Hand-held thoracic sonography for detecting post-traumatic pneumothoraces: the Extended Focused Assessment with Sonography for Trauma (EFAST)

Beyond focused assessment with sonography for trauma: ultrasound creep in the trauma resuscitation area and beyond

PURPOSE OF REVIEW

The use of ultrasound for the management of the injured patient has expanded dramatically in the last decade. The focused assessment with sonography for trauma (FAST) has become one of the fundamental skills incorporated into the initial evaluation of the trauma patient. However, there are significant limitations of this diagnostic modality as initially described. Novel ultrasound examinations of the injured patient, although useful, must also be considered carefully.

RECENT FINDINGS

Increasing evidence supports the high specificity of FAST for detecting a pericardial effusion and intra-abdominal free fluid (hemorrhage) in the patient with blunt injury. On the other hand, a so-called negative FAST result still requires further diagnostic work up given its low sensitivity. Similarly, the role of FAST in penetrating abdominal trauma appears to be limited because of lower sensitivity for visceral injury compared to other modalities. Extended FAST (EFAST), that adds a focused thoracic examination, has high accuracy for the detection of pneumothorax comparable to computed tomographic scan, the significance of which is not currently known. Finally, the utility of intensivist-performed ultrasound in the ICU is expanding to limited hemodynamic assessment and facilitation of central venous catheter placement.

SUMMARY

The indications for FAST and additional ultrasound studies in the injured patient continue to evolve. Application of sound clinical evidence will avoid unsubstantiated indications for ultrasound to creep into our clinical practice.

Portable bedside ultrasound: the visual stethoscope of the 21st century

Over the past decade technological advances in the realm of ultrasound have allowed what was once a cumbersome and large machine to become essentially hand-held. This coupled with a greater understanding of lung sonography has revolutionized our bedside assessment of patients. Using ultrasound not as a diagnostic test, but instead as a component of the physical exam, may allow it to become the stethoscope of the 21st century.

Should bedside sonography be used first to diagnose pneumothorax secondary to blunt trauma?

BACKGROUND.: Our purpose was to evaluate the effectiveness of bedside sonography (US) in the detection of pneumothorax secondary to blunt thoracic trauma. METHODS.: In this prospective study, 240 hemithoraces of 120 consecutive patients with multiple trauma were evaluated with chest radiographs (CXR) and bedside thoracic US for the diagnosis of pneumothorax. CT examinations were performed in 68 patients. Fifty-two patients who did not undergo CT examinations were excluded from the study. US examinations were performed independently at bedside by two radiologists who were not informed about CXR and CT findings. CXRs were interpreted by two radiologists who were unaware of the US and CT results. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CXR and US were calculated. RESULTS.: One hundred thirty-six hemithoraces were assessed in 68 patients. A total of 35 pneumothoraces were detected in 33 patients. On US, the diagnosis of pneumothorax was correct in 32 hemithoraces. In 98 hemithoraces without pneumothorax, US was normal. With US examination, there were three false-positive and three false-negative results. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of US were 91.4%, 97%, 91.4%, 97%, and 97%, respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CXR were 82.7%, 89.7%, 68.5%, 95%, and 89.5%, respectively. CONCLUSIONS.: Bedside thoracic US is an accurate method that can be used in trauma patients instead of CXR for the detection of pneumothorax.

Simple, almost anywhere, with almost anyone: remote low-cost telementored resuscitative lung ultrasound

BACKGROUND

Apnea (APN) and pneumothorax (PTX) are common immediately life-threatening conditions. Ultrasound is a portable tool that captures anatomy and physiology as digital information allowing it to be readily transferred by electronic means. Both APN and PTX are simply ruled out by visualizing respiratory motion at the visceral-parietal pleural interface known as lung sliding (LS), corroborated by either the M-mode or color-power Doppler depiction of LS. We thus assessed how economically and practically this information could be obtained remotely over a cellular network.

METHODS

Ultrasound images were obtained on handheld ultrasound machines streamed to a standard free internet service (Skype) using an iPhone. Remote expert sonographers directed remote providers (with variable to no ultrasound experience) to obtain images by viewing the transmitted ultrasound signal and by viewing the remote examiner over a head-mounted webcam. Examinations were conducted between a series of remote sites and a base station. Remote sites included two remote on-mountain sites, a small airplane in flight, and a Calgary household, with base sites located in Pisa, Rome, Philadelphia, and Calgary.

RESULTS

In all lung fields (20/20) on all occasions, LS could easily and quickly be seen. LS was easily corroborated and documented through capture of color-power Doppler and M-mode images. Other ultrasound applications such as the Focused Assessment with Sonography for Trauma examination, vascular anatomy, and a fetal wellness assessment were also demonstrated.

CONCLUSION

The emergent exclusion of APN-PTX can be immediately accomplished by a remote expert economically linked to almost any responder over cellular networks. Further work should explore the range of other physiologic functions and anatomy that could be so remotely assessed.

