Assessment of the agreement between photoplethysmographic and arterial waveform respiratory variation in patients undergoing spine surgery

Abstract

Respiratory variation in the arterial blood pressure and photoplethysmographic (PPG) waveforms have both been shown to predict the haemodynamic response to volume administration. Whether or not the two can be considered interchangeable is controversial. Twenty-three patients undergoing spine surgery received both a 20 gauge intra-arterial catheter and a Masimo adult adhesive SpHb sensor connected to a Radical-7 monitor. Pulse pressure variation (PPV) was calculated off-line at 1-min intervals. Pleth Variability Index (PVI) and Perfusion Index data were recorded. After exclusion of outliers, agreement between PPV and PVI was assessed using a repeated measures Bland-Altman approach. Concordance between changes in PPV and PVI was assessed using a four-quadrant plot with a 20% zone of exclusion. In total, 6549 min of data were collected. Repeated measures Bland-Altman analysis identified a bias of 2.2% and 95% confidence intervals of ±15.3% (limits of agreement -13.1 and +17.6%). The concordance rate between changes in PPV and changes in PVI was 51%. The agreement between respiratory variation in the arterial blood pressure and PPG waveforms is poor and these two should not be considered interchangeable. Changes in PPV are unrelated to changes in PVI. The data, combined with recently published work from other authors, suggests that the low frequency oscillations in the PPG waveform are not related to the low frequency oscillation in the systemic arterial blood pressure tracing and may be related to changes in venous pressure, peripheral tone or other physiologic phenomena yet to be described.

Respiratory Variations in Pulse Pressure Reflect Central Hypovolemia during Noninvasive Positive Pressure Ventilation

“…As shown in Table 1 and Figure 2, we found that ΔPOP increased with progressive LBNP, but due to large confidence intervals this increase was not statistically significant. Other studies have demonstrated wide limits of agreement between ΔPP and ΔPOP during surgery and intensive care [9, 21, 23, 24]. The physiology behind the photoplethysmographic signal is very complex, influenced by cardiac and autonomic as well as respiratory factors [25].…”

“…In spontaneously breathing subjects, only passive leg raise and the end-expiratory occlusion test have been shown to consistently reflect preload dependency [4, 5]. However, the literature is divided on two major issues concerning the usefulness of dynamic variables: whether they are applicable during spontaneous breathing [6, 7] and whether the photoplethysmographic waveform derived variables are useful alternatives to pulse pressure variation [8, 9]. Due to this uncertainty, the applicability of dynamic variables is currently limited to patients on controlled mechanical ventilation.…”

Inter-device differences in monitoring for goal-directed fluid therapy

“…[82][83][84][85] Despite the growing body of data suggesting that PVI is capable of predicting fluid responsiveness, there does not seem to be strong agreement between PVI and PPV. [86][87][88][89][90] The reasons for this paradox (excellent predictor of fluid responsiveness yet not in agreement with arterial-derived metrics) are not clear but may be related to the dependence of PVI on perfusion. 91 While the Masimo device may not be as effective as its more invasive counterparts during periods of malperfusion, it has three major advantages -relative low cost in comparison with its competitors, the ubiquity of pulse oximetry (which of course is a Canadian Anesthesiologists' Society basic monitoring standard), 92 and ease of use.…”

Advances in photoplethysmography: beyond arterial oxygen saturation

“…While some studies have shown a meaningful correlation between the two, 52,53 the majority of studies comparing arterial and PPG respiratory variation point to a relatively weak correlation. [54][55][56][57][58] Solus-Biguenet et al, for instance, found a weak correlation of 0.29. 54 Nevertheless, despite this weak correlation, the majority of fluid responsiveness studies suggest that the respiratory variation in the PPG tracing is predictive of the hemodynamic response to fluid loading, [59][60][61][62][63] although this finding is not universal.…”