LAUSR

Background Acute type 2 respiratory failure (AT2RF) is the failure of ventilatory mechanism which results in hypercapnia(>6kPa). Current treatment is non-invasive ventilation(NIV) which has a high failure rate. High flow nasal therapy (HFNT) showed a variety of benefits for AT2RF patients such as, CO2 clearance, ability of communication and comfort. This systematic review aims to determine whether the use of HFNT for patients with AT2RF improves 1)arterial CO2(PaCO2) and 2)clinical and patient-centred outcomes and 3)to assess any potential harms. Method We searched relevant electronic databases from 1999 to August 2019. We included randomised trials and cohort studies comparing HFNT with low-flow oxygen (LFO) or NIV. Two authors independently assessed studies for eligibility, data extraction and trial quality. Results From 539 publications reviewed, three studies (n=340 participants) met the inclusion criteria: two RCTs and one cohort. There was no significant difference between HFNT vs NIV and HFNT vs simple nasal prong (SNP) in PaCO2 at different time points (see table 1). Respiratory parameters including, PaO2 and pH showed no significant difference between HFNT and NIV. For patient comfort no significant differences were reported by two studies except, patients found SNP to be quieter than HFNT Pilcher et al. (MD 1.30, 95% CI 0.44, 2.16). For dyspnoea score no significant difference were reported between HFNT and NIV. Intubation rate showed no difference between HFNT and NIV, Doshi et al. at 72 hours (OR 0.48 95% CI 0.18, 1.27), Lee et al. at 30 days (OR 0.89 95% CI 0.34, 2.30). mortality rate of 30-day showed no difference between HFNT and NIV, Lee et al. (OR 0.85 95% CI 0.28, 2.59). No difference in hospital stay between patients in HFNT and NIV groups. Conclusion Our systematic review has identified a small number of trials related to AT2RF patients with variability of outcomes measured. The benefits of HFNT for AT2RF patients are supported by low to very low quality of evidence. Thus use of HFNT for AT2RF cannot be recommended. Current evidence does suggest similar improvements in PaCO2, pH, intubation and mortality rate with HFNT when compared to NIV suggesting potential benefit. However, there is an urgent need for high quality randomised controlled trials.