Sensation and Skin Pressures Under Blood-Draw Tourniquets
Condition: Skin Pressures Under Blood Draw-tourniquets
Study type: Interventional

Summary: 
      Purpose: This research study seeks to determine whether surface pressures generated by
      elastic tourniquets used by phlebotomists during blood-draws can penetrate to deeper tissues
      where major arteries and nerves lie. Additionally, investigators will also determine the
      effects of prolonged tourniquet application on hand sensation using a controlled,
      reproducible force stimulus. In conjunction, the investigators will also track changes in
      skin surface pressures and pain levels over this prolonged tourniquet application.
      Hypothesis: The investigators hypothesize the use of common elastic tourniquets used for
      blood draws does not significantly impact sensation and will not elicit nerve or tissue
      damage. Technologies used: Monofilaments and Pressure Sensor
    

Detailed description: 
      The objective of this study is to investigate the reproducibility and consequently the safety
      of common elastic tourniquet methods for blood draws. Specifically, the study will
      investigate whether the surface pressures produced by blood draw tourniquets when applied by
      experienced phlebotomists are significant enough to penetrate to deeper tissue near bone
      where major arteries and nerves lie. By relating factors including tourniquet width and
      patient arm circumference to our surface pressure measurements and comparing our results to
      previous literature, the investigators hope to determine the safety of current blood draw
      tourniquet procedures.

      In addition, the investigators will track changes in skin surface pressures over time to
      determine if prolonged exposure to these tourniquet pressures has the potential to
      permanently affect nerve function and muscle in tissues near bone.

      Hand sensation will be investigated during a prolonged tourniquet application trial of the
      study to test the effects of the generated pressures on median, ulnar, and radial nerve
      viability over time.
    

Intervention name(s): Sensation and Skin Surface Pressures Under Blood-Draw Tourniquets
Intervention type(s): Other
Intervention description(s): Phase 1: Skin surface pressures will be recorded by an investigator during each of the 10 applications of the tourniquet. All 10 tourniquet skin pressure measurements will take place in the Blood Draw clinic at the UCSD Medical Center in Hillcrest on the same day for a subject.
Phase 2: The same 20 subjects will be subjected to a prolonged blood-draw tourniquet application for a duration of 70 minutes. The purpose of phase 2 is to determine whether there is an effect on sensation from prolonged blood tourniquet use. External skin pressures will not exceed 60mmHg. During this prolonged tourniquet application the investigators will monitor changes in hand sensation at 10-minute intervals using Semmes-Weinstein monofilaments on three peripheral nerves of the hand (median, radian, and ulnar).
Intervention model: Single Group Assignment
Intervention model description: In order to acquire our data, a Microlab PicoPress device will be employed. It has been shown to provide accurate, linear, and reproducible measures of surface pressure between the skin and device. For tourniquets, the investigators will be using a MedSource perforated tourniquet, which is the type of elastic tourniquet the phlebotomists are accustomed to using in their daily practice. For each experiment throughout both phases of the study, the PicoPress pressure sensor will be folded in half and taped over the lateral aspect of the right arm, approximately 2 inches distal to the deltoid muscle along the brachialis muscle. Arm circumferences will be taken prior to experimentation at this same location. For each trial, the phlebotomists will tie the 2.5cm elastic tourniquet around the arm and pressure sensor while ensuring that the tourniquet is not knotted directly on top of the sensor. The study will be divided into two phases of experimentation conducted sequentially.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: blood draw tourniquets; skin surface pressure; blood draw band; elastic tourniquet; phlebotomy; tourniquet pressure