High flow nasal oxygen for acute type two respiratory failure: a systematic review

Abstract

Background: Acute type two respiratory failure (AT2RF) is characterized by high carbon dioxide levels (PaCO2 >6kPa). Non-invasive ventilation (NIV), the current standard of care, has a high failure rate. High flow nasal therapy (HFNT) has potential additional benefits such as CO2 clearance, the ability to communicate and comfort. The primary aim of this systematic review is to determine whether HFNT in AT2RF improves 1) PaCO2, 2) clinical and patient-centred outcomes and 3) to assess potential harms. Methods: We searched EMBASE, MEDLINE and CENTRAL (January 1999-January 2021). Randomised controlled trials (RCTs) and cohort studies comparing HFNT with low flow nasal oxygen (LFO) or NIV were included. Two authors independently assessed studies for eligibility, data extraction and risk of bias. We used Cochrane risk of bias tool for RCTs and Ottawa-Newcastle scale for cohort studies. Results: From 727 publications reviewed, four RCTs and one cohort study (n=425) were included. In three trials of HFNT vs NIV, comparing PaCO2 (kPa) at last follow-up time point, there was a significant reduction at four hours (1 RCT; HFNT median 6.7, IQR 5.6 – 7.7 vs NIV median 7.6, IQR 6.3 – 9.3) and no significant difference at 24-hours or five days. Comparing HFNT with LFO, there was no significant difference at 30-minutes. There was no difference in intubation or mortality. Conclusions: This review identified a small number of studies with low to very low certainty of evidence. A reduction of PaCO2 at an early time point of four hours post-intervention was demonstrated in one small RCT. Significant limitations of the included studies were lack of adequately powered outcomes and clinically relevant time-points and small sample size. Accordingly, systematic review cannot recommend the use of HFNT as the initial management strategy for AT2RF and trials adequately powered to detect clinical and patient-relevant outcomes are urgently warranted.

High-Flow Nasal Cannula versus Noninvasive Ventilation in AECOPD Patients with Respiratory Acidosis: A Retrospective Propensity Score-Matched Study

“…High-fow nasal cannula (HFNC) is a high-fow oxygen delivery system that can provide well-heated and humidifed oxygen at continuous high fow rates up to 60 L/min via a large-bore nasal cannula [5]. Previous studies and literature reviews showed that HFNC had many benefcial efects in stable COPD patients, including a constant fraction of inspired oxygen delivery, dead space washout, improved comfort and tolerance, better communication, enhanced secretion clearance, and positive end-expiratory pressure (PEEP) efect, resulting in decreased PaCO 2 , reduced inspiratory efort, lower rate of moderate/severe exacerbations, and prolonged duration without exacerbations [6][7][8][9][10][11][12][13]. In AECOPD patients, recent studies also showed that HFNC can reduce PaCO 2 and improve capillary pH as well as the work of breathing and patient comfort [14][15][16].…”