Noninvasive ventilation usage time and survival rate in patients with acute respiratory failure: some key insights.

The possibility of avoiding adverse events by recommending early determination of mask-on proportions in the first 24 h of admission and, consequently, NIV failure in ARF patients https://bit.ly/2T0QYVN.

To the Editor:

One of the major causes of emergency admissions is acute respiratory failure (ARF) [1]. Noninvasive ventilation (NIV) is increasingly used for ARF management because of its efficacy (particularly in hypercapnic patients), achievable goals and because it can be outside the intensive care unit [2]. The benefits of NIV are still under investigation in various hypoxaemic respiratory failure (HRF) aetiologies, such as asthma, pneumonia, immunosuppression and acute respiratory distress syndrome [1].

We read with great interest the study presented by Hukins et al. [3], which for the first time, successfully displays a dose–response relationship between the actual mask-on usage period and hospital survival in ARF patients. Notably, the authors took great efforts to compare their results with previous trials, which mainly investigated the total period of NIV therapy, including both mask-on and mask-off times. The study also provides beneficial data regarding the survival rate and its relationship with therapy intensity calculated as a proportion of mask-on usage from a total NIV period, as well as the association of survival with concomitant patient comorbidities. The large sample size (n=654) collected over 5 years was considered a major advantage of this retrospective study, as it increased the applicability of its findings, especially in patients with hypercapnic respiratory failure (HCRF), who represented ∼91% of the included patients. However, we feel that with regard to the methodology, some key aspects require clarification. First, HCRF and HRF groups are not matched so the study outcomes are mainly based on the HCRF group, with a ceiling effect at 24 h of cumulative mask-on usage. The reliability of the results in hypoxaemic patients is therefore limited and further investigations are needed.

Secondly, the exclusion criteria for acute NIV need to be defined in detail in the methodology. Additionally, the authors determine that a number of patients ceased NIV before clinical stability, which was due to intolerance or ineffectiveness of therapy, but did not illustrate the alternative therapy provided. If those patients were stepped up to a more invasive technique, why was the intubation rate not calculated as a secondary outcome, as in many previous studies [4-6]?

Finally, the authors stated that an inverse dose–response relationship was noted between survival and the intensity of therapy in the HCRF group, and the same was noted in the HFR group but not in a dose–response manner, with the highest mortality seen in patients requiring mask-on proportions of 80–100% of acute NIV therapy. We wonder whether the intubation delay in patients with high disease severity contributed to high mortality, and whether it was possible to avoid such adverse events by early recommendation of mask-on proportions in the first 24 h of admission, consequently avoiding NIV failure in ARF patients [7]. Further clinical trials are needed to confirm these results.