Upper Limits Of Agreement Research Articles

Consuming a low-calorie amount of routine food and drink does not affect bioimpedance body fat percentage in healthy individuals

Objectives: Bioimpedance analysis is a simple, safe, and relatively inexpensive method to assess body composition. The bioimpedance guidelines recommend that the test be performed after fasting and avoiding the consumption of liquids. Studies have verified the effects of consuming liquids and food on bioimpedance; however, these studies used preestablished meals and hydration. The aim of the present study is to identify whether ad libitum food and liquid intake interfere with body composition parameters estimated via bioimpedance. MethodsThe evaluations were carried out over 2 d. On the first d, the hydration protocol was applied and on the second d, the food protocol. In both cases, bioimpedance was performed after an 8-h overnight fast. The test was repeated 30 min after the intake of liquids or food depending on the protocol. The reproducibility between the pre- and posttest evaluations was assessed using the Bland–Altman method. We considered deviations of up to 5% in the limits of agreement to be clinically acceptable. ResultsIn the hydration protocol, the mean difference in fat percentage (FP) was –0.50 (P = 0.05), the lower limit of agreement was –3.60%, and the upper limit of agreement was 2.61%. In the food protocol, the mean difference in FP was 0.002 (P = 0.99), the lower limit of agreement was –3.20%, and the upper limit of agreement was 3.20%. ConclusionsOur study shows that ad libitum food and liquid intake do not cause a change above clinically acceptable levels in the FP estimated by bioimpedance.

Evaluation of the accuracy of a non-invasive hemoglobin-monitoring device in schoolchildren

Iron deficiency anemia (IDA) is a public health problem in children and adolescents that is characterized by reduced hemoglobin (Hb) levels. Non-invasive monitoring devices can measure Hb levels continuously without pain or discomfort; however, little is known about their accuracy in children and adolescents. This study estimated the accuracy of a non-invasive Hb monitor in this age group. Participants were outpatients visiting the Tokyo Metropolitan Children's Medical Center for blood tests between January and March 2019. Hb levels were measured using both non-invasive Astrim Fit monitoring devices and invasive blood collection followed by automated analysis. Bland-Altman analysis assessed the agreement between the two measurements. Overall, 120 schoolchildren (9-15 years old, 51% female) were enrolled. The non-invasive measuring device recorded Hb levels of 13.5±1.6g/dL (mean±standard deviation [SD]), while the mean Hb level obtained from the collected blood was 13.7±1.7g/dL. Therefore, the mean difference of bias and SD of precision was 0.17±1.95g/dL. Values of lower and upper limits of agreement were -3.65 and 3.99, respectively. There was no systematic fixed or proportion bias. Fifty-nine participants (49%) had a relative error of ± 0.10. The Astrim Fit non-invasive Hb monitor can be used to evaluate Hb levels among schoolchildren for health promotion or research purposes because of its extremely low bias (or precision), no systematic biases (including fixed or proportion biases), and positive correlation between non-invasive monitoring and blood drawing. However, it is difficult to assess Hb levels in children and adolescents using the Astrim Fit device for diagnostic purposes.

Comparison of Quantitative Flow Ratio and Invasive Physiology Indices in a Diverse Population at a Tertiary United States Hospital

BackgroundQuantitative flow ratio (QFR) is a technology to evaluate the coronary stenosis significance on 3-dimensional quantitative coronary angiography. The aim of this study is to evaluate and compare the QFR versus fractional flow reserve (FFR) and/or instantaneous free-wave ratio (iFR) in a US population with a fair African American population representation. Methods and resultsThis was a retrospective, observational and single-center study that enrolled 100 patients who underwent coronary angiography. The diagnostic performance of QFR in terms of sensitivity was 0.80 (95%CI 0.64–0.97) and specificity was 0.95 (95% CI 0.90–1.00), the positive predictive value (PPV) was 0.83 (0.68–0.98), while the negative predictive value (NPV) was 0.94 (0.88–0.99). The overall accuracy was 0.91 and area under the curve (AUC) was 0.92 (95% CI 0.87–0.97).The R-squared was 0.54 and the Bland-Altman plot showed a bias of 0.0016 (SD 0.063) and limits of agreement (LOA): Upper LOA 0.13 and Lower LOA −0.12. In African Americans (n = 33), accuracy, AUC, sensitivity, specificity (94%; 0.90 [0.80–1.00]; 0.90 [0.71–1.00]; 0.96 [0.87–1.00], respectively) were better than those for the overall population. ConclusionsIn a US-based representative population, vessel QFR accuracy and agreement with FFR as reference is high. Diagnostic performance of QFR in African Americans is also excellent.

App-Based Versus Standard Six-Minute Walk Test in Pulmonary Hypertension: Mixed Methods Study.

