Reply to the comment by Drs. Cannesson et al.

Using ventilation-induced plethysmographic variations to optimize patient fluid status

“…In the intensive care unit, in a septic hypotensive cohort, Feissel et al [21] showed that a DPOP value of 14% before volume expansion allowed discrimination between responders and nonresponders with 94% sensitivity and 80% specificity. It is interesting to underline that patients were all under vasoactive drugs in this last study and that it did not seem to impact the ability of this index to predict fluid responsiveness [37,38]. Finally, Natalini et al [22] studied 22 hypotensive patients in the intensive care unit and showed that a DPOP greater than 15% could predict fluid responsiveness (receiver operating characteristic area ¼ 0.72, P ¼ 0.9).…”

A Review of Signal Processing Used in the Implementation of the Pulse Oximetry Photoplethysmographic Fluid Responsiveness Parameter

“…Hence, results reported should be interpreted in the context of the method used to produce them. This is achieved by setting a threshold for PPV (ranging between 8.8% and 15% for the studies considered here 4,7,11,12,15,19,21,22,25,33 ), and finding the sensitivity and specificity pairs for varying ∆POP thresholds (i.e., computing the receiver operator curve). " We may also determine other measures, such as sensitivity and specificity and AUC values corresponding to the substitution of ∆POP for PPV as a fluid responsiveness measure.…”

“…Natalini et al 4 recognized that ventilation-induced photoplethysmographic changes are caused by blood volume changes both in the arterial and venous bed and further that the variation in photoplethysmographic waveform amplitude depends on the "intravascular pulse pressure as well as on the distensibility of the vascular wall." Feissel et al 19 commented on the influence of vasomotor tone on the plethysmographic waveform especially in patients receiving norepinephrine. Feissel et al 19 commented on the influence of vasomotor tone on the plethysmographic waveform especially in patients receiving norepinephrine.…”

“…Cannesson et al 12 recognized the need for the "automated calculation of ∆POP." Chandler et al, 26 in a study of children, 32 also echo this sentiment: "To use this index clinically would require an automated method of calculation," whereas Feissel et al 19 suggest standardizing the way in which the "data are recorded and analyzed. "…”