Comparing the Sensitivity of a Low Frequency Versus a High Frequency Probe in the Detection of Pneumothorax in a Swine Model

BACKGROUND: Correct diagnosis of pneumothorax in trauma patients is essential. Under-diagnosis can lead to development of life-threatening tension pneumothorax, but overdiagnosis leads to placement of unnecessary chest tubes with potential related morbidity and pain. It is unclear from previous work if there is a benefit to switching from the phased array (low frequency) probe to the linear (high frequency) probe. Is the improvement in image quality worth the time lost changing probes?

METHODS: We compared the sensitivity and specificity of a low frequency and high frequency ultrasound probe for the detection of pneumothorax. Images were obtained using swine models and were interpreted by Emergency Medicine residents, attendings, and physician assistants.

RESULTS: We found a specificity of 89% and sensitivity of 99% for the low frequency probe and specificity of 96% and sensitivity of 99% for the high frequency probe. There was a statistically different specificity between the two probes, suggesting that the linear probe may be the superior probe for confirming the presence of pneumothorax.

CONCLUSION: We conclude switching to the linear probe for the thoracic portion of the Extended-Focused Assessment in Trauma will lead to more accurate diagnosis of pneumothorax and decreased false-positive exams.