Heart rate and oxygen uptake kinetics obtained from continuous measurements with wearable devices during outdoor walks of patients with COPD: Validation study (Preprint)

BACKGROUND Continuous physiological measurements during a laboratory-based exercise test can provide physiological biomarkers, such as heart rate (HR) and oxygen uptake (V̇O2) kinetics, that carry clinically relevant information. In contrast, it is not yet clear how continuous data generated during daily life routines by wearable devices could provide meaningful biomarkers that, in turn, could improve telemonitoring applications. OBJECTIVE To determine whether valid HR and V̇O2 kinetics can be obtained from measurements with wearable devices during outdoor walks in patients with chronic obstructive pulmonary disease (COPD). As a secondary objective, we aimed to determine whether the amount of valid kinetics and kinetic model performance was comparable between outdoor walks and a conventional, laboratory-based exercise test. METHODS Eight patients with COPD measured HR (Polar Belt) and V̇O2 (METAMAX 3B) during three outdoor walks of different intensities and a six-minute walk test. For every patient and walk/test, HR and V̇O2 data were extracted after the following physical activity transitions: (i) starting a walk/test, (ii) finishing a walk/test and (iii) walking upstairs. An additional, averaged HR and V̇O2 response during outdoor walks was generated for each type of transition of every patient. Kinetic models were used to describe every separate and averaged HR and V̇O2 response when participants started a walk, finished a walk and walked upstairs. HR and V̇O2 kinetics were considered valid if the response magnitude and model fit were adequate, and model parameters were reliable. Kinetic model performance was assessed by model fit and standard errors of the parameter estimates. RESULTS Most HR kinetics were valid when starting (range 75% to 100% for separate walks; 100% for the averaged response) or finishing (range 63% to 88% for separate walks; 100% for the averaged response) an outdoor walk, but not when walking upstairs (≤29%). Many V̇O2 kinetics were valid when finishing (range 63% to 100% for separate walks; 100% for the averaged response), but not when starting an outdoor walk (range 38% to 50% for separate walks; 88% for the averaged response) or when walking upstairs (0%). The amount of valid kinetics, and kinetic model performance (P>.05), when starting/finishing an outdoor walk was comparable to starting (HR: 100%; V̇O2: 50%) or finishing (HR: 88%; V̇O2: 75%) a laboratory-based six-minute walk test. CONCLUSIONS Continuous measurements with wearable devices can provide valid HR kinetics when starting or finishing, and valid V̇O2 kinetics when finishing, an outdoor walk in patients with COPD. The amount of valid kinetics and kinetic model performance was comparable between outdoor walks and a conventional, laboratory-based exercise test. We envision that telemonitoring applications for patients with COPD could be improved by incorporating regular assessments of HR (and possibly V̇O2) kinetics, as obtained from continuous measurements with wearable devices during outdoor walks.

Mass and density of individual frozen hydrometeors

A new precipitation sensor, the Differential Emissivity Imaging Disdrometer (DEID), is used to provide the first continuous measurements of the mass, diameter, and density of individual hydrometeors. The DEID consists of an infrared camera pointed at a heated aluminum plate. It exploits the contrasting thermal emissivity of water and metal to determine individual particle mass by assuming that energy is conserved during the transfer of heat from the plate to the particle during evaporation. Particle density is determined from a combination of particle mass and morphology. A Multi-Angle Snowflake Camera (MASC) was deployed alongside the DEID to provide refined imagery of particle size and shape. Broad consistency is found between derived mass–diameter and density–diameter relationships and those obtained in prior studies. However, DEID measurements show a generally weaker dependence with size for hydrometeor density and a stronger dependence for aggregate snowflake mass.

Measuring the Degree of Balance between Urban and Tourism Development: An Analytical Approach Using Cellular Data

This study presents an analytical approach for measuring the degree of balance between urban and tourism development, which has been previously analyzed qualitatively and was difficult to measure. With the help of 1012 million cellular data records generated by 20 million users in two weeks, we tracked the behavior of residents, commuters, and tourists at a set of historical conservation areas in central Shanghai. We calculated the degree of balance and visualized it via ternary graphs. Moreover, the relationships between key urban features derived from multi-sourced urban data and balanced degrees of tourism development were analyzed via multinomial logistic analysis. Insights gained from this analysis will help to achieve a more scientific decision-making process toward balanced urban development for historical conservation area. Achievements in this study contribute to the development of human-centered planning through providing continuous measurements of an “unmeasurable” quality.

Measurement report: Mass and Density of Individual Frozen Hydrometeors

A new precipitation sensor, the Differential Emissivity Imaging Disdrometer (DEID), is used to provide the first continuous measurements of the mass, diameter, and density of individual hydrometeors. The DEID consists of an infrared camera pointed at a heated aluminum plate. It exploits the contrasting thermal emissivity of water and metal to determine individual particle mass by assuming that energy is conserved during the transfer of heat from the plate to the particle during evaporation. Particle density is determined from a combination of particle mass and morphology. A Multi-Angle Snowflake Camera (MASC) was deployed alongside the DEID to provide refined imagery of particle size and shape. Broad consistency is found between derived mass-diameter and density-diameter relationships and those obtained in prior studies. However, DEID measurements show a generally weaker dependence with size for hydrometeor density and a stronger dependence for aggregate snowflake mass.

Temporal variability of methane emissions from a closed landfill at Denmark

<p>Methane (CH<sub>4</sub>) emissions from landfills contribute to global warming, impacting significantly the environment and human health. Landfill CH<sub>4</sub> emissions strongly depend on changes in barometric pressure, inducing short-term CH<sub>4</sub> emission variation of several orders of magnitude. Estimating the temporal variability of CH<sub>4</sub> emitted into the atmosphere could help us reducing the uncertainties of annual emission estimates from landfills. In this study, we focus on the temporal variability of CH<sub>4</sub> emissions under the impact of barometric pressure changes.</p><p>CH<sub>4</sub> emissions of a closed landfill (Skellingsted, Western Zealand, Denmark) were measured with two different methods from December 2019 to June 2020; continuously with the eddy covariance method (EC) and discretely with the dynamic tracer dispersion method (TDM). The EC method allows continuous measurements from a confined surface area, with most likely limited representativeness of the whole landfill site due to the considerable horizontal heterogeneity. The TDM method is able to quantify the emission from the whole site insensitive of the topography with the limited representativeness for the temporal variability.</p><p>CH<sub>4</sub> emissions to the atmosphere measured by the TDM and fluxes measured by the EC ranged from to 0 to almost 100 kg h<sup>-1</sup> and from 0 to 10 μmol m<sup>-2</sup> s<sup>-1</sup>, respectively. The CH<sub>4</sub> fluxes measured continuously using the EC method were highly correlated with the emissions from the periodic measurements using the TDM and fluctuated according to the pressure tendency. Under decreasing barometric pressure the highest CH<sub>4</sub> emissions where observed, while increasing barometric pressure suppressed them almost to 0.</p><p>Our results demonstrate the value of implementing two different complementary measurement techniques in parallel that will help to quantify total annual CH<sub>4</sub> emission from a landfill. EC method provides continuous measurements describing accurately the temporal variation of emissions, while TDM method is able to quantify emissions from the whole site.</p>