Non-intubated intensive care patients commonly receive supplemental oxygen by high-flow face mask (HFFM), simple face mask (FM) and nasal prongs (NP) during their ICU admission. However, high-flow nasal prongs (HFNP) offer considerable performance capabilities that may sufficiently meet all their oxygen therapy requirements.To assess the feasibility, safety and cost-effectiveness of introducing a protocol in which HFNP was the primary oxygen delivery device for non-intubated intensive care patients.Prospective 4-week before-and-after study (6 months apart) for all adult patients admitted to a 22-bed tertiary ICU in Melbourne, Australia.117 patients (57 before, 60 after) were included: 86 (73.5%) received mechanical ventilation. Feasibility revealed a significant reduction in HFFM (52.6-0%, p<.001), FM (35.1-8.3%, p=.002) and NP (75.4-36.7%, p<.001) use and an increase in HFNP use (31.6-81.7%, p<.05) during the after period. Following extubation, there was a significant reduction in HFFM use (65.7% vs. 0%, p<.05) and an increase HFNP use (8.6% vs. 87.5%, p<.05). Costing was in favour of the after period with a consumable cost saving per patient (AUD $32.56 vs. $17.62, p<.05). During the after period, more patients were discharged from ICU with HFNP than during the before period (5 vs. 33 patients, p<.05) and fewer patients (5 vs. 14 patients) used three or more oxygen delivery devices. Safety outcomes demonstrated no significant difference in the number of intubations, re-intubations, readmissions or non-invasive ventilation use between the two time periods.Using HFNP as the primary oxygen delivery method for non-intubated intensive care patients was feasible, appeared safe, and the oxygen device costs were reduced. The findings of our single-centre study support further multi-centre evaluations of HFNP therapy protocols in non-ventilated intensive care patients.