Animal laboratory training improves lung ultrasound proficiency and speed.

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.

A wearable microwave instrument can detect and monitor traumatic abdominal injuries in a porcine model.

Abdominal injury is a frequent cause of death for trauma patients, and early recognition is essential to limit fatalities. There is a need for a wearable sensor system for prehospital settings that can detect and monitor bleeding in the abdomen (hemoperitoneum). This study evaluates the potential for microwave technology to fill that gap. A simple prototype of a wearable microwave sensor was constructed using eight antennas. A realistic porcine model of hemoperitoneum was developed using anesthetized pigs. Ten animals were measured at healthy state and at two sizes of bleeding. Statistical tests and a machine learning method were used to evaluate blood detection sensitivity. All subjects presented similar changes due to accumulation of blood, which dampened the microwave signal ([Formula: see text]). The machine learning analysis yielded an area under the receiver operating characteristic (ROC) curve (AUC) of 0.93, showing 100% sensitivity at 90% specificity. Large inter-individual variability of the healthy state signal complicated differentiation of bleedings from healthy state. A wearable microwave instrument has potential for accurate detection and monitoring of hemoperitoneum, with automated analysis making the instrument easy-to-use. Future hardware development is necessary to suppress measurement system variability and enable detection of smaller bleedings.

Offshore telementored ultrasound: a quality assessment study.

BACKGROUND: Telementored ultrasound (US) connects experts to novices through various types of communication and network technologies with the overall aim to bridge the medical imaging gap between patients' diagnostic needs and on-site user experience. The recurrent theme in previous research on remote telementored US is the limited access to US machines and experienced users. This study was conducted to determine whether telementored US was feasible in a remote offshore setting. The aim was to assess if an onshore US expert can guide an offshore nurse through focused US scanning protocols by connecting an US machine to existing videoconference units at the offshore hospitals and to evaluate the diagnostic quality of the images and cineloops procured. RESULTS: The diagnostic quality of cineloops was scored on a five-point scale. The percentage of cineloops suitable for interpretation (score 3 ≥) for the FATE and e-FAST protocols was 96.4 and 79.1. Lung sliding and seashore sign could be identified in all volunteers. The scan time for the FAST protocol (n = four scanning positions), FATE protocol (n = six scanning positions) and both lungs (n = two scanning positions) was 1 min 20 s, 4 min 15 s and 32 s, respectively. CONCLUSION: A novice US user can be guided by a remote expert through focused US protocols within an acceptable time frame and with good diagnostic quality using existing communication and network systems found onboard offshore oil rigs.

Effect of nasal or nasopharyngeal apneic oxygenation on desaturation during induction of anesthesia and endotracheal intubation in the operating room: A narrative review of randomized controlled trials.

OBJECTIVES: To determine whether apneic oxygenation through nasal or nasopharyngeal catheters can counteract hypoxemia and desaturation during induction of anesthesia and endotracheal intubation. DESIGN: Narrative review of randomized controlled trials. SETTING: Operating room. PATIENTS: 295 ASA I-II patients in elective surgery. INTERVENTION: PubMed and Embase databases were searched for studies with apneic oxygenation. The review included randomized controlled trials with apneic oxygenation through nasal or nasopharyngeal catheters as the intervention in the setting of endotracheal intubation in adults. MEASUREMENTS: Outcome measures were time until desaturation or degree of hypoxemia. MAIN RESULTS: Eight randomized controlled trials were included, with a total of 295 patients. Apneic oxygenation was administered by nasopharyngeal catheter in four studies and by nasal catheter in four studies. The eight included articles studied apneic oxygenation at flow rates of 3-10 l/min in ASA I-II patients undergoing elective anesthesia in the operating room. Apneic oxygenation significantly prolonged time until desaturation opposed to the control groups in seven of the eight studies of patients undergoing anesthesia for elective surgery. CONCLUSION: Apneic oxygenation through nasal or nasopharyngeal catheters can prolong time to desaturation and decrease degree of desaturation during induction of anesthesia and endotracheal intubation in adult ASA I-II patients undergoing anesthesia for elective surgery.

Using thoracic ultrasonography to accurately assess pneumothorax progression during positive pressure ventilation: a comparison with CT scanning.

