Aston, Philip

Beale, Richard

Camporota, Luigi

Charlton, Peter

Christie, Mark Ian

Nandi, Manasi

Smith, John

Acutely-ill hospital patients are at risk of clinical deteriorations. Attractor reconstruction (AR) analysis of the arterial blood pressure (ABP) signal has recently been proposed as a method for measuring the changes in cardiovascular state which accompany deteriorations. Since ABP signals are only available in a minority of clinical scenarios, we sought to determine whether AR could also be performed on more widely available pulse oximetry (photoplethysmogram, PPG) signals. AR analysis was performed on simultaneous ABP and PPG signals before, during and after a change in cardiovascular state. A novel quality metric was used to eliminate windows of low quality AR. A high level of agreement was found between the detected periodicity of each signal. The remaining cardiovascular parameters derived using AR analysis exhibited similar trends between the two signals in response to the change in state, although there was poor agreement between their absolute values. This demonstrates the feasibility of applying AR to the PPG signal. Since the PPG signal is measured every 4-6 hours during routine nursing observations, this suggests that AR analysis could be performed automatically as part of routine practice. This may facilitate early identification of deteriorations such as sepsis, which has a profound effect on cardiovascular state

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                       King’s Research Portal  Document VersionPeer reviewed versionLink to publication record in King's Research PortalCitation for published version (APA):Charlton, P., Camporota, L., Smith, J., Nandi, M., Christie, M. I., Aston, P., & Beale, R. (2015). Non-invasiveattractor reconstruction analysis for early detection of deteriorations.Citing this paperPlease note that where the full-text provided on King's Research Portal is the Author Accepted Manuscript or Post-Print version this maydiffer from the final Published version. If citing, it is advised that you check and use the publisher's definitive version for pagination,volume/issue, and date of publication details. 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Oct. 2023Non-invasive attractor reconstruction analysis for early detection of deteriorations P.H. Charlton12, L. Camporota2, J. Smith2, M. Nandi1, M. Christie1, P.J. Aston3, R. Beale2   1King’s College London 2Guy’s and St Thomas’ NHS Foundation Trust  3University of Surrey This research was supported by the National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. PC acknowledges much valued support from SJ Charlton. Contact:    Peter.Charlton [at] gstt.nhs.uk The importance of early detection of deteriorations Clinical deteriorations of hospital patients leading to events such as cardiac arrests, critical illnesses, and deaths must be recognised early to maintain patient safety. Deteriorations are commonly preceded by changes in cardiovascular state. However, routinely measured cardiovascular parameters such as blood pressure often provide only minimal advanced warning (see right). Dataset   Arterial blood pressure and pulse oximetry signals acquired from six critically ill patients were used to compare attractor reconstruction of the signals. Recordings were obtained before, during and after a change in cardiovascular state caused by increased vasopressor dosage (shown by grey shading) [1]. References  [1] J. Smith et al., “Effects of norepinephrine-driven change in arterial blood pressure on four different continuous cardiac output systems in critically ill patients,” Int Care Med., vol. 37 S1, p. S280, 2011.  The paper accompanying this poster is:  Charlton, P. H. et al., “Measurement of cardiovascular state using attractor reconstruction analysis,”Conf Proc EUSIPCO., 2015. [in press] Attractor reconstruction as an early marker Changes in cardiovascular variability have been observed to occur earlier than changes in cardiovascular parameters. Attractor reconstruction quantifies the variability of cardiovascular signals, so may provide improved markers of deterioration. It represents a signal as an attractor in 2D phase space (see left). Non-invasive measurement Attractor reconstruction has previously been applied to arterial blood pressure signals. These are only available in critical care via invasive measurement. In contrast, pulse oximetry signals are measured every 4-12 hours in hospital patients. We hypothesised that cardiovascular variability could be measured using this non-invasive signal instead. If so, attractor reconstruction could be used with all hospital patients, rather than just those in critical care. Elimination of low quality measurements If attractor reconstruction is to be used in hospital then it must be robust to artifact due to factors such as movement or loosening of sensor attachments. The Attractor Quality Index was proposed to discriminate between high and low quality attractor reconstruction. As shown below, high quality measurements result in a high density of points at the three vertices of a triangular attractor. The attractor quality index quantifies the presence or absence of these high density regions to determine the quality of attractor reconstruction.  1. Early detection of deteriorations using attractor reconstruction 2. Proposed developments for clinical use 3. Clinical evaluation of developments Data: MIMIC II Clinical Database, with thanks to Marco Pimentel. Pulse oximetry measures arterial blood volume, so is closely related to arterial blood pressure (left). It can be easily measured as shown below. Agreement between signals’ heart rates Heart rates (right) derived from arterial blood pressure and pulse oximetry signals using attractor reconstruction agreed very closely. Similar trends in variability measures Measures of cardiovascular variability (left) trended similarly between the two signals, although absolute values did not agree.. Identification of low quality measurements As shown below, there was high agreement between the heart rates derived from each signal when the Attractor Quality Index was below a threshold value (to the left of the red dashed line). Otherwise, there was poor agreement, demonstrating the ability of the Attractor Quality Index to discriminate between high and low quality measurements. 

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Non-invasive attractor reconstruction analysis for early detection of deteriorations

https://kclpure.kcl.ac.uk/portal/files/42032524/Att_Recon_Poster.pdf

Non-invasive attractor reconstruction analysis for early detection of deteriorations

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