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