Reliability of the determination of the ventilatory threshold in patients with COPD

Purpose The ventilatory threshold (VT) is a physiological turning point that can be used to guide for exercise prescription, as a tool to monitor response to an intervention and as a prognostic marker, but the presence of respiratory disease may limit the reliability of its measurement. This project aimed to determine the reliability of the assessment of the ventilatory threshold among human and computerized observers, in patients with chronic obstructive pulmonary disease (COPD) and controls. Methods VT was identified from incremental exercise testing graphs of 115 subjects (23 controls and 23 in each COPD severity class) by two human observers and a computer analysis, using the V-slope method and the VEM. Agreement between observers for VO2 at VT (VO2VT) and heart rate at VT (HRVT) were evaluated using intra-class correlation (ICC) for humans and Passing-Bablok regression analysis (human vs computer). Results For humans, ICCs for VO2VT were higher in controls [0.98 (0.97-0.99) both with V-slope and with VEM] than in COPD patients [0.72 (0.60-0.81) with V-slope and 0.64 (0.50-0.74) with VEM]. Human and computerized values of VO2VT were interchangeable in controls, but not in COPD patients. FEV1 and peak-ventilation were independent predictors of a lesser reliability of VO2VT. Inter-observer differences in HRVT ranged from 2±1 beats/minute (controls) to 10±3 beats/minute (GOLD 4). Conclusions In COPD, the reliability of human estimation of VO2VT is less in than in controls and not interchangeable with a computerized analysis. This should be taken into account when using VT in the clinical and research settings

Physiological Validation of an Airborne Ultrasound Based Surface Motion Camera for a Contactless Characterization of Breathing Pattern in Humans

Characterizing the breathing pattern in naturally breathing humans brings important information on respiratory mechanics, respiratory muscle, and breathing control. However, measuring breathing modifies breathing (observer effect) through the effects of instrumentation and awareness: measuring human breathing under true ecological conditions is currently impossible. This study tested the hypothesis that non-contact vibrometry using airborne ultrasound (SONAR) could measure breathing movements in a contactless and invisible manner. Thus, first, we evaluated the validity of SONAR measurements by testing their interchangeability with pneumotachograph (PNT) measurements obtained at the same time. We also aimed at evaluating the observer effect by comparing breathing variability obtained by SONAR versus SONAR-PNT measurements. Twenty-three healthy subjects (12 men and 11 women; mean age 33 years – range: 20–54) were studied during resting breathing while sitting on a chair. Breathing activity was described in terms of ventilatory flow measured using a PNT and, either simultaneously or sequentially, with a SONAR device measuring the velocity of the surface motion of the chest wall. SONAR was focused either anteriorly on the xiphoid process or posteriorly on the lower part of the costal margin. Discrete ventilatory temporal and volume variables and their coefficients of variability were calculated from the flow signal (PNT) and the velocity signal (SONAR) and tested for interchangeability (Passing-Bablok regression). Tidal volume (VT) and displacement were linearly related. Breathing frequency (BF), total cycle time (TT), inspiratory time (TI), and expiratory time (TE) met interchangeability criteria. Their coefficients of variation were not statistically significantly different with PNT and SONAR-only. This was true for both the anterior and the posterior SONAR measurements. Non-contact vibrometry using airborne ultrasound is a valid tool for measuring resting breathing pattern

Extraction and analysis of T waves in electrocardiograms during atrial flutter

Analysis of T waves in the electrocardiogram (ECG) is an essential clinical tool for diagnosis, monitoring and followup of patients with heart dysfunction. During atrial flutter, this analysis has been so far limited by the perturbation of flutter waves superimposed over the T wave. This paper presents a method based on missing data interpolation for eliminating flutter waves from the ECG during atrial flutter. To cope with the correlation between atrial and ventricular electrical activations, the CLEAN deconvolution algorithm was applied to reconstruct the spectrum of the atrial component of the ECG from signal segments corresponding to TQ intervals. The location of these TQ intervals, where the atrial contribution is presumably dominant, were identified iteratively. The algorithm yields the extracted atrial and ventricular contributions to the ECG. Standard T-wave morphology parameters (T-wave amplitude, T peak – T end duration, QT interval) were measured. This technique was validated using synthetic signals, compared to average beat subtraction in a patient with a pacemaker and tested on pseudo-orthogonal ECGs from patients in atrial flutter. Results demonstrated improvements in accuracy and robustness of T-wave analysis as compared to current clinical practice

Evaluation of a subject-specific transfer-function-based nonlinear QT interval rate-correction method

The QT interval in the electrocardiogram (ECG) is a measure of total duration of depolarization and repolarization. Correction for heart rate is necessary to provide a single intrinsic physiological value that can be compared between subjects and within the same subject under different conditions. Standard formulas for the corrected QT (QTc) do not fully reproduce the complexity of the dependence in the preceding interbeat intervals (RR) and inter-subject variability. In this paper, a subject-specific, nonlinear, transfer function-based correction method is formulated to compute the QTc from Holter ECG recordings. The model includes five parameters: three describing the static QT–RR relationship and two representing memory/hysteresis effects that intervene in the calculation of effective RR values. The parameter identification procedure is designed to minimize QTc fluctuations and enforce zero correlation between QTc and effective RR. Weighted regression is used to better handle unbalanced or skewed RR distributions. The proposed optimization approach provides a general mathematical framework for further extensions of the model. Validation, robustness evaluation and comparison with existing QT correction formulas is performed on ECG signals recorded during sinus rhythm, atrial pacing, tilt-table tests, stress tests and atrial flutter (29 subjects in total). The resulting average modeling error on the QTc is 4.9 ± 1.1 ms with a sampling interval of 2 ms, which outperforms correction formulas currently used. The results demonstrate the benefits of subject-specific rate correction and hysteresis reduction