BackgroundPulmonary arterial hypertension (PAH) is a chronic disease of the pulmonary vasculature that can lead to heart failure and premature death. Assessment of patients with PAH includes performing a 6-minute walk test (6MWT) in clinics. We developed a smartphone app to compute the walked distance (6MWD) indoors, by counting U-turns, and outdoors, by using satellite positioning.ObjectiveThe goal of the research was to assess (1) accuracy of the indoor 6MWTs in clinical settings, (2) validity and test-retest reliability of outdoor 6MWTs in the community, (3) compliance, usability, and acceptance of the app, and (4) feasibility of pulse oximetry during 6MWTs.MethodsWe tested the app on 30 PAH patients over 6 months. Patients were asked to perform 3 conventional 6MWTs in clinic while using the app in the indoor mode and one or more app-based 6MWTs in outdoor mode in the community per month.ResultsBland-Altman analysis of 70 pairs of conventional versus app-based indoor 6MWDs suggests that the app is sometimes inaccurate (14.6 m mean difference, lower and upper limit of agreement: –133.35 m to 162.55 m). The comparison of 69 pairs of conventional 6MWDs and community-based outdoor 6MWDs within 7 days shows that community tests are strongly related to those performed in clinic (correlation 0.89), but the interpretation of the distance should consider that differences above the clinically significant threshold are not uncommon. Analysis of 89 pairs of outdoor tests performed by the same patient within 7 days shows that community-based tests are repeatable (intraclass correlation 0.91, standard error of measurement 36.97 m, mean coefficient of variation 12.45%). Questionnaires and semistructured interviews indicate that the app is usable and well accepted, but motivation to use it could be affected if the data are not used for clinical decision, which may explain low compliance in 52% of our cohort. Analysis of pulse oximetry data indicates that conventional pulse oximeters are unreliable if used during a walk.ConclusionsApp-based outdoor 6MWTs in community settings are valid, repeatable, and well accepted by patients. More studies would be needed to assess the benefits of using the app in clinical practice.Trial RegistrationClinicalTrials.gov NCT04633538; https://clinicaltrials.gov/ct2/show/NCT04633538

The use of electrical impedance tomography (EIT) to evaluate pulse rate in anaesthetised horses

Electrical impedance tomography (EIT) provides clinically useful lung images; however, it would be an advantage to extract additional cardiovascular information from the data. The aim of this study was to evaluate if cardiac-related changes measured by EIT can be used to measure pulse rate (PR) under physiological as well as high and low blood pressure states in anaesthetised horses. Electrical impedance tomography data and PR from seven horses anaesthetised in dorsal recumbency were recorded over 1 min during mechanical ventilation and 1 min of apnoea. Data were collected at four measurement time points; before and during intravenous administration of nitroprusside and phenylephrine, respectively. Nine pixels, estimated to represent the heart, were chosen from the EIT image. A novel algorithm detected peaks of impedance change for these pixels over 10 s intervals. Concurrent PR measured using an invasive blood pressure trace, was recorded every 10 s. EIT- and pulse-rate data were compared using Bland-Altman assessment for multiple measurements on each horse.Overall, 288 paired datasets from six of seven horses were available for analysis. There was excellent agreement for baseline measurements, as well as during hypertension and hypotension, with a bias of −0.26 and lower and upper limit of agreement at −2.22 (95% confidence intervals [CI], −2.89 to −1.86) and 1.69 (95% CI, 1.34–2.36) beats per min, respectively. EIT can be used to evaluate PR using cardiac-related impedance changes. More work is required to determine bias that might occur in anaesthetised horses in other recumbencies or clinical situations.

Accuracy of dual-energy x-ray absorptiometry for assessing longitudinal change in visceral adipose tissue in patients with coronary artery disease.

Visceral adipose tissue (VAT) is a key target of interventions for obesity-related diseases. Dual-energy x-ray absorptiometry (DXA) can estimate VAT, however its accuracy to measure longitudinal change in VAT compared to gold-standard techniques such as magnetic resonance imaging (MRI), has not been studied in adults. This study aimed to determine the accuracy of DXA compared with gold-standard MRI for cross-sectional VAT assessment, and for detecting longitudinal change in VAT. Adults with coronary artery disease (64 ± 8 years; BMI 27.8 ± 3.5 kg/m2; 88% male) were assessed for VAT by DXA and MRI at baseline (n = 34) and during implementation of an exercise intervention study at 3- and 12-months (n = 29). To match the 5.2 cm DXA measurement site for Hologic software (InnerCoreTM), VAT cross-sectional area (CSA) was measured by MRI using a single slice at L4/L5 junction, and VAT volume measured by 10 × 5 mm slices over the L4/L5 junction. MRI slices were quantified for VAT using semi-automated specialised software. Relationships between DXA and MRI for cross-sectional VAT and longitudinal change in VAT were determined by linear regression. Accuracy between the methods was assessed by Bland-Altman analysis, with data presented as mean difference (95% confidence interval), lower and upper limits of agreement (LoA). Strong correlations were found between DXA-VAT and MRI-VAT at baseline (r = 0.90; p < 0.001), and longitudinal change in DXA-VAT and MRI-VAT over 3- and 12-months (r = 0.67; p < 0.001). In contrast, Bland-Altman analysis revealed significant overestimation by DXA-VAT volume at baseline by 13% [-104 cm3 (-157, -52 cm3), p < 0.001; LoA (-398, 189 cm3)], and underestimation of change in DXA-VAT volume over 3-months by 33% [-41 cm3 (-77, -4 cm3), p = 0.030; LoA (-228, 147 cm3)] and 12-months by 47% [-65 cm3 (-114, -17 cm3), p = 0.010; LoA (-316, 185 cm3)]. Results were similar for VAT CSA. Compared with MRI, DXA substantially underestimated longitudinal changes in VAT. Therefore, DXA is not currently a valid alternative to MRI for quantifying VAT changes and may under-represent the effectiveness of interventions for obesity management.

