory Medicine, Odense University Hospital, Sdr, Boulevard 29, 5000 Odense C, Denmark.

The first Danish Society for Emergency Medicine (DASEM) recommendations for the use of clinical ultrasound in emergency departments has been made. The recommendations describes what DASEM believes as being current best practice for training, certification, maintenance of acquired competencies, quality assurance, collaboration and research in the field of clinical US used in an ED.
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http://dx.doi.org/10.1186/1757-7241-22-25DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3989792PMC
April 2014

Animal laboratory training improves lung ultrasound proficiency and speed.

J Emerg Med 2013 Sep 15;45(3):e71-8. Epub 2013 May 15.

Department of Research and Development, Norwegian Air Ambulance Foundation, Droebak, Norway.

Background: Although lung ultrasound (US) is accurate in diagnosing pneumothorax (PTX), the training requirements and methods necessary to perform US examinations must be defined.

Objective: Our aim was to test whether animal laboratory training (ALT) improves the diagnostic competency and speed of PTX detection with US.

Methods: Twenty medical students without lung US experience attended a 1-day course. Didactic, practical, and experimental lectures covered the basics of US physics, US machines, and lung US, followed by hands-on training to demonstrate the signs of normal lung sliding and PTX. Each student's diagnostic skill level was tested with three subsequent examinations (at day 1, day 2, and 6-month follow-up) using experimentally induced PTX in porcine models. The outcome measures were sensitivity and specificity for US detection of PTX, self-reported diagnostic confidence, and scan time.

Results: The students improved their skills between the initial two examinations: sensitivity increased from 81.7% (range 69.1%-90.1%) to 100.0% (range 94.3%-100.0%) and specificity increased from 90.0% (range 82.0%-94.8%) to 98.9% (range 92.3%-100.0%); with no deterioration 6 months later. There was a significant learning curve in choosing the correct answers (p = 0.018), a 1-point increase in the self-reported diagnostic confidence (7.8-8.8 on a 10-point scale; p < 0.05), and a 1-min reduction in the mean scan time per lung (p < 0.05).

Conclusions: Without previous experience and after undergoing training in an animal laboratory, medical students improved their diagnostic proficiency and speed for PTX detection with US. Lung US is a basic technique that can be used by novices to accurately diagnose PTX.
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http://dx.doi.org/10.1016/j.jemermed.2013.03.029DOI Listing
September 2013

The intrapleural volume threshold for ultrasound detection of pneumothoraces: an experimental study on porcine models.

Scand J Trauma Resusc Emerg Med 2013 Mar 1;21:11. Epub 2013 Mar 1.

Department of Research and Development, Norwegian Air Ambulance Foundation, Mailbox 94, Droebak, 1441, Norway.

Background: Small pneumothoraxes (PTXs) may not impart an immediate threat to trauma patients after chest injuries. However, the amount of pleural air may increase and become a concern for patients who require positive pressure ventilation or air ambulance transport. Lung ultrasonography (US) is a reliable tool in finding intrapleural air, but the performance characteristics regarding the detection of small PTXs need to be defined. The study aimed to define the volume threshold of intrapleural air when PTXs are accurately diagnosed with US and compare this volume with that for chest x-ray (CXR).

Methods: Air was insufflated into a unilateral pleural catheter in seven incremental steps (10, 25, 50, 100, 200, 350 and 500 mL) in 20 intubated porcine models, followed by a diagnostic evaluation with US and a supine anteroposterior CXR. The sonographers continued the US scanning until the PTXs could be ruled in, based on the pathognomonic US "lung point" sign. The corresponding threshold volume was noted. A senior radiologist interpreted the CXR images.

Results: The mean threshold volume to confirm the diagnosis of PTX using US was 18 mL (standard deviation of 13 mL). Sixty-five percent of the PTXs were already diagnosed at 10 mL of intrapleural air; 25%, at 25 mL; and the last 10%, at 50 mL. At an air volume of 50 mL, the radiologist only identified four out of 20 PTXs in the CXR pictures; i.e., a sensitivity of 20% (95% CI: 7%, 44%). The sensitivity of CXR increased as a function of volume but leveled off at 67%, leaving one-third (1/3) of the PTXs unidentified after 500 mL of insufflated air.

Conclusion: Lung US is very accurate in diagnosing even small amounts of intrapleural air and should be performed by clinicians treating chest trauma patients when PTX is among the differential diagnoses.
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http://dx.doi.org/10.1186/1757-7241-21-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3602194PMC
March 2013

Microdialysis: characterisation of haematomas in myocutaneous flaps by use of biochemical agents.

Br J Oral Maxillofac Surg 2013 Mar 20;51(2):117-22. Epub 2012 Apr 20.

Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.

Metabolic markers are measured by microdialysis to detect postoperative ischaemia after reconstructive surgery with myocutaneous flaps. If a haematoma develops around the microdialysis catheter, it can result in misinterpretation of the measurements. The aim of the present study was to investigate whether a haematoma in a flap can be identified and dissociated from ischaemia, or a well-perfused flap, by a characteristic chemical profile. In 7 pigs, the pedicled rectus abdominal muscle flap was mobilised on both sides. A haematoma was made in each flap and two microdialysis catheters were placed, one in the haematoma, and the other in normal tissue. One flap was made ischaemic by ligation of the pedicle. For 6 hours, the metabolism was monitored by measurement every half-an-hour of the concentrations of glucose, lactate, pyruvate, and glycerol from all 4 catheters. After 3 hours of monitoring, intravenous glucose was given as a challenge test to identify ischaemia. The non-ischaemic flap could be differentiated from the ischaemic flap by low glucose, and high lactate, concentrations. It was possible to identify a catheter surrounded by a haematoma in ischaemic as well as non-ischaemic muscle from a low or decreasing concentration of glucose together with a low concentration of lactate. All four sites could be completely dissociated when the concentrations of glucose and lactate were evaluated and combined with the lactate:glucose ratio and a flow chart. The challenge test was useful for differentiating between haematomas in ischaemic and non-ischaemic tissue.
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http://dx.doi.org/10.1016/j.bjoms.2012.03.017DOI Listing
March 2013
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