Ability of a New Smartphone Pulse Pressure Variation and Cardiac Output Application to Predict Fluid Responsiveness in Patients Undergoing Cardiac Surgery

BACKGROUND: Pulse pressure variation (PPV) can be used to predict fluid responsiveness in anesthetized patients receiving controlled mechanical ventilation but usually requires dedicated advanced monitoring. Capstesia (Galenic App, Vitoria-Gasteiz, Spain) is a novel smartphone application that calculates PPV and cardiac output (CO) from a picture of the invasive arterial pressure waveform obtained from any monitor screen. The primary objective was to compare the ability of PPV obtained using the Capstesia (PPVCAP) and PPV obtained using a pulse contour analysis monitor (PPVPC) to predict fluid responsiveness. A secondary objective was to assess the agreement and the trending of CO values obtained with the Capstesia (COCAP) against those obtained with the transpulmonary bolus thermodilution method (COTD). METHODS: We studied 57 mechanically ventilated patients (tidal volume 8 mL/kg, positive end-expiratory pressure 5 mm Hg, respiratory rate adjusted to keep end tidal carbon dioxide [32–36] mm Hg) undergoing elective coronary artery bypass grafting. COTD, COCAP, PPVCAP, and PPVPC were measured before and after infusion of 5 mL/kg of a colloid solution. Fluid responsiveness was defined as an increase in COTD of >10% from baseline. The ability of PPVCAP and PPVPC to predict fluid responsiveness was analyzed using the area under the receiver-operating characteristic curve (AUROC), the agreement between COCAP and COTD using a Bland-Altman analysis and the trending ability of COCAP compared to COTD after volume expansion using a 4-quadrant plot analysis. RESULTS: Twenty-eight patients were studied before surgical incision and 29 after sternal closure. There was no significant difference in the ability of PPVCAP and PPVPC to predict fluid responsiveness (AUROC 0.74 [95% CI, 0.60–0.84] vs 0.68 [0.54–0.80]; P = .30). A PPVCAP >8.6% predicted fluid responsiveness with a sensitivity of 73% (95% CI, 0.54–0.92) and a specificity of 74% (95% CI, 0.55–0.90), whereas a PPVPC >9.5% predicted fluid responsiveness with a sensitivity of 62% (95% CI, 0.42–0.88) and a specificity of 74% (95% CI, 0.48–0.90). When measured before surgery, PPV predicted fluid responsiveness (AUROC PPVCAP= 0.818 [P = .0001]; PPVPC= 0.794 [P = .0007]) but not when measured after surgery (AUROC PPVCAP= 0.645 [P = .19]; PPVPC= 0.552 [P = .63]). A Bland-Altman analysis of COCAP and COTD showed a mean bias of 0.3 L/min (limits of agreement: −2.8 to 3.3 L/min) and a percentage error of 60%. The concordance rate, corresponding to the proportion of CO values that changed in the same direction with the 2 methods, was poor (71%, 95% CI, 66–77). CONCLUSIONS: In patients undergoing cardiac surgery, PPVCAP and PPVPC both weakly predict fluid responsiveness. However, COCAP is not a good substitute for COTD and cannot be used to assess fluid responsiveness. Accepted for publication June 7, 2018. A. Joosten and C. Boudart contributed equally and share first authorship. Funding: None. Conflicts of Interest: See Disclosures at the end of the article. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (https://ift.tt/KegmMq). Registration: Clinicaltrials.gov (NCT02692222). Reprints will not be available from the authors. Address correspondence to Alexandre Joosten, MD, Department of Anesthesiology, Hopital Erasme, 808 Rt de Lennik, 1070 Bruxelles, Brussels, Belgium. Address e-mail to Alexandre.Joosten@erasme.ulb.ac.be. © 2018 International Anesthesia Research Society

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