Extracorporeal Closed-Loop Respiratory Regulation for Patients with Respiratory Difficulty Using a Soft Bionic Robot

Comprehensive Academic Report on a Scientific Paper

In modern medicine, respiratory regulation is crucial for patients with respiratory dysfunction. However, currently used clinical positive pressure ventilators have issues such as long-term dependence and injury. While external auxiliary devices like the “iron lung” offer non-invasive alternatives, current artificial actuators have not achieved the effectiveness of bionic respiratory muscles. Based on this, the authors of this paper propose a bionic soft exoskeleton robot that can achieve extracorporeal closed-loop respiratory regulation by simulating natural respiration.

Academic Background

Ventilators are widely used clinically, but with the aging population and the continuous impact of the COVID-19 pandemic, the demand for respiratory function assistance has greatly increased. Current respiratory assistance devices, including positive and negative pressure ventilators, have certain limitations. For instance, positive pressure ventilators can cause barotrauma and adverse hemodynamic effects. Although negative pressure ventilators are closer to natural breathing, they are generally rigid and bulky. Existing bionic respiratory assistance devices also have some drawbacks, such as lacking active inhalation and exhalation assistance. Therefore, developing a soft robotic respiratory assistance device that provides natural-like bi-directional support and is wearable is crucial.

Source of the Paper

This paper, titled “Extracorporeal Closed-Loop Respiratory Regulation for Patients with Respiratory Difficulty Using a Soft Bionic Robot,” was conducted by researchers from Beihang University and Peking University Third Hospital, including Yan Zhang, Qinggang Ge, Zongyu Wang, etc., and has been accepted for publication in IEEE Transactions on Biomedical Engineering.

Research Workflow

The research team designed a soft exoskeleton robot for non-invasive respiratory regulation. This system includes two modules: an inhalation module and an exhalation module. The inhalation module forms a vacuum chamber through a variable stiffness shell, applying negative pressure to the thorax to increase lung capacity. The exhalation module uses a soft origami array to compress the abdominal muscles and lift the diaphragm under positive pressure to facilitate exhalation.

1. Design and Performance of the Inhalation Module: The module design involves a variable stiffness shell achieved through the folding structure of layered materials. Additionally, a skin-friendly sealing ring was designed to ensure the shell maintains its form when negative pressure is applied. Experiments showed that the shell maintained its shape under clamping conditions at -15 kPa negative pressure and collapsed when relaxed. The negative pressure cavity exhibited good pressure response under continuous control signals.

2. Design and Performance of the Exhalation Module: The exhalation module consists of eight soft origami actuators, each made from silicone rubber and Kevlar reinforced materials. After applying a positive pressure ranging from 15 kPa to 25 kPa, the actuators produced delayed output forces but could provide up to 400N, suitable for assisting respiration.

3. Extracorporeal Respiratory Monitoring and Data Analysis: A small inertial measurement unit (IMU) sensor was used to detect chest movements and trigger robotic assistance. By comparing lung volume changes measured through a respiratory mask, a real-time respiratory detection algorithm was designed based on IMU, effectively capturing the patient’s respiratory movements.

4. Closed-Loop Control System Design: A human-machine coupled respiratory mechanics model was constructed, and a model-based controller was designed to achieve continuous, real-time respiratory regulation by adjusting respiratory system parameters. The target respiratory curve was designed as a triangular waveform and fitted with actual IMU data to ensure control precision.

5. Testing on Healthy Subjects and Patients with Respiratory Difficulty: Tests were conducted on 10 healthy subjects and 10 patients with respiratory difficulties. Results indicated that the respiratory amplitude significantly increased with robotic assistance in healthy subjects. Parameters like peak inspiratory flow, peak expiratory flow, and tidal volumes showed significant improvement. For patients with respiratory dysfunction, the soft robot significantly improved ventilation capacity, and blood gas test results also showed noticeable improvements.

Research Results

1. Performance of Inhalation and Exhalation Modules: The inhalation module maintained its hardened shell shape under clamping conditions and exerted significant expansion force on the chest at -5 kPa negative pressure. The exhalation module provided sufficient compression force for respiratory assistance despite a brief delay in response to control signals.

2. Respiratory Monitoring and Data Analysis: Data from IMU sensors were highly consistent with respiratory mask measurements, accurately reflecting the subjects’ respiratory conditions. The designed algorithm allowed the IMU to detect the start and end of respiration timely, ensuring accurate control assistance.

3. Effectiveness of the Closed-Loop Control System: The target respiratory curve showed high fitting accuracy with real-time IMU data, with control errors within acceptable range. Especially for participants without respiratory dysfunction, the robotic-assisted respiratory amplitude was similar to or even greater than forced breathing.

4. Respiratory Regulation Results in Healthy Subjects and Patients: In healthy subjects, the respiratory amplitude significantly increased with robotic assistance, and respiratory parameters improved considerably. For patients, the ventilation capacity significantly improved after respiratory regulation, and some patients showed noticeable improvements in blood gas indicators, proving the potential application of this soft robot in patients with respiratory difficulties.

Research Conclusion and Value

This study proposed a soft exoskeleton robotic system capable of non-invasively achieving respiratory regulation, showing significant auxiliary effects for patients with respiratory dysfunction. Whether in hospitals or home environments, this robot has potential for assisting respiratory function, particularly for patients requiring long-term ventilatory support. Moreover, by providing bi-directional support simulating natural breathing, this system offers a non-invasive alternative to existing respiratory devices.

Research Highlights

1. Design for Simulating Natural Breathing: The soft robot achieves bi-directional active assistance for natural-like breathing by expanding the thorax through negative pressure and compressing the abdominal muscles through positive pressure.

2. Real-time Monitoring and Closed-Loop Control: By using IMU sensors for real-time respiratory status monitoring and dynamically adjusting robot parameters through a closed-loop control system, precise respiratory regulation is achieved.

3. Wide Applicability: This robot is effective not only for patients with respiratory dysfunction but also shows potential in improving ventilation capacity in healthy subjects, making it suitable for hospitals, homes, or even high-altitude hypoxic environments.

Future Research Directions

Although this soft robot demonstrates certain advantages, further optimization is needed to improve its sealing performance and dynamic response. Additionally, adaptive control strategies should be developed for different types of respiratory diseases to better meet specific clinical needs. This research provides an innovative and effective solution for respiratory assistance technology, with significant scientific value and application prospects.