Accuracy of Pulse Pressure Variations Measured by a Non Invasive Digital Device to Predict Fluid Responsiveness
Accuracy of Pulse Pressure Variations Measured by a Non Invasive Digital Device to Predict Fluid Responsiveness
It has been well established that only 40 to 60% of the patients hospitalized for
 inflammatory response syndrome (SIRS) positively respond to volume expansion (VE). The fluid
 responsiveness is usually estimated by assessing VE-induced change in stroke volume (SV). To
 guide prescriptions and possibly avoid deleterious effects of inappropriate VE, several
 clinical studies demonstrated that invasive dynamic indices based on heart-lung interactions
 permit an accurate prediction of the hemodynamic effects induced by VE.

 Mechanical ventilation induces cyclic changes in intrathoracic and transpulmonary pressures
 that transiently affect venous return, right and left ventricular preload, resulting in
 pronounced cyclic changes in SV in preload-dependent, but not in preload-independent
 patients. These cyclic changes in SV can be evaluated by the cyclic changes in arterial pulse
 pressure. Several studies have shown that pulse pressure variation is able to predict fluid
 responsiveness in patients in the operating room and intensive care unit (ICU).

 However, this technique requires percutaneous arterial catheterization, which is associated
 with several rare but serious complications (thrombosis, infections, pseudoaneurysm,hematoma,
 and bleeding).

 A method for assessing noninvasive arterial blood pressure using an electropneumatic control
 loop was introduced by Penaz in 1973. Briefly, the blood volume in a finger is measured and
 kept constant by applying corresponding external pressure. The continuously changing external
 pressure needed to keep the volume constant directly corresponds to the arterial pressure
 and, therefore can be used as continuous measurement of arterial blood pressure. Numerous
 studies evaluating the accuracy of this technology, e.g., Finapres™ (Ohmeda Monitoring
 Systems, Englewood, CO), and more recently of the Infinity CNAP™ SmartPod (Dräger Medical AG
 & Co.KG, Lübeck, Germany).

 The basic operating principle of the CNAP™ is similar to the Finapres™, but CNAP™ uses
 multiple control loops. It has recently been shown that CNAP provides real-time estimates of
 mean arterial blood pressure (MAP) comparable with those measured by an invasive
 intraarterial catheter system during general anaesthesia.

 The accuracy of the measures and the respiratory variations in pulse pressure obtained with
 the CNAP system have not yet been studied in ICU.
Inclusion Criteria:

 -  Adult patients of the intensive care units of the Lille university-hospital.

 -  Age greater than or equal to 18.

 -  Patient insured

 -  Mechanical ventilation without spontaneous respiratory cycles

 -  Regular cardiac rhythm

 -  Prescription by the physician in charge of the patients of a 500 mL volume expansion
 in less than 30 minutes.

 -  Patients with sepsis with at least one sign of acute circulatory failure:

 -  Tachycardia with heart rate> 100/min

 -  systolic blood pressure <90mmHg or a decrease >40mmHg in previously hypertense
 patient

 -  Oliguria <0.5ml/kg/hour for at least one hour

 -  skin mottling

 Exclusion Criteria:

 -  high-grade aortic insufficiency

 -  transthoracic echogenicity unsuitable for measuring the stroke volume by echo-Doppler

 -  Spontaneous breathing

 -  clinical or ultrasonographic evidence of pulmonary edema due to heart failure

 -  pregnancy

 -  abdominal compartment syndrome

 -  Irregular cardiac rhythm