Testing preload responsiveness by the tidal volume challenge assessed by the photoplethysmographic perfusion index
Résumé
In critically ill patients ventilated with Vt = 6 mL/kg PBW and no spontaneous breathing, haemodynamic (PICCO 2 system) and photoplethysmographic (Masimo-SET technique, sensor placed on the finger or the forehead) data were recorded during a Vt-challenge and a PLR test.
Among 63 screened patients, 21 (33%) were excluded because of an unstable PI signal and/or atrial fibrillation and 42 were included. During the Vt-challenge in the 16 preload responders, CI decreased by 4.8 ± 2.8% (percent change), PPV increased by 4.4 ± 1.9% (absolute change), PI finger decreased by 14.5 ± 10.7% (percent change), PVI finger increased by 1.9 ± 2.6% (absolute change), PI forehead decreased by 18.7 ± 10.9 (percent change) and PVI forehead increased by 1.0 ± 2.5 (absolute change). All these changes were larger than in preload non-responders. The area under the ROC curve (AUROC) for detecting preload responsiveness was 0.97 ± 0.02 for the Vt-challenge-induced changes in CI (percent change), 0.95 ± 0.04 for the Vt-challenge-induced changes in PPV (absolute change), 0.98 ± 0.02 for Vt-challengeinduced changes in PI forehead (percent change) and 0.85 ± 0.05 for Vt-challenge-induced changes in PI finger (percent change) (p = 0.04 vs. PI forehead ). The AUROC for the Vt-challenge-induced changes in PVI forehead and PVI finger was significantly larger than 0.50, but smaller than the AUROC for the Vt-challenge-induced changes in PPV.
In patients under mechanical ventilation with no spontaneous breathing and/or atrial fibrillation, changes in PI detected during Vt-challenge reliably detected preload responsiveness. The reliability was better when PI was measured on the forehead than on the fingertip. Changes in PVI during the Vt-challenge also detected preload responsiveness, but with lower accuracy.