Estimation of cardiac output variations induced by hemodynamic interventions using multi-beat analysis of arterial waveform: a comparative off-line study with transesophageal Doppler method during non-cardiac surgery

Multi-beat analysis (MBA) of the radial arterial pressure (AP) waveform is a new method that may improve cardiac output (CO) estimation via modelling of the confounding arterial wave reflection. We evaluated the precision and accuracy using the trending ability of the MBA method to estimate absolute CO and variations (ΔCO) during hemodynamic challenges. We reviewed the hemodynamic challenges (fluid challenge or vasopressors) performed when intra-operative hypotension occurred during non-cardiac surgery. The CO was calculated offline using transesophageal Doppler (TED) waveform (COTED) or via application of the MBA algorithm onto the AP waveform (COMBA) before and after hemodynamic challenges. We evaluated the precision and the accuracy according to the Bland & Altman method. We also assessed the trending ability of the MBA by evaluating the percentage of concordance with 15% exclusion zone between ΔCOMBA and ΔCOTED. A non-inferiority margin was set at 87.5%. Among the 58 patients included, 23 (40%) received at least 1 fluid challenge, and 46 (81%) received at least 1 bolus of vasopressors. Before treatment, the COTED was 5.3 (IQR [4.1–8.1]) l min−1, and the COMBA was 4.1 (IQR [3–5.4]) l min−1. The agreement between COTED and COMBA was poor with a 70% percentage error. The bias and lower and upper limits of agreement between COTED and COMBA were 0.9 (CI95 = 0.82 to 1.07) l min−1, −2.8 (CI95 = −2.71 to−2.96) l min−1 and 4.7 (CI95 = 4.61 to 4.86) l min−1, respectively. After hemodynamic challenge, the percentage of concordance (PC) with 15% exclusion zone for ΔCO was 93 (CI97.5 = 90 to 97)%. In this retrospective offline analysis, the accuracy, limits of agreements and percentage error between TED and MBA for the absolute estimation of CO were poor, but the MBA could adequately track induced CO variations measured by TED. The MBA needs further evaluation in prospective studies to confirm those results in clinical practice conditions.

Self-navigated 3D whole-heart MRA for non-enhanced surveillance of thoracic aortic dilation: a comparison to CTA

Abstract Funding Acknowledgements Type of funding sources: None. Background The natural history of thoracic aortic aneurysm (TAA) is one of progressive expansion. Asymptomatic patients who do not meet criteria for repair require conservative management including ongoing aneurysm surveillance, mostly carried out by contrast-enhanced computed tomography angiography (CTA). Purpose To prospectively compare image quality and reliability of a prototype non-contrast, self-navigated 3D whole-heart magnetic resonance angiography (MRA) with contrast-enhanced computed tomography angiography (CTA) for sizing of thoracic aortic aneurysm (TAA). Methods Self-navigated 3D whole-heart 1.5 T MRA was performed in 20 patients (aged 67 ± 8.6 years, 75% male) for sizing of TAA; a subgroup of 18 (90%) patients underwent additional contrast-enhanced CTA on the same day. Subjective image quality was scored according to a 4-point Likert scale and ratings between observers were compared by Cohen’s Kappa statistics. Continuous MRA and CTA measurements were analyzed with regression and Bland-Altman analysis. Results Overall subjective image quality as rated by two observers was 1 [interquartile range (IQR) 1-2] for self-navigated MRA and 1.5 [IQR 1-2] for CTA (p = 0.717). For MRA a perfect inter-observer agreement was found for presence of artefacts and subjective image sharpness (κ=1). Subjective signal inhomogeneity correlated highly with objectively quantified inhomogeneity of the blood pool signal (r = 0.78-0.824, all p &amp;lt;0.0001). Maximum diameters of TAA as measured by self-navigated MRA and CTA showed excellent correlation (r = 0.997, p &amp;lt; 0.0001) without significant inter-method bias (bias -0.0278, lower and upper limit of agreement -0.74 and 0.68, p = 0.749). Inter- and intraobserver correlation of aortic aneurysm as measured by MRA was excellent (r = 0.963 and 0.967, respectively) without significant bias (all p ≤ 0.05). Conclusion Self-navigated 3D whole-heart MRA enables reliable contrast- and radiation free aortic dilation surveillance without significant difference to standardized CTA while providing predictable acquisition time and by offering excellent image quality. Abstract Figure.

