The Impact of High-Flow Nasal Cannula on Olfactory Function

BACKGROUND: Oxygen therapy provided via high-flow nasal cannula (HFNC) improves gas exchange lung compliance and results in increased lung expiratory volumes. Previous data indicate that hyperbaric and humid states improve the olfactory thresholds compared to hypobaric and dry conditions. This prospective, observational study aimed to determine the impact of oxygen delivery through HFNC on olfactory function in subjects admitted to the ICU for acute respiratory failure (ARF). METHODS: 30 subjects who were admitted to the ICU for ARF underwent an olfactory sniff test before and after oxygen therapy with HFNC. Baseline olfactory function of subjects with ARF was also compared against 30 healthy controls. Odor threshold (OT), odor discrimination (OD), odor identification (OI) and global olfactory score (TDI) were recorded for all subjects. RESULTS: The OT, OD, OI, and TDI scores were significantly higher in the control group compared to the baseline scores of the subjects with ARF (P < .001 for all comparisons). In subjects with ARF, administration of oxygen with HFNC led to significant improvements in OT (P = .02), OD (P = .001), OI (P = .02), and TDI (25S +/- 3.8 vs 27.1 +/- 3.5, P < .001) scores. CONCLUSIONS: Our results indicate that subjects with ARF had relative olfactory dysfunction compared to healthy controls. These results also suggest that implementation of HFNC to relieve hypoxemia in subjects presenting with ARF can lead to a significant improvement in olfactory function.