Peripheral Perfusion and Oxygenation in Areas of Risk of Skin Integrity Impairment Exposed to Pressure Patterns.

Sample: the preclinical phase will be conducted in 20 healthy volunteers enrolled in the Faculty of Health Sciences of the University of Malaga. Clinical phase will take place in 12 subjects admitted to acute hospitalization in 'Costa del Sol' Health Agency and 12 subjects admitted to nursing homes in the District of Primary Knowing this information will identify different thresholds start in peripheral microcirculation disorders associated with various systems of body position and consequent pressure levels. This particular seems a reasonable need from baseline parameters allow to further explore specific situations of tissue injury and isolate direct and indirect causal factors. It is also necessary to conduct the study in subjects from different environments (home, hospital) to determine under real clinical practice how these parameters behave and how it can affect common procedures performed in clinical practice, such as repositioning or using pressure surfaces. This sample of 24 subjects was calculated taking into account a change in the capillary flow of 30% between baseline and the first hour of exposure to pressure, according to data of Kallman et al. (15) with an 80% output and statistical confidence level of 95%. In total, each subject will provide a total of 28 hours of measurement.

Phase 1: Inclusion criteria:Healthy volunteers, between 20 and 65 years old, with no cardiovascular, neurological, digestive, endocrine, renal, gynecological, respiratory, hematologic, infectious, dermatological, autoimmune or diagnosed musculoskeletal disease or functional limitations, with tissue integrity and BMI between 18.5 to 25.9 kg/cm2 without scars in the sacred, back-lumbar, trochanteric, heels, elbows and shoulder blades areas.

Exclusion criteria: The usual consumption for any reason of alpha-beta-blocking agents, or alpha-beta agonists, or directly or indirectly vasodilator-vasoconstrictor action drugs of any kind, anticoagulants, topical or systemic steroids, presence of pacemakers or implantable defibrillator, smoking, high consumption of alcohol (>20g/week), presence of tattoos in the areas of measurement, and lower limb amputation

Phase 2: Inclusion criteria: Patients admitted to acute hospitalization, with risk of skin integrity deterioration assessed by Braden scale (punctuation lower than 16) without pressure ulcers, who agree to participate in the study. Exclusion criteria: presence infusion of vasoactive drugs at the time of the study (dopamine, epinephrine, norepinephrine, dobutamine, nitroprusside, nitroglycerin, calcium channel blockers, ACE inhibitors). Regular oral treatment of alpha and beta-blockers and/or agonists or calcium channel blockers, nitrates, ACE inhibitors, angiotensin, renin inhibitors, diuretics, SSRIs, NSAIDs, will be accepted. Also patients with pacemakers and/or implanted defibrillator, fever, anemia with Hb <10g/dl, hypotension with systolic blood pressure <80 mmHg, presence of transfusions in the past 4 weeks, consumption and derivatives of erythropoietin, iron supplements, oral or parenteral anticoagulants will be excluded.

Interventions: Different positions will be applied to subjects in order to measure preipheral tissue oxygenation, pressure, and changes in microvascular flow.

The subject will be placed in each of the standard positions for the experiment: supine decubitus (SD) right lateral decubitus (RLD), left lateral decubitus (LLD). SD measurements will be made at 0, 30 and 45 degrees of inclination to bed. RLD and LLD positions will be evaluated with a body inclination of 30 and 90 degrees, aided by pillows, as is done in routine clinical practice. The subjects will lie down on a memory foam mattress for an articulated bed, as are commonly used at home, residential or hospital care. Between the subject and the mattress will be inserted the pressure measuring surface. Measurements in each position will be made during intervals of 0-4 hours in the same position (SD-RLD-LLD) in each of the inclinations of the bed (0º, 30°, 45 °) or body (30º, 90º), respectively.

In case of patients, if the institutional protocol sets repositioning with a frequency of less than 4 hours, measurements will be made to the maximum that is set in each protocol. Otherwise, the maximum time for each position will be 4 hours.

Measuring instruments:

Pressure measurements will be made with the XSENSOR PX100: 64.160.02 (31.2 x 203.2 cm) pressure sensor, with 12.7 mm of space resolution of, which has 10,240 measuring points. The pressure sensor is composed with two perpendicularly oriented networks of parallel conductive strips, which are separated by a fine compressible elastomer. The intersection of two strips forms a capacitive node, determined by the surface of intersection of the two strips, and the distance separation between them, and with the elastomer. When pressure is applied to the node, the elastomer is compressed, the bands approach and capacity increases. This change in capacitance is correlated with pressure through a calibration process. The pressure range that is able to detect varies between 0.2 to 3.87 psi.

Tissue perfusion, oxygenation and temperature of the assessed area will be made with the system Periflux 5000, composed of 2 units of Laser Doppler Flowmetry (LDF): PeriFlux 5001, which includes the laser source; and PeriFlux 5002, which provides temperature and tissue oxygenation measurements. The information of both instruments will be collected and integrated into a software that allows the simultaneous measurement of all signals. Tissue oxygenation will be measured by transcutaneous oximetry (TcpO2), a noninvasive procedure that reflects the amount of oxygen diffuses into the capillaries through the epidermis. This process depends on the state of respiratory oxygenation, the oxygen carrying capacity of blood and the overall circulatory condition. Any deterioration in any of these three members, immediately affect the skin tissue perfusion, which allows to evaluate how these factors affect the PU risk. It is measured by an electrode that heats the underlying tissue to create a local hyperemia that intensifies blood perfusion and, consecuently, oxygen pressure increases. The heat dissolves the lipid structure of the keratinized layers of the epidermis, allowing the skin permeability to gas diffusion.