Physiological Measurement (PHYSIOL MEAS)

Publications in this journal

• Article: Compression-induced hyperaemia in the rabbit masseter muscle: a model to investigate vascular mechano-sensitivity of skeletal muscle

  Marco Turturici and Silvestro Roatta
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  ABSTRACT: Recent evidence suggests that the mechano-sensitivity of the vascular network may underlie rapid dilatory events in skeletal muscles. Previous investigations have been mostly based either on in vitro or on whole-limb studies, neither preparation allowing one to assess the musculo-vascular specificity under physiological conditions. The aim of this work is to characterize the mechano-sensitivity of an exclusively-muscular vascular bed in vivo. In five anesthetized rabbits, muscle blood flow was continuously monitored in the masseteric artery, bilaterally (n = 10). Hyperaemic responses were evoked by compressive stimuli of different extent (50, 100 and 200 mm Hg) and duration (0.5, 1, 2 and 5 s) exerted by a servo-controlled motor on the masseter muscle. Peak amplitude of the hyperaemic response ranged from 340 ± 30% of baseline (at 50 mm Hg) to 459 ± 57% (at 200 mm Hg) (P < 0.05), did not depend on stimulus duration and exhibited very good reliability (ICC = 0.98) when reassessed at 30 min intervals. The time course of the response depended neither on applied pressure nor on the duration of the stimulus. In conclusion, for its high sensitivity and reliability this technique is adequate to characterize mechano-vascular reactivity and may prove useful in the investigation of the underlying mechanisms, with implications in the control of vascular tone and blood pressure in health and disease.
  Physiological Measurement 02/2013; 34(3).
• Article: Fast Track Communications

  Richard Bayford, Jon Ruffle
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  ABSTRACT: Physiological Measurement (PMEA) is introducing a new article type—Fast Track Communications (FTCs)—with immediate effect. FTCs are outstanding short papers reporting important, timely new developments in physiological measurement and biomedical engineering. Fast Track Communications are intended for very high quality research, reporting highly significant new results, should not normally exceed eight journal pages (or 5000 words) in length so must be written in a clear and concise style, are sent to the Editor/Board Member for review in the first instance, benefit from accelerated publication (the average time from submission to online publication is expected to be under 3 months), and are placed at the front of the journal. When submitting FTCs for publication authors should provide a written justification to the Editor, explaining why the article meets our stringent quality and novelty criteria and justifies faster publication. The initial assessment of FTCs will be made by the Editor/Board Member. If they fail to reach the required standard this may slow down publication. In such cases FTCs may be recommended for consideration as a regular paper or possibly a note. (Notes will continue as a submission category for shorter, more technical communications than papers, both otherwise having the same review criteria.) Previously we have occasionally published short papers as 'Letters to the Editor'. These are now discontinued. However, authors may still submit letter-type comments about previously published PMEA papers, which will be published (alongside a reply from the original authors) only if they are considered by the Board to be of high interest to the general PMEA readership. We look forward to publishing our first Fast Track Communications in 2011. Richard Bayford Editor-in-Chief Jon Ruffle Publisher
  Physiological Measurement 03/2011; 32(4).
• Article: Martin Black award for the best paper published in 2009

