SAMBA21 collected data on organisational structure and resource availability from 153 hospitals. The response rate was 66.7% across all UK hospitals. This included 139 hospitals from England (response rate 79%), 5 hospitals from Scotland (response rate 17.2%), 4 hospitals from Northern Ireland (response rate 33.3%) and 5 hospitals from Wales (response rate 38.5%). Responses to the questions designed to ascertain the prevalence of ultrasound equipment and trained clinicians were provided by 123 hospitals (response rate 80.4%). A map demonstrating the location of SAMBA participating hospitals and regional variation in response rate in relation to the ultrasound specific questions is provided in Fig. 1.

Map demonstrating coverage of SAMBA21. A SAMBA21 participating hospitals and non-participating hospitals. B Ultrasound question response rate at the regional level with total number of hospitals (SAMBA participating and non-participating) as the denominator *grey = no response to question

Access to dedicated ultrasound equipment on the AMU was reported in 97 (78.9%) hospitals. AMUs with access to dedicated ultrasound equipment tended to have more beds (with: mean 44 beds, without: mean 37 beds, p-value < 0.05) and were located within hospitals with a larger number of total beds (with: mean 582 beds, without: mean 456 beds, p-value < 0.05). At the regional level, the proportion of responding hospitals with direct access to US equipment on the AMU ranged from 40 to 100%. Geographical variation in access to equipment is provided in Fig. 2 and Table 1.

Geographical variation in access to ultrasound equipment at the regional level amongst SAMBA participating hospitals. *grey = zero responses available to calculate %

There was variation in utilization of POCUS by non-training grade clinicians at the national level. A total of 271 clinicians were reported to regularly use POCUS located across 81 hospitals. The median number of clinicians that regularly used POCUS per hospital was 2 (range 0–20). POCUS was not regularly utilized by any non-training grade clinicians in 42 (34.1%) hospitals. There was considerable variation in POCUS use at the regional level (Table 1, Fig. 3). Geographical differences at a regional level were largely driven by a small number of hospitals with a relatively large number of clinicians that regularly utilized POCUS (Fig. 3).

Geographical variation in the number of non-training grade clinicians that regularly use point of care ultrasound. A Map of demonstrating the number of clinicians within ITL2 boundaries. B Histogram showing counts at the Hospital level C Histogram showing counts at the ITL2 level. *grey = no response to question

There are currently 121 registered FAMUS supervisors. The average incidence of FAMUS registered supervisors is 17.1 (SD 4.6) per year (Fig. 4). At the post graduate deanery level, all jurisdictions had at least one FAMUS supervisor (median 8, range 1–19) (Table 1). At a regional level, FAMUS supervisors were present in 42 (89.4%) regions (median 3, range 0–16). At least one FAMUS supervisor was present in 67 hospitals (29.1%). In hospitals with at least one FAMUS supervisor, the median number of supervisors was 1 (range 1–6).

Annual and cumulative growth rate of FAMUS supervisors aggregated at the national level and hospital level

New FAMUS registered supervisors were more likely to emerge from hospitals with an existing FAMUS supervisor. The average number of FAMUS supervisors registering in hospitals without a prior FAMUS supervisor is 9.5 (SD 4.1) per year. Regional differences in the presence of FAMUS supervisors are demonstrated in Fig. 5. The national growth rate in the number of FAMUS supervisors was largely driven by increases in a small number of geographical regions (Fig. 5). The average rate of growth was greater than 1 FAMUS supervisor per year in 4 (8.5%) regions.

Geographical distribution of FAMUS supervisors in the UK. A All hospitals in the UK with a type 1 ED stratified by the presence of at least one FAMUS supervisors. B Regional variation in the growth rate of FAMUS supervisors