OBJECTIVE: Photo-plethysmography (PPG) sensors are often used to detect pulse transit time (PTT) for potential cuff-less blood pressure (BP) measurement. It is known that the contact pressure (CP) of the PPG sensor markedly alters the PPG waveform amplitude. The objective was to test the hypothesis that PTT detected via PPG sensors is likewise impacted by CP. METHODS: A device was built to measure the time delay between ECG and finger PPG waveforms (i.e., pulse arrival time (PAT) - a popular surrogate of PTT) and the PPG sensor CP at different CP levels. These measurements and finger cuff BP were recorded while the CP was slowly varied in 17 healthy subjects. RESULTS: Over a physiologic range of CP, the maximum deviations of PAT detected at the PPG foot and peak were 22±2 and 40±7 ms (p<0.05), which translate to ∼11 and ∼20 mmHg BP error based on the literature. The curve relating PAT detected at the PPG foot to CP was U-shaped with minimum near finger diastolic BP. A conceptual model accounting for finger artery viscoelasticity and nonlinearity explained this curve. CONCLUSION: Since the regulatory bias error for BP measurement is limited to 5 mmHg, PPG sensor CP should be taken into account for cuff-less BP measurement via PTT. SIGNIFICANCE: This study suggests that widely pursued PPG-based BP measurement devices including those that detect PTT should maintain the CP or include a CP measurement in the calibration equation for deriving BP.
OBJECTIVE: Photo-plethysmography (PPG) sensors are often used to detect pulse transit time (PTT) for potential cuff-less blood pressure (BP) measurement. It is known that the contact pressure (CP) of the PPG sensor markedly alters the PPG waveform amplitude. The objective was to test the hypothesis that PTT detected via PPG sensors is likewise impacted by CP. METHODS: A device was built to measure the time delay between ECG and finger PPG waveforms (i.e., pulse arrival time (PAT) - a popular surrogate of PTT) and the PPG sensor CP at different CP levels. These measurements and finger cuff BP were recorded while the CP was slowly varied in 17 healthy subjects. RESULTS: Over a physiologic range of CP, the maximum deviations of PAT detected at the PPG foot and peak were 22±2 and 40±7 ms (p<0.05), which translate to ∼11 and ∼20 mmHg BP error based on the literature. The curve relating PAT detected at the PPG foot to CP was U-shaped with minimum near finger diastolic BP. A conceptual model accounting for finger artery viscoelasticity and nonlinearity explained this curve. CONCLUSION: Since the regulatory bias error for BP measurement is limited to 5 mmHg, PPG sensor CP should be taken into account for cuff-less BP measurement via PTT. SIGNIFICANCE: This study suggests that widely pursued PPG-based BP measurement devices including those that detect PTT should maintain the CP or include a CP measurement in the calibration equation for deriving BP.
Authors: Omer T Inan; Pierre-Francois Migeotte; Kwang-Suk Park; Mozziyar Etemadi; Kouhyar Tavakolian; Ramon Casanella; John Zanetti; Jens Tank; Irina Funtova; G Kim Prisk; Marco Di Rienzo Journal: IEEE J Biomed Health Inform Date: 2014-10-07 Impact factor: 5.772
Authors: Peter H Charlton; Panicos A Kyriaco; Jonathan Mant; Vaidotas Marozas; Phil Chowienczyk; Jordi Alastruey Journal: Proc IEEE Inst Electr Electron Eng Date: 2022-03-11 Impact factor: 10.961
Authors: Mohammad Yavarimanesh; Robert C Block; Keerthana Natarajan; Lalit K Mestha; Omer T Inan; Jin-Oh Hahn; Ramakrishna Mukkamala Journal: IEEE Trans Biomed Eng Date: 2022-05-19 Impact factor: 4.756
Authors: Keerthana Natarajan; Robert C Block; Mohammad Yavarimanesh; Anand Chandrasekhar; Lalit K Mestha; Omer T Inan; Jin-Oh Hahn; Ramakrishna Mukkamala Journal: IEEE Trans Biomed Eng Date: 2021-12-23 Impact factor: 4.538
Authors: Peter H Charlton; Birutė Paliakaitė; Kristjan Pilt; Martin Bachler; Serena Zanelli; Dániel Kulin; John Allen; Magid Hallab; Elisabetta Bianchini; Christopher C Mayer; Dimitrios Terentes-Printzios; Verena Dittrich; Bernhard Hametner; Dave Veerasingam; Dejan Žikić; Vaidotas Marozas Journal: Am J Physiol Heart Circ Physiol Date: 2021-12-24 Impact factor: 4.733