Abstract
DPOP quantifies respiratory modulations in the photoplethysmogram. It has been proposed as a noninvasive surrogate for pulse pressure variation (PPV) used in the prediction of the response to volume expansion in hypovolemic patients. The correlation between DPOP and PPV may degrade due to low perfusion effects. We implemented an automated DPOP algorithm with an optional correction for low perfusion. These two algorithm variants (DPOPa and DPOPb) were tested on data from 20 mechanically ventilated OR patients split into a benign “stable region” subset and a whole record “global set.” Strong correlation was found between DPOP and PPV for both algorithms when applied to the stable data set: R = 0.83/0.85 for DPOPa/DPOPb. However, a marked improvement was found when applying the low perfusion correction to the global data set: R = 0.47/0.73 for DPOPa/DPOPb. Sensitivities, Specificities, and AUCs were 0.86, 0.70, and 0.88 for DPOPa/stable region; 0.89, 0.82, and 0.92 for DPOPb/stable region; 0.81, 0.61, and 0.73 for DPOPa/global region; 0.83, 0.76, and 0.86 for DPOPb/global region. An improvement was found in all results across both data sets when using the DPOPb algorithm. Further, DPOPb showed marked improvements, both in terms of its values, and correlation with PPV, for signals exhibiting low percent modulations.
Highlights
DPOP (Delta-POP or ΔPOP) is a physiological parameter calculated from the pulse oximeter signal—the photoplethysmogram or “pleth”—which measures the strength of respiratory modulations present in the waveform
The parameter has been shown to be useful as an index of fluid responsiveness with many studies showing favourable correlation between it and pulse pressure variation (PPV), often used in the determination of the response to volume expansion [1,2,3,4,5,6,7]
During the development of the DPOP code we found that an improvement in the correlation between DPOP and PPV could be achieved at low perfusion values by adding an extra postprocessing code module
Summary
DPOP (Delta-POP or ΔPOP) is a physiological parameter calculated from the pulse oximeter signal—the photoplethysmogram or “pleth”—which measures the strength of respiratory modulations present in the waveform. PPV is, an invasive parameter requiring an arterial line, whereas a measure based on the pulse oximeter would provide an entirely noninvasive technology. This is the main driver of the current interest in this area. Cannesson et al [8] suggested DPOP as measure of the “respiratory variation in pulse oximetry plethysmographic (POP) waveform amplitude” and defined it as follows: DPOP = (AMPmax − AMPmin) , (1). Note that the equation for DPOP has the same mathematical formulation as PPV [9, 10] and other similar formulations for pleth-based fluid responsiveness parameter were proposed by other groups at around the same time as Cannesson’s 2005 paper [11, 12]
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