Application of a machine learning contouring tool for the evaluation of left ventricular strain in clinical practice

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): AK has been funded by the Egyptian cultural centre and educational bureau of the Egyptian embassy in London and the Ministry of higher education in Egypt. SEP acknowledges support from the “SmartHeart” EPSRC programme grant (www.nihr.ac.uk; EP/P001009/1) and the London Medical Imaging and AI Centre for Value-Based Healthcare. This new centre is one of the UK Centres supported by a £50m investment from the Data to Early Diagnosis and Precision Medicine strand of the government’s Industrial Strategy Challenge Fund, managed and delivered by UK Research and Innovation (UKRI). SEP acknowledges support from the CAP-AI programme, London’s first AI enabling programme focused on stimulating growth in the capital’s AI Sector. CAP-AI is led by Capital Enterprise in partnership with Barts Health NHS Trust and Digital Catapult and is funded by the European Regional Development Fund and Barts Charity. SEP also acts as a paid consultant to Circle Cardiovascular Imaging Inc., Calgary, Canada and Servier onbehalf Barts Heart Centre, St Bartholomew’s Hospital, Barts Health NHS Trust, West Smithfield, London, UK Background Manual contouring of cardiovascular magnetic resonance (CMR) cine images remains common practice and the reference standard for left ventricular (LV) volumes and mass evaluation. However, it is time-consuming and machine learning (ML) may significantly reduce the time required for contouring. Accurate LV contours are the basis for reliable LV strain analysis using tissue tracking. Purpose To assess the impact of a ML contouring tool alone versus expert adjusted contours on LV strain. Methods We retrospectively selected 402 CMR studies with diagnoses of myocardial infarction (n = 108), myocarditis (n = 130) and healthy controls (n = 164) from the Barts BioResource between January 2015 to June 2018. CMR examinations were obtained using 1.5T and 3T scanners (Siemens Healthineers, Germany). We excluded 32 cases due to phase inconsistency between short (SAX) and long axes (LAX) cine images or suboptimal cine image quality. For the remaining 370 cases, steady state free precession cine images for LAX and SAX were analysed by the ML contouring tool (using CVI42 research prototype software 5.11). Manual expert adjustment for the contours was done for each case if considered suboptimal for strain analysis in the reference end-diastolic phase. Strain results from ML and expert adjusted ML methods were compared for strain agreement. Times taken by these methods were recorded and compared against the time taken for standard manual contouring. Results SAX and LAX derived strains by ML and expert adjusted ML methods showed good agreement by Bland-Altman analysis (Figure 1) with excellent coefficient of concordance using Kendall W which is 0.98 for global SAX, radial and circumferential strains (mean difference(MD) = -1.7% (lower and upper limits of agreement (UL,LL) -6.6,3.2), MD = 0.5% (-1.0,2.1)) and is 0.95 for global LAX derived strain (radial and longitudinal, MD = 0.7% (UL,LL -8.7 ,7.4),MD= 0.2% (-1.9,2.5), respectively). Time taken for adjustment of ML contours was significantly shorter than manual contouring (1.35 minutes vs 8.0 minutes, around 590% time saving in ML adjusted method). Conclusions ML contouring compared to expert manual adjustment has a clinically reasonable agreement when used for measuring LV strain. Also, using the ML tool with expert adjustment shows significant time saving for analysis and reporting time compared to entirely manual analysis, favouring its application in routine clinical practice. Abstract Figure.

Cervical tooth anatomy considerations for prefabricated anatomic healing abutment design: A mathematical formulation