Battlefield applications for handheld ultrasound

Combat medical care provides unique challenges and opportunities for military medical teams. The austerity of the environment severely limits access to many diagnostic and therapeutic tools. Because of their compact size, handheld ultrasound (US) machines are increasingly being used in these constrained environments. A growing body of literature documents the diagnostic utility of handheld US for trauma encountered in the battlefield. Furthermore, US guidance may assist in the performance of some procedures performed in battlefield medical care. This review will provide an overview of the history, current status, limitations and potential future of US utility for the battlefield.

Needle decompression for tension pneumothorax in Tactical Combat Casualty Care: do catheters placed in the midaxillary line kink more often than those in the midclavicular line?

BACKGROUND

Tactical Combat Casualty Care (TCCC) is a system of prehospital trauma care designed for the combat environment. Needle decompression (ND) is a critical TCCC intervention, because previous data suggest that up to 33% of all preventable deaths on the battlefield result from tension pneumothoraces. There has recently been increased interest in performing ND at the fifth intercostal space in the midaxillary line to prevent complications associated with landmarking second intercostal space in the midclavicular line site. We developed a model to assess whether catheters placed in the midaxillary line for decompressing tension pneumothoraces are more prone to kinking than those placed in the midclavicular line because of adducted arms during military transport.

METHODS

To simulate ND, we secured segments of porcine chest walls over volunteer soldiers' chests and placed 14-gauge, 1.5-inch angiocatheters through the porcine wall segments which were affixed to either the midaxillary or midclavicular location on the volunteers. We then assessed for occlusion and kinking by flow of normal saline (NS) through the angiocatheter in situ. The angiocatheter was then transduced using standard arterial line manometry, and the opening pressures required to initiate flow through the catheters were measured. The opening pressures were then converted to mm Hg. We also assessed for catheter occlusion after the physical manipulation of the patient, by simulated patient transport.

RESULTS

We observed that there was a significant pressure difference required to achieve free flow through the in situ angiocatheter between the fifth intercostal space midaxillary line versus the second intercostal space midclavicular line site (13.1 ± 3.6 mm Hg vs. 7.9 ± 1.8 mm Hg).

CONCLUSIONS

This study suggests that the 14-gauge, 1.5-inch angiocatheter used for ND in the midaxillary line may partially and temporarily occlude in patients who will be transported on military stretchers. The pressure of 12.8 mm Hg has been documented in animal models as the pressure at which hemodynamic instability develops. This may contribute to the reaccumulation of tension pneumothoraces and ultimate patient deterioration in military transport.

Can cervical spine computed tomography assist in detecting occult pneumothoraces?

INTRODUCTION

Screening CT often detects posttraumatic pneumothoraces that were not diagnosed on a preceding supine anteroposterior chest radiograph (occult pneumothoraces (OPTXs)). Because abdominal CT imaging misses OPTXs in the upper thorax, the objective of this study was to evaluate the utility of cervical spine (C-spine) CT screening for diagnosing OPTXs.

METHODS

A dual-institution (Foothills Medical Centre and Grady Memorial Hospital) retrospective review of consecutive OPTXs was performed. The accuracy of various CT screening protocols in detecting OPTXs was compared.

RESULTS

OPTXs were detected in 75 patients. Patient demographics and injury characteristics were similar between centres (65% male; 97% blunt mechanism; 29% hemodynamically unstable; mean ISS=27; mean length of stay=22 days; mortality=9%)(p>0.05). Patients received either abdominal (41%) or thoraco-abdominal (59%) CT imaging. Most patients (89%) also underwent C-spine CT imaging. OPTXs were evident on thoracic CT in 100% (44/44), abdominal CT in 83% (62/75), and C-spine CT in 82% (55/67) of cases. All patients with OPTXs identified solely on thoracic CT (i.e. not abdominal) who also underwent imaging of their C-spine could have had their OTPXs diagnosed by using the pulmonary windows setting of their C-spine CT series. Combining C-spine and abdominal CT screening diagnosed all OPTXs (67/67) detected on thoracic CT, for patients who also underwent these investigations.

CONCLUSIONS

OPTXs were evident on thoracic (and not abdominal) CT in 17% of severely injured patients. For patients who also underwent C-spine imaging, all OPTXs isolated to thoracic CT could be diagnosed by using the pulmonary windows setting of their C-spine CT imaging protocol. All OPTXs, regardless of intra-thoracic location, could also be detected by combining C-spine and abdominal CT screening.

Prospective trial evaluating sonography after thoracic surgery in postoperative care and decision making

OBJECTIVE

Following thoracic surgery, daily chest X-rays (CXRs) are performed to assess patient evolution and to make decisions regarding chest tube removal and patient discharge. Sonography after thoracic surgery (SATS) has the potential to be an effective, convenient, inexpensive and easy to learn tool in the post-operative management of thoracic surgery patients. We hypothesized that SATS could alleviate the need for repetitive CXRs, thus reducing the related risks, costs and inconvenience.

METHODS

This study consisted of a prospective cohort trial. All patients scheduled to undergo thoracic surgery at a single academic medical centre were eligible. Post-operative bedside pleural ultrasound was performed whenever a CXR was ordered by the treating team. Investigators specifically assessed patients with the goals of identifying pleural effusions and pneumothoraces. Study investigators were blinded to CXR results. SATS findings were compared with CXRs, which were considered the gold standard in routine post-operative pleural space evaluation.

