Providing healthcare to homeless people is a key and challenging task, both for society as a whole and for medical and psychosocial professionals. It must be noted that the standard healthcare system is hardly used, or can only be used to an insufficient extent, by homeless people, and therefore does not comprehensively reach this group. One low-threshold and acceptance-oriented service outside the standard care system is the Johanniter-Hilfsmobil, which was established on June 3, 2024, as an innovative approach to healthcare for homeless people in Augsburg and will be scientifically examined in the following study.

The aim is to compare acute and chronic wounds in people experiencing housing emergencies who are treated by the Johanniter-Hilfsmobil with those of patients who attend the outpatient wound clinic at the Clinic for Vascular Surgery at Augsburg University Hospital.

In addition, a saliva test will be carried out to estimate the amount and type of substance consumed, and a survey will be conducted among drug-dependent test subjects who present themselves either via the Johanniter-Hilfsmobil or via the substitution outpatient clinic of the Clinic for Psychiatry, Psychotherapy, and Psychosomatics at Augsburg District Hospital.

Another focus of research is the quantitative and qualitative analysis of the psychosocial living situation and environmental influences on users of the Johanniter-Hilfsmobil.

The primary endpoint is to identify positive and negative influences of environmental factors on the development, progression, and healing of somatic and psychiatric illnesses in homeless people in Augsburg. The answers to the resulting research questions listed below should contribute to the development of a sustainable diagnosis and therapy system by the Johanniter-Hilfsmobil for people in housing emergencies without access to the regular health care system in Augsburg, optimizing addiction treatment for homeless people in the region, and establishing a prevention program for people experiencing housing emergencies in Augsburg, thereby positively influencing the environmental factors described. The long-term plan is to set up a wound and vascular consultation service for people experiencing housing emergencies to improve medical treatment and reintegration into the regular healthcare system.

A comparison will be made between acute and chronic wounds in people experiencing housing emergencies who are treated by the Johanniter mobile emergency service and those of patients who attend outpatient wound consultations at the Clinic for Vascular Surgery at Augsburg University Hospital. The following data will be collected: wound area and volume, as well as qualitative and quantitative analysis of bacterial and/or fungal colonization by taking swabs from the wound bed and performing corresponding laboratory chemical analysis. In addition, the cause or origin of the wounds, the type of diagnostics performed, and causal therapeutic measures taken to date, as well as the number and regularity of check-ups performed, will be recorded. Furthermore, the influence of environmental factors (including temperature, light, radiation), comorbidities, and nutritional status on wound healing and the effects of dressing sets provided as part of the study on the healing process of the wounds will be analyzed. Data collection will be carried out on an outpatient basis during treatment in the Johanniter-Hilfsmobil. In addition, the existing cardiovascular risk factors will be assessed and a vascular step-by-step diagnosis will be performed, including pulse status assessment and, in the event of pathological findings, non-invasive vascular imaging using ankle-brachial index determination and color-coded duplex sonography (FKDS).

In addition, semi-quantitative and quantitative saliva tests and a questionnaire survey are conducted among drug-dependent subjects who present themselves either via the Johanniter-Hilfsmobil or via the substitution outpatient clinic of the Clinic for Psychiatry, Psychotherapy, and Psychosomatics at Augsburg District Hospital.

Another focus of research is the quantitative analysis of the psychosocial living situation due to exceptional environmental influences based on subjective and/or objective recording of the following constructs and categories among users of the Johanniter-Hilfsmobil using a standardized questionnaire: Life situation index (material situation, gainful employment, housing, health, safety, participation/social networks), environmental influences and weather conditions (heat/cold, precipitation, wind, air quality, noise, garbage/unhygienic conditions), opportunities for a healthy lifestyle (nutrition, access to drinking water, sleep, regeneration), use of public space and urban infrastructure (mobility, participation, defensive architecture), experiences of loneliness, and experiences with and access to the medical and psychosocial care system. The questionnaire integrates the following measurement instruments/scales, among others: "Life Situation Index for Homeless People", "RTLS - Rasch-Type Loneliness Scale".

However, since this is a very specific target group that has been largely neglected in scientific analysis, the questionnaire also requires some self-formulated items that are appropriate for the research project.

In a final step, a qualitative analysis will be conducted through guided interviews with users of the Johanniter-Hilfsmobil to gain a deeper understanding of the quantitative findings on the psychosocial living situation and the environmental influences to which they are exposed.

Inclusion Criteria:

• Age over 18
• Existing capacity to consent to participation in the study, which will be verified and documented by the study physicians
• Inclusion of patients who present for wound treatment at the Johanniter-Hilfsmobil, the wound consultation hour of the Clinic for Vascular Surgery at Augsburg University Hospital and/or the substitution outpatient clinic of the Clinic for Psychiatry, Psychotherapy and Psychosomatics at Augsburg District Hospital
• Written consent to participate in the study has been obtained from the test subject.

Exclusion Criteria:

• Minderjährigkeit
• Fehlende schriftliche Einwilligung zur Studienteilnahme
• Instabiler somatischer Zustand der Betroffenen
• Akute Selbst- und Fremdgefährdung

As people in housing emergencies are a particularly vulnerable group requiring protection, in accordance with the positive ethical opinion of the Ethics Committee at the Medical Faculty of Ludwig Maximilian University Munich, there are no plans to make the pseudonymised data available to other study centres for further processing.