  Richard Bayford, Jon Ruffle
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  ABSTRACT: The publishers of Physiological Measurement (PMEA), IOP Publishing, in association with the journal owners, the Institute of Physics and Engineering in Medicine (IPEM), jointly award an annual prize for the best paper published in PMEA during the previous year. The responsibility for deciding the ultimate winner falls to the Editorial and International Advisory boards of the journal. However, a shortlist of papers has to first be put together. Since a paper published early in the volume will have more exposure than one published later, it would be unfair to use download or citation statistics to judge papers. For this reason, the shortlist is constructed using the comments and ratings of our expert referees. For the 2009 award, 6 papers were considered. After the construction of the shortlist, it was then down to our board members to personally assess and rank the papers. This year, we have a clear and worthy winner. We have much pleasure in advising readers that the 2009 Martin Black award goes to Andy Adler et al for their paper on electrical impedance tomography. GREIT: a unified approach to 2D linear EIT reconstruction of lung images Andy Adler, John Arnold, Richard Bayford, Andrea Borsic, Brian Brown, Paul Dixon, Theo Faes, Inez Frerichs, Herve Gagnon, Yvo Garber, Bartlomiej Grychtol, Gunter Hahn, William Lionheart, Anjum Malik, Robert P Patterson, Janet Stocks, Andrew Tizzard, Norbert Weiler and Gerhard K Wolf 2009 Physiol. Meas. 30 S35–55 All of the shortlisted papers were of great merit, and the full top-6 is listed below (in alphabetical order). Richard Bayford Editor-in-Chief Jon Ruffle Publisher References Adler A, Arnold J H, Bayford R, Borsic A, Brown B, Dixon P, Faes T J C, Frerichs I, Gagnon H, Gärber Y, Grychtol B, Hahn G, Lionheart W R B, Malik A, Patterson R P, Stocks J, Tizzard A, Weiler N and Wolf G K 2009 GREIT: a unified approach to 2D linear EIT reconstruction of lung images Physiol. Meas. 30 S35–55 Aelen P, Jurkov A, Aulanier A and Mintchev M P 2009 Pilot acute study of feedback-controlled retrograde peristalsis invoked by neural gastric electrical stimulation Physiol. Meas. 30 309–22 Borsic A, Halter R, Wan Y, Hartov A and Paulsen K D 2009 Sensitivity study and optimization of a 3D electric impedance tomography prostate probe Physiol. Meas. 30 S1–18 Kim K K, Kim J S, Lim Y G and Park K S 2009 The effect of missing RR-interval data on heart rate variability analysis in the frequency domain Physiol. Meas. 30 1039–50 Remme E W, Hoff L, Halvorsen P S, Nærum E, Skulstad H, Fleischer L A, Elle O J and Fosse E 2009 Validation of cardiac accelerometer sensor measurements Physiol. Meas. 30 1429–44 Wang L, Su S W, Celler B G, Chan G S H, Cheng T M and Savkin A V 2009 Assessing the human cardiovascular response to moderate exercise: feature extraction by support vector regression Physiol. Meas. 30 227–44
  Physiological Measurement 07/2010; 31(9).
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  Available from: ucl.ac.uk

  Article: Reply to 'Comment on "Estimating a modified Grubb's exponent in healthy human brains with near infrared spectroscopy and transcranial Doppler"'.

  Terence S Leung, Ilias Tachtsidis, Martin M Tisdall, Caroline Pritchard, Martin Smith, Clare E Elwell
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  ABSTRACT: Grubb's exponent is a useful parameter quantifying cerebral hemodynamics. This letter is a reply to the Comment by Boas and Payne (2009 Physiol. Meas. 30 L9-11). We reiterated our view that Grubb's exponent estimated by linear regression is theoretically inappropriate to be used to predict cerebral blood flow (CBF). In their Comment, Boas and Payne proposed the novel use of total least squares (TLS) to estimate Grubb's exponent which we also agreed is a better technique than linear regression, and Grubb's exponent estimated by TLS will allow the prediction of CBF from cerebral blood volume (CBV).
  Physiological Measurement 10/2009; 30(10):L13-4.
• Article: Real-time detection of transient cardiac ischemic episodes from ECG signals.

