Long-term effects of oxygen-enriched high-flow nasal cannula treatment in COPD patients with chronic hypoxemic respiratory failure

Abstract

Background: This study investigated the long-term effects of humidified high-flow nasal cannula (HFNC) in COPD patients with chronic hypoxemic respiratory failure treated with long-term oxygen therapy (LTOT).

Patients and methods: A total of 200 patients were randomized into usual care ± HFNC. At inclusion, acute exacerbation of COPD (AECOPD) and hospital admissions 1 year before inclusion, modified Medical Research Council (mMRC) score, St George's Respiratory Questionnaire (SGRQ), forced expiratory volume in 1 second (FEV₁), 6-minute walk test (6MWT) and arterial carbon dioxide (PaCO₂) were recorded. Patients completed phone interviews at 1, 3 and 9 months assessing mMRC score and AECOPD since the last contact. At on-site visits (6 and 12 months), mMRC, number of AECOPD since last contact and SGRQ were registered and FEV₁, FEV₁%, PaCO₂ and, at 12 months, 6MWT were reassessed. Hospital admissions during the study period were obtained from hospital records. Hours of the use of HFNC were retrieved from the high-flow device.

Results: The average daily use of HFNC was 6 hours/day. The HFNC group had a lower AECOPD rate (3.12 versus 4.95/patient/year, p<0.001). Modeled hospital admission rates were 0.79 versus 1.39/patient/year for 12- versus 1-month use of HFNC, respectively (p<0.001). The HFNC group had improved mMRC scores from 3 months onward (p<0.001) and improved SGRQ at 6 and 12 months (p=0.002, p=0.033) and PaCO₂ (p=0.005) and 6MWT (p=0.005) at 12 months. There was no difference in all-cause mortality.

Conclusion: HFNC treatment reduced AECOPD, hospital admissions and symptoms in COPD patients with hypoxic failure.

Keywords: 6-minute walk test; 6MWT; AECOPD; COPD; HFNC; exacerbation; high-flow heated and humidified oxygen; mMRC score; modified Medical Research Council score.

Figure 1

Enrollment, inclusion, follow-up and discontinuation of HFNC-treated patients and controls. Abbreviations: AECOPD, acute exacerbation of COPD; HFNC, high-flow nasal cannula.

Figure 2

Fitted exacerbation rates (combined reported exacerbations and hospitalized exacerbations) (A, B) and hospital admission rates (C, D). Notes: In (A and C), blue (control) and red (HFNC) bars show rates per group as randomized (intention-to-treat analysis). In (B and D), the regression line for exacerbations (B) and admissions (D) relates actual device use, zero for the control group and 12 months for the study completers, with withdrawal subjects ranging in between (per-protocol analysis) to the number of events per patient, showing longer actual use giving lower rates of exacerbation and admission. Abbreviation: HFNC, high-flow nasal cannula.

Figure 3

Fitted values, based on number of exacerbations in the year prior to study, of the expected number of exacerbations with zero use (blue dashed) and the HFNC-treated (red solid). Abbreviation: HFNC, high-flow nasal cannula.

Figure 4

Fitted data on mMRC score (A), SGRQ (B), arterial partial pressure of CO₂ (C) and 6MWT (D), in high-flow, humidified, nasal cannula delivered oxygen (HFNC) patients (red solid line) or controls (blue dashed lines) during the study. Notes: Dots represent assessment times. p-values show differences between the HFNC and control groups. Abbreviations: HFNC, high-flow nasal cannula; mMRC, modified Medical Research Council; 6MWT, 6-minute walk test; SE, standard error; SGRQ, St George’s Respiratory Questionnaire.