Statement of problemA custom emergence profile offers the ideal horizontal dimensions for an anatomic healing abutment. However, developing such an emergence profile can be a time-consuming and complex process. PurposeThe purpose of this study was to develop a mathematical formula defining horizontal cervical tooth geometry to design prefabricated, tooth-specific, healing abutments. Material and methodsCone beam computed tomography (CBCT) horizontal cross sections of 989 teeth on 54 participants were measured. For anterior and premolar teeth, 2 perpendicular ellipses were fitted onto the cervical tooth cross section that was defined by 3 parameters. The lingual ellipse followed the lingual outline of the tooth, and its diameter was the largest mesiodistal diameter of the tooth (parameter “a”); its buccolingual radius became parameter “b.” The buccal ellipse was perpendicular to the lingual ellipse and followed the buccal outline of the tooth. The buccolingual radius of the smaller ellipse became parameter “c.” For molars, the first ellipses followed the mesial outline of the tooth, and its larger diameter (parameter “a”) matched the largest buccolingual diameter of the tooth. Its smaller radius became parameter “h1.” The second ellipse was parallel to the first ellipse and followed the distal outline of the tooth. Its larger diameter became parameter “b”, and its mesiodistal diameter became parameter “h2”. Statistical differences between parameters were evaluated by the linear mixed model (α=.05 after Bonferroni adjustment). Pairwise comparisons were made separately for each parameter of the molars and separately for each parameter for the anterior teeth plus premolars. Teeth were put into the same parameter cluster if no significant differences were found between them for a specific parameter. If neither parameter (4 for molars and 3 for the other teeth) was different for 2 teeth, they were put into the same abutment cluster. The abutment clusters determined the type of anatomic healing abutment. The areas were calculated from the developed mathematical formula by using the parameters. In addition, cervical areas of 106 randomly chosen teeth were measured directly with a photo-editing software program. A computer algorithm was used to select 5 CBCT scans from the 54 by using the simple randomization method. The agreement between the 2 methods was evaluated by Bland-Altman analysis. ResultsThe lower and upper limits of agreement between the 2 methods were -8.57 and 7.36 mm2, respectively, with no bias (-0.61 mm2, P=.224). Significant differences were found between most parameters among the 14 tooth types (P<.001). Based on the parameters, 12 specifically distinct clusters were defined. Two tooth types were pooled into 1 abutment cluster: the maxillary first and second premolars and the mandibular first and second molars. ConclusionsThe cervical tooth cross section can be accurately defined by combining 2 elliptical elements. A comprehensive array of tooth specific emergence profiles can be provided by just 12 different prefabricated abutments, designed as per the recommended parameters.

Correlation between Central Venous Pressure and Peripheral Venous Pressure in Medical Intensive Care Unit Patients

Introduction: Central venous pressure (CVP) is a hemodynamic variable commonly used in the intensive care setting to estimate right arterial pressure for evaluation and monitoring a patient's volume status. Risks such as infection, arterial puncture, hematoma, and pneumothorax associated with central venous cannulation can outweigh its benefits. This study was undertaken to determine if peripheral venous pressure (PVP) predicts CVP in medical intensive care unit (ICU) patients. Materials and Methods: This study was conducted on patients admitted to the medical ICU at AlJamhoriya Teaching Hospital in the period from January to September 2009. Sixty-six patients (aged 40–70 years) who were required a central venous line (CVL) were included prospectively in the study. CVP measured through internal jugular vein or subclavian vein by three ways CVL set insertion; and CVL placement was confirmed by chest X-ray. We used the manometers for the measurement of PVP; and 66 paired recordings of CVP and PVP were made. The correlation and Bland-Altman analysis of agreement were performed. Results: The mean (standard deviation [SD]; range) CVP was 11.3778 cmH2O (±5.6; −1.0–27.0); the mean PVP was 15.80 cmH2O (±5.9; 0.0–33.0); offset (bias) of PVP &gt; CVP was 4.42 cmH2O with SD ± 3.62. The correlation of PVP on CVP was r = 0.8059, (r 2 = 0.65), P &lt; 0.0001. The 95% confidence intervals for the bias were 3.5352–5.3133 cmH2O. In the Bland-Altman analysis, lower and upper limits of agreement (95% LOA) were 2.7 (4.43–−7.20) and 11.63 (4.4–7.2) cmH2O. Four out of 66 points were outside the LOA. The dashed zero lies between the LOA. Conclusion: Measurement of PVP from both antecubital area and dorsum of the hand correlated with CVP measurement with acceptable agreement. PVP measurement may be a noninvasive alternative way for estimating CVP.

Testing the accuracy of a novel digital peak flow meter aligned with a smartphone app compared to a lab spirometer: A pilot work.

BackgroundA new digital peak flow meter, known as Smart Peak Flow (SPF), has been developed to monitor asthma patients’ peak expiratory flow (PEF) at home. It is connected wirelessly to any type of smartphone and it is used by asthma patients to self-monitor progress of their clinical condition. Thus evaluation of the SPF’s ability to provide accurate PEF values is essential. The aim of this pilot work was to provide preliminary in-vivo data about the measurement agreement between the SPF and a lab spirometer for a first time.MethodsPEF measurements were obtained by 9 healthy adults as this pilot work was terminated earlier than it was expected due to COVID-19 restrictions. PEF readings (n=27) were recorded by the comparable devices at the same time during three different expiratory maneuvers performed by each participant. The Bland and Altman plot was used to assess the agreement.ResultsGood agreement between the SPF and the lab spirometer was found with the mean bias being estimated 0.29 L/min. The lower and upper limits of agreement (LOA) were estimated 30.03 L/min and −30.61 L/min respectively.ConclusionDue to a small sample size, no firm conclusions can be drawn regarding the SPF’s accuracy. However the current promising results encourage further testing in the future.