  L Dranca, A Goñi, A Illarramendi
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  ABSTRACT: We propose a new algorithm to detect and classify transient cardiac ischemia episodes, designed with the goal of providing a real-time execution without penalizing the classifier accuracy much. The algorithm is based on a novel mixture of time-domain analysis and machine learning techniques, specifically bagging of decision trees, and it has been developed using a well-recognized and freely distributed database, namely the long-term ST database. The ST episode detection sensitivity/positive predictivity using the annotation protocol A for this database is 68.26%/74.91%. The sensitivity result increases until 93.97% for the most dangerous episodes in terms of duration and magnitude (annotated according to protocol C). The test of the algorithm over the freely distributed part of the European Society of Cardiology database has shown results of sensitivity and positive predictivity of 83.33% and 77.31%, respectively. Those results are close to the results obtained by related works that present approaches to detect ischemia episodes off-line, which is remarkable if we take into account that in our real-time approach, less information is available during the classification process.
  Physiological Measurement 10/2009; 30(9):983-98.
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  Available from: surrey.ac.uk

  Article: Nonlinear measure of synchrony between blood oxygen saturation and heart rate from nocturnal pulse oximetry in obstructive sleep apnoea syndrome.

  D Alvarez, R Hornero, D Abásolo, F del Campo, C Zamarrón, M López
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  ABSTRACT: This study focuses on analysis of the relationship between changes in blood oxygen saturation (SaO(2)) and heart rate (HR) recordings from nocturnal pulse oximetry (NPO) in patients suspected of suffering from obstructive sleep apnoea (OSA) syndrome. Two different analyses were developed: a classical frequency analysis based on the magnitude squared coherence (MSC) and a nonlinear analysis by means of a recently developed measure of synchrony, the cross-approximate entropy (cross-ApEn). A data set of 187 subjects was studied. We found significantly higher correlation and synchrony between oximetry signals from OSA positive patients compared with OSA negative subjects. We assessed the diagnostic ability to detect OSA syndrome of both the classical and nonlinear approaches by means of receiver operating characteristic (ROC) analyses with tenfold cross-validation. The nonlinear measure of synchrony significantly improved the results obtained with classical MSC: 69.2% sensitivity, 90.9% specificity and 78.1% accuracy were reached with MSC, whereas 83.7% sensitivity, 84.3% specificity and 84.0% accuracy were obtained with cross-ApEn. Our results suggest that the use of nonlinear measures of synchrony could provide essential information from oximetry signals, which cannot be obtained with classical spectral analysis.
  Physiological Measurement 10/2009; 30(9):967-82.
• Article: Energy scavenging sources for biomedical sensors.

  E Romero, R O Warrington, M R Neuman
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  ABSTRACT: Energy scavenging has increasingly become an interesting option for powering electronic devices because of the almost infinite lifetime and the non-dependence on fuels for energy generation. Moreover, the rise of wireless technologies promises new applications in medical monitoring systems, but these still face limitations due to battery lifetime and size. A trade-off of these two factors has typically governed the size, useful life and capabilities of an autonomous system. Energy generation from sources such as motion, light and temperature gradients has been established as commercially viable alternatives to batteries for human-powered flashlights, solar calculators, radio receivers and thermal-powered wristwatches, among others. Research on energy harvesting from human activities has also addressed the feasibility of powering wearable or implantable systems. Biomedical sensors can take advantage of human-based activities as the energy source for energy scavengers. This review describes the state of the art of energy scavenging technologies for powering sensors and instrumentation of physiological variables. After a short description of the human power and the energy generation limits, the different transduction mechanisms, recent developments and challenges faced are reviewed and discussed.
  Physiological Measurement 10/2009; 30(9):R35-62.
• Article: Ventricular rhythm in atrial fibrillation under anaesthetic infusion with propofol.

  R Cervigón, J Moreno, R B Reilly, J Pérez-Villacastín, F Castells
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  ABSTRACT: Changes in patients' autonomic tone and specific pharmacologic interventions may modify the ventricular response (actual heart rate) during atrial fibrillation (AF). Hypnotic agents such as propofol may modify autonomic balance as they promote a sedative state. It has been shown that propofol slightly slows atrial fibrillatory activity, but the net global effect on the ventricular response remains unknown. We aimed to evaluate in patients in AF the effect of a propofol bolus on the ventricular rate and regularity at ECG. We analysed the possible relation with local atrial fibrillatory activities, as ratios between atrial and ventricular rates (AVRs), analysing atrial activity from intracardiac electrograms at the free wall of the right and left atria and at the interatrial septum. We compared data at the baseline and after complete hypnosis. Propofol was associated with a more homogeneous ventricular response and lower AVR values at the interatrial septum.
  Physiological Measurement 09/2009; 30(8):833-45.
• Article: MREIT conductivity imaging of the postmortem canine abdomen using CoReHA.

