TY - JOUR T1 - Optimizing High-Flow Nasal Cannula Flow Settings Based on Peak Inspiratory Flow During Tidal Breathing JF - Respiratory Care VL - 66 IS - Suppl 10 SP - 3611308 AU - Jie Li AU - Brady Scott AU - James B Fink AU - Brooke Reed AU - Oriol Roca AU - Rajiv Dhand Y1 - 2021/10/01 UR - http://rc.rcjournal.com/content/66/Suppl_10/3611308.abstract N2 - Background: There is little guidance on optimal flow settings during therapy with high-flow nasal cannula (HFNC) based on breathing patterns in patients with acute hypoxemic respiratory failure (AHRF). Methods: After approval by the ethic committee in Rush University (No. 18102503-IRB01) and registration on clinicaltrials.gov (NCT03738345), we conducted a prospective clinical study that included adult patients with hypoxemia treated by HFNC with a fraction of inspired oxygen (FIO2) ≥ 0.4. Peak tidal inspiratory flow (PTIF) was measured on each study participant, and HFNC flows were set to match their PTIF and then increased by 10 L/min up to a maximum flow of 60 L/min. FIO2 was titrated to maintain pulse oximetry (SpO2) of 90-97% at each flow setting. SpO2/ FIO2, respiratory rate (RR), ROX index ([SpO2/FIO2]/RR), and patient comfort were recorded after 5–10 min on each HFNC setting. We also conducted an in-vitro study replicating the breathing pattern acquired from the clinical study to explore the relationship between the HFNC flow settings and the tracheal FIO2, peak inspiratory and expiratory pressures. Results: Forty-nine hypoxemic patients (25 had COVID-19) age 58.0 (SD 14.1) y were enrolled. Mean PTIF (34.1 [8.5] L/min) was similar in COVID-19 and non-COVID-19 patients. As HFNC flow increased, SpO2/ FIO2 and ROX index significantly improved (P < 0.05) (Figure 1). In the in-vitro study, when the HFNC flow was set >PTIF, tracheal peak inspiratory and expiratory pressures increased as HFNC flow increased but the FIO2 did not change (Figure 2). Conclusions: Hypoxemic patients, with and without COVID-19, present similar PTIF values of ~30 to 40 L/min. We observed improvement in oxygenation with HFNC flows set above the patient’s PTIF. Thus, a pragmatic approach to set optimal flows in patients with AHRF would be to initiate HFNC flow at ~40 L/min and titrate the flow based on improvement in oxygenation and patient tolerance. Fig 1. The correlation between SpO2/FIO2 ratio and flow ratio Fig 2. The correlation between flow ratio and FIO2, peak inspiratory and expiratory pressure at trachea in the in-vitro study. ER -