Agreement between rebound (Icare ic200) and applanation tonometry (Perkins) in patients with primary congenital glaucoma.

To examine agreement between intraocular pressure (IOP) measurements made using the rebound tonometer Icare ic200 (RT200) and the Perkins handheld applanation tonometer (PAT) in patients with primary congenital glaucoma (PCG). The impacts of several covariables on measurements using the two devices were also assessed. Intraocular pressure measurements were made in a single session in 86 eyes of 86 patients with PCG (46 under anaesthesia, 40 in the office). The order was RT200 then PAT. The variables age, central corneal thickness (CCT), corneal state and anaesthesia were recorded in each patient. Data were compared by determining interclass correlation coefficients (ICC) for each tonometer and representing the differences detected as Bland-Altman plots. Effects of covariables were assessed through univariate and multivariate regression. Mean IOP difference between tonometers (RT200 minus PAT) was 1.26mmHg (95%: 0.22-2.31). Absolute agreement (ICC) was 0.73 (95% CI: 0.62-0.82). Lower and upper limits of agreement (95%) were -8.06mmHg (95% CI: -9.87 to -6.25) and 10.59mmHg (95% CI: 8.77-12.40), respectively. The tonometers showed systematic differences (a=-4.63mmHg; 95% CI: -9.11 to -1.44) and proportional differences; for each mmHg increase in PAT-IOP, the RT200 reading increased by 1.28mmHg (b=1.28; 95% CI: 1.12-1.53). None of the variables tested as predictors were able to explain differences between the tonometers. Despite the good overall agreement between both tonometers, caution should be taken in high values of IOP, considering the interchangeability of its readings as systematic and proportional differences appear to exist between both methods.

Self-navigated 3D whole-heart MRA for non-enhanced surveillance of thoracic aortic dilation: A comparison to CTA

PurposeTo prospectively compare image quality and reliability of a non-contrast, self-navigated 3D whole-heart magnetic resonance angiography (MRA) sequence with contrast-enhanced computed tomography angiography (CTA) for sizing of thoracic aortic aneurysm (TAA). MethodsSelf-navigated 3D whole-heart 1.5 T MRA was performed in 20 patients (aged 67 ± 9 years, 75% male) for sizing of TAA; a subgroup of 18 (90%) patients underwent additional contrast-enhanced CTA on the same day. Subjective image quality was scored according to a 4-point Likert scale and ratings between observers were compared by Cohen's Kappa statistics. For MRA, subjective motion blurring and signal inhomogeneity was rated according to a 3-point scale, respectively. Objective signal inhomogeneity of MRA was quantified as standard deviation of the voxel intensities in a circular region of interest (ROI) placed in the ascending aorta divided by their mean value. Continuous MRA and CTA measurements were analyzed with regression and Bland-Altman analysis. ResultsOverall subjective image quality as rated by two observers was 1 [interquartile range (IQR) 1–2] for self-navigated MRA and 1.5 [IQR 1–2] for CTA (p = 0.717). For MRA, perfect inter-observer agreement was found regarding presence of artefacts and subjective image sharpness (κ = 1). Subjective signal inhomogeneity agreed moderately between the observers (κ = 0.58, p = 0.007), however, it correlated strongly with objectively quantified inhomogeneity of the blood pool signal (r = 0.78, p < 0.0001). Maximum diameters of TAA as measured by self-navigated MRA and CTA showed very strong correlation (r = 0.99, p < 0.0001) without significant inter-method bias (bias −0.03 mm, lower and upper limit of agreement −0.74 and 0.68 mm, p = 0.749). Inter-observer correlation of aortic aneurysm as measured by MRA was very strong (r = 0.96) without significant bias (p = 0.695). ConclusionSelf-navigated 3D whole-heart MRA enables reliable contrast- and radiation free aortic dilation surveillance without significant difference to standardized CTA while providing predictable acquisition time and offering excellent image quality.

A Textile Sleeve for Monitoring Oxygen Saturation Using Multichannel Optical Fibre Photoplethysmography.

