Yongjoon Chee

Bio: Yongjoon Chee is an academic researcher from Seoul National University. The author has contributed to research in topics: Air mattress. The author has an hindex of 1, co-authored 1 publications receiving 108 citations.

Air mattress sensor system with balancing tube for unconstrained measurement of respiration and heart beat movements

Abstract: The cardio-respiratory signal is a fundamental vital sign used for assessment of a patient's status. Additionally, the cardio-respiratory signal provides a great deal of information to healthcare providers wishing to monitor healthy individuals. The air mattress sensor system allows the measurement of the respiration and heart beat movements without the use of a harness or sensor on the subject's body, which eliminates the difficulties these pose for long term measurements. In order to increase the sensitivity, a differential measurement technique between two air cells was used. The concept of a balancing tube between two air cells is suggested in order to increase the robustness against postural changes during the measurements. With this balancing tube, the meaningful frequency range could be selected using a pneumatic method. A mathematical model was constructed and validation experiments were performed for step and sinusoidal input signals. This technique was applied to measurements of respiration and heart beat movements in the supine posture on the bed, which showed potential for applications in sleep analysis, unconstrained healthcare monitoring and neonate monitoring.

Monitoring, predicting and treating clinical episodes

Abstract: Apparatus and methods are provided for use with a subject who is undergoing respiration. A motion sensor senses motion of a subject. A breathing pattern analysis unit analyzes components of the sensed motion that result from the subject's respiration. The breathing pattern analysis unit includes double-movement-respiration-cycle-pattern-identification functionality that designates respiration cycles as being double-movement-respiration-cycles (DMRC's) by determining that the cycles define two subcycles. Double-movement-respiration-cycle-event-identification functionality of the breathing pattern analysis unit identifies a DMRC event by detecting that the subject has undergone a plurality of DMRC's. An output is generated that is indicative of the subject having used accessory muscles in breathing, in response to identification of the double-movement-respiration-cycle event. Other embodiments are also described.

Ballistocardiography and Seismocardiography: A Review of Recent Advances

Abstract: In the past decade, there has been a resurgence in the field of unobtrusive cardiomechanical assessment, through advancing methods for measuring and interpreting ballistocardiogram (BCG) and seismocardiogram (SCG) signals. Novel instrumentation solutions have enabled BCG and SCG measurement outside of clinical settings, in the home, in the field, and even in microgravity. Customized signal processing algorithms have led to reduced measurement noise, clinically relevant feature extraction, and signal modeling. Finally, human subjects physiology studies have been conducted using these novel instruments and signal processing tools with promising results. This paper reviews the recent advances in these areas of modern BCG and SCG research.

Techniques for prediction and monitoring of clinical episodes

Abstract: A method is provided for predicting an onset of an asthma attack. The method includes sensing at least one parameter of a subject without contacting or viewing the subject or clothes the subject is wearing, and predicting the onset of the asthma attack at least in part responsively to the sensed parameter. Also provided is a method for predicting an onset of an episode associated with congestive heart failure (CHF), including sensing at least one parameter of a subject without contacting or viewing the subject or clothes the subject is wearing, and predicting the onset of the episode at least in part responsively to the sensed parameter. Other embodiments are also described.

ECG Recording on a Bed During Sleep Without Direct Skin-Contact

Abstract: A new indirect contact (IDC) electrocardiogram (ECG) measurement method (IDC-ECG) for monitoring ECG during sleep that is adequate for long-term use is provided The provided method did not require any direct conductive contact between the instrument and bare skin This method utilizes an array of high-input-impedance active electrodes fixed on the mattress and an indirect-skin-contact ground made of a large conductive textile sheet A thin cotton bedcover covered the mattress, electrodes, and conductive textile, and the participants were positioned on the mattress over the bedcover An ECG was successfully obtained, although the signal quality was lower and the motion artifact was larger than in conventional direct-contact measurements (DC-ECG) The results showed that further studies are required to apply the provided method to an ECG diagnosis of cardiovascular diseases However, currently the method can be used for HRV assessment with easy discrimination of R-peaks

Adaptive Beat-to-Beat Heart Rate Estimation in Ballistocardiograms

Abstract: A ballistocardiograph records the mechanical activity of the heart. We present a novel algorithm for the detection of individual heart beats and beat-to-beat interval lengths in ballistocardiograms (BCGs) from healthy subjects. An automatic training step based on unsupervised learning techniques is used to extract the shape of a single heart beat from the BCG. Using the learned parameters, the occurrence of individual heart beats in the signal is detected. A final refinement step improves the accuracy of the estimated beat-to-beat interval lengths. Compared to many existing algorithms, the new approach offers heart rate estimates on a beat-to-beat basis. The agreement of the proposed algorithm with an ECG reference has been evaluated. A relative beat-to-beat interval error of 1.79% with a coverage of 95.94% was achieved on recordings from 16 subjects.