The use of high flow nasal oxygen in COPD patients

Abstract

High flow nasal oxygen (HFNO) is one of the interventions a physician may opt to prescribe in hypoxemic patients. It involves the delivery of heated and humidified oxygen at rates of up to 60L/min via large bore nasal cannulae in a controlled manner, with variables such as the fraction of inspired oxygen (FiO2) which may be controlled independently. The set-up of HFNO consists of an oxygen generator, a flow meter, a humidifier and wide bore nasal cannulae. There are 5 physiologic mechanisms that are believed to be responsible for the efficacy of HFNO. These include physiological dead space washout of waste gases including carbon dioxide (CO2), decreased respiratory rate, positive end-expiratory pressure, increased tidal volume and increased end-expiratory volume. These mechanisms account for the multiple applications of HFNO in hypoxemic patients, both in the acute and chronic settings. The use of HFNO in the management of COPD has risen along the years. It plays a role in both acute and stable COPD patients, however, the present evidence is insufficient for HFNO to be utilised preferentially especially in the acute setting. Larger scale studies are necessary to establish its role especially in these scenarios where NIV is currently recommended as the first line mode of oxygenation and HFNO is reserved for those unable to tolerate NIV.