Textile-based systems are an attractive prospect for wearable technology as they can provide monitoring of key physiological parameters in a comfortable and unobtrusive form. A novel system based on multichannel optical fibre sensor probes integrated into a textile sleeve is described. The system measures the photoplethysmogram (PPG) at two wavelengths (660 and 830 nm), which is then used to calculate oxygen saturation (SpO2). In order to achieve reliable measurement without adjusting the position of the garment, four plastic optical fibre (POF) probes are utilised to increase the likelihood that a high-quality PPG is obtained due to at least one of the probes being positioned over a blood vessel. Each probe transmits and receives light into the skin to measure the PPG and SpO2. All POFs are integrated in a stretchable textile sleeve with a circumference of 15 cm to keep the sensor in contact with the subject’s wrist and to minimise motion artefacts. Tests on healthy volunteers show that the multichannel PPG sensor faithfully provides an SpO2 reading in at least one of the four sensor channels in all cases with no need for adjusting the position of the sleeve. This could not be achieved using a single sensor alone. The multichannel sensor is used to monitor the SpO2 of 10 participants with an average wrist circumference of 16.0 ± 0.6 cm. Comparing the developed sensor’s SpO2 readings to a reference commercial oximeter (reflectance Masimo Radical-7) illustrates that the mean difference between the two sensors’ readings is −0.03%, the upper limit of agreement (LOA) is 0.52% and the lower LOA is −0.58%. This multichannel sensor has the potential to achieve reliable, unobtrusive and comfortable textile-based monitoring of both heart rate and SpO2 during everyday life.

Instrumental validity and intra/inter-rater reliability of a novel low-cost digital pressure algometer.

BackgroundPain assessment is a key measure that accompanies treatments in a wide range of clinical settings. A low-cost valid and reliable pressure algometer would allow objective assessment of pressure pain to assist a variety of health professionals. However, the pressure algometer is often expensive, which limits its daily use in both clinical and research settings.ObjectivesThis study aimed to assess the instrumental validity, and the intra- and inter-rater reliability of an inexpensive digital adapted pressure algometer.MethodsA single rater applied 60 random compressions on a force platform. The pressure pain thresholds of 20 volunteers were collected twice (3 days apart) by two raters. The main outcome measurements were as follows: the maximal peak force (in kPa) and the pressure pain threshold (adapted pressure algometer vs. force platform). Cronbach’s α test was used to assess internal consistency. The standard error of measurement provided estimates of measurement error, and the measurement bias was estimated with the Bland–Altman method, with lower and upper limits of agreement.ResultsNo differences were observed when comparing the compression results (P = 0.51). The validity and internal intra-rater consistencies ranged from 0.84 to 0.99, and the standard error of measurement from 0.005 to 0.04 kPa. Very strong (r = 0.73–0.74) to near-perfect (r = 0.99) correlations were found, with a low risk of bias for all measurements. The results demonstrated the validity and intra-rater reliability of the digitally adapted pressure algometer. Inter-rater reliability results were moderate (r = 0.55–0.60; Cronbach’s α = 0.71–0.75).ConclusionThe adapted pressure algometer provide valid and reliable measurements of pressure pain threshold. The results support more widespread use of the pressure pain threshold method among clinicians.

Validity of Hemodynamic Monitoring Using Inert Gas Rebreathing Method in Patients With Chronic Heart Failure and Those Implanted With a Left Ventricular Assist Device

ObjectiveThe present study assessed agreement between resting cardiac output estimated by inert gas rebreathing (IGR) and thermodilution methods in patients with heart failure and those implanted with a left ventricular assist device (LVAD). Methods and ResultsHemodynamic measurements were obtained in 42 patients, 22 with chronic heart failure and 20 with implanted continuous flow LVAD (34 males, aged 50 ± 11 years). Measurements were performed at rest using thermodilution and IGR methods. Cardiac output derived by thermodilution and IGR were not significantly different in LVAD (4.4 ± 0.9 L/min vs 4.7 ± 0.8 L/min, P = .27) or patients with heart failure (4.4 ± 1.4 L/min vs 4.5 ± 1.3 L/min, P = .75). There was a strong relationship between thermodilution and IGR cardiac index (r = 0.81, P = .001) and stroke volume index (r = 0.75, P = .001). Bland–Altman analysis showed acceptable limits of agreement for cardiac index derived by thermodilution and IGR, namely, the mean difference (lower and upper limits of agreement) for patients with heart failure –0.002 L/min/m2 (–0.65 to 0.66 L/min/m2), and –0.14 L/min/m2 (–0.78 to 0.49 L/min/m2) for patients with LVAD. ConclusionsIGR is a valid method for estimating cardiac output and should be used in clinical practice to complement the evaluation and management of chronic heart failure and patients with an LVAD.

