Detection of Hypovolemia Using Pleth Variability Index (PVI)
Condition: Hypovolemia
MeSH terms: Hypovolemia
Study type: Observational

Summary: 
      The purpose with the planned study is to study Pleth Variability Index (PVI) as a non
      invasive indicator for mild hypovolemia during spontaneous breathing in healthy subjects.
      Lower body negative pressure (LBNP), a well established technique is used to create defined
      levels of hypovolemia.

      Primary hypothesis: By applying a breathing resistance (positive end expiratory pressure
      PEEP) to spontaneous breathing, the respiratory synchronous variation in the pulse oximeter
      signal (PVI) is enhanced and enables PVI to detect and grade the level of mild hypovolemia.

      Secondary hypothesis: 1) When tidal volume is increased, the respiratory synchronous
      variation in the pulse oximeter signal (PVI) will also increase. 2) The earlobe is superior
      to the finger in detecting PVI 3) Hemoglobin (Hb), detected non invasively by pulse oximetry,
      is not affected by hypovolemia created by LBNP
    

Detailed description: 
      The subjects are placed supine on a bed. Non invasive equipment for recording pulse and blood
      pressure is placed on a finger on the right hand. From this equipment total peripheral
      resistance and cardiac output are recorded. A pulse oximeter for saturation, perfusion index
      and PVI is placed on a finger and on the ear lobe. Data are recorded in parallel from the
      finger and the ear lobe. In addition non invasive haemoglobin (Hb) is recorded from the pulse
      oximeter on the finger. The subjects breathe through a mask connected to a simple Y-connector
      with an inspiratory valve on one side and an expiratory valve on the other. A positive
      pressure valve is applied on the expiratory side. Tidal volume is measured on-line by a
      connector connected to a spirometer and the tidal volume is displayed to the subjects. Stroke
      volume, total peripheral resistance and cardiac output is measured using ultra sound via the
      jugular fossa.

      Baseline data are recorded with the subjects in the supine position breathing with normal
      tidal volume without PEEP and without LBNP applied. Data are then recorded with LBNP applied
      in two steps (40 and 15 mmHg). Recordings are continued 5 minutes after releasing the
      negative pressure. Data are collected in total in four different series; normal tidal volume
      without PEEP; normal tidal volume with PEEP 5cm H2O; three doubled tidal volume without PEEP;
      three doubled tidal volume with PEEP 5 cm H20. Respiratory rate is not controlled. The order
      of the four series is randomized. Between the series a 20 minute period of rest is allowed to
      the subjects. This period is also necessary to restore steady state between provocations.
    

Intervention name(s): Lower body negative pressure (LBNP)
Intervention type(s): Other
Intervention description(s): The purpose with the planned study is to study pleth variability index (PVI) as a non invasive indicator for mild hypovolemia during spontaneous breathing in healthy subjects. Lower body negative pressure (LBNP), a well established technique, is used to create defined levels of hypovolemia.
Baseline data are recorded with the subjects in the supine position breathing with normal tidal volume without PEEP and without LBNP applied. Data are then recorded with LBNP applied in two steps (40 and 15 mmHg). Recordings are continued 5 minutes after releasing the negative pressure. Data are collected in total in four different series; normal tidal volume without PEEP; normal tidal volume with PEEP 5cm H2O; three doubled tidal volume without PEEP; three doubled tidal volume with PEEP 5 cm H20.
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Healthy subjects between 18-30 years old without any medications affecting circulatory or
        respiratory system
      
Keywords: Hypovolemia; Lower body negative pressure; Photoplethysmography