RESULTS

One hundred and twenty patients were prospectively enrolled over a 5.5-month period. Three hundred and fifty-two ultrasound examinations were performed (mean = 3.0 ± 2.4 exams per patient). The time interval between the ultrasound and the comparative CXR was 166 ± 149 min. The mean time required to perform SATS was 11 ± 6 min per exam. In the detection of pleural effusion, SATS yielded a sensitivity of 83.1% and a specificity of 59.3%. In the detection of pneumothoraces, a sensitivity of 21.2% and a specificity of 94.7% were obtained.

CONCLUSIONS

Post-operative ultrasound may alleviate the need to perform routine CXR in patients with a previously ruled out pneumothorax. SATS used selectively may be able to reduce the number of routine CXRs performed; however, it does not have high enough accuracy to replace CXRs.

Anteroposterior chest radiograph vs. chest CT scan in early detection of pneumothorax in trauma patients

Pneumothorax is a common complication following blunt chest wall trauma. In these patients, because of the restrictions regarding immobilization of the cervical spine, Anteroposterior (AP) chest radiograph is usually the most feasible initial study which is not as sensitive as the erect chest X-ray or CT chest for detection of a pneumothorax. We will present 3 case reports which serve for better understanding of the entity of occult pneumothorax. The first case is an example of a true occult pneumothorax where an initial AP chest X-ray revealed no evidence of pneumothorax and a CT chest immediately performed revealed evidence of pneumothorax. The second case represents an example of a missed rather than a truly occult pneumothorax where the initial chest radiograph revealed clues suggesting the presence of pneumothorax which were missed by the reading radiologist. The third case emphasizes the fact that "occult pneumothorax is predictable". The presence of subcutaneous emphesema and pulmonary contusion should call for further imaging with CT chest to rule out pneumothorax. Thoracic CT scan is therefore the "gold standard" for early detection of a pneumothorax in trauma patients. This report aims to sensitize readers to the entity of occult pneumothorax and create awareness among intensivists and ER physicians regarding the proper diagnosis and management.

Test characteristics of ultrasonography for the detection of pneumothorax: a systematic review and meta-analysis

BACKGROUND

A pneumothorax is a potentially life-threatening condition. Although CT scan is the reference standard for diagnosis, chest radiographs are commonly used to rule out the diagnosis. We compared the test characteristics of ultrasonography and supine chest radiography in adult patients clinically suspected of having a pneumothorax, using CT scan or release of air on chest tube placement as reference standard.

METHODS

We searched for English literature in MEDLINE and EMBASE and performed hand searches. Two independent investigators used standardized forms to review articles for inclusion, quality (QUADAS tool), and data extraction. We calculated κ agreement for study selection and evaluated clinical and quality homogeneity before meta-analysis.

RESULTS

We reviewed 570 articles and selected 21 for full review (κ, 0.89); eight articles (total of 1,048 patients) met all inclusion criteria (κ, 0.81). All studies but one used the ultrasonographic signs of lung sliding and comet tail to rule out pneumothorax. Chest radiography data were available for 864 of 1,048 patients evaluated with ultrasonography. Ultrasonography was 90.9% sensitive (95% CI, 86.5-93.9) and 98.2% specific (95% CI, 97.0-99.0) for the detection of pneumothorax. Chest radiography was 50.2% sensitive (95% CI, 43.5-57.0) and 99.4% specific (95% CI, 98.3-99.8).

CONCLUSIONS

Performance of ultrasonography for the detection of pneumothorax is excellent and is superior to supine chest radiography. Considering the rapid access to bedside ultrasonography and the excellent performance of this simple test, this study supports the routine use of ultrasonography for the detection of pneumothorax.

Current role of emergency ultrasound of the chest

OBJECTIVE

Chest sonography has gained clinical significance in the diagnosis of various pulmonary, pleural, cardiac, and mediastinal emergency conditions. Therefore, the current role of emergency ultrasound are assessed.

DATA SOURCE

A systematic literature search of MEDLINE database was performed to identify all studies dealing with transthoracic sonography/chest ultrasound in combination with pulmonary embolism, pneumothorax, pneumonia, pleural effusion, pulmonary edema, and lung contusion. The relevant sonographic studies between 1988 and 2010 were evaluated.

CONCLUSIONS

The noninvasive ultrasound-based diagnosis is relatively portable permitting the technique to be performed at any time, in any place, and on any patient, an ideal method for emergency conditions. Sonography allows immediate diagnosis of pulmonary embolism, pneumothorax, pneumonia, pleural effusion as well as rib fracture, and it provides a basis for further diagnostic- and treatment-related decisions. The key sonographic features associated with these most common emergency chest diseases are illustrated herein.

Prehospital ultrasound as the evolution of the Franco-German model of prehospital EMS

Purpose

To evaluate, throughout model analysis and evaluation of existing literature and personal experience, which can be the benefits of routine performance of prehospital ultrasound in the different models of prehospital emergency medical service.

