Sensitivity of Bedside Ultrasound and Supine Anteroposterior Chest Radiographs for the Identification of Pneumothorax After Blunt Trauma

Objectives: Supine anteroposterior (AP) chest radiographs in patients with blunt trauma have poor sensitivity for the identification of pneumothorax. Ultrasound (US) has been proposed as an alternative screening test for pneumothorax in this population. The authors conducted an evidence‐based review of the medical literature to compare sensitivity of bedside US and AP chest radiographs in identifying pneumothorax after blunt trauma. Methods: MEDLINE and EMBASE databases were searched for trials from 1965 through June 2009 using a search strategy derived from the following PICO formulation of our clinical question: patients included adult (18 + years) emergency department (ED) patients in whom pneumothorax was suspected after blunt trauma. The intervention was thoracic ultrasonography for the detection of pneumothorax. The comparator was the supine AP chest radiograph during the initial evaluation of the patient. The outcome was the diagnostic performance of US in identifying the presence of pneumothorax in the study population. The criterion standard for the presence or absence of pneumothorax was computed tomography (CT) of the chest or a rush of air during thoracostomy tube placement (in unstable patients). Prospective, observational trials of emergency physician (EP)‐performed thoracic US were included. Trials in which the exams were performed by radiologists or surgeons, or trials that investigated patients suffering penetrating trauma or with spontaneous or iatrogenic pneumothoraces, were excluded. The methodologic quality of the studies was assessed. Qualitative methods were used to summarize the study results. Data analysis consisted of test performance (sensitivity and specificity, with 95% confidence intervals [CIs]) of thoracic US and supine AP chest radiography. Results: Four prospective observational studies were identified, with a total of 606 subjects who met the inclusion and exclusion criteria. The sensitivity and specificity of US for the detection of pneumothorax ranged from 86% to 98% and 97% to 100%, respectively. The sensitivity of supine AP chest radiographs for the detection of pneumothorax ranged from 28% to 75%. The specificity of supine AP chest radiographs was 100% in all included studies. Conclusions: This evidence‐based review suggests that bedside thoracic US is a more sensitive screening test than supine AP chest radiography for the detection of pneumothorax in adult patients with blunt chest trauma. ACADEMIC EMERGENCY MEDICINE 2010; 17:11–17 © 2010 by the Society for Academic Emergency Medicine     

Ultrasound Findings in Tension Pneumothorax: A Case Report

Background

Delayed recognition of tension pneumothorax can lead to a mortality of 31% to 91%. However, the classic physical examination findings of tracheal deviation and distended neck veins are poorly sensitive in the diagnosis of tension pneumothorax. Point-of-care ultrasound is accurate in identifying the presence of pneumothorax, but sonographic findings of tension pneumothorax are less well described.

Emergency Bedside Ultrasound to Detect Pneumothorax

A relatively new application of emergency ultrasound is its use in the diagnosis of pneumothorax. In patients with major trauma, early detection and treatment of pneumothorax are vital. Chest radiography in these patients is limited to anteroposterior (AP) supine films, in which radiographic features of pneumothorax may be quite subtle. Hence, rapid and accurate bedside ultrasonography can expedite resuscitation. Sonographic features of pneumothorax have been identified in a number of studies. The technique involves identification of the pleural line and observation for features such as "lung sliding" and comet-tail artifacts, which are absent in pneumothorax. Based on a review of the literature, the author describes these features and discusses the utility of emergency ultrasound in detecting pneumothorax.     

Potential Errors in the Diagnosis of Pericardial Effusion on Trauma Ultrasound for Penetrating Injuries

OBJECTIVE: To evaluate ultrasound error in patients presenting with penetrating injury with a potential for pericardial effusion. METHODS: Residents and faculty from an emergency medicine training program at Level 1 trauma center with an active ultrasound program were asked to view digitized video clips of subxiphoid cardiac examinations in patients with chest trauma. Participants were asked to fill out a standardized questionnaire on each video clip asking whether a pericardial effusion was present. Other questions included size of effusion and presence of tamponade. The study also asked participants to rate their confidence in their impressions. Data were analyzed using interquartile ranges and confidence levels. RESULTS: All participants had difficulty distinguishing between epicardial fat pads and true pericardial effusions. The overall sensitivity was 73% and specificity was 44%. Confidence shown by participants in their answers increased with level of training or experience, regardless of whether they were correct or incorrect. Additional views were frequently requested to help decide whether an effusion was present. CONCLUSIONS: A serious potential exists for misdiagnosing epicardial fat pads as pericardial effusion in critically ill trauma patients. Emergency physicians need to be aware of this and should consider one of two suggested alternative methods to improve the accuracy of diagnosis.     