An Enhanced Planar Linked Segment Model for Predicting Lumbar Spine Loads during Symmetric Lifting Tasks

The present technical note aimed at enriching the planar linked segment model originally proposed by Chaffin with the prediction of the moment arm and of the orientation of the line of action of the back extensor muscles during symmetric lifting tasks. The prediction equations proposed by van Dieen and de Looze for their single equivalent muscle model were used for such a purpose. Their prediction was based on the thorax-to-pelvis flexion angle as computed from 3D video-based motion capture. In order to make these prediction equations compliant with a two-dimensional analysis, the planar angle formed by the segment joining L5/S1 to the shoulder with the longitudinal axis of the pelvis was introduced. This newly computed planar trunk flexion angle was used to feed van Dieen and de Looze’s equations, comparing the results with the original model. A full-body Plug-in-Gait model relative to 10 subjects performing manual lifting activities using a stoop and a squat technique was used for model validation. A strong association was found between the proposed planar trunk flexion angle and that used by van Dieen and de Looze (r = 0.970). A strong association and a high level of agreement were found between the back extensor muscle moment arm (r = 0.965; bias &lt; 0.001 m; upper limit of agreement (LOA) = 0.002 m; lower LOA &lt; 0.001 m) and the orientation of the line of action (r = 0.970; bias = 2.8°; upper LOA = 5.3°; lower LOA = 0.2°) as computed using the two methods. For both the considered variables, the prediction error fell within the model sensitivity.

Comparison of cardiac output estimates by echocardiography and bioreactance at rest and peak dobutamine stress test in heart failure patients with preserved ejection fraction.

To assess the agreement between cardiac output estimated by two-dimensional echocardiography and bioreactance methods at rest and during dobutamine stress test in heart failure patients with preserved left ventricular ejection fraction (HFpEF). Hemodynamic measurements were assessed in 20 stable HFpEF patients (12 females; aged 61±7years) using echocardiography and bioreactance methods during rest and dobutamine stress test at increment dosages of 5, 10, 15, and 20μg/kg/min until maximal dose was achieved or symptoms and sign occurred, that is, chest pain, abnormal blood pressure elevation, breathlessness, ischemic changes, or arrhythmia. Resting cardiac output and cardiac index estimated by bioreactance and echocardiography were not significantly different. At peak dobutamine stress test, cardiac output and cardiac index estimated by echocardiography and bioreactance were significantly different (7.06±1.43 vs 5.71±1.59L/min, P<.01; and 4.27±0.67 vs 3.43±0.87L/m2 /min; P<.01) due to the significant differences in stroke volume. There was a strong positive relationship between cardiac outputs obtained by the two methods at peak dobutamine stress (r=.79, P<.01). The mean difference (lower and upper limits of agreement) between bioreactance and echocardiography cardiac outputs at rest and peak dobutamine stress was -0.45 (1.71 to -2.62)L/min and -1.35 (0.60 to -3.31)L/min, respectively. Bioreactance and echocardiography methods provide different cardiac output values at rest and during stress thus cannot be used interchangeably. Ability to continuously monitor key hemodynamic variables such as cardiac output, stroke volume, and heart rate is the major advantage of bioreactance method.

Evaluating The Validity Of Heart Rate Measured By The Suunto Spartan Sport Watch During Trail Running

PURPOSE: In the last decade or so, a plethora of fitness tracking devices have come to market. With this, use of these devices has increased exponentially. Among these devices’ many functions is the ability to monitor heart rate (HR). The purpose of this investigation was to determine if HR measured by the Suunto Spartan Sport watch was statistically comparable to that of our criterion, the Polar H7 HR monitor. METHODS: Twenty-one participants (male n = 11, female n = 10, age = 31±2 yrs [mean±SE], ht = 173±2 cm, wt = 76±3 kg) completed a two-mile trail run which included elevation changes of 48 m (McCullough Hills Trail, Henderson, NV), 55m (Three Peaks Trail, Cedar City, UT) or 104m (Bristlecone Trail, Mt Charleston, NV). Heart rate was obtained from the Suunto Spartan Sport watch with accompanying heart strap and the Polar H7 chest-worn heart rate monitor as the criterion reference. Validity was determined using the Mean Absolute Percent Error (MAPE), Bland-Altman analysis with accompanying bias and Limits of Agreement (LoA), and single measures Intraclass Correlations (ICC). A Pearson Product Moment Correlation Coefficient was used to determine the relationship between the validity measures with significance accepted at p<0.05. RESULTS: During uphill running, the MAPE was 1.46%, and the lower and upper LoA were -11.53 and 12.34, respectively. The single measures ICC was 0.95 with a 95% CI of 0.953 to 0.956 (F(14834, 14834) = 43.15, p < 0.000). During downhill running, the MAPE was 2.18% with the lower and upper LoA at -15.76 and 14.15, respectively. The single measures ICC was .94 with a 95% CI of 0.946 to 0.951 (F(9075, 9075) = 38.45, p < 0.000). CONCLUSIONS: These results demonstrate a there was a very low percentage of error for the Suunto Spartan Sport watch in recording HR for both uphill and downhill running. This suggests that The Suunto Spartan Sport might be a valid and reliable option for consumers wishing to monitor HR during outdoor trail running activities.