Methods

The existing literature was reviewed.

Conclusions

The ultrasound can be a very valuable asset in both the Anglo-American and the Franco-German models. In the latter, however, its role is further emphasized since US-enhanced on-spot early diagnosis performed by the physician can be beneficial to the whole system and not just the single patient.

Diagnosis of pneumothorax by radiography and ultrasonography: a meta-analysis

OBJECTIVE

This study compares, by meta-analysis, the use of anterior-posterior chest radiography (CR) with transthoracic ultrasonography for the diagnosis of pneumothorax.

METHODS

English-language articles on the performance of CR and ultrasonography in the diagnosis of a pneumothorax were selected. In eligible studies, data were recalculated, and the forest plots and summary receiver operating characteristic (sROC) curves were analyzed.

RESULTS

Pooled sensitivity and specificity were 0.88 and 0.99, respectively, for ultrasonography, and 0.52 and 1.00, respectively, for CR. For ultrasonography performed by clinicians other than radiologists, pooled sensitivity and specificity were 0.89 and 0.99, respectively. The sROC areas under the curve were compared, and no significant differences between ultrasonography and CR were found. Meta-regression analysis implied that the operator is strongly associated with accuracy (relative diagnostic OR, 0.21; 95% CI, 0.05-0.96; P = .0455).

CONCLUSIONS

The meta-analysis indicated that bedside ultrasonography performed by clinicians had higher sensitivity and similar specificity compared with CR in the diagnosis of pneumothorax, but the accuracy of ultrasonography in the diagnosis of pneumothorax depended on the skill of the operators.

Extended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax: experience at a community based level I trauma center

INTRODUCTION

Early identification of pneumothorax is crucial to reduce the mortality in critically injured patients. The objective of our study is to investigate the utility of surgeon performed extended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax.

METHODS

We prospectively analysed 204 trauma patients in our level I trauma center over a period of 12 (06/2007-05/2008) months in whom EFAST was performed. The patients' demographics, type of injury, clinical examination findings (decreased air entry), CXR, EFAST and CT scan findings were entered into the data base. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated.

RESULTS

Of 204 patients (mean age--43.01+/-19.5 years, sex--male 152, female 52) 21 (10.3%) patients had pneumothorax. Of 21 patients who had pneumothorax 12 were due to blunt trauma and 9 were due to penetrating trauma. The diagnosis of pneumothorax in 204 patients demonstrated the following: clinical examination was positive in 17 patients (true positive in 13/21, 62%; 4 were false positive and 8 were false negative), CXR was positive in 16 (true positive in 15/19, 79%; 1 false positive, 4 missed and 2 CXR not performed before chest tube) patients and EFAST was positive in 21 patients (20 were true positive [95.2%], 1 false positive and 1 false negative). In diagnosing pneumothorax EFAST has significantly higher sensitivity compared to the CXR (P=0.02).

CONCLUSIONS

Surgeon performed trauma room extended FAST is simple and has higher sensitivity compared to the chest X-ray and clinical examination in detecting pneumothorax.

Ultrasonographic finding of lung sliding in patients on mechanical ventilation with alveolar-interstitial syndrome

BACKGROUND AND OBJECTIVES

To determine the visibility of pleural lung sliding in alveolar-interstitial syndrome (AIS) in patients on mechanical ventilation at two different time points, as a confirmatory ultrasonographic method for excluding pneumothorax.

METHODS

Fifty-two mechanically ventilated patients in the semirecumbent position in a surgical/neurosurgical intensive care unit with ultrasonographic lung 'comet tails' in three upper anterolateral intercostal spaces, indicating the presence of AIS, were scanned for lung sliding in the same three intercostal spaces with a linear 5-10 MHz transducer after starting mechanical ventilation and on weaning trials. Pneumothorax and atelectasis were excluded by chest radiograph.

RESULTS

Absent lung sliding was found in 22.7% of intercostal spaces scanned after starting mechanical ventilation and in 21.2% of scans taken on weaning trials. The lowest invisible rate was in patients with acute heart failure and the highest in patients with acute respiratory distress syndrome.

CONCLUSION

Lung sliding specificity in AIS during mechanical ventilation was 78%. Our opinion is that different levels of airway pressure between starting mechanical ventilation and weaning trials have no influence on lung sliding visibility.

2010 Trauma Association of Canada presidential address: why the Trauma Association of Canada should care about space medicine

The Trauma Association of Canada is now 27 years old, having been officially founded in 1983, at the meetings of the Royal College as a maturation of the trauma committee of the Canadian Association of General Surgeons. The first page of the official minutes also stressed the need to welcome other disciplines into the fold. Personally, it has taken me years of involvement, as well as the Presidency, to truly appreciate the depth of our Founding Members commitment. These individuals set lofty mission goals for the organization, namely: to strive to improve the quality of care provided to the injured patient, including prehospital management and transport, acute care hospitalization, and reintegration into society; to support, conduct, and apply basic science and clinical and outcome research related to trauma; to encourage effective and efficient use of healthcare resources in the delivery of trauma care; and to foster professional and community education in the field of injury prevention and in the care of the injured patient. As daunting as these responsibilities are, I am suggesting one more: to overcome the great penalty of geography that challenges our nation and penalizes many of our citizens by aspiring to optimize these four goals, for all Canadians, irrespective of where they live--our potential fifth mission. Furthermore, I believe that lessons from space medicine may offer some strategies to accomplish this goal.

