Heart rate and oxygen uptake kinetics obtained from continuous measurements with wearable devices during outdoor walks of patients with COPD

Figure 1.. The upper panel visualises the heart rate response of a subject walking on the orange trail. The start and the end of the walk are indicated by the two thick black lines. Light grey zones indicate the considered time windows for every physical activity transition. The curly braces above the figure represent the time periods that were used to calculate the magnitude of the heart rate response related to the different physical activity transitions. The lower panel zooms in on the considered time window when starting a walk to visualise the meaning of heart rate kinetics (e.g., mean response time and amplitude), as extracted from a kinetic model (orange line).

Figure 2.. An average heart rate response for starting an outdoor walk (blue line) was generated by taking the second-by-second mean of the three resampled heart rate responses when starting the different outdoor walks (green, orange and red lines). The black line represents the heart rate response when starting a 6-minute walk test (6MWT). Heart rate values are displayed as the heart rate increase above the heart rate level prior to the start of the walk/test.

Figure 3.. The bars represent the amount of physical activity transitions resulting in a small heart rate response, a poor model fit, unreliable model parameters or valid kinetics for the 6-minute walk test (6MWT), outdoor walks on the green, orange and red trail and the averaged response (Avg). Percentages indicate the relative amount of valid kinetics for the 6MWT, outdoor walks (green, orange and red) and the averaged response.

Figure 4.. The bars represent the amount of physical activity transitions resulting in a small oxygen uptake response, a poor model fit, unreliable model parameters or valid kinetics for the 6-minute walk test (6MWT), outdoor walks on the green, orange and red trail and the averaged response (Avg). Percentages indicate the relative amount of valid kinetics for the 6MWT, outdoor walks (green, orange and red) and the averaged response.

Green, orangeand red urban trails. Walking happened on sidewalks, so patients were not required to walk on sand.