To introduce an external landmark for optimizing probe placement during Focused Assessment with Sonography for Trauma (FAST) exam.
This prospective study was conducted in two phases. First, the students and emergency medicine residents were trained in FAST exam utilizing the horizontal subxiphoid (HS) landmark. The landmark consists of the crossing points of a horizontal line extending from the xiphoid process to the right midaxillary line (H point) and left posterior axillary line (S point). Second, the trained students and residents performed FAST among Emergency Departments patients at two teaching hospitals. The primary outcome was a target organ acquisition score for each view, derived from the number of target organs visualized on an initial probe placement. Secondary endpoints included: time required to obtain the requisite images, and the impact of patient characteristics on landmark prediction rate.
Forty-eight providers performed 477 exams. The collective prediction rate of the HS landmark was 86.6% for both H and S points upon first attempt without further probe adjustments. Operators visualized all required target structures at the first probe placement site in 430 out of 477 (90.1%) cases at the right upper quadrant, and in 392 out of 474 (82.7%) cases at the left upper quadrant without further probe adjustments. Limited probe adjustment (<2 cm from the initial landmark site) improved the success rate up to 95.6 and 90% to the right upper quadrant and left upper quadrant, respectively. As BMI increased, precision score decreased and image acquisition time increased.
The HS line is an external landmark that may optimize probe placement and facilitates teaching and performance of FAST examination.