## 3 Discussion  
Flexible device technologies such as wearable sensors have significantly advanced in recent years, enabling continuous monitoring of various physiological parameters. Although these technologies have yet to be demonstrated in critical care management, their potential to revolutionize the clinical setting is considerable. In this study, we propose a wearable cardiopulmonary monitoring system that can be used in the ICU environment where healthcare workers and patients are prone to fatigue and error due to equipment complexity. The proposed system with a cable-less design is suggested to overcome the limitation of the existing monitoring system caused by the complex arrangement of multiple electrode cables and power lines. By eliminating the numerous wires and power lines, the proposed device system is anticipated to relieve patients' discomfort, promote their mobility, and improve the work efficiency of medical staff. This cable-less design should also reduce the risk of accidents and disconnections caused by the tangling of cables. This system integrates all ECG, SpO\({}_{2}\), and respiratory monitoring subsystems into a single device with its user interface. The BLE profile streamlines the monitoring process, enhancing convenience and eliminating the necessity for multiple separate monitoring devices. The modularized structure of the device should offer cost-effectiveness through the reusability of high-cost modules and enable the replacement and customization of sensing modules. To see the usefulness, we will compare the measured ECG parameters, including HRV, RR changes, and SpO\({}_{2}\) measured in this novel device, to conventionally measured data. Then, we will use the questionnaires to prove the ICU workflow's efficacy indirectly. Therefore, the proposed system has the potential to provide both economical and  
Figure 3: Experimental setup for the pre-validation process of the signal from the proposed device. (**a**) Experimental setup for the pre-validation process and measurement site of the reference ECG, PPG, and respiration signal. (**b**) Photograph of the manufactured device attached to the human chest during the pre-validation process.  
practical benefits, offering a more integrated and adaptable approach to patient monitoring in clinical situations for both medical staff and patients.  
Meanwhile, arrhythmias, ventricular tachycardia, or atrial fibrillation during hospitalization or clinical treatment are well-known predictors of poor prognoses, such as sudden cardiac death or rehospitalization, highlighting the necessity of periodic post-discharge monitoring for patients with CVDs [49; 50; 51]. The conventional monitoring system has significant limitations for post-discharge monitoring, including difficulties in self-use by patients. Such difficulties come from its lack of portability and integrity between several measurement devices with their cumbersome design accompanied by numerous cables. However, the proposed device integrates all measurement functions into a stand-alone device mounted on a single measurement site and measures vital signals without obstructive cables. Patients are expected to be able to mount or remove the device themselves easily, and the signals from the integrated device will be monitored through their personal PC or smartphone in real time. Thus, it may be seamlessly used for patients' care pathways from hospitalization to post-discharge monitoring.