A Survey of Bedside Ultrasound Use by Emergency Physicians in California

Objective. The purpose of this study was to investigate the current practice of emergency physician–performed bedside ultrasound examinations in California and to assess differences between academic and community practice. Methods. We queried all emergency departments (EDs) in California to determine whether bedside ultrasound was used by emergency physicians. Among EDs that were using bedside ultrasound, we administered a survey to assess use patterns, credentialing criteria, and quality assurance (QA) programs. Results. We contacted all eligible EDs (n = 293) by telephone and had a 100% response rate for our primary question: 101 EDs (34%) reported use of bedside ultrasound. Of these 101 EDs, 97 (96%) responded to the secondary survey, showing the following: (1) 48% of physicians at each site were credentialed to use ultrasound in at least 1 modality; (2) 70% of EDs used American College of Emergency Physicians (ACEP) criteria for credentialing guidelines; and (3) 33% had an ultrasound QA program. Comparing practice settings, 68% of academic departments used bedside ultrasound compared with 29% of community departments (difference, 39%; 95% confidence interval [CI], 23% to 54%; P < .0001). In academic departments, a mean of 60% of physicians were credentialed, compared with 41% in community EDs (difference, 19%; 95% CI, 2.5% to 35%; P = .036). Conclusions. Most California EDs do not use bedside ultrasound. Although most EDs using ultrasound report that they follow ACEP emergency ultrasound guidelines, most do not have a QA program as recommended by these guidelines. Compared with community EDs, academic EDs are more likely to use bedside ultrasound, have physicians credentialed in ultrasound use, and have QA programs.     

The Diagnostic Accuracy of Ultrasonography for the Diagnosis of Rib Fractures in Patients Presenting to Emergency Department With Blunt Chest Trauma

BackgroundRib fractures are the most common complications of blunt chest trauma (BCT). Computed tomography (CT) is the modality of choice for BCT, but with several disadvantages. Ultrasonography (US) is an inexpensive, readily available, and relatively harmless imaging alternative. However, a direct comparison of the sonographic evaluation of the rib as a whole with CT as a reference has not been performed to date.ObjectiveThis study aimed to compare the diagnostic accuracy of US with CT for the detection of rib fractures in patients who presented to emergency department (ED) with BCT.MethodsWe included a convenience sample of adult patients who presented to the ED with thoracic pain after BCT in the last 24 h in this prospective, observational, diagnostic accuracy study. The diagnostic utility of US performed by an emergency physician was compared with thorax CT.ResultsThe final study population included 145 patients. The diagnostic accuracy of US was 80% with a sensitivity of 91.2% and specificity of 72.7% for the detection of any rib fracture (positive likelihood ratio 3.4 and negative likelihood ratio 0.12). If we considered each rib separately, the sensitivity of US decreased to 76.7% and specificity increased to 82.7% (81.3% accuracy).ConclusionsA negative US of the site of the highest tenderness and neighboring ribs in a patient with BCT who presented to the ED with lateralizing pain decreases the possibility of a rib fracture significantly. However, a positive US performs poorly to specify the exact location and number of the fractured ribs.     

A Study of Bedside Ocular Ultrasonography in the Emergency Department

The use of ocular ultrasonography for the evaluation of emergency patients has recently been described in the emergency medicine (EM) literature. There are a number of potential uses that may greatly aid the emergency physician (EP) and avoid lengthy consultation or other diagnostic tests. OBJECTIVE: To examine the accuracy of bedside ultrasonography as performed by EPs for the evaluation of ocular pathology. METHODS: This prospective, observational study took place in a high-volume, suburban community hospital with an EM residency program. All patients arriving with a history of eye trauma or acute change in vision were eligible to participate in the study. A 10-MHz linear-array transducer was used for imaging. All imaging was performed through a closed eyelid, using water-soluble ultrasound gel. Investigators filled out standardized data sheets and all examinations were taped for review. All ultrasound examinations were followed by orbital computed tomography or complete ophthalmologic evaluation from the ophthalmology service. Statistical analysis included sensitivity, specificity, and positive and negative predictive values. RESULTS: Sixty-one patients were enrolled in the study; 26 were found to have intraocular pathology on ultrasound. Of these, three had penetrating globe injuries, nine had retinal detachments, one had central retinal artery occlusion, and two had lens dislocations. The remaining pathology included vitreous hemorrhage and vitreous detachment. Emergency sonologists were in agreement with the criterion standard examination in 60 out of 61 cases. CONCLUSIONS: Emergency bedside ultrasound is highly accurate for ruling out and diagnosing ocular pathology in patients presenting to the emergency department. Further, it accurately differentiates between pathology that needs immediate ophthalmologic consultation and that which can be followed up on an outpatient basis.     