Ultrasonography versus chest radiography after chest tube removal for the detection of pneumothorax

BACKGROUND

Bedside ultrasound technology is an innovative, cost-effective, safe, and reproducible method used to make efficient decisions that directly affect the care of critical care patients.

PURPOSE

To validate the use of ultrasound technology when compared with the use of standard chest radiography for the detection of pneumothorax following chest tube removal.

METHODS

A prospective observational comparison study of 50 cardiothoracic patients with surgically placed pleural chest tubes was conducted. The accuracy of bedside ultrasound technology was compared with standard chest radiography to detect pneumothorax.

RESULTS

The sample kappa statistic was 1.000, indicating a perfect agreement between bedside ultrasonography and chest radiography in the detection of pneumothorax. Completion of the bedside ultrasound procedure took significantly less time than chest radiography.

CONCLUSIONS

Bedside ultrasound technology is as accurate as chest radiography in detecting pneumothorax following chest tube removal and can save institutions' time and money.

Emergency ultrasound identification of a lung mass

Introduction

A 49-year-old woman with HIV and remote tobacco use presented with fever and 2 months of progressive dyspnea. A chest radiograph showed a right upper lobe pneumonia and treatment for community-acquired pneumonia was initiated.

Materials and methods

The emergency physician performed a bedside lung ultrasound that suggested a more complicated process and prompted computed tomography of the chest. This revealed a right upper lobe mass and lymphadenopathy consistent with neoplasm which was subsequently confirmed on bronchoscopy.

Conclusions

The role of lung ultrasound in the Emergency Department is reviewed and a new potential application of identifying patients in whom further diagnostic testing may be indicated is described.

Sonographic diagnosis of pneumothorax

PURPOSE

Over the last decade, the use of ultrasound as a technique to look for pneumothorax has rapidly evolved. This review aims to analyze and synthesize current knowledge on lung ultrasound targeted at the diagnosis of pneumothorax. The technique and its usefulness in different scenarios are explained, and its merits over conventional radiology are highlighted.

METHODS

A systematic literature search (1995-2010) was performed, involving PubMed, to describe the more recent scientific evidence on the topic. Moreover, this review is also a synopsis of experts' opinion and personal clinical experience.

RESULTS AND CONCLUSIONS

Ultrasound diagnosis of pneumothorax relies on the recognition of four sonographic artifact signs: the lung sliding, the B lines, the lung point, and the lung pulse. Combining these few signs, it is possible to accurately rule in or rule out pneumothorax at the bedside in several different clinical scenarios. Sensitivity of a lung ultrasound in the detection of pneumothorax is higher than that of conventional anterior-posterior chest radiography, and similar to that of computerized tomography. A major benefit of a lung ultrasound is that it can be used quickly to diagnose pneumothorax at the bedside in any critical situation, like cardiac arrest and hemodynamically unstable patients. Moreover, it can be used to detect radio-occult pneumothorax and to quantify the extension of the air layer. Advantages in terms of reduced complexity, feasibility at the bedside, and absence of exposure to ionizing radiation make lung ultrasound the method of choice in several common clinical situations.

Portable ultrasonography in mass casualty incidents: The CAVEAT examination

Ultrasonography used by practicing clinicians has been shown to be of utility in the evaluation of time-sensitive and critical illnesses in a range of environments, including pre-hospital triage, emergency department, and critical care settings. The increasing availability of light-weight, robust, user-friendly, and low-cost portable ultrasound equipment is particularly suited for use in the physically and temporally challenging environment of a multiple casualty incident (MCI). Currently established ultrasound applications used to identify potentially lethal thoracic or abdominal conditions offer a base upon which rapid, focused protocols using hand-carried emergency ultrasonography could be developed. Following a detailed review of the current use of portable ultrasonography in military and civilian MCI settings, we propose a protocol for sonographic evaluation of the chest, abdomen, vena cava, and extremities for acute triage. The protocol is two-tiered, based on the urgency and technical difficulty of the sonographic examination. In addition to utilization of well-established bedside abdominal and thoracic sonography applications, this protocol incorporates extremity assessment for long-bone fractures. Studies of the proposed protocol will need to be conducted to determine its utility in simulated and actual MCI settings.

