flow rates of high-flow nasal cannula and extubation outcome

Conditions: Hypoxemic Respiratory Failure

Summary: this is a single-center, open-label, randomized controlled trial to evaluate the effect of high-flow nasal cannula with a flow rate of 60 l/min versus 40 l/min after planned extubationon on a composite outcome of reintubation and use of niv.

this is a single-center, open-label, randomized controlled trial to evaluate the effect of high-flow nasal cannula with a flow rate of 60 l/min versus 40 l/min after planned extubationon on a composite outcome of reintubation and use of niv in patients who are intubated for hypoxemic respiratory failure. \[study procedures\] set flow rates of hfnc the flow rates of hfnc(high-flow nasal cannula) are set as 40 l/min and 60 l/min, respectively in the two trial groups. fio2 was down-titrated to the minimal level to keep so2 ≥ 92%. after that, the flow rate setting is fixed for 24hrs +/- 6 hrs in the two groups. after that, the flow rate setting in both groups would be tapered to 30 l/min and would be kept for 12 hours. then, hfnc would be changed to conventional oxygen therapy to keep spo2≥ 92%. \[outcome measures\] to increase the statistical power of this pilot trial, we used a composite outcome of niv use and or reintubation in 48 hours for the primary endpoint. secondary endpoints include mortality of different time points, physiological parameters(respiratory rate, heart rate), ventilation/oxygenation data(pao2/fio2 ratio, ph) and patient comfort. exploratory endpoints include comparison between different flow rate settings. \[primary endpoint\] we hypothesized that higher flow setting of hfnc can reduce work of breathing and can increase washout of dead space, which could result in lower re-intubation rate and lower niv use rate after planned extubation in hypoxemic patients. the primary endpoint is a composite outcome of niv use or reintubation in 48 hours between two groups of different flow rates. \[secondary endpoints\] icu mortality in-hospital mortality 28-day mortality time to successful liberation from mechanical ventilation auc(area under curve) of respiratory rate (0-24 hours) auc of heart rate (0-24 hours) pao2/fio2 ratio at 4 and 24 hours change of arterial co2 level(mmhg) at 4 and 24 hours proportion of respiratory acidosis (arterial blood gas: ph\<7.35) at 4 and 24 hours proportion of intolerance (up titration of flow or/and fio2; down titration of flow) in 24 hours \[sample size\] the event rate of primary endpoint, defined as a composite outcome of niv use and or reintubation in 48 hours, was assumed to be 40% in the 40 l/min arms and 20% in the 60 l/min. we estimated that with a sample of 180 patients, the study would have 80% power to detect a 20% absolute reduction in proportion of composite outcomes, at a two-sided type i error rate of 5%.

Eligibility criteria:
inclusion criteria: * invasive mechanical ventilation \> 48 hours * acute hypoxemic respiratory failure(pao2/fio2 \< 300 mmhg) as a main cause of invasive mechanical ventilation. * planned extubation \& already passed a spontaneous breathing trial (sbt) exclusion criteria: * \< 20 years of ages * refusal to re-intubation * with terminal cancer * pregnant women * with a tracheal stoma or tracheostomy tube in situ * not feasible for high-flow nasal cannula(decided by the primary care team) * must required to use non-invasive ventilation immediately after extubation (decided by the primary care team)

Keywords: high-flow nasal cannula hypoxemic respiratory failure oxygen therapy postextubation respiratory failure