The Use of High-Flow Nasal Cannula Oxygen Outside the ICU

High-flow nasal cannula (HFNC) oxygen therapy is a routine, evidence-based treatment in the ICU. Due to its ease of application, non-evidence-based use of HFNC has spread to non-ICU wards. This study reports on the experience with HFNC outside the ICU.

This is an observational study of HFNC prescribed by treating physicians in non-ICU areas. Primary outcomes included change in dyspnea visual analog scale score and physiological variables both before and 30 min after initiation of HFNC treatment. Secondary outcomes included mortality, ICU admission, and intubation.

We observed decreased median (interquartile range) visual analog scale scores after initiation of HFNC: 8 (6-9) versus 5 (4-6) (P < .001) in 90 of 111 subjects (81%, 95% CI 72.5-87.9%, P < .001). Breathing frequency (31 ± 10 vs 26 ± 7 breaths/min, P < .001) and saturation (84 ± 12% vs 94 ± 5%, P < .001) also improved. Overall cohort mortality was 55 of 111 subjects (50%); however, 41 of 111 subjects (33%) had a do not resuscitate (DNR) order. Among 70 non-DNR subjects, early mortality (< 72 h) occurred in 9 of 70 subjects (13%), and late mortality in 12 of 70 subjects (17%). The composite end point (ie, discharged alive, non-intubated, not admitted to ICU) was met by 35 of 70 subjects (50%) without a DNR order. An increased ROX index ([S_pO /F_IO ]/breathing frequency) was the only independent predictor associated with achieving the composite outcome (odds ratio 1.51, 95% CI 1.1-2.0, P = .01). Higher pre-connection visual analog scale score (odds ratio 1.75, 95% CI 1.35-2.28, P < .001) and a history of respiratory disease (odds ratio 3.52, 95% CI 1.27-9.72, P = .01) were predictors of greater improvement in dyspnea with HFNC. No variable predicted mortality.

HFNC outside the ICU was associated with improved visual analog scale score, breathing frequency, and saturation but with a relatively high mortality, even in non-DNR subjects. HFNC was used in many subjects who had a DNR order. This therapy may have been palliative in intent. Care should be exercised in using this therapy in a setting that is not continuously monitored.