  Kiwan Jeon, Atul S Minhas, Young Tae Kim, Woo Chul Jeong, Hyung Joong Kim, Byeong Teck Kang, Hee Myung Park, Chang-Ock Lee, Jin Keun Seo, Eung Je Woo
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  ABSTRACT: Magnetic resonance electrical impedance tomography (MREIT) is a new bio-imaging modality providing cross-sectional conductivity images from measurements of internal magnetic flux densities produced by externally injected currents. Recent experimental results of postmortem and in vivo imaging of the canine brain demonstrated its feasibility by showing conductivity images with meaningful contrast among different brain tissues. MREIT image reconstructions involve a series of data processing steps such as k-space data handling, phase unwrapping, image segmentation, meshing, modelling, finite element computation, denoising and so on. To facilitate experimental studies, we need a software tool that automates these data processing steps. In this paper, we summarize such an MREIT software package called CoReHA (conductivity reconstructor using harmonic algorithms). Performing imaging experiments of the postmortem canine abdomen, we demonstrate how CoReHA can be utilized in MREIT. The abdomen with a relatively large field of view and various organs imposes new technical challenges when it is chosen as an imaging domain. Summarizing a few improvements in the experimental MREIT technique, we report our first conductivity images of the postmortem canine abdomen. Illustrating reconstructed conductivity images, we discuss how they discern different organs including the kidney, spleen, stomach and small intestine. We elaborate, as an example, that conductivity images of the kidney show clear contrast among cortex, internal medulla, renal pelvis and urethra. We end this paper with a brief discussion on future work using different animal models.
  Physiological Measurement 09/2009; 30(9):957-66.
• Article: Arbitrary units are a composite and useful measure of muscle sympathetic nerve activity.

  Tushar P Thakre, Hemant Kulkarni, Manju R Mamtani, Michael Smith
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  ABSTRACT: In humans, the muscle sympathetic nerve activity (MSNA) signal is challenging to detect, record and analyze. Several methods exist that attempt to capture the latent construct of MSNA. We directly compared the performance of five MSNA parameters: burst frequency, burst incidence, median burst amplitude, arbitrary units (AU) and fractal dimension (FD). The MSNA signal was recorded in 33 subjects for approximately 30 min before, during and after the application of a graded cold pressor test stimulus at 18 degrees C, 10 degrees C and 2 degrees C in random order with an adequate wash-out period. Using coefficient of variation, Shannon's entropy and principal component analysis, we observed that these five parameters defined two physical and conceptual domains of MSNA-frequency and amplitude. Since AU combines information from both these domains, we observed that it explained maximum inter-subject and inter-experimental segment variation. FD did not explain the inter-subject variability and was identified as a unique parameter in the factor analysis. Epidemiological studies that attempt to quantify MSNA may consistently use AU as the parameter for quantification of MSNA.
  Physiological Measurement 09/2009; 30(8):861-8.
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  Available from: unb.br

  Article: Estimation of the knee joint angle from surface electromyographic signals for active control of leg prostheses.

