On Better Estimating and Normalizing the Relationship between Clinical Parameters: Comparing Respiratory Modulations in the Photoplethysmogram and Blood Pressure Signal (DPOP versus PPV)‎

Abstract EN

DPOP (ΔPOP or Delta-POP) is a noninvasive parameter which measures the strength of respiratory modulations present in the pulse oximeter waveform.

It has been proposed as a noninvasive alternative to pulse pressure variation (PPV) used in the prediction of the response to volume expansion in hypovolemic patients.

We considered a number of simple techniques for better determining the underlying relationship between the two parameters.

It was shown numerically that baseline-induced signal errors were asymmetric in nature, which corresponded to observation, and we proposed a method which combines a least-median-of-squares estimator with the requirement that the relationship passes through the origin (the LMSO method).

We further developed a method of normalization of the parameters through rescaling DPOP using the inverse gradient of the linear fitted relationship.

We propose that this normalization method (LMSO-N) is applicable to the matching of a wide range of clinical parameters.

It is also generally applicable to the self-normalizing of parameters whose behaviour may change slightly due to algorithmic improvements.