A Computerized Method to Measure Systolic Pressure Variation (SPV) in Mechanically Ventilated Patients

Introduction. Intrathoracic pressure variation duringmechanical ventilation has different effects on cardiac preload andstroke volume in both ventricles. Changes in left ventricle strokevolume are reflected by fluctuations of the arterial pressure waveformor Systolic Pressure Variation (SPV). SPV has been proposed as a way toevaluate vascular volume status in mechanically ventilated patients aswell as responsiveness of the left ventricle stroke volume to volumeloading. Objective. In this paper an automated system ispresented which is designed in order to provide physicians withinformation on SPV in mechanically ventilated patients. Methods. The developed system acquires the pressure transducer signal andanalyses the pressure waveform in order to detect and identify thehemodynamic changes. Five patients underwent the clinical protocol inorder to evaluate the software reliability. Each patient underwentmeasurements with positive end-expiratory pressure (PEEP) equal to 0 cmH 2 O, at an increase of 30% tidal volume, and at 15 cmH 2 O of PEEP, before and after infusion of 7 ml/kg of colloidsolution. Results. The reliability of the automated procedure hasbeen verified by comparing the obtained results with data collectedmanually in order to test on whether the new method data are correlatedwith the conventional procedure. Our results show that in the worst casewhen the widest range for the limits of agreement is considered, theerror is within 15%. Conclusions. The automated SPVmeasurement requires less time as well as human errors compared to themanual method; this makes SPV calculation a competitive alternative tomethods for the measurements of stroke volume variations as arterialthermodilution technique and transesophageal echocardiography, whichrequire sophisticated equipment and specific experience.