Assessing Fluid Responsiveness With PWTT
Condition: Fluid Therapy; Monitoring, Intraoperative
Study type: Observational

Summary: 
      Pulse wave Transit time (PWTT) is a parameter calculated from ECG and pulseoximeter. It is
      supposed to help assessing the preload Status and guide intraoperative fluid therapy. This
      Project aims to validate the benefit of PWTT assessment in an observational clinical fluid
      study. In case of hypovolemia, patients will receive a fluid Bolus and hemodynamic data from
      clinical Standard Monitoring, esophageal doppler and PWTT will be recorded before and after
      the fluid Bolus. Receiver operating characteristic (ROC) curve will be used to determine the
      validity of PWTT as indicator for fluid responsiveness and its cut off value.
    

Detailed description: 
      PWTT is determined by measuring the beginning and the end of pulse wave duration and can be
      calculated as the time interval from the ECG R-wave peak to the rise point of the pulse
      oximeter wave.

      it consists of two components: pre ejection period (PEP) and arterial pulse wave transit time
      (a-PWTT). PEP is defined as the time from the ECG R wave to the rise point of the aortic root
      pressure wave. a-PWTT is defined as the time from the rise point of the aortic pressure wave
      to the rise point of the pulse oximeter wave. a-PWTT is the component which is directly
      related to the velocity of the pulse wave. However noninvasively, we can measure only PWTT,
      which also includes PEP. In general, PEP change over short periods of time is negligible in
      most cases, so we can assume that PWTT corresponds to

      a-PWTT. In studies using several studies using animals and healthy volunteers, PWTT showed
      good correlation with stroke volume or systolic blood pressure. Also in experimental and
      clinical setting, it is shown that PEP changes indicate change in preloads.

      It is not known at this moment, which of the following factors to be considered in processing
      raw data to acquire accurate PWTT value on predicting fluid responsiveness.

        1. The beginning of pulse wave can be assessed by the appearance of either Q wave, which
           represents the initial phase of depolarisation going through the interventricular septum
           or R wave, which represents the ventricular depolarisation in ECG.

        2. The end of pulse wave duration can be assessed by peripheral plethysmography mostly from
           a finger tip but also from an ear lobe.

        3. The pulse wave time can be simply measured as it is, but can also be adjusted by heart
           rate using Bazett-Formula.

        4. Not only the simple PWTT but also ventilatory induced fluctuation of PWTT (ΔPWTT) may be
           used for predicting fluid responsiveness.
    

Intervention name(s): Assessing fluid responsiveness by PWTT value
Intervention type(s): Diagnostic Test
Intervention description(s): PWTT value will be analysed to find the cutoff values compared by esophageal doppler and pulse pressure variation.
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients who are scheduled for elective open abdominal surgery