RT Journal Article
SR Electronic
T1 Optimizing High-Flow Nasal Cannula Flow Settings Based on Peak Inspiratory Flow During Tidal Breathing
JF Respiratory Care
FD American Association for Respiratory Care
SP 3611308
VO 66
IS Suppl 10
A1 Jie Li
A1 Brady Scott
A1 James B Fink
A1 Brooke Reed
A1 Oriol Roca
A1 Rajiv Dhand
YR 2021
UL http://rc.rcjournal.com/content/66/Suppl_10/3611308.abstract
AB 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.