Occult pneumothorax, revisited

Pneumothorax is a recognized cause of preventable death following chest wall trauma where a simple intervention can be life saving. In cases of trauma patients where cervical spine immobilization is mandatory, supine AP chest radiograph is the most practical initial study. It is however not as sensitive as CT chest for early detection of a pneumothorax. "Occult" pneumothorax is an accepted definition of an existing but usually a clinically and radiologically silent disturbance that in most patients can be tolerated while other more urgent trauma needs are attended to. However, in certain patients, especially those on mechanical ventilation (with subsequent increase of intrapleural air with positive pressure ventilation), missing the diagnosis of pneumothorax can be deleterious with fatal consequences. This review will discuss the occult pneumothorax in the context of 3 radiological examples, which will further emphasize the entity. Because a negative AP chest radiograph can dangerously delay its recognition, we recommend that any trauma victim presenting to the emergency department with symptoms of respiratory distress should be screened with either thoracic ultrasonography or chest CT scan to avoid missing a pneumothorax.

A method to detect occult pneumothorax with chest radiography

Small pneumothoraces are often not visible on supine screening chest radiographs because they develop anteriorly to the lung. These pneumothoraces are termed occult. Occult pneumothoraces account for an astonishingly high 52% to 63% of all traumatic pneumothoraces. A 19-year-old obese woman was involved in a head-on car accident. The admission anteroposterior chest radiographs were unremarkable. Because of the presence of right chest tenderness and an abrasion, we suspected the presence of a pneumothorax. Thus, we decided to take a supine oblique chest radiograph of the right side of the thorax, which clearly revealed a visceral pleural line, consistent with a diagnosis of traumatic pneumothorax. A pneumothorax may be present when a supine chest radiograph reveals either an apparent deepening of the costophrenic angle (the "deep sulcus sign") or the presence of 2 diaphragm-lung interfaces (the "double diaphragm sign"). However, in practice, supine chest radiographs have poor sensitivity for occult pneumothoraces. Oblique chest radiograph is a useful and fast screening tool that should be considered for cases of blunt chest trauma, especially when transport of critically ill patients to the computed tomographic suite is dangerous or when imminent transfer to another hospital is being arranged and early diagnosis of an occult pneumothorax is essential.

Inadequate needle thoracostomy rate in the prehospital setting for presumed pneumothorax: an ultrasound study

OBJECTIVE

The purpose of this study was to evaluate the frequency of inadequate needle chest thoracostomy in the prehospital setting in trauma patients suspected of having a pneumothorax (PTX) on the basis of physical examination.

METHODS

This study took place at a level I trauma center. All trauma patients arriving via emergency medical services with a suspected PTX and a needle thoracostomy were evaluated for a PTX with bedside ultrasound. Patients too unstable for ultrasound evaluation before tube thoracostomy were excluded, and convenience sampling was used. All patients were scanned while supine. Examinations began at the midclavicular line and included the second through fifth ribs. If no sliding lung sign (SLS) was noted, a PTX was suspected, and the lung point was sought for definitive confirmation. When an SLS was noted throughout and a PTX was ruled out on ultrasound imaging, the thoracostomy catheter was removed. Descriptive statistics were calculated.

RESULTS

A total of 57 patients were evaluated over a 3-year period. All had at least 1 needle thoracostomy attempted; 1 patient underwent 3 attempts. Fifteen patients (26%) had a normal SLS on ultrasound examination and no PTX after the thoracostomy catheter was removed. None of the 15 patients were later discovered to have a PTX on subsequent computed tomography.

CONCLUSIONS

In this study, 26% of patients who received needle thoracostomy in the prehospital setting for a suspected PTX appeared not to have had a PTX originally, nor had 1 induced by the needle thoracostomy. It may be prudent to evaluate such patients with bedside ultrasound instead of automatically converting all needle thoracostomies to tube thoracostomies.

Comparison of Web-versus classroom-based basic ultrasonographic and EFAST training in 2 European hospitals

STUDY OBJECTIVE

Training physicians in new skills through classroom-based teaching has inherent cost and time constraints. We seek to evaluate whether Web-based didactics result in similar knowledge improvement and retention of basic ultrasonographic principles and the Extended Focused Assessment with Sonography for Trauma (EFAST) compared with the traditional method.

METHODS

Physicians from 2 German emergency departments were randomized into a classroom group with traditional lectures and a Web group who watched narrated lectures online. All participants completed a pre- and posttest and a second posttest 8 weeks later. Both groups underwent hands-on training after the first posttest. A control group completed the 2 initial tests without didactic intervention.

RESULTS

Fifty-five subjects participated in the study. Both the classroom and Web group showed significant improvement in pre- and posttest 1 scores (75.9% versus 93.9% and 77.8% versus 92.5%; P<.001 for both), with similar knowledge retention after 8 weeks (88.6% and 88.9%; P=.87). No statistically significant difference in mean test scores could be found between the 2 groups at each point: -1.9% (95% confidence interval [CI] -5.2% to 1.4%) for the pretest, 1.4% (95% CI -0.6% to 3.4%) for posttest 1, and -0.3% (95% CI -3.9% to 3.3%) for posttest 2. The control group showed no learning effect without intervention (83.3% versus 82.8%, ; P=.88).

CONCLUSION

Web-based learning provides the potential to teach physicians with greater flexibility than classroom instruction. Our data suggest that Web-based ultrasonography and EFAST didactics are comparable to traditional classroom lectures and result in similar knowledge retention.

