Addition of Mask to High-flow Nasal Oxygen: A Strategy to Improve Oxygenation in Hypoxemic Respiratory Failure Secondary to COVID-19

High-flow nasal cannula (HFNO) reduces the need for invasive mechanical ventilation in COVID-19 patients with hypoxemic-respiratory failure. During HFNO entrainment of room air dilutes the delivered fractional inspiratory oxygen (FiO ), thereby preventing improvement in oxygenation. The placement of a mask over HFNO to improve oxygenation has provided conflicting results. We aimed to determine and compare the effect of placing various mask types over HFNO on oxygen saturation (SPO ). In this prospective physiological study 40 patients with COVID-19-associated hypoxemic respiratory failure on HFNO with O concentration 92% was higher with the use of N95 masks (47.5%) or NRB with O (45%) over HFNO compared to SM (35%) and NRB without O (35%). No significant change was observed in heart rate, blood pressure, and CO level with the use of any mask over HFNO. This study demonstrates improvement in oxygenation and reduction in respiratory rate with the use of various masks over HFNO in patients of COVID-19-related hypoxemic-respiratory-failure. Significantly greater benefit was achieved with the use of N95 or NRB with O2 compared to SM or NRB without O2.