Study to assess the feasibility of an external ultrasound fixator (ProbeFix)

Rationale: Study to assess the feasibility of an external ultrasound fixator (ProbeFix) Objective: Cardiac output measurements using transthoracic ultrasound (TTE) with and without the use of the probeFixR will be evaluated in terms of accuracy. The TTE measurements will be combined with another form of cardiac output measurements (FlotracR) after a passive leg rasing (PLR) test.

Study design prospective, feasibility study Study population: Adult Intensive Care patients ( > 18 years)

Intervention (if applicable):

Consecutive adult patients on the ICU in which the FlotracR monitor is used will be evaluated after detection of hypovolemia.

Main study parameters/endpoints:

• Percentage of patients in which the ProbeFixR can be used
• The correlation between the measurements done by FlotracR and TTE with and TTE without ProbeFixR

Although no side effects are to be expected the investigators will monitor the patients after the ProbeFix is removed for any skin damage. The investigators will grade this damage into 3 categories:

• No skin marks
• Mild skin marks (no treatment necessary)
• Severe skin marks (surgical or medical treatment necessary)
• If the patients are awake the investigators will ask them whether they felt the ProbeFixR to be unpleasant on a scale of 0-10 (0 being: I did not feel anything and 10 being very unpleasant).

Inclusion Criteria:

• Adult Intensive Care patients ( > 18 years), with hypovolemia detected with Flotrac (SVV > 10%)

Exclusion Criteria:

• Pregnancy
• Atrial fibrillation or other irregular heart rhythm
• Pulmonary edema
• PLR not possible (eg neurological disease, spinal trauma, restricted limb movement, deep venous thrombosis, or any other reason as indicated by the attending intensivist).
• age < 18 years