Vented Chest Seals for Prevention of Tension Pneumothorax in a Communicating Pneumothorax

Background

Tension pneumothorax accounts for 3%–4% of combat casualties and 10% of civilian chest trauma. Air entering a wound via a communicating pneumothorax rather than by the trachea can result in respiratory arrest and death. In such cases, the Committee on Tactical Combat Casualty Care advocates the use of unvented chest seals to prevent respiratory compromise.

Objective

A comparison of three commercially available vented chest seals was undertaken to evaluate the efficacy of tension pneumothorax prevention after seal application.

Methods

A surgical thoracostomy was created and sealed by placing a shortened 10-mL syringe barrel (with plunger in place) into the wound. Tension pneumothorax was achieved via air introduction through a Cordis to a maximum volume of 50 mL/kg. A 20% drop in mean arterial pressure or a 20% increase in heart rate confirmed hemodynamic compromise. After evacuation, one of three vented chest seals (HyFin^®, n = 8; Sentinel^®, n = 8, SAM^®, n = 8) was applied. Air was injected to a maximum of 50 mL/kg twice, followed by a 10% autologous blood infusion, and finally, a third 50 mL/kg air bolus. Survivors completed all three interventions, and a 15-min recovery period.

Results

The introduction of 29.0 (±11.5) mL/kg of air resulted in tension physiology. All three seals effectively evacuated air and blood. Hemodynamic compromise failed to develop with a chest seal in place.

Conclusions

HyFin^®, SAM^®, and Sentinel^® vented chest seals are equally effective in evacuating blood and air in a communicating pneumothorax model. All three prevented tension pneumothorax formation after penetrating thoracic trauma.     

Bedside Ultrasound for Hip Dislocations

Background

Bedside ultrasound in the emergency department is being used with increasing frequency and for an increasing scope of conditions.

Objectives

Demonstrate the use of bedside ultrasound as an adjunct for diagnosis of hip dislocation.

Case Report

A traumatic anterior hip dislocation was diagnosed with bedside ultrasound after an initial normal plain radiograph.

Conclusion

Although the current standard of care for diagnosis of hip dislocation is plain radiographs, this case demonstrates that bedside ultrasound may be used as a diagnostic adjunct in this time-sensitive and potentially catastrophic diagnosis.     

Bedside Ultrasound vs X-Ray for the Diagnosis of Forearm Fractures in Children

Background

Painful forearm injuries after a fall occur frequently in children. X-ray study is currently the gold standard investigation. Ultrasound (US) is a potential alternative that avoids exposure to ionizing radiation and may be less painful than x-ray study; and familiarity and skill with US is increasing among emergency physicians.

Tissue Harmonic Imaging Improves Organ Visualization in Trauma Ultrasound When Compared with Standard Ultrasound Mode

The focused abdominal sonography for trauma (FAST) examination is complicated by brightly lit trauma bays, limited time, and body habitus. Recently, new ultrasound (US) technology has become available that improves organ visualization in abdominal scans. OBJECTIVE: The hypothesis was that a new US mode, tissue harmonic (TH) imaging, improves visualization of critical organ relationships in the FAST examination by making use of previously unused frequencies. The authors performed a blind, prospective observational study to compare the images obtained in typical FAST views with those obtained in standard US and TH modes. METHODS: Blunt trauma patients presenting to a level I trauma center between April and September 2000 were enrolled on a convenience basis. Typical FAST views were obtained in standard and TH modes. The emergency ultrasonographer (EU) switched between modes for each view, optimizing the gain each time. Multiple digital still images were made with all indications of the mode used disguised. For each view on a patient, the best image in each mode was selected in a blinded fashion. Three experienced EUs, blinded to the mode used, rated each image pair for resolution, detail, and total image quality as previously defined on a ten-point Likert scale, 10 being the best for each category. Wilcoxon signed-ranks test, 95% confidence intervals (95% CIs), and interobserver correlation were calculated. RESULTS: A total of 76 image groups (39 of Morison's pouch, 20 splenorenal, and 17 bladder) from 52 patients were rated. Tissue harmonics produced improved resolution, detail, and quality when compared with the standard US mode, with median scores of 6.7 vs. 6.0, 6.7 vs. 6.0, and 6.3 vs. 6.0, respectively. The differences of 0.7 (95% CI = 0.4 to 0.93), 0.7 (95% CI = 0.4 to 0.93), and 0.33 (95% CI = 0.17 to 0.67) were statistically significant, with p = 0.0001, 0.0001, and 0.0003, respectively. There was good interobserver agreement (kappa = 0.74; 95% CI = 0.68 to 0.79). CONCLUSIONS: Tissue harmonics produced FAST images higher in detail, resolution, and total image quality than standard-mode US images.     

