A computerized method to measure systolic pressure variation (SPV) in mechanically ventilated patients

Intrathoracic pressure variation during mechanical ventilation has different effects on cardiac preload and stroke volume in both ventricles. Changes in left ventricle stroke volume are reflected by fluctuations of the arterial pressure waveform or Systolic Pressure Variation (SPV). SPV has been proposed as a way to evaluate vascular volume status in mechanically ventilated patients as well as responsiveness of the left ventricle stroke volume to volume loading.

In this paper an automated system is presented which is designed in order to provide physicians with information on SPV in mechanically ventilated patients. Methods. The developed system acquires the pressure transducer signal and analyses the pressure waveform in order to detect and identify the hemodynamic changes. Five patients underwent the clinical protocol in order to evaluate the software reliability. Each patient underwent measurements with positive end-expiratory pressure (PEEP) equal to 0 cm H2O, at an increase of 30% tidal volume, and at 15 cm H2O of PEEP, before and after infusion of 7 ml/kg of colloid solution.

The reliability of the automated procedure has been verified by comparing the obtained results with data collected manually in order to test on whether the new method data are correlated with the conventional procedure. Our results show that in the worst case when the widest range for the limits of agreement is considered, the error is within 15%.

The automated SPV measurement requires less time as well as human errors compared to the manual method; this makes SPV calculation a competitive alternative to methods for the measurements of stroke volume variations as arterial thermodilution technique and transesophageal echocardiography, which require sophisticated equipment and specific experience.