Microvascular Sex and Age-related Day-to-day Variability in Healthy Subjects
Condition: Healthy Subjects
Study type: Observational

Summary: 
      The goal of this observational study is to learn more about the microcirculation in the skin
      by examining sex and age-related day-to-day variability in healthy subjects. The main
      questions the trial aims to answer are:

        -  What is the day-to-day variability of the optical measurement techniques in the
           microcirculation, and does age and gender affect this?

        -  Does the day-to-day variability differ in the foot compared to the arm?

      Participants will rest whilst skin measurement by optical measurement techniques are
      performed. Baseline measurements and post-occlusive reactive hyperemia will be studied on the
      forearm and foot. This measurement procedure is repeated within one week, in order to study
      variability.
    

Detailed description: 
      The microcirculation consists of arterioles, capillaries and venules and is essential for
      nutrients and oxygen to be delivered to the tissue as well as waste products to be removed.
      The skin is often used as a model for studying microcirculation.

      There are many different ways to study the microcirculation, most commonly are noninvasive
      optical techniques which measures the reflection of light used. Laser Doppler Flowmetry (LDF)
      has been the golden standard, but one limitation with the technique is that it measures the
      bloodflow in a small area (about 1 mm3). In this study the investigators will be using
      single-point measurement with a technique called EPOS and larger area measurements with a
      technique called PSI-X. EPOS, based on LDF and diffuse reflectance spectroscopy (DRS),
      analyze speed-resolved perfusion, variations in red blood cell tissue fraction, oxygen
      saturation and vessel diameter. PSI-X, based on multi-exposure laser speckle contrast imaging
      (MELSCI) and multispectral imaging (MSI), analyze conventional perfusion, speed-resolved
      perfusion and oxygen saturation.

      Flowmotion is the rhythmical variations in measured skin blood flow that arise due to global
      and local regulation of the vessels and can be studied using frequency analysis of
      time-resolved blood flow signals. Since EPOS and PSI-X collect data of time-resolved blood
      flow, flowmotion analysis will also be conducted in the study.

      To study day-to-day variability, data will be collected from each subject on two separate
      days within seven days, on the same location of the foot as well as the arm. Once the subject
      arrives to the lab, a questionnaire will be filled in regarding the subjects physical
      activity level, exercise habits and usage of medication and nicotine. The subject will also
      confirm to not have eaten two hours and not used nicotine or caffeine three hours prior to
      the experiment. Thereafter the subject's length and weight will be measured and BMI
      calculated. The subjects skin type will be determined using the Fitzpatrick scale. All of
      this is only done on the first day of measurement, on the second day the subject will skip
      right to the following part.

      An acclimatization period of 15 minutes begins and the subject will remove socks and lay
      down. While the subject rests the equipment will be set up. A blood pressure cuff is placed
      around the upper arm as well as around the ankle. An EPOS-probe is placed on the dorsal side
      of the foot as well as the volar side of the forearm. A marker pen is used to mark the skin
      around the probes which enables the probe to be placed on the same location on the next
      measurement. Once five minutes has passed, the subject's blood pressure and pulse is noted.
      Thereafter the PSI-X camera is set up and angled to film the plantar side of the foot from a
      distance of about 25 cm. The subject is asked to lay as still as possible during the
      measurement. Once the acclimatization period has passed, the lights in the lab are turned off
      and the measurement will begin. Firstly baseline data will be collected as the subject rest
      for 10 minutes without provocation. Thereafter the blood pressure cuff on the ankle will
      inflate to 250 mmHg for five minutes whilst data is collected. Lastly data is collected for
      five minutes after the blood pressure cuff deflates. Thereafter the PSI-X camera is moved and
      angled to film the forearm from a 25 cm distance. The protocol described above is repeated
      for the arm. The subject will return within seven days to repeat the data collection
      protocol.
    

Intervention name(s): Occlusion of the circulation in the arm and foot
Intervention type(s): Other
Intervention description(s): A blood pressure cuff occludes the circulation in the upper arm as well as around the ankle.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        12 healthy men and 12 healthy women aged 20-30 years old. 12 healthy men and 12 healthy
        women aged 50-60 years old.

        In total 48 participants will be included.