Eliciting Awe in the Spectator: The Case of a Dhrupad-Based Dance Performance

This paper describes “Kalos, eîdos, skopeîn,” an immersive Dhrupad-based dance installation designed to elicit feelings of awe in the spectators, in a real-life artistic context. This study used a mixed-methods approach in order to explore spectators’ awe experience (N=45), using specific scales and interpretative phenomenological analysis. Results suggested that “Kalos, eîdos, skopeîn,” with its combination of nature motifs and the slow dance-walk associated with the Dhrupad music in the choreography, was able to produce awe-related moments in some spectators and inspire a degree of positive emotions. Our qualitative results viewed awe explicitly as a positive emotion and showed that generally the spectator narratives, involving the whole performance, were based on modified states of consciousness. Three themes emerged: the main theme is “A rich experience of modified states of consciousness” involving the whole performance, and two interconnected sub-themes “Captivated by the slowness of the dancers” associated with the slow movement and “I can still hear the mantra in my head” in rapport with Dhrupad music. This study was carried out as part of the Canadian FRQSC/FCI Project (2019-RC2-260306)

Eliciting Awe in the Spectator: The Case of a Dhrupad-Based Dance Performance

This paper describes “Kalos, eîdos, skopeîn,” an immersive Dhrupad-based dance installation designed to elicit feelings of awe in the spectators, in a real-life artistic context. This study used a mixed-methods approach in order to explore spectators’ awe experience (N=45), using specific scales and interpretative phenomenological analysis. Results suggested that “Kalos, eîdos, skopeîn,” with its combination of nature motifs and the slow dance-walk associated with the Dhrupad music in the choreography, was able to produce awe-related moments in some spectators and inspire a degree of positive emotions. Our qualitative results viewed awe explicitly as a positive emotion and showed that generally the spectator narratives, involving the whole performance, were based on modified states of consciousness. Three themes emerged: the main theme is “A rich experience of modified states of consciousness” involving the whole performance, and two interconnected sub-themes “Captivated by the slowness of the dancers” associated with the slow movement and “I can still hear the mantra in my head” in rapport with Dhrupad music. This study was carried out as part of the Canadian FRQSC/FCI Project (2019-RC2-260306)

Assessing Communities of Practice in health policy : A conceptual framework as a first step towards empirical research

Peer reviewe

Cardiac anisotropy in boundary-element models for the electrocardiogram

The boundary-element method (BEM) is widely used for electrocardiogram (ECG) simulation. Its major disadvantage is its perceived inability to deal with the anisotropic electric conductivity of the myocardial interstitium, which led researchers to represent only intracellular anisotropy or neglect anisotropy altogether. We computed ECGs with a BEM model based on dipole sources that accounted for a “compound” anisotropy ratio. The ECGs were compared with those computed by a finite-difference model, in which intracellular and interstitial anisotropy could be represented without compromise. For a given set of conductivities, we always found a compound anisotropy value that led to acceptable differences between BEM and finite-difference results. In contrast, a fully isotropic model produced unacceptably large differences. A model that accounted only for intracellular anisotropy showed intermediate performance. We conclude that using a compound anisotropy ratio allows BEM-based ECG models to more accurately represent both anisotropies

Nicotinic Receptor Gene CHRNA4 Interacts with Processing Load in Attention

Background: Pharmacological studies suggest that cholinergic neurotransmission mediates increases in attentional effort in response to high processing load during attention demanding tasks [1]. Methodology/Principal Findings: In the present study we tested whether individual variation in CHRNA4, a gene coding for a subcomponent in a4b2 nicotinic receptors in the human brain, interacted with processing load in multiple-object tracking (MOT) and visual search (VS). We hypothesized that the impact of genotype would increase with greater processing load in the MOT task. Similarly, we predicted that genotype would influence performance under high but not low load in the VS task. Two hundred and two healthy persons (age range = 39–77, Mean = 57.5, SD = 9.4) performed the MOT task in which twelve identical circular objects moved about the display in an independent and unpredictable manner. Two to six objects were designated as targets and the remaining objects were distracters. The same observers also performed a visual search for a target letter (i.e. X or Z) presented together with five non-targets while ignoring centrally presented distracters (i.e. X, Z, or L). Targets differed from non-targets by a unique feature in the low load condition, whereas they shared features in the high load condition. CHRNA4 genotype interacted with processing load in both tasks. Homozygotes for the T allele (N = 62) had better tracking capacity in the MOT task and identified targets faster in the high load trials of the VS task. Conclusion: The results support the hypothesis that the cholinergic system modulates attentional effort, and that commo