## 2 Materials and Methods
### Data Collection  
Before the study, a questionnaire (Table 2) for intensive care unit medical staff will be completed regarding their experience with the conventional monitoring system. After obtaining documentation of informed written consent from the participating patients by the corresponding investigator (Y.-M.H.), continuous ECG monitoring will be attained from both systems only during participants' ICU hospitalization. Oxygen saturation data are conventionally monitored continuously. However, saturation data are recorded to the EMR every 1 to 4 h, while the newer device monitors and records them continuously and simultaneously. Participants who want to discontinue the study will be excluded from the analysis. To compare the correlation and accuracy between the two monitoring systems, ten patients with at least 20 recordings per patient are planned. After the study, a questionnaire will be completed by intensive care unit medical staff regarding their experience with the new device (Table 3).  
Before the clinical experiment, the pre-validation process of the signal will be conducted. The complexity of single-cycle ECG waveforms will be analyzed to validate the reliability of the ECG signal from the proposed device. As a quantitative indicator, the time-domain heart rate variability (HRV), such as the mean RR peak interval (mean heart rate), the standard deviation of normal-to-normal intervals (SDNN), the root-mean-square of successive differences of normal-to-normal intervals (RMSSD), and the frequency-domain HRV such as a power spectral analysis will be analyzed. After measuring the HRV data from each device, the correlation coefficient (R) value will be calculated to measure the accuracy of the proposed device compared with that of the reference devices. To evaluate the performance of the respiration sensor, the respiration rate per minute and the duration of inhalation and exhalation for each respiration will be compared. After the pre-validation process in the lab, the clinical experiment with ten patients in the ICU/surgical ICU patients will be conducted. An ECG Holter recorder and patient monitoring device will be attached to all test patients in advance. In the clinical experiment, vital signs such as heart rate, respiration, and SpO\({}_{2}\) will be acquired from the proposed device and compared with those from the conventional patient monitoring systems currently used in the ICU (Figure 3). All files and data generated by this protocol will be stored in a secured safe box or as copied files with passwords with only the investigators' accessibility. Data from this study will not be further openly accessible because of the personal identifier or sensitive information included. Since the questionnaires proposed in this study needed to confirm their reliability, we performed an interobserver agreement test with each of the questionnaires to two ICU physicians unrelated to this study. [PERSON]'s kappa was 0.98 and 0.99 for the pre-questionnaire (Table 2) and post-questionnaire (Table 3).  
Based on the intensive care unit medical staff survey, the primary end point is to assess the necessity of simplified ICU monitoring devices. Secondary end points include an accuracy comparison of ECG, saturation measured by the conventional system, and the device developed.