Adapting smartphone-based photoplethysmograpy to suboptimal scenarios

Abstract

Photoplethysmography (PPG) is an optical technique used to measure the heart rate (HR) and other cardiovascular variables by analyzing volume changes in the microvascular bed of tissue. At the moment, smartphone users can already measure their HR using PPG applications that use the smartphone's built-in camera. However, available applications are unreliable when artifacts are present, such as those caused by movement, finger pressure, or ambient light changes. This contribution aims to analyze the limitations of a smartphone-based PPG algorithm capable of measuring N-N intervals when such artifacts are present by comparing it to a 2-lead electrocardiography (ECG). By using a Bandpass filter and a zero-crossing detection algorithm on a PPG signal captured at 800 × 600 pixels and 30 Hz, we have designed an approach capable of assessing N-N intervals when movement artifacts are present. An evaluation performed on n = 31 users shows our algorithm is capable of measuring N-N intervals with an average relative error of 9.23 ms, when compared to a 2-lead ECG. Our approach proves the reliability of smartphone-based photoplethysmography to measure N-N intervals, even under the presence of movement artifacts, and opens the door for its future use in remote diagnosis scenarios.

Recent advances in rehabilitation for Parkinson’s Disease with Exergames: A Systematic Review

“…Regarding future work, in addition to providing further, high-quality clinical trials in order to confirm the hypotheses so far presented, studies should focus on adapting existing therapies to home scenarios, adding further data collection procedures, such as monitoring hand tremors, perhaps with a finger sensor [82]. Additional variables such as dysphonia [83] and heart rate variability [84] may also be of interest. Evaluating the feasibility of expanding PD Exergame therapy to patients with PD-MCI and PDD, and including new interaction techniques such as fine motoric training and speech control are also points of interest.…”

Enhancing the Robustness of Smartphone Photoplethysmography: A Signal Quality Index Approach

“…The current study included five frequently used FPDTs to compare the agreement between smartphone PPG and the reference ECG [26,29,[58][59][60][61][62][63][64] (Table 2 and Figure 2c).…”

“…Smartphone PPG detects heartbeats by recording videos of fingertips using the in-built camera [24,25].The primary motivation for using smartphone PPG, compared to other wearable devices, is that it requires minimal equipment. Given that smartphones with in-built cameras have become a part of modern life, using them to access health information is an ideal alternative when ECGs or similar medical devices are not available [26]. In addition, there have been several reported techniques for increasing the accuracy of smartphone PPG, such as point-of-interest selection [27], bandpass filtering [28], adaptive signal thresholding [29], motion detection techniques [30][31][32], interpolation techniques [33], and signal decomposition methods [34][35][36].…”

“…The sampling rate can be as high as 1000 Hz for medical equipment [44]; however, for most smartphone cameras, it is less than 30 Hz [40], and this can result in the fiducial point detection technique (FPDT) easily missing the actual point. Frame rate instability-as a design to prevent the CPU from overloading or overheating-further degrades the acquisition performance [26,45].While it is difficult to ensure the robustness of using smartphone PPG in assessing HRV against a less controlled environment, other strategies can be employed to make smartphone PPG practically workable. Users today are familiar with various consumer-grade healthcare devices such as home blood pressure monitors or ECG chest straps.…”

“…The sampling rate can be as high as 1000 Hz for medical equipment [44]; however, for most smartphone cameras, it is less than 30 Hz [40], and this can result in the fiducial point detection technique (FPDT) easily missing the actual point. Frame rate instability-as a design to prevent the CPU from overloading or overheating-further degrades the acquisition performance [26,45].…”