Nils Petter Oveland

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.

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.

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 students 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.

Using thoracic ultrasound to accurately assess pneumothorax progression during positive pressure ventilation: a comparison with computed tomography

Objectives While 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 (i.e. the area where the collapsed lung still adheres to the inside of the chest wall) using the two modalities ultrasound (US) and computed tomography (CT), to determine whether US can reliably be used to assess PTX progression in a positive pressure ventilated porcine model.

The intrapleural volume threshold for ultrasound detection of pneumothoraxes

Objectives Small pneumothoraxes (PTXs) may not impart an immediate threat to trauma patients after chest injuries. However, if these patients require positive pressure ventilation even a small amount of pleural air may be relevant. Point-of-care lung ultrasonography (US) is a reliable tool in the diagnosis of PTX, but the performance characteristics regarding detection of miniscule PTXs needs to be defined. We aimed at finding the volume threshold of intrapleural air where PTXs confidently can be diagnosed.

Dynamic ultrasound assessment of pneumothorax extension: a comparison with computer tomography

Methods Air was introduced into 5 hemithoraces (HTs) of 3 PPV porcine models. An anaesthesiologist experienced in US, identified LPs during the inspiratory phase and delineated the topography and extension of the PTX with subcutaneous needles. This was compared with the points where the lung detached from the inside of the chest wall identified by CT. The distance from sternum to the LP (S-LP) and PTX area were measured in two preset levels.

Ultrasound Detection of Pneumothorax. Development of a porcine pneumothorax model to assess and teach lung ultrasound diagnostics.

Pneumothorax (PTX) is common after blunt chest injury, and failure to diagnose and rapidly treat an enlarging PTX may cause patient death. Occult PTXs missed on supine chest X‐ray (CXR) may subsequently be found by computed tomography (CT) scans, but both of these diagnostic tools are not readily available for the patient. Furthermore, other problems associated with these techniques include the radiation hazard, the time delay after ordering, and obtaining the specialized radiologists dictation of the CXR and CT results. Contrary, lung ultrasonography (US) is a harmless point‐of‐care examination to accurately diagnose PTX. The debate is whether lung US should replace CXR as the preferred diagnostic study of injured patients with suspected PTX. This study sought to answer the following remaining questions: