**3. Results**

An initial descriptive analysis of the study data shows that in 2019, the eight doctors who performed ultrasound scans in the Primary Care Centres (PCCs) in Osona county carried out a total of 1556 scans (Table 2). Almost half of the tests (48.5%) corresponded to abdominal ultrasound scans, more than a quarter to vesico-renal examinations and the remainder, in order of frequency, corresponded to ultrasound scans of the thyroid, soft tissue, joints and a small number of vascular ultrasounds. The average number of ultrasound scans, per professional, during the study year was 194.5 (42–449), with a standard deviation of up to 117.


**Table 2.** Types of ultrasound scans performed by the different primary care professionals according to whether they work in a rural or urban centre.

1PCC Prof: primary care centre professionals; We show in a bold format the grouped results of rural and urban centers' professionals.

Most of the ultrasound scans 1045/1556 (67.2%) were performed by doctors belonging to rural health centres, while 511/1556 (32.8%) were performed by doctors from urban centres.

The number of ultrasound scans performed according to the type of examination and characteristics of the centre (rural or urban) adjusted for the population served by the centre (population assigned to the centre \* 10,000 inhabitants) showed an average of 229.7 tests for every 104 users assigned (SD 115.7) in rural centres and 108.6 (SD 56.4) in urban centres (Table 3). When comparing this rate according to the type of ultrasound scan, abdominal ultrasounds show a mean of 50.5 (SD 21.3) in urban centres vs. 117.2 (SD 27.7) for rural centres (*p* = 0.06).


**Table 3.** Ultrasound scan rate per inhabitant in rural vs. urban centres.

1PCC Prof: primary care centre professionals; We show in a bold format the grouped results of rural and urban centers' professionals.

Of the total number of ultrasound scans performed, a total of 36 cases required a referral to a specialist radiology service for a face-to-face scan. Therefore, the percentage of face-to-face consultations avoided by conducting an ultrasound scan in a PCC was 97.7% (Table 4).

**Table 4.** Face-to-face consultations and consultations avoided by conducting ultrasound scans in primary care centres.


Table 5 shows the distance of the journeys avoided due to conducting ultrasound scans at PCCs and the time and cost savings of the journey in terms of unused fuel. The average round trip distance between a PCC and the radiology referral service was 17.8 km, with an average saving in travel time of 21.4 min. The journeys avoided during the year the study was conducted totaled 27,123 km, with a total saving of travel time of more than 22 days. Likewise, this meant a saving of 1872 L of fuel, with an associated total cost of €2658 per year.


**Table 5.** Reduction in journeys according to distance, time, fuel and cost.

\* All nonparametric tests (Mann–Whitney U test) to determine if there were significant differences using rurality as an independent variable were significant (*p* < 0.001). Source: Cost of fuel in Spain [30].

If we focus on the health professionals' movements, the variations are minimal or non-existent since neither family doctors nor technicians or radiologists from specialized units changed their mobility. This was different in the case of maintenance staff in charge of installing, updating and maintaining the ultrasound scanners. The maintenance contract included the installation and comprehensive maintenance of the equipment (including those located in the specialized service and those located in primary care centres, as well as at least two preventive visits per year). Car journeys due to the

maintenance of the devices accumulates a total of 10 annual trips in the case of ultrasound scanners located in primary care teams, and only two in the case of ultrasound scanners located in the specialized service. We do not have data relating to the travel costs to install and configure the devices for the first use, but this does not appear to be significant as they only involved one visit. Although it seems that the most used equipment requires the greatest amount of technical assistance, there is no evidence that more trips were needed during the year of the study.

Table 6 shows a breakdown of the reduction in air pollutant emissions. The total reduction in pollutants was equivalent to 92.7 kg of carbon monoxide, 22.3 kg of nitric oxide and 4 kg of sulphur dioxide per year. This represents an average reduction on each trip of 61.4 g of carbon monoxide, 14.8 g of nitric oxide and 2.7 g of sulphur dioxide.


**Table 6.** Reductions in the emissions of pollutant gases.

\*All nonparametric tests (Mann–Whitney U test) to check if there were significant differences using rurality as an independent variable were significant (*p* < 0.001). Emissions are calculated in grams (gr) using formula in Table 1: number of vehicles × distance travelled × emission factor by pollutant.

As has already been observed when examining the fuel consumption and costs of the journeys avoided, as expected the reduction in pollutant emissions was also significantly higher (for all pollutants studied) in the journeys avoided from rural areas versus those originating from urban areas, given their greater average distance from the radiology referral service.

Demographic mortality data of the year 2019 was obtained from Catalonian Demographical Institute's (IDCAT) data, and the relative risk estimates (and 95% confidence intervals) for a 10 μg/m<sup>3</sup> PM10 increase were obtained from previous studies [31]. With 1426 deaths in 2019 from a total population of 153,000 inhabitants, by calculating the impact of reducing the average PM10 concentrations observed in the area (24.52 μg/m3) to 20 μg/m<sup>3</sup> (recommended by WHO) and multiplying with the adjusted relative risk of 1.006 (1.004, 1.008) [30], we determined that reducing PM10 by an average of 4.52 μg/m<sup>3</sup> could avoid four (3–6) deaths per year. The study shows that the total amount of PM10 generated with the avoided journeys was only 0.00025 ug/m<sup>3</sup> per day which is not enough to prevent any deaths.
