이중유량 시스템: 정상인과 저산소성 호흡부전 환자들을 대상으로 한 탐색적 임상연구

Abstract

Background: High-flow nasal cannula (HFNC) devices are widely used for oxygen supplementation. However, it supplies the same flow rate during inspiration and expiration, causing turbulence and increased respiratory resistance in the nasopharynx during expiration, leading to patient discomfort. We developed a bi-level high-flow system (Bi-flow) to improve this problem, providing additional flow during inspiration. Objective: We investigated the physiologic effects of applying Bi-flow in healthy individuals and patients with hypoxemic respiratory failure and compared it with conventional HFNC (Uniflow) usage. Methods: For healthy individuals, Uniflow (U30, U40, U50) and Bi-flow (basal flow 10, 20, 30L/min) modes were randomly assigned. Each mode varied the [inspiration/expiration rate] by increasing additional flow during inspiration, as follows: 30/10, 30/20, 40/10, 40/20, 40/30, 50/20, 50/30 trials. Physiologic data (respiratory rate, heart rate, transcutaneous CO2, modified Borg scale) and lung volume (monitored through Electrical Impedance Tomography-EIT) were recorded. Nasal pressure- time product (N-PTP) was calculated as a surrogate marker for work of breathing (WOB). In the hypoxemic patient’s study, Uniflow and Bi-flow modes (BF25, BF50, BF75) were randomly allocated. Bi-flow mode maintained the same inspiratory flow as Uniflow, but supplied a portion of the total flow as additional flow (in percentage). The four modes were compared by analyzing patients’ ROX index (the ratio of oxygen saturation as measured by pulse oximetry/FiO2 to respiratory rate), lung volume, and N-PTP. Results: The healthy individual’s study included twelve healthy individuals. When Bi-flow was applied, a reduction in respiratory rates was observed compared with natural breathing. Additionally, a decrease in inspiratory and expiration N-PTP was noted with Bi-flow. For the 24 patients with hypoxic respiratory failure, there were no significant differences in the ROX index (UF: BF25: BF50: BF75; 13.2: 13.7: 13.4 13.9; p=0.98). However, there was a slight decrease in inspiratory N-PTP in the Bi- flow modes (UF: BF25: BF50: BF75; 11.2: 8.4: 6.0: 9.9; p=0.03). Lung volume data monitored through EIT did not show any significant statistical differences. Conclusion: We applied Bi-flow to healthy individuals and patients with hypoxemic respiratory failure, and the results showed a partial decrease in N-PTP, a proxy of work of breathing. Furthermore, no significant adverse effects were observed. (KCT0006100, KCT0007352)