Fig. 2

The relationship between inhaled dose and the ratio of HFNC gas flow to patient’s inspiratory flow in adult, toddler, and infant models. Mean and (±) SD values are shown. Figure modified from references [29, 30]. In adult, toddler, and infant in vitro models, as the ratio of HFNC gas flow to patient’s inspiratory flow increased, the delivered dose decreased, with a steep decline in aerosol delivery when HFNC gas flow was more than 2-fold higher than the patient’s inspiratory flow. Inhaled dose peaked when the HFNC gas flow was 0.1–0.5 of the patient’s inspiratory flow. For illustration, data from ratios of 0.1–0. 5, 0.51–1.0, 1.01–2.0, and > 2.0 in the original studies have been combined for this graphic. HFNC, high-flow nasal cannula