Delaying intubation with high-flow nasal cannula therapy: a dilemma between the technique and clinical management!

Abstract

Dear Editor, We read with interest the article by Kang et al. [1] suggesting that highflow nasal cannula (HFNC) could potentially have a harmful effect on outcome and survival by delaying the intubation time in unselected patients with acute hypoxemic respiratory failure (AHRF). HFNC is an emerging oxygenation technique with numerous physiological advantages [2]. Consequently, HFNC has been shown to be more tolerated and associated with better oxygenation than standard oxygen therapy, allowing one to rapidly relieve the AHRF symptoms [3]. First of all, the clinical benefit of HFNC on adult AHRF patient outcome has now been demonstrated in a large French prospective randomized controlled trial, the ‘‘FLORALI’’ study, which is currently under consideration for publication [4]. In fact, the Kang et al. [1] retrospective study emphasizes more the risks of HFNC management than those of the technique per se. We understand that the routine HFNC strategy used (greater than 9 l/min of conventional oxygen needed) was also applied to patients in general wards. Despite the management by a skilled medical emergency team, this clinical practice could be highly hazardous in terms of surveillance and prompt intubation. In this way, it would be interesting to know the late intubation rate performed in ICU and general ward, respectively. Also, no data is provided regarding the level of HFNC gas flow used in the two groups. Indeed, gas flow is essential to consider as many physiological mechanisms of HFNC are highly related to the level used. In practice, it should be recommended to start HFNC with high gas flow (at least 50 l/min) in order to rapidly reverse AHRF symptoms [3]. Although HFNC was not applied in patients with hypercapnia, this may be questionable as more than 30 % of ARF etiologies occurred in acute-onchronic respiratory failure patients and more patients with hypercapnic ARF were intubated and died in the late intubation group. Although some physiological mechanisms of HFNC may suggest its potential benefit in hypercapnic ARF, no clinical study has been yet conducted in this selected population and noninvasive ventilation (NIV) remains, currently, the ventilatory strategy recommended in these patients. The median duration of HFNC before intubation was also very different between the early (10 h) and late (126 h) intubation groups. Clearly, maintaining AHRF patients on HFNC for more than 5 days does not appear reasonable and such a delay has never been previously reported, even in do-notintubated ARF patients [5]. Paradoxically, numerous patients (31 %) have been tracheostomized in the early intubation group and considering tracheostomy as a weaning success may be debatable. The overall ICU mortality was very high in the study (46 %) and higher in the late (67 %) than the early (39 %) intubation group. This could be due to the high proportion of immunocompromised patients (more than 50 %), but also to the severity of the underlying organ failure, 9 % exhibiting a septic shock. In our view, HFNC should be reserved for patients without hemodynamic instability. Finally, the 14and 28-day mortality was not different, suggesting that hospital mortality was similar between both groups. This result should greatly limit the study interpretation and conclusion. Nevertheless, the study by Kang et al. [1] has the merit of pointing out the potential risk of HFNC to unnecessary delay the intubation time, as it has been and may be still debated with NIV. Therefore, clinicians should be aware of this risk and, like NIV, HFNC success should consider the population selection, experience and close monitoring with HFNC in a safe environment. Moreover simple and very early clinical signs of HFNC failure have been described and should be very useful for routine practice [3].