[Utility of the lung ultrasound in the intensive medicine unit]

The radiological diagnostic approach of the thorax in the critically ill patient has traditionally been based on the anteroposterior chest X-ray. However, it is generally accepted that it has important limitations regarding its diagnostic accuracy of pleuro-pulmonary disease. The introduction of computed tomography largely solved this problem, but with the dual disadvantage of a larger radiation dose and the unavoidable transportation outside of the ICU. In this context, the lung ultrasound has become an alternative technique, with the advantage that due to its portability, it is done at the patient's bedside. In the lung ultrasound, the ribs, spine and air in the thorax act as barriers to the ultrasounds, causing artifacts that must be recognized and interpreted for a correct diagnosis. However, intrathoracic diseases, existence of fluid in the pleural space and consolidation, or atelectasis in the lung provide a sufficient ultrasound window for the correct evaluation. In this review, we explain the lung and pleural ultrasound technique, define the normal pattern and the artifacts that serve to detect the abnormalities and we explain the criteria for the main diseases (consolidation, pleural effusion, pulmonary edema and pneumothorax). We also discuss the possible utility and limitations of the lung ultrasound in our daily practice, such as diagnosis of acute respiratory failure, detection, quantification and drainage of a pleural effusion, chest trauma, management and complications of acute respiratory distress syndrome and tracheal intubation success or failure.

Opening Pandora’s box: the potential benefit of the expanded FAST exam is partially confounded by the unknowns regarding the significance of the occult pneumothorax

Introduction

Point of care (POC) ultrasound brings another powerful dimension to the physical examination of the critically ill. A contemporary challenge for all care providers, however, is how to best incorporate ultrasound into contemporary algorithms of care. When POC ultrasound corroborates pre-examination clinical suspicion, incorporation of the findings into decision-making is easier. When POC ultrasound generates new or unexpected findings, decision-making may be more difficult, especially with conditions that were previously not appreciated with older diagnostic technologies. Pneumothoraces (PTXs), previously seen only on computed tomography and not on supine chest radiographs known as occult pneumothoraces (OPTXs), which are now increasingly appreciated on POC ultrasound, are such an example.

Methods

The relevant literature concerning POC ultrasound and PTXs was reviewed after an electronic search using PubMed supplemented by ongoing research by the Canadian Trauma Trials Collaborative of the Trauma Association of Canada.

Results

OPTXs are frequently encountered in the critically injured who often require mechanical ventilation with positive pressure breathing (PPB). Standard recommendations for post-traumatic PTXs and the setting of PPB mandate chest drainage, recognizing a significant rate of complications related to this procedure itself. Whether these standard recommendations generated in response to obvious overt PTXs apply to these more subtle OPTXs is currently unknown, and evidence-based recommendations regarding appropriate therapy are impossible due to the lack of clinical studies.

Conclusions

OPTXs are a condition that illustrates how incorporation of POC ultrasound findings brings further responsibilities to critically appraise the significance of these findings in terms of patient outcomes and overall care. Adequately powered and adequately followed-up clinical trials addressing the treatment are required.

An Evidence-Based Approach for Integrating Bedside Ultrasound Into Routine Practice in the Assessment of Undifferentiated Shock

Undifferentiated hypotension remains a central diagnostic and therapeutic challenge in emergency and critical care medicine. Increasingly, bedside ultrasound conducted by intensivists and emergency medicine providers is assuming a central role in diagnosis and resuscitation of hypotension. This review discusses sample algorithms for the bedside ultrasonographic assessment of undifferentiated shock and outlines an evidence-based framework for the intensivist seeking to incorporate bedside ultrasound into daily clinical practice. The literature regarding specific applications including cardiac, thoracic, pulmonary, and vascular assessment is briefly reviewed, as is the evidence pertaining to effective implementation, training, credentialing, and ongoing quality assurance.

Pleural ultrasound compared with chest radiographic detection of pneumothorax resolution after drainage

BACKGROUND

Pleural ultrasonography (PU) is more sensitive than chest radiograph (CXR) for diagnosing pneumothorax and could be useful for detecting resolution of pneumothorax after drainage. The aim of this prospective double-blind observational study was to assess PU accuracy during pneumothorax follow-up after drainage.

METHODS

All patients hospitalized with pneumothorax requiring drainage were eligible. After drainage, residual pneumothorax was assessed by CXR and PU (1) 24 h after bubbling in the aspiration device had stopped, (2) 6 h after clamping the pleural catheter, and (3) 6 h after removing the pleural catheter. Pneumothorax indicated by PU but not CXR was confirmed by CT scan or by aspiration of > 10 mL of air.

RESULTS

Forty-four unilateral pneumothoraces were studied (primary spontaneous: 70.5%), and 162 pairs of examinations (CXR and PU) were performed. Twenty residual pneumothoraces were detected by both CXR and PU. Furthermore, PU suspected 14 pneumothoraces that were not identified by CXR; 13 were confirmed. All of these pneumothoraces resulted in therapeutic intervention. Thus, 39% (13/33) of the confirmed residual pneumothoraces were missed by CXR. In patients with primary spontaneous pneumothorax, the positive predictive value of PU for residual pneumothorax diagnosis was 100%; for other pneumothoraces, this value ranged from 90% in the absence of a lung point to 100% when a lung point was observed. PU results were obtained faster than results from CXR (35 +/- 34 min vs 71 +/- 56 min, P < .0001).

