Feasibility of Paramedic Performed Prehospital Lung Ultrasound in Medical Patients with Respiratory Distress.

OBJECTIVE: Prehospital ultrasound is not yet widely implemented. Most studies report on convenience samples and trauma patients, often by prehospital physicians or critical care clinicians. We assessed the feasibility of paramedic performed prehospital lung ultrasound in medical patients with respiratory distress.
METHODS: Paramedics at 2 ambulance stations in the city of Pittsburgh, Pennsylvania, USA underwent a 2-hour training session in prehospital lung ultrasound using the SonoSite iViz, a handheld ultrasound device. Emergency medical services (EMS) command center (EMS-CC) physicians were instructed in the interpretation of lung ultrasound images. Paramedics enrolled patients presenting with signs and symptoms of respiratory distress over a 3-month period. The ultrasound exam included anterior and lateral views from both sides of the chest. Images were transmitted wirelessly using a mobile hotspot device and uploaded into an online image archiving system. Images were interpreted remotely by the EMS-CC physicians, and 2 expert sonographers provided an overread. We assessed agreement between EMS-CC physicians and experts, as well as between chart-review derived ED diagnosis and both EMS-CC physician and expert interpretation. We defined four a priori hypotheses that would need to be met for the intervention to be considered "feasible."
RESULTS: A total of 34 of 78 (43.6%) eligible patients had an ultrasound exam completed. Image transmission was successful in 25 (73.5%) of cases where ultrasound was performed. The primary reason for not enrolling an otherwise eligible patient was equipment failure (25.0%), followed by patient acuity and patient refusal (18.2% each). A total of 20 (58.8%) completed scans were deemed uninterpretable upon expert review. Agreement between EMS physicians and experts was poor. Agreement between EMS-CC physicians and ED diagnosis, as well as between experts and ED diagnosis, was fair. The predetermined thresholds for feasibility were not met.
CONCLUSIONS: Paramedic performed prehospital lung ultrasound for patients with respiratory distress and remote interpretation by EMS physicians did not meet the predetermined thresholds to be considered "feasible" in a real-world environment with currently available technologies. This study identified important barriers to the implementation of prehospital lung ultrasound, which should be addressed in future studies.