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Annals of Intensive Care
Fig. 3 | Annals of Intensive Care

Fig. 3

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

Fig. 3

Three principal types of respiratory modulation of the plethysmogram signal (PPG) that are used for respiratory rate estimation. a Unmodulated PPG waveform. b Baseline modulation [BM]; the red dashed line depicts the baseline modulation related to the respiratory rate component. c Amplitude modulation (AM); the two red dashed lines depict the signal envelope related to the respiratory rate component. d Frequency modulation (FM); this modulation of the heart rate, also called “respiratory sinus arrythmia”, is synchronized with the respiratory rate

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