Peripheral Tissue Perfusion and Oxygenation in Areas at Risk of Press Ulcer (POTER-OIL)

The study objectives will be:

Primary objectives:

1. To determine the effects on oxygenation and tissue perfusion of applying HFA (Hyperoxygenated Fatty Acids) or EVOO (Extra Virgin Olive Oil) to the heels of healthy subjects, evaluating the maximum variation of oxygenation and flow when the heels are subjected to pressure.
2. To determine the levels of tissue oxygenation and perfusion associated with the appearance of blanching erythema in the heels of acute hospitalised patients and patients admitted to social health centers for the elderly.

Secondary objectives:

1. To determine whether there are differences in oxygenation and peripheral tissue perfusion between heels to which HFA vs. EVOO is applied.
2. To evaluate the possible progressive loss of the efficacy of HFA and EVOO in terms of tissue oxygenation and perfusion in patients who are bedridden for extended periods.

Methodology:

Experimental study in two phases: preclinical and clinical. Phase 1 with healthy subjects, with a randomized and open design, with an intrasubject control group. Phase 2 with hospitalized subjects and patients admitted to social health centers for the elderly, with a randomized and open design, with an intrasubject control group.

The study participants will be subjected to simple randomisation to receive HFA or EVOO . The phase 1 will be carried out in healthy volunteers recruited at the Faculty of Health Sciences in the University of Malaga (Spain). Inclusion criteria: Healthy volunteers, aged \>20 years, with no cardiovascular, neurological, digestive, endocrine, renal, gynaecological, respiratory, haematological, infectious, dermatological, autoimmune or osteomuscular diseases diagnosed, nor functional limitations, with objective tissue integrity, BMI of 18.5-25.9 kg/cm2 and no scars on the heels.

The phase 2 will be carried out patients admitted to acute hospitalised patients and patients admitted to social health centers for the elderly, at risk of deterioration of skin integrity according to Braden score \<16, no presence of PU, who agree to participate in the study.

Measurement instruments Perfusion and tissue temperature data will be obtained by laser doppler flowmetry (LDF), with MoorVMS-LDF equipment. This system has two monitoring probes (one for each heel) that are brought into contact with the skin. The laser light is transmitted through an optical fibre to the tissue, reaching a depth of approximately 1 mm. The scattered light is collected by optical fibres and, at the same time, transmitted to a photodetector. The system has a measuring range of 5-50º C, a resolution of 0.1º C and an accuracy of ± 0.3º C.

Tissue oxygenation will be measured by near-infrared spectroscopy, with the MoorVMS-NIRS instrument. As in the previous case, the system contains two monitoring probes that are placed in contact with the skin. This method measures oxygen saturation (SpO2), which is calculated from absolute concentrations of oxygenated and deoxygenated haemoglobin in the tissue. Each probe consists of a detector head, containing two identical photodiodes, and an emitter head, with two infrared LEDs that emit light at approximately 750-850 nm. The system has a measurement range of 0-99%, a resolution of 1% and an accuracy of ± 3%.

All information on capillary blood flow, local temperature and tissue oxygenation will be monitored continuously and simultaneously using appropriate software. All measurement procedures are non-invasive. Both Moor instruments are certified to ISO 13485: 2016.

Eligibility Criteria:
PHASE ONE HEALTHY SUBJECTS

Inclusion criteria:

* Healthy volunteers, aged \> 20 years without functional limitation.
* BMI of 18.5-25.9 kg/cm2.
* No scars on the heels.

Exclusion criteria:

* Failure to meet all of the above criteria.
* Smokers.
* Consume high levels of alcohol (\> 20g/week).
* Tattoos in the measurement areas.

PHASE TWO - PATIENTS

Inclusion criteria:

* Patients aged \> 20.
* Patients with risk of deterioration of skin integrity according to Braden score \<16.
* no presence of Press Ulcer.

Exclusion criteria:

* Presence of vasoactive drugs in infusion
* Subjects with a pacemaker and/or implanted defibrillator.
* Fever and anaemia with Hb \<10 g/dl.
* Hypotension with systolic blood pressure \<80 mmHg.
* Transfusion during the last four weeks.