Oxygenation by helmet, high flow didn't affect mortality in COVID-19, studies find
One trial randomized patients to helmet noninvasive ventilation or usual forms of respiratory support and found no differences. Another comparing high-flow and standard oxygen found a decrease in intubation rate with the former, but no change in any other outcome.
Two new studies found no difference in mortality between methods of providing oxygen to hospitalized patients with COVID-19.
The first study, conducted in Saudi Arabia and Kuwait and published by JAMA on Sept 20, randomized patients with acute hypoxemic respiratory failure (AHRF) due to suspected or confirmed COVID-19 to helmet noninvasive ventilation (n=159) or usual respiratory support (n=161), which included mask noninvasive ventilation, high-flow nasal oxygen, and standard oxygen. Among the 320 patients included in the primary analysis, 28-day mortality was 27.0% in the helmet group versus 26.1% in the usual care group (risk difference, 1.0% [95% CI, −8.7% to 10.6%]; P=0.85). The groups were similar in their rates of intubation (47.2% vs. 50.3%) and on all other prespecified secondary end points. The authors concluded that helmet noninvasive ventilation did not significantly reduce 28-day mortality but added that “interpretation of the findings is limited by imprecision in the effect estimate, which does not exclude potentially clinically important benefit or harm.” Limitations of the study include 4.6% of patients initially assigned to the helmet group declining the therapy and an additional 36.5% discontinuing it due to reported intolerance.
High-flow and standard oxygen were compared in the SOHO-COVID trial, conducted in 34 ICUs in France. Patients with respiratory failure due to COVID-19 and a ratio of PaO2 to FIO2 equal to or below 200 mm Hg were randomized to high-flow oxygen (n=357) or standard oxygen delivered through a nonrebreathing mask initially set at a minimum of 10 L/min (n=354). Among the 711 patients included in the final analysis, 28-day mortality rates were similar (10% with high flow vs. 11% with standard oxygen; absolute difference, –1.2% [95% CI, –5.8% to 3.4%]; P=0.60). Only one of 13 prespecified secondary outcomes differed significantly between groups: The intubation rate was 45% with high-flow oxygen and 53% with standard oxygen (absolute difference, –7.7% [95% CI, –14.9% to –0.4%]; P=0.04). Results were published by JAMA on Sept. 27.
The trial's results confirm those of a previous one in Colombia, which also found decreased risk of intubation with high-flow oxygen and no change in mortality, but differ from those of a British study that found no effect on either outcome, the study authors noted. Mortality rates from COVID-19 decreased as the trial was underway, leading it to be potentially underpowered to show a difference on that outcome, they added. “Although high-flow oxygen had no significant effect on the primary outcome of mortality, the decreased risk of intubation and need for invasive mechanical ventilation may be considered an important outcome for patients with acute respiratory failure. In addition, it may also help avoid the use of ICU ventilators in resource-constrained settings during a pandemic,” the authors wrote.
An accompanying editorial reviewed the many recent trials of oxygenation strategies in COVID-19. “The available evidence suggests that the initial choice of supplemental oxygen therapy for patients with COVID-19–related AHRF does not influence mortality,” said the editorial, noting that the effects on other outcomes are less certain. “Particular attention should be given to the potential for complications with each approach, as well as patient preference and tolerance of the selected therapy.”
