P8. Humidification and nasal high flow (NHF) therapy

Several trials have shown that nasal high flow (NHF) humidified air in stable COPD patients reduces transcutaneous CO₂ (PtCO₂) and respiratory rate (Fraser 2016, Biselli 2017, McKinstry 2018, 2019).

A randomised trial by Rea et al (Rea 2010) found that NHF for up to 2 hours daily reduced annual exacerbation days and days to first exacerbation but not hospital admission compared with usual care in a group of 108 patients, with COPD/ bronchiectasis. Quality of life and lung function also improved. No sham treatment was given.

In a small study crossover by Nagata et al, use of nocturnal NHF in addition to LTOT also demonstrated significant benefit in quality of life (St George’s Respiratory Questionnaire COPD [SGRQ-C]) score improved by 7.8 points; (95% CI 3.7-11.9; p<0.01) and measured PCO₂ (-4.1, 95% CI -6.5 to -1.7) (Nagata 2018), though other studies have not demonstrated benefits in patient related outcomes. In a 12-month multi-centre study of just over 100 patients with severe COPD and resting hypercapnia on LTOT in Japan by Nagata (2022), reductions were found in annual moderate to severe exacerbation rates and days to first exacerbation in the group receiving high flow nasal oxygen in addition to long term oxygen therapy, but there were no changes in breathlessness scores, for example, between the groups, over the duration of the study. No sham treatment was given in these studies by Rea and Nagata, and in the 2022 Nagata study, hospitalisation rate was not reported. The arm without the high flow nasal canula intervention had significantly higher combined moderate and severe exacerbations, which was the primary outcome of interest, by an adjusted odds ratio of 2.85 (95% CI 1.48-5.47). Hospital admissions were classed as severe exacerbations but were not significantly reduced (Nagata 2022) [evidence level II].

In a 12-month study by Storgaard et al (Storgaard 2018), 200 Danish patients with stable hypoxaemic COPD who had commenced long-term oxygen therapy (LTOT) within the preceding 3 months were randomised to LTOT alone or LTOT plus NHFNHF at 20 litres/minute with oxygen flow unchanged (mean 1.75 (0.8) L) for at least 6 hours per day. 67 patients in the NHF group completed the trial and 71 in LTOT group. Analysis was by intention to treat. Exacerbation rate was decreased in the NHF group but not hospitalisations.

A systematic review and meta-analysis of 4 RCTs (n=440) with median follow-up of 12 months examined the effects of NHF in patients with stable hypercapnic COPD (Pitre 2023) [evidence level I]. All 4 RCTs included in the analysis (n=440) reported exacerbations, and 3 trials reported mortality (n=397; 31 deaths). Compared to standard care, NHF was found to reduce acute exacerbations (RR 0.77 [95 % CI 0.66 to 0.89]; moderate certainty) and improve quality of life (MD in SGRQ 8.12 units lower [95% CI 13.30 to 2.95 lower]; low certainty) but did not reduce hospital admissions (RR 0.87 [95% CI 0.69 to 1.09]) or mortality in patients with COPD and chronic hypercapnia.

Two systematic reviews and meta-analyses from 2023 examined the role of NHF cannula in a range of settings for COPD (Yang 2023; Zhang 2023). However, both reviews comprised of poor quality, heterogeneous or non-relevant studies, limiting the reliability of the overall meta-analyses.

The role of long-term domiciliary NHF is as yet still unclear. Prospective randomised controlled trials in the appropriate COPD patient population with meaningful clinical endpoints are required before long-term domiciliary NHF can be broadly recommended.

In the acute setting, NHF has a role in hypoxic respiratory failure where hypercapnia has been excluded (Stephan 2015, Frat 2015). Please see section X3.2.1 for further details.