Physiological measurement
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Physiological measurement · Jul 2010
Contactless and continuous monitoring of heart rate based on photoplethysmography on a mattress.
This paper reports a novel contactless monitoring method to record photoplethysmogram (PPG) on a mattress for the continuous measurement of heart rate (HR). PPGs were obtained from subjects' fingers and backs with and without making a direct contact between the PPG sensor and their skin when they rested in a supine position on the mattress. Electrocardiograms (ECGs) were measured from the subjects' limbs for reference. ⋯ Beat-to-beat HR derived from contactless PPG measurement was comparable to those measured from contact PPG and ECG measurements. Thus we found that contactless PPG could be captured from the subjects' backs and it was sufficient to provide accurate HR measurements. This contactless monitoring of PPG has the potential to reduce obstruction in sleep and provide clinical evaluation in sleep study.
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Physiological measurement · Jul 2010
Respiratory variations in the photoplethysmographic waveform: acute hypovolaemia during spontaneous breathing is not detected.
Recent studies using photoplethysmographic (PPG) signals from pulse oximeters have shown potential to assess hypovolaemia during spontaneous breathing. This signal is heavily filtered and reports are based on respiratory variations in the small pulse synchronous variation of PPG. There are stronger respiratory variations such as respiratory synchronous variation (PPGr) in the baseline of the unfiltered PPG signal. ⋯ The amplitude of PPGr did not change significantly at any measurement site. The strongest effect was seen at the ear, where the LBNP of 60 cmH(2)O gave an amplitude increase from 1.0 (0.0) to 1.31 (2.24) AU. PPG baseline respiratory variations cannot be used for detecting hypovolaemia in spontaneously breathing subjects.