Helmet non-invasive ventilation!

Source: JAMA. 2021 May 4;325(17):1731-1743

Contributed by Dr Rini Bandyopadhyay, CMC, Vellore

Acute hypoxemic respiratory failure is the most common organ failure and cause of admission to the ICU among patients with moderate to severe COVID-19 disease. The role of non-invasive respiratory support in patients with acute hypoxemic respiratory failure is debated. The main concerns remain, high failure rate with NIV leading to the need for intubation and invasive mechanical ventilation in approximately 42%-47% with moderate to severe acute respiratory distress syndrome and the additional risk of high mortality with intubation (approximately 45%). These outcomes may be attributable to injurious high tidal volumes generated with NIV, insufficient alveolar recruitment, or high work of breathing.

This study evaluated whether helmet noninvasive ventilation can increase the days free of respiratory support in patients with COVID-19 compared with high-flow nasal oxygen alone. The intervention was the early application of 48 hours of helmet NIV or HFNO and the primary outcome was days free of respiratory support at 28 days. A total of 109 patients with moderate to severe hypoxemia (ratio of partial pressure of arterial oxygen to fraction of inspired oxygen ≤200) were recruited between October and December 2020. Clearly defined criteria for treatment failure (intubation) were used and a protocolized approach to weaning from each treatment was applied. Study participants were randomly assigned to receive continuous treatment with helmet noninvasive ventilation (positive end-expiratory pressure, 10-12 cm H2O; pressure support, 10-12 cm H2O) for at least 48 hours eventually followed by high-flow nasal oxygen (n = 54) or high-flow oxygen alone (60 L/min) (n = 55).

110 patients were randomized, of which 109 (99%) completed the trial (median age, 65 years [interquartile range {IQR}, 55-70]; 21 women [19%]). The median days free of respiratory support within 28 days after randomization were 20 (IQR, 0-25) in the helmet group and 18 (IQR, 0-22) in the high-flow nasal oxygen group, a difference that was not statistically significant (mean difference, 2 days [95% CI, −2 to 6]; P = .26). Several clinically important secondary outcomes differed between the groups: a significantly lower incidence of intubation in the helmet NIV group (30% vs 51% for HFNO; P = .03) and a higher number of invasive mechanical ventilation–free days at 28 days in the helmet NIV group (28 days [IQR, 13-28] vs 25 days [IQR, 4-28]; P = .04).

This is the first trial to directly compare helmet NIV vs HFNO in patients with a relatively homogeneous cause of AHRF. The study clearly demonstrates that among critically ill patients with moderate to severe hypoxemic respiratory failure due to COVID-19, treatment with helmet noninvasive ventilation, compared with high-flow nasal oxygen, resulted in no significant difference in the number of days free of respiratory support within 28 days. Although a difference in the primary endpoint was not seen, this likely relates to the study being underpowered. The primary outcome of this study is important from the perspective of resource allocation during a pandemic and, hence, larger trials would be informative. Additionally, the study demonstrated a substantial decrease in the proportion of patients intubated in the helmet NIV group. This finding is intriguing and requires further evaluation in future studies since if oxygenation and work of breathing improved (both criteria for intubation), less intubation would be expected. Larger studies need to further evaluate whether these findings translate into important patient-centered outcomes such as mortality and longer-term functional outcomes.