  Alberto L Delis, João L A Carvalho, Adson F da Rocha, Renan U Ferreira, Suélia S Rodrigues, Geovany A Borges
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  ABSTRACT: The surface electromyographic (SEMG) signal is very convenient for prosthesis control because it is non-invasively acquired and intrinsically related to the user's intention. This work presents a feature extraction and pattern classification algorithm for estimation of the intended knee joint angle from SEMG signals acquired using two sets of electrodes placed on the upper leg. The proposed algorithm uses a combination of time-domain and frequency-domain approaches for feature extraction (signal amplitude histogram and auto-regressive coefficients, respectively), a self-organizing map for feature projection and a Levenberg-Marquardt multi-layer perceptron neural network for pattern classification. The new algorithm was quantitatively compared with the method proposed by Wang et al (2006 Med. Biol. Eng. Comput. 44 865-72), which uses wavelet packet feature extraction, principal component analysis and a multi-layer perceptron neural classifier. The proposed method provided lower error-to-signal percentage and peak error amplitudes, higher correlation and fewer error events. The algorithm presented in this work may be useful as part of a myoelectric controller for active leg prostheses designed for transfemoral amputees.
  Physiological Measurement 09/2009; 30(9):931-46.
• Article: The monitoring of relative changes in compartmental compliances of brain.

  Dong-Joo Kim, Magdalena Kasprowicz, Emmanuel Carrera, Gianluca Castellani, Christian Zweifel, Andrea Lavinio, Peter Smielewski, Michael P F Sutcliffe, John D Pickard, Marek Czosnyka
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  ABSTRACT: The study aimed to develop a computational method for assessing relative changes in compartmental compliances within the brain: the arterial bed and the cerebrospinal space. The method utilizes the relationship between pulsatile components in the arterial blood volume, arterial blood pressure (ABP) and intracranial pressure (ICP). It was verified by using clinical recordings of intracranial pressure plateau waves, when massive vasodilatation accompanying plateau waves produces changes in brain compliances of the arterial bed (C(a)) and compliance of the cerebrospinal space (C(i)). Ten patients admitted after head injury with a median Glasgow Coma Score of 6 were studied retrospectively. ABP was directly monitored from the radial artery. Changes in the cerebral arterial blood volume were assessed using Transcranial Doppler (TCD) ultrasonography by digital integration of inflow blood velocity. During plateau waves, ICP increased (P = 0.001), CPP decreased (P = 0.001), ABP remained constant (P = 0.532), blood flow velocity decreased (P = 0.001). Calculated compliance of the arterial bed C(a) increased significantly (P = 0.001); compliance of the CSF space C(i) decreased (P = 0.001). We concluded that the method allows for continuous monitoring of relative changes in brain compartmental compliances. Plateau waves affect the balance between vascular and CSF compartments, which is reflected by the inverse change of compliance of the cerebral arterial bed and global compliance of the CSF space.
  Physiological Measurement 08/2009; 30(7):647-59.
• Source

  Available from: flinders.edu.au

  Article: Vessel calibre and haemoglobin effects on pulse oximetry.

  M P McEwen, G P Bull, K J Reynolds
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  ABSTRACT: Despite its success as a clinical monitoring tool, pulse oximetry may be improved with respect to the need for empirical calibration and the reports of biases in readings associated with peripheral vasoconstriction and haemoglobin concentration. To effect this improvement, this work aims to improve the understanding of the photoplethysmography signal-as used by pulse oximeters-and investigates the effect of vessel calibre and haemoglobin concentration on pulse oximetry. The digital temperature and the transmission of a wide spectrum of light through the fingers of 57 people with known haemoglobin concentrations were measured and simulations of the transmission of that spectrum of light through finger models were performed. Ratios of pulsatile attenuations of light as used in pulse oximetry were dependent upon peripheral temperature and on blood haemoglobin concentration. In addition, both the simulation and in vivo results showed that the pulsatile attenuation of light through fingers was approximately proportional to the absorption coefficients of blood, only when the absorption coefficients were small. These findings were explained in terms of discrete blood vessels acting as barriers to light transmission through tissue. Due to the influence of discrete blood vessels on light transmission, pulse oximeter outputs tend to be dependent upon haemoglobin concentration and on the calibre of pulsing blood vessels-which are affected by vasoconstriction/vasodilation. The effects of discrete blood vessels may account for part of the difference between the Beer-Lambert pulse oximetry model and empirical calibration.
  Physiological Measurement 08/2009; 30(9):869-83.
• Article: Parametric estimation of pulse arrival time: a robust approach to pulse wave velocity.