BACKGROUND: Although thoracic ultrasonography accurately determines the size and extent of occult pneumothoraces (PTXs) in spontaneously breathing patients, there is uncertainty about patients receiving positive pressure ventilation. We compared the lung point (ie, the area where the collapsed lung still adheres to the inside of the chest wall) using the two modalities ultrasonography and CT scanning to determine whether ultrasonography can be used reliably to assess PTX progression in a positive-pressure-ventilated porcine model. METHODS: Air was introduced in incremental steps into fi ve hemithoraces in three intubated porcine models. The lung point was identified on ultrasound imaging and referenced against the lateral limit of the intrapleural air space identified on the CT scans. The distance from the sternum to the lung point (S-LP) was measured on the CT scans and correlated to the insufflated air volume. RESULTS: The mean total difference between the 131 ultrasound and CT scan lung points was 6.8 mm (SD, 7.1 mm; range, 0.0-29.3 mm). A mixed-model regression analysis showed a linear relationship between the S-LP distances and the PTX volume ( P , .001). CONCLUSIONS: In an experimental porcine model, we found a linear relation between the PTX size and the lateral position of the lung point. The accuracy of thoracic ultrasonography for identifying the lung point (and, thus, the PTX extent) was comparable to that of CT imaging. These clinically relevant results suggest that ultrasonography may be safe and accurate in monitoring PTX progression during positive pressure ventilation.

[Gelatine phantom for training of ultrasound guided vascular access]. / Gelatinefantom til træning af ultralydvejledt vaskulær adgang.

This article describes the production of a low-cost training phantom for ultrasound guided invasive procedures of peripheral and central veins and presents a video of the process. The phantom can be adapted for use with other ultrasound techniques. It is a universal useful skill training tool for ultrasound guided invasive procedures. The phantom is easily made of concentrated gelatine. It is cheap and recyclable. The shelf life is prolonged by cold storage in a freezer. The gelatine phantom is a useful tool for practice of probe handling techniques and needle dexterity when placing peripheral and central venous catheters.

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

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.

A porcine pneumothorax model for teaching ultrasound diagnostics.

OBJECTIVES: Ultrasound (US) is a sensitive diagnostic tool for detecting pneumothorax (PTX), but methods are needed to optimally teach this technique outside of direct patient care. In training and research settings, porcine PTX models are sometimes used, but the description of the PTX topography in these models is lacking. The study purpose was to define the distribution of air using the reference imaging standard computed tomography (CT), to see if pleural insufflation of air into a live anaesthetized pig truly imitates a PTX in an injured patient. METHODS: A unilateral catheter was inserted into one pleural cavity of each of 20 pigs, and 500 mL of air was insufflated. After a complete thoracic CT scan, the anterior, lateral, medial, basal, apical, and posterior components of the PTXs were compared. The amount of air in each location was quantified by measuring the distance from the lung edge to the chest wall (LE-CW). A supine anteroposterior chest radiograph (CXR) was taken from each model and interpreted by a senior radiologist, and the image results were compared to CT. RESULTS: All 20 hemithoraces with PTX were correctly identified by CT, while six remained occult after interpreting the CXRs. The PTXs were anterior (100%), lateral (95%), medial (80%), basal (60%), apical (45%), and posterior (15%). The major proportion of the insufflated 500-mL volume was found in the anterior, medial, and basal recesses. CONCLUSIONS: The authors found the distribution of the intrathoracic air to be similar between a porcine model and that to be expected in human trauma patients, all having predominantly anterior PTX topographies. In a training facility, the model is easy to set up and can be scanned by the participants multiple times. To acquire the necessary skills to perform thoracic US examinations for PTX, the porcine models could be useful.

Insulin-induced hypoglycemia stimulates gastric vagal activity and motor function without increasing cardiac vagal activity.

BACKGROUND/AIMS: We investigated whether increasing the efferent vagal activity by insulin-induced hypoglycemia would enhance gastric emptying and volumes in healthy subjects. METHODS: Twenty healthy volunteers (10 males) were examined with and without vagal stimulation by insulin-induced hypoglycemia using a glucose clamp technique. Stomach function was tested by drinking meat soup (0.04 kcal ml(-1)) at a rate of 100 ml min(-1) until maximal capacity. Intragastric volume at maximal drinking capacity was determined by three-dimensional ultrasound. Respiratory sinus arrhythmia (RSA) was used as an index of cardiac vagal activity and plasma pancreatic polypeptide (PP) as a measure of gastric vagal activity, and skin conductance (SC) as a measure of sympathetic tone. RESULTS: Insulin-induced hypoglycaemia increased drinking capacity (p = 0.002), gastric emptying (p = 0.02), PP (p = 0.004) and SC (p = 0.004), while intragastric volume was unchanged (p = 0.7) and RSA decreased (p = 0.03). CONCLUSION: Enhancement of gastric vagal activity by insulin-induced hypoglycemia increased drinking capacity and gastric emptying similarly, resulting in an unchanged intragastric volume. Enhanced efferent vagal activity to the stomach (as measured by PP) was not associated by enhanced cardiac vagal activity (as measured by RSA), possibly a consequence of stress-induced sympathetic activation during the procedure.