Increasing signal processing sophistication in the calculation of the respiratory modulation of the photoplethysmogram (DPOP).

Paul S Addison,Sergio D Bergese,Alberto A Uribe,Rui Wang

doi:10.1007/s10877-014-9613-3

Abstract

DPOP (∆POP or Delta-POP) is a non-invasive parameter which measures the strength of respiratory modulations present in the pulse oximetry photoplethysmogram (pleth) waveform. It has been proposed as a non-invasive surrogate parameter for pulse pressure variation (PPV) used in the prediction of the response to volume expansion in hypovolemic patients. Many groups have reported on the DPOP parameter and its correlation with PPV using various semi-automated algorithmic implementations. The study reported here demonstrates the performance gains made by adding increasingly sophisticated signal processing components to a fully automated DPOP algorithm. A DPOP algorithm was coded and its performance systematically enhanced through a series of code module alterations and additions. Each algorithm iteration was tested on data from 20 mechanically ventilated OR patients. Correlation coefficients and ROC curve statistics were computed at each stage. For the purposes of the analysis we split the data into a manually selected ‘stable’ region subset of the data containing relatively noise free segments and a ‘global’ set incorporating the whole data record. Performance gains were measured in terms of correlation against PPV measurements in OR patients undergoing controlled mechanical ventilation. Through increasingly advanced pre-processing and post-processing enhancements to the algorithm, the correlation coefficient between DPOP and PPV improved from a baseline value of R = 0.347 to R = 0.852 for the stable data set, and, correspondingly, R = 0.225 to R = 0.728 for the more challenging global data set. Marked gains in algorithm performance are achievable for manually selected stable regions of the signals using relatively simple algorithm enhancements. Significant additional algorithm enhancements, including a correction for low perfusion values, were required before similar gains were realised for the more challenging global data set.

Highlights

Volume expansion is commonly used for the critically ill patient to optimize hemodynamic status
Through increasingly advanced pre-processing and post-processing enhancements to the algorithm, the correlation coefficient between DPOP and pulse pressure variation (PPV) improved from a baseline value of R = 0.347 to R = 0.852 for the stable data set, and, correspondingly, R = 0.225 to R = 0.728 for the more challenging global data set
The R values found in the present study for the final algorithm match well with many of the results reported in the literature for both OR and ICU data [3,4,5,6,7,8,9,10, 12, 13]

Summary

Introduction

Volume expansion is commonly used for the critically ill patient to optimize hemodynamic status. Respiratory variation in stroke volume (SVV) allows the clinician to determine where on the Frank-Starling curve the patient’s hemodynamic system is operating. Respiratory modulations in the arterial blood pressure waveform are known to be a good indicator of likely response to fluid loading in the mechanically ventilated patient [1]. The use of this pulse pressure variation (PPV) parameter to indicate the volemic status of a patient is increasingly widespread in practice, and has been the focus of much attention in this area [2].

Methods

Results

Conclusion