Pulse oximeter plethysmograph variation and its relationship to the arterial waveform in mechanically ventilated children

Abstract

The variations induced by mechanical ventilation in the arterial pulse pressure and pulse oximeter plethysmograph waveforms have been shown to correlate closely and be effective in adults as markers of volume responsiveness. The aims of our study were to investigate: (1) the feasibility of recording plethysmograph indices; and (2) the relationship between pulse pressure variation (ΔPP), plethysmograph variation (ΔPOP) and plethysmograph variability index (PVI) in a diverse group of mechanically ventilated children. A prospective, observational study was performed. Mechanically ventilated children less than 11 years of age, with arterial catheters, were enrolled during the course of their clinical care in the operating room or in the pediatric intensive care unit. Real time monitor waveforms and trend data were recorded. ΔPP and ΔPOP were manually calculated and the relationships between ΔPP, ΔPOP and PVI were compared using Bland-Altman analysis and Pearson correlations. Forty-nine children were recruited; four (8%) subjects were excluded due to poor quality of the plethysmograph waveforms. ΔPP and ΔPOP demonstrated a strong correlation (r = 0.8439, P < 0.0001) and close agreement (Bias = 1.44 ± 6.4%). PVI was found to correlate strongly with ΔPP (r = 0.7049, P < 0.0001) and ΔPOP (r = 0.715, P < 0.0001). This study demonstrates the feasibility of obtaining plethysmographic variability indices in children under various physiological stresses. These data show a similarly strong correlation to that described in adults, between the variations induced by mechanical ventilation in arterial pulse pressure and the pulse oximeter plethysmograph.

Calculation of the Respiratory Modulation of the Photoplethysmogram (DPOP) Incorporating a Correction for Low Perfusion

“…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 [1–7]. PPV is, however, an invasive parameter requiring an arterial line, whereas a measure based on the pulse oximeter would provide an entirely noninvasive technology.…”

“…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. Problems with low perfusion are well documented in the literature and, in fact, low perfusion is cited as an exclusion criterion in the studies by Cannesson [1, 2] and Chandler et al [7]. Hence, we developed two versions of the algorithm: DPOPa, which provides a robust DPOP parameter as given by the formulation of (1) and DPOPb, which modifies the DPOP value at perfusion indices <3% by decreasing it proportionately as the perfusion index tends to zero.…”

Using non invasive dynamic parameters of fluid responsiveness in children: there is still much to learn

“…In the study presented by Chandler et al [1] in this issue of the Journal of Clinical Monitoring and Computing, the authors show that there is a strong relationship between PPV and DPOP in children under mechanical ventilation and general anesthesia and that this relationship is not impacted by the child's age. While this study did not test the ability of DPOP or PPV to predict fluid responsiveness per se, the authors have to be congratulated for conducting such an in depth analysis of the plethysmographic waveform which is unfortunately lacking in most of the recent studies focusing on the topic.…”

“…In this issue of the Journal of Clinical Monitoring and Computing, Chandler et al [1] investigated the relationship between respiratory variation in the amplitude of the plethysmographic waveform (DPOP) and in the arterial pulse pressure (PPV) in children.…”

“…This may be explained by the fact that different methods are used to assess the same parameters and that there is no true analysis of the plethysmographic waveform or of the stroke volume. The Chandler et al [1] paper presented here is a model since it presents a correct analysis of the SpO2 waveform together with a recording of PVI. The automatic gain control was turned off on the SpO2 monitor and realtime raw plethysmographic waveform was recorded and then analyzed using a specific SpO2 analysis software (Pulse Oximetry Data Acquisition Viewer (PODAV) software (Convergent Engineering, Gainesville, FL, USA)) [18].…”