A Porcine Training Model for Ultrasound Diagnosis of Pneumothoraces

Background

Ultrasound for the evaluation of pneumothoraces has been extensively studied. Several medical specialties have recognized the benefit of this technique; however, a training model has not been established.

Objective

Using a porcine model, we attempt to establish a model for the training of ultrasound diagnosis of pneumothoraces.

Methods

Two pigs were anesthetized on two separate occasions. A pneumothorax was introduced each time. Participants were blinded to the study design and were not aware of the number of pneumothoraces present. A brief training lecture was given before performing the ultrasound, and the results of each lung examination were recorded. The data were collected and analyzed for the accuracy of assessment.

Results

A total of 18 individuals participated in the study, with six individuals participating on both days. Ninety-six lung ultrasound examinations were completed; 69% of the lung examinations were correctly diagnosed on the first day and 94% on the second. Participants correctly diagnosed a pneumothorax 50% of the time at the first laboratory and 100% of the time at the second. Participants who attended both laboratories increased their ability to diagnose a pneumothorax from 66% to 100%.

Conclusion

We believe this porcine model can be used for the training of ultrasound diagnosis of pneumothoraces. Participants who completed two training sessions improved their accuracy from 66% to 100% in the diagnosis of pneumothoraces. Study participants rated the educational experience highly on a post-laboratory questionnaire, and feel they will be more comfortable using it in a real-life situation.     

A Prospective Comparison of Ultrasound-guided and Blindly Placed Radial Arterial Catheters

Background
Arterial cannulation for continuous blood-pressure measurement and frequent arterial-blood sampling commonly are required in critically ill patients.
Objectives
To compare ultrasound (US)-guided versus traditional palpation placement of arterial lines for time to placement, number of attempts, sites used, and complications.
Methods
This was a prospective, randomized interventional study at a Level 1 academic urban emergency department with an annual census of 78,000 patients. Patients were randomized to either palpation or US-guided groups. Inclusion criteria were any adult patient who required an arterial line according to the treating attending. Patients who had previous attempts at an arterial line during the visit, or who could not be randomized because of time constraints, were excluded. Enrollment was on a convenience basis, during hours worked by researchers over a six-month period. Patients in either group who had three failed attempts were rescued with the other technique for patient comfort. Statistical analysis included Fisher's exact, Mann-Whitney, and Student's t-tests.
Results
Sixty patients were enrolled, with 30 patients randomized to each group. Patients randomized to the US group had a shorter time required for arterial line placement (107 vs. 314 seconds; difference, 207 seconds; p = 0.0004), fewer placement attempts (1.2 vs. 2.2; difference, 1; p = 0.001), and fewer sites required for successful line placement (1.1 vs. 1.6; difference, 0.5; p = 0.001), as compared with the palpation group.
Conclusions
In this study, US guidance for arterial cannulation was successful more frequently and it took less time to establish the arterial line as compared with the palpation method.     

Ultrasound Image Quality Comparison between an Inexpensive Handheld Emergency Department (ED) Ultrasound Machine and a Large Mobile ED Ultrasound System

Questions have been raised regarding image quality (IQ) provided by portable ultrasound (US) machines. OBJECTIVES: To determine if a difference exists between images obtained with a common portable US machine and those obtained with a more expensive, larger US machine when comparing typical views used by emergency physicians. METHODS: The authors performed a cross-sectional, blinded comparison of images from similar sonographic windows obtained on healthy models using a SonoSite 180 Plus and a General Electric (GE) 400 US machine. Both machines were optimized by company representatives. Images obtained included typical abdominal and vascular applications using the abdominal and linear transducers on each machine. All images were printed on identical high-resolution printers and then digitized using a bitmap format at 300 dots-per-inch resolution (RES). Images were then cropped, masked, and placed into random order comparing each view per model by a commercial Web design company (loracs.com). Three credentialed emergency physician sonologists, blinded to machine type, rated each image pair for RES, detail (DET), and total IQ as previously defined in the literature using a ten-point Likert scale; 10 was the best rating for each category. Paired t-test, 95% confidence intervals (95% CIs), and interobserver correlation were calculated. RESULTS: A total of 49 image pairs were evaluated. Mean GE 400 RES, DET, and IQ scores were 6.8, 6.8, and 6.6, respectively. Corresponding SonoSite means were 6.3, 6.3, and 6.0, respectively. The difference of 0.5 (95% CI = 0.13 to 1.1) for DET was not statistically significant (p = 0.06). The differences of 0.5 (95% CI = 0.1 to 1.1) and 0.6 (95% CI = 0.2 to 1.2) for RES and IQ were statistically significant, with p = 0.01 and 0.01. There was good interobserver agreement (kappa = 0.71; 95% CI = 0.67 to 0.78). CONCLUSIONS: A statistically significant difference was seen between GE 400 and SonoSite in IQ and RES, but not DET.