CONCLUSIONS

The accuracy of PU is excellent for detecting residual pneumothorax during pneumothorax follow-up after drainage.

Portable ultrasound for remote environments, part II: current indications

BACKGROUND

With recent advances in ultrasound technology, it is now possible to deploy lightweight portable imaging devices in the field. Techniques and studies initially developed for hospital use have been extrapolated out of the hospital setting in a wide variety of environments in an effort to increase diagnostic accuracy in austere or prehospital environments.

OBJECTIVES

This review summarizes current ultrasound applications used in out-of-hospital arenas and highlights existing evidence for such use. The diversity of applications and environments is organized by indication to better inform equipment selection as well as future directions for research and development.

DISCUSSION

Trauma evaluation, casualty triage, and assessment for pneumothorax, acute mountain sickness, and other applications have been studied by field medical teams. A wide range of outcomes have been reported, from alterations in patient care to determinations of accuracy compared to clinical judgment or other diagnostic modalities.

CONCLUSIONS

The use of lightweight portable ultrasound shows great promise in augmenting clinical assessment for field medical operations. Although some studies of diagnostic accuracy exist in this setting, further research focused on clinically relevant outcomes data is needed.

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.

Training guidelines for ultrasound: worldwide trends

Sound travels through objects that block light. Only very recently has technology advanced enough to decipher ultrasound for medical use. Machines have become smaller, cheaper, more versatile and more advanced than ever before. The medical use of ultrasound spreads across many fields so that traditional areas no longer have a monopoly. With this comes the question of training doctors. This has been done by various colleges and societies worldwide. Some have been quicker to act than others. There also needs to be an understanding of when broad experience and advanced technical skills are required or when limited skills will do. In addition, some procedures can be performed more safely with ultrasound where the knowledge of ultrasound is not paramount. This article covers current provision of training in echocardiography and ultrasound in areas relevant to anaesthetists who are working in critical care (including accident and emergency) and complex surgery (mainly cardiac).

Are live instructors replaceable? Computer vs. classroom lectures for EFAST training

BACKGROUND

The EFAST (extended focused assessment with sonography for trauma) is part of the recommended curriculum for Emergency Medicine and Surgery residents. Computer-based lectures may represent a time-efficient alternative to traditional lectures.

OBJECTIVES

Our hypothesis was that computer lectures in basic ultrasound and the EFAST are not inferior to classroom lectures in test score improvement for residents with or without prior training.

METHODS

First-year Emergency Medicine and Surgery residents were enrolled and completed a pre-test. Subjects were then randomized into a classroom group, which attended traditional lectures, and a computer group, which listened to narrated lectures on computers. After the didactic training, all subjects completed a post-test.

RESULTS

Forty-four subjects completed the study: 64% were General Surgery residents, 66% were male. Overall, mean test score improvements were higher in the classroom than in the computer group (28.0% vs. 18.4%). In 25 residents without prior training, mean improvements in the computer and classroom groups were 25% and 27%, respectively. The 95% confidence limit around the difference was 9%, falling within the a priori non-inferiority range of 10%, and consistent with non-inferiority of computer-based lectures. In 19 residents with prior training, mean test score improvements for the computer and classroom groups were 13% and 29%, respectively. The 95% confidence limit of 24% exceeded the non-inferiority range, consistent with inferiority of computer-based lectures.

CONCLUSIONS

Computer-based lectures are not inferior to classroom lectures and may represent a worthwhile substitution in subjects without prior ultrasound education. Our data suggest that didactic ultrasound training through classroom lectures is more effective than computer-based lectures in individuals with prior training.

Can emergency medical services personnel identify pneumothorax on focused ultrasound examinations?

Background

Ultrasound is of proven accuracy in the diagnosis of pneumothorax. In certain locations, pre-hospital providers are adopting its use for the management of critically ill patients.

Objectives

To determine the sensitivity and specificity of emergency medical service (EMS) providers in identifying pneumothorax on ultrasound examinations.

Methods

This was an educational study evaluating 33 EMS providers. Each subject went through a brief didactic session covering the use of ultrasound in diagnosis of pneumothorax. They were then given an examination consisting of 20 individual ultrasound real-time video cases depicting either a pneumothorax or normal lung sliding. Sensitivities and specificities with 95% confidence intervals (95% CIs) were calculated for recognition of pneumothorax.

Results

The 33 study participants were able to identify pneumothorax with a sensitivity of 82% (95% CI 77–86%), specificity of 94% (95% CI 90–96%), positive predictive value of 93% (95% CI 89–95%), and negative predictive value of 84% (95% CI 80–87%).

Conclusions

Emergency medical service providers were able to identify pneumothorax at a relatively high rate. Real-time scanning by the study subjects might lead to even better results.