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Annals of Intensive Care
Fig. 2 | Annals of Intensive Care

Fig. 2

From: Photoplethysmographic determination of the respiratory rate in acutely ill patients: validation of a new algorithm and implementation into a biomedical device

Fig. 2

Correlation and Bland–Altman plot for reference and estimated respiratory rate during the prospective evaluation phase. Reference respiratory rate (RR) values are provided as the chronometric measurement measured over 30 s under spontaneous ventilation or as the ventilatory rate for patients under ventilatory assistance. Estimated RR was performed using the plethysmographic curve analysis (RR-PPG). On the 30 ICU patients’ recordings, prospective estimation of the RR-PPG was well correlated with the reference method (r = 0.78; p < 0.001). Comparison of the methods using the Bland–Altman method depicted a low bias (0.5 c/min) and acceptable deviation (< ± 5.5 c/min). Most of the estimation errors were related to difficult PPG signal acquisition, mostly due to artefacts and/or bad signals

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