Comparison between Respiratory Variations in Pulse Oximetry Plethysmographic Waveform Amplitude and Arterial Pulse Pressure during Major Abdominal Surgery
ABSTRACT : To assess preload dependence, the variation of the plethysmographic waveform of pulse oximetry (ΔPOP) has been proposed as a surrogate of the pulse pressure variation (ΔPP). The aim of the study was to assess the ability of the pulse oximeter-derived plethysmographic analysis to accurately trend ΔPP in patients undergoing major abdominal surgery by using standard monitors.
: A continuous recording of arterial and plethysmographic waveform was performed in 43 patients undergoing abdominal surgery. ΔPP and ΔPOP were calculated on validated respiratory cycles.
: For analysis, 92,467 respiratory cycles were kept (73.5% of cycles recorded in 40 patients). The mean of intrapatient coefficients of correlation was low (r = 0.22). The Bland and Altman analysis showed a systematic bias of 5.21; the ΔPOP being greater than the ΔPP, this bias increased with the mean value of the two indices and the limits of agreement were wide (upper 21.7% and lower -11.3%). Considering a ΔPP threshold at 12% to classify respiratory cycles as responders and nonresponders, the corresponding best cutoff value of ΔPOP was 13.6 ± 4.3%. Using these threshold values, the observed classification agreement was moderate (κ = 0.50 ± 0.09).
: The wide limits of agreement between ΔPP and ΔPOP and the weak correlation between both values cast doubt regarding the ability of ΔPOP to substitute ΔPP to follow trend in preload dependence and classify respiratory cycles as responders or nonresponders using standard monitor during anesthesia for major abdominal surgery.
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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.Anesthesiology Research and Practice 08/2014; 2014:980149. DOI:10.1155/2014/980149
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ABSTRACT: ΔPOP is a physiological parameter derived from the respiration-induced change in the pulse oximetry plethysmographic (POP) waveform or "pleth." It has been proposed as a proxy for pulse pressure variation used in the determination of the response to intravascular volume expansion in hypovolemic patients. Many studies have now reported on the parameter, and many research groups have constructed algorithms for its computation from the first principles where the implementation details have been described. This review focuses on the signal processing aspects of ΔPOP, as reported in the literature, and aims to provide a comprehensive summary of the wide-ranging algorithmic strategies that have been attempted in its computation. A search was conducted for articles concerning the use of ΔPOP as a fluid responsiveness parameter. In particular, articles concerning the correlation between ΔPOP and pulse pressure variation were targeted. Comments and replies to comments by the authors in which signal processing aspects were discussed were also included in the review. The parameter is first defined, and a history of the early work surrounding pleth-based fluid responsiveness parameters is presented. This is followed by an overview of the signal processing methods used in the reported studies, including details of exclusion criteria, manual filtering (preprocessing), gain change issues, acquisition details, selection of registration periods, averaging methods, physiological influences on the pleth, and comments by the investigators themselves. It is concluded that to develop a robust, fully automated ΔPOP algorithm for use in the clinical environment, more rigorous signal processing is required. Specifically, signals should be evaluated over significant periods of time, with emphasis on the quality and temporal relevance of the information.Anesthesia & Analgesia 12/2014; 119(6):1293-306. DOI:10.1213/ANE.0000000000000392 · 3.42 Impact Factor
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ABSTRACT: Objectives Noninvasive measurement of digital plethysmographic variability index (PVIdigital) has been proposed to predict fluid responsiveness, with conflicting results. The authors tested the hypothesis that cephalic sites of PVI measurement (namely PVIear and PVIforehead) could be more discriminant than PVIdigital to predict fluid responsiveness after cardiac surgery. Design A prospective observational study. Setting A cardiac surgical intensive care unit of a university hospital. Participants Fifty adult patients. Interventions Investigation before and after fluid challenge. Measurement and Main Results Patients were prospectively included within the first 6-hour postoperative period and investigated before and after fluid challenge. A positive response to fluid challenge was defined as a 15% increase in cardiac index. PVIdigital, PVIear, PVIforehead, and invasive arterial pulse-pressure variation (PPV) measurements were recorded simultaneously, and receiver operating characteristic (ROC) curves were built. Forty-one (82%) patients were responders and 9 (18%) patients were nonresponders to fluid challenge. ROCAUC were 0.74 (95% confidence interval [95% CI]: 0.60-0.86), 0.81 (95% CI: 0.68-0.91), 0.88 (95% CI: 0.75-0.95) and 0.87 (95% CI: 0.75-0.95) for PVIdigital, PVIear, PVIforehead, and PPV, respectively. Significant differences were observed between PVIforehead and PVIdigital (absolute difference in ROCAUC = 0.134 [95% CI: 0.003-0.265], p = 0.045) and between PPV and PVIdigital (absolute difference in ROCAUC = 0.129 [95% CI: 0.011-0.247], p = 0.033). The percentage of patients within the inconclusive class of response was 46%, 70%, 44%, and 26% for PVIdigital, PVIear, PVIforehead, and PPV, respectively. Conclusions PVIforehead was more discriminant than PVIdigital and could be a valuable alternative to arterial PPV in predicting fluid responsiveness.Journal of Cardiothoracic and Vascular Anesthesia 09/2014; 28(6). DOI:10.1053/j.jvca.2014.05.003 · 1.48 Impact Factor