From the Journals

Helmet interface for ventilation likely superior in acute hypoxemic respiratory failure



For adults with acute hypoxemic respiratory failure (AHRF), treatment using a helmet interface is likely superior to a face mask interface, according to a systematic review of recent randomized controlled trials examining different noninvasive oxygenation strategies for AHRF treatment.

The meta-analysis of 36 trials) found also that helmet interface probably lowers mortality and risk of mechanical intervention, and reduces hospital and ICU stay.

The COVID-19 pandemic has underscored the benefits of optimizing noninvasive strategies to avoid unnecessary intubation. Intubation may be avoided in patients with AHRF through noninvasive oxygenation strategies, including high flow nasal cannula (HFNC), continuous positive airway pressure (CPAP) and noninvasive bilevel ventilation, noted Tyler Pitre, MD, department of medicine, McMaster University, Hamilton, Ont., and colleagues. CPAP and bilevel ventilation can be delivered through different interfaces, most commonly face mask or helmet. While research has shown noninvasive strategies to be associated with reductions in risk for invasive mechanical ventilation, mortality assessments and analyses comparing specific modalities (i.e., CPAP vs. bilevel ventilation) have been limited. The incremental reduction in diaphragmatic effort and improved gas exchange demonstrated for bilevel ventilation compared with CPAP in COPD patients suggests that responses in AHRF may differ for CPAP and bilevel ventilation, state Dr. Pitre and colleagues. On the other hand, the increased drive pressure of bilevel ventilation may compound patient self-induced lung injury with concomitant lung inflammation and need for prolonged respiratory support. New evidence from several large, high quality randomized controlled trials (RCTs) in COVID-19-related AHRF offered an opportunity to reassess comparative efficacies, the researchers noted.

The retrospective study encompassed RCTs with all types of AHRF, including COVID-19 related, with a total of 7,046 patients whose median age was 59.4 years (61.4% were males). Thirty of the 36 RCTs reported on mortality (6,114 patients and 1,539 deaths). The study’s analysis showed with moderate certainty that helmet CPAP reduces mortality (231 fewer deaths per 1,000 [95% confidence interval (CI), 126-273]) while the 63 fewer deaths per 1,000 (95% CI, 15-102) indicated with low certainty that HFNC may reduce mortality compared with standard oxygen therapy (SOT). The analysis showed also that face mask bilevel (36 fewer deaths per 1,000 [84.0 fewer to 24.0 more]) and helmet bilevel ventilation (129.0 fewer deaths per 1,000 [195.0 to 24.0 fewer]) may reduce death compared with SOT (all low certainty). The mortality benefit for face mask CPAP compared with SOT was uncertain (very low certainty) (9 fewer deaths per 1,000 [81 fewer deaths to 84 more]). For helmet CPAP vs. HFNC ventilation, the mortality benefit had moderate certainty (198.1 fewer events per 1,000 [95% CI, 69.75-248.31].

Mechanical ventilation and ICU duration

The authors found that HFNC probably reduces the need for invasive mechanical ventilation (103.5 fewer events per 1,000 [40.5-157.5 fewer]; moderate certainty). Helmet bilevel ventilation and helmet CPAP may reduce the duration of ICU stay compared with SOT (both low certainty) at (4.84 days fewer [95% CI 2.33 to 16 7.36 days fewer]) and (1.74 days fewer [95% CI 4.49 fewer to 1.01 more]), respectively. Also, SOT may be more comfortable than face mask noninvasive ventilation (NIV) and no different in comfort compared with HFNC (both low certainty).

“Helmet noninvasive ventilation interfaces is probably effective in acute hypoxic respiratory failure and is superior to face mask interfaces. All modalities including HFNC probably reduce the risk of need for invasive mechanical ventilation,” the researchers wrote.

“This meta-analysis shows that helmet noninvasive ventilation is effective in reducing death, and need for invasive mechanical ventilation based on a moderate certainty of evidence,” Shyamsunder Subramanian, MD, chief, division of pulmonary critical care and sleep medicine, Sutter Health, Tracy, Calif., said in an interview. “It is premature based on the results of this meta-analysis to conclude that guideline changes are needed. Use of helmet based ventilation remains limited in scope. We need appropriately designed prospective trials across multiple centers to get sufficient rigor of scientific evidence before any change in guidelines or practice recommendations can be formulated about the appropriate use of helmet NIV in acute respiratory failure.”

The researchers cited the relative heterogeneity of the population included in this analysis as a study limitation.

Dr. Pitre and Dr. Subramanian disclosed that they have no relevant conflicts of interest.

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