  Josep Solà, Rolf Vetter, Philippe Renevey, Olivier Chételat, Claudio Sartori, Stefano F Rimoldi
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  ABSTRACT: Pulse wave velocity (PWV) is a surrogate of arterial stiffness and represents a non-invasive marker of cardiovascular risk. The non-invasive measurement of PWV requires tracking the arrival time of pressure pulses recorded in vivo, commonly referred to as pulse arrival time (PAT). In the state of the art, PAT is estimated by identifying a characteristic point of the pressure pulse waveform. This paper demonstrates that for ambulatory scenarios, where signal-to-noise ratios are below 10 dB, the performance in terms of repeatability of PAT measurements through characteristic points identification degrades drastically. Hence, we introduce a novel family of PAT estimators based on the parametric modeling of the anacrotic phase of a pressure pulse. In particular, we propose a parametric PAT estimator (TANH) that depicts high correlation with the Complior(R) characteristic point D1 (CC = 0.99), increases noise robustness and reduces by a five-fold factor the number of heartbeats required to obtain reliable PAT measurements.
  Physiological Measurement 08/2009; 30(7):603-15.
• Article: Quantitative myotonia assessment using force relaxation curve modelling.

  J-Y Hogrel
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  ABSTRACT: The lack of a robust quantitative measure of myotonia has been underlined in previous studies. Recent publications have proposed methods to quantify myotonia based on the measurement of force relaxation times during maximal contractions. However, they present several drawbacks mainly due to unstable force, odd peaks or digital noise. A possible solution to this issue consists in fitting the force curve with a convenient regression model. The aim of this study was, therefore, to provide a regression model in order to fit the force relaxation time curve automatically and to provide a robust index for quantitative assessment of myotonia in clinical settings. Force curves were fitted by an asymmetric sigmoidal function. The inverse function was then used to compute various absolute and relative relaxation times automatically. These variables were calculated for 16 controls and 16 patients with myotonic dystrophy type 1 (DM1). All variables were significantly increased in DM1 patients compared to controls. For instance, the relaxation time between 40 and 60% of the initial contraction level was 18.2 (SD: 3.3) ms in controls and 40.1 (SD: 17.7) ms in DM1 patients. All relaxation variables were highly discriminant. Force curve modelling provides an objective and effective quantification of myotonia.
  Physiological Measurement 08/2009; 30(7):719-27.
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  Available from: univ-angers.fr

  Article: Multifractal analysis of central (electrocardiography) and peripheral (laser Doppler flowmetry) cardiovascular time series from healthy human subjects.

  Anne Humeau, Benjamin Buard, François Chapeau-Blondeau, David Rousseau, Guillaume Mahe, Pierre Abraham
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  ABSTRACT: Analysis of the cardiovascular system (CVS) activity is important for several purposes, including better understanding of heart physiology, diagnosis and forecast of cardiac events. The central CVS, through the study of heart rate variability (HRV), has been shown to exhibit multifractal properties, possibly evolving with physiologic or pathologic states of the organism. An additional viewpoint on the CVS is provided at the peripheral level by laser Doppler flowmetry (LDF), which enables local blood perfusion monitoring. We report here for the first time a multifractal analysis of LDF signals through the computation of their multifractal spectra. The method for estimation of the multifractal spectra, based on the box method, is first described and tested on a priori known synthetic multifractal signals, before application to LDF data. Moreover, simultaneous recordings of both central HRV and peripheral LDF signals, and corresponding multifractal analyses, are performed to confront their properties. With the scales chosen on the partition functions to compute Renyi exponents, LDF signals appear to have broader multifractal spectra compared to HRV. Various conditions for LDF acquisitions are tested showing larger multifractal spectra for signals recorded on fingers than on forearms. The results uncover complex interactions at central and peripheral CVS levels.
  Physiological Measurement 08/2009; 30(7):617-29.