We conducted a longitudinal study to evaluate changes in POCUS use reported by physicians 50 months after participating in a standardized, hands-on POCUS training course. A significant increase in the performance of cardiac, lung, vascular, and abdominal POCUS exams was seen and the proportion of physicians performing ≥ 1 POCUS exams of different organ systems per week. Additionally, we have revealed important facilitators and barriers to continued POCUS use post-course that can guide POCUS implementation efforts.

Past studies have demonstrated immediate improvements in POCUS knowledge and skills after participating in a hands-on POCUS course [13, 14, 21], but few studies have followed course participants longitudinally to determine actual POCUS use in clinical care [15,16,17,18]. Two small studies (n = 17–20) from limited-resource settings in Africa reported retention of POCUS knowledge and skills by physicians in-practice after 9–12 months and increased POCUS use post-course; however, details about increased use were not provided [18, 22]. A study of physicians practicing in the Department of Veterans Affairs demonstrated sustained improvement of both POCUS knowledge and skills at 8 months post-course, and course participants reported a significant increase in multi-system POCUS use (heart, lungs, abdomen, and vascular access) in clinical care from pre-course to 8 months post-course [15]. To assess how physicians in-practice use POCUS beyond 12 months post-course, we surveyed physicians in-practice longitudinally after > 3 years to determine if increased POCUS use was sustained in clinical practice and better understand factors that may be associated with sustained increased POCUS use. A statistically significant increase in POCUS use to ≥ 1 time per week was seen for all organ systems. Specifically, the frequency of cardiac, lung, vascular, and abdominal ultrasound use increased by approximately half of physicians at 50 months post-course. However, the increase in lung and vascular ultrasound use ≥ 1 time per week was relatively low (17% and 8%, respectively) compared to cardiac and abdominal ultrasound (41% and 36%, respectively). The main barriers associated with not increasing lung and vascular ultrasound use were “lack of supervising physicians” and “lack of confidence.” We speculate that physicians were unable to obtain adequate supervised practice to gain comfort and competence in performing lung and vascular ultrasound exams after returning to their home institutions.

Barriers and facilitators to POCUS use in different specialties and settings have been described in several studies [2,3,4,5,6,7,8,9,10,11, 23]. In general, lack of access to ultrasound equipment and lack of POCUS training, including availability and time for training, have been the two most common barriers reported to start using POCUS. However, little is known about barriers and facilitators to sustained POCUS use after physicians have received training. Based on our literature review, our study is the first to evaluate provider- and facility-level facilitators and barriers associated with increasing or not increasing POCUS use in clinical practice > 3 years post-course. Having a colleague with whom to learn POCUS was the only facilitator that was shown to be significantly associated with sustained increased POCUS usage. On the contrary, among physicians who did not increase POCUS use post-course, the most frequently reported specific barrier was lack of supervising physicians to provide guidance.

The implications of our study are important for hospitals and health systems seeking to standardize and implement POCUS use systemwide. First, for physicians in-practice, brief hands-on POCUS training courses of 2–3 days have been shown to increase clinical POCUS use for 6–12 months post-course, and our study adds that increased clinical POCUS use is sustained > 3 years post-course among a significant proportion of physicians. Second, the most common barriers to starting POCUS use, namely lack of access to ultrasound equipment and lack of training, are different from the barriers to sustaining its use. A supportive clinical environment with readily available POCUS experts who can provide ongoing supervision and adequate departmental and hospital support are critical for long-term success of POCUS implementation [24]. Third, since having a colleague with whom to pursue POCUS training together facilitated long-term clinical POCUS use, it is plausible that organizing training cohorts may be a more effective approach to deploy systemwide POCUS training which can be trialed in future training studies.

We recognize our study has limitations. Most important, our post-course survey response rate was 20%, and the possibility of sample bias due to the low response rates cannot be ruled out. Though we had a relatively low post-course response rate, the absolute number of completed surveys was 112 which is higher than most similar studies. Of note, the pre-course survey response rate was 100% because answering the pre-course survey was a mandatory part of the application process. Additionally, we collected self-reported data that may not accurately reflect actual clinical practice. Finally, we were unable repeat POCUS knowledge and skills testing to assess retention because course participants came from 43 of 47 prefectures across Japan and coordinating logistics for testing was not feasible.