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The respective effects of PEEP and pressure support delivered through the helmet interface in hypoxemic patients need to be better understood.To assess the respective effects of helmet pressure support (NIV) and continuous positive-airway pressure (CPAP) compared to high-flow nasal oxygen (HFNO) on effort to breathe, lung inflation and gas exchange in hypoxemic patients (PaO2/FiO2≤200).Fifteen patients underwent 1-hour phases (constant FiO2) of HFNO (60 L/min), helmet NIV (PEEP=14 cmH2O, pressure support=12 cmH2O) and CPAP (PEEP=14 cmH2O) in randomized sequence.Inspiratory esophageal (ΔPES) and transpulmonary pressure (ΔPL) swings were used as surrogates for inspiratory effort and lung distension, respectively. Tidal volume (VT) and end-expiratory lung volume were assessed with electrical impedance tomography.ΔPES was lower during NIV vs. CPAP and HFNO (5[3-9] cmH2O vs. 13[10-19] vs. 10[8-13], p=0.001 and p=0.01). ΔPL was not statistically different between treatments. PaO2/FiO2 ratio was significantly higher during NIV and CPAP vs. HFNO (166[136-215] and 175[158-281] vs. 120[107-149], p=0.002 and p=0.001). NIV and CPAP similarly increased VT vs. HFNO (mean change: 70%[95%CI: 17-122], p=0.02; 93% [95%CI: 30-155], p=0.002) and end-expiratory lung volume (mean change: 198%[95%CI: 67-330], p=0.001; 263%[95%CI: 121-407], p=0.001), mostly due to increased aeration/ventilation in dorsal lung regions. During HFNO, 14/15 patients had pendelluft involving10% of VT: pendelluft was mitigated by CPAP and further by NIV.Compared to HFNO, helmet NIV, but not CPAP, reduced ΔPES. CPAP and NIV similarly increased oxygenation, end-expiratory lung volume and VT, without affecting ΔPL. NIV, and to a lesser extent, CPAP, mitigated pendelluft. Clinical trial registration available at www.gov, ID: NCT04241861.

In non-COVID 19 acute hypoxemic respiratory failure, the entity of dyspnea has been associated with severity of hypoxemia, and represents a factor predicting noninvasive ventilation (NIV) failure, the need for endotracheal intubation and mortality [1].

IMPORTANCE: High-flow nasal oxygen is recommended as initial treatment for acute hypoxemic respiratory failure and is widely applied in patients with COVID-19. OBJECTIVE: To assess whether helmet noninvasive ventilation can increase the days free of respiratory support in patients with COVID-19 compared with high-flow nasal oxygen alone. DESIGN, SETTING, AND PARTICIPANTS: Multicenter randomized clinical trial in 4 intensive care units (ICUs) in Italy between October and December 2020, end of follow-up February 11, 2021, including 109 patients with COVID-19 and moderate to severe hypoxemic respiratory failure (ratio of partial pressure of arterial oxygen to fraction of inspired oxygen ≤200). INTERVENTIONS: Participants were randomly assigned to receive continuous treatment with helmet noninvasive ventilation (positive end-expiratory pressure, 10-12 cm H(2)O; pressure support, 10-12 cm H(2)O) for at least 48 hours eventually followed by high-flow nasal oxygen (n = 54) or high-flow oxygen alone (60 L/min) (n = 55). MAIN OUTCOMES AND MEASURES: The primary outcome was the number of days free of respiratory support within 28 days after enrollment. Secondary outcomes included the proportion of patients who required endotracheal intubation within 28 days from study enrollment, the number of days free of invasive mechanical ventilation at day 28, the number of days free of invasive mechanical ventilation at day 60, in-ICU mortality, in-hospital mortality, 28-day mortality, 60-day mortality, ICU length of stay, and hospital length of stay. RESULTS: Among 110 patients who were randomized, 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). Of 9 prespecified secondary outcomes reported, 7 showed no significant difference. The rate of endotracheal intubation was significantly lower in the helmet group than in the high-flow nasal oxygen group (30% vs 51%; difference, −21% [95% CI, −38% to −3%]; P = .03). The median number of days free of invasive mechanical ventilation within 28 days was significantly higher in the helmet group than in the high-flow nasal oxygen group (28 [IQR, 13-28] vs 25 [IQR 4-28]; mean difference, 3 days [95% CI, 0-7]; P = .04). The rate of in-hospital mortality was 24% in the helmet group and 25% in the high-flow nasal oxygen group (absolute difference, −1% [95% CI, −17% to 15%]; P > .99). CONCLUSIONS AND RELEVANCE: Among patients with COVID-19 and moderate to severe hypoxemia, 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. Further research is warranted to determine effects on other outcomes, including the need for endotracheal intubation. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04502576

BACKGROUND: The efficacy of noninvasive oxygenation strategies (NIOS) in treating COVID-19 disease is unknown. We conducted a prospective observational study to assess the rate of NIOS failure in subjects treated in the ICU for hypoxemic respiratory failure due to COVID-19. METHODS: Patients receiving first-line treatment NIOS for hypoxemic respiratory failure due to COVID-19 in the ICU of a university hospital were included in this study; laboratory data were collected upon arrival, and 28-d outcome was recorded. After propensity score matching based on Simplified Acute Physiology (SAPS) II score, age, P aO 2 /F IO 2 and P aCO 2 at arrival, the NIOS failure rate in subjects with COVID-19 was compared to a previously published cohort who received NIOS during hypoxemic respiratory failure due to other causes. RESULTS: A total of 85 subjects received first-line treatment with NIOS. The most frequently used methods were helmet noninvasive ventilation and high-flow nasal cannula; of these, 52 subjects (61%) required endotracheal intubation. Independent factors associated with NIOS failure were SAPS II score (P = .009) and serum lactate dehydrogenase at enrollment (P = .02); the combination of SAPS II score ≥ 33 with serum lactate dehydrogenase ≥ 405 units/L at ICU admission had 91% specificity in predicting the need for endotracheal intubation. In the propensity-matched cohorts (54 pairs), subjects with COVID-19 showed higher risk of NIOS failure than those with other causes of hypoxemic respiratory failure (59% vs 35%, P = .02), with an adjusted hazard ratio of 2 (95% CI 1.1–3.6, P = .01). CONCLUSIONS: As compared to hypoxemic respiratory failure due to other etiologies, subjects with COVID-19 who were treated with NIOS in the ICU were burdened by a 2-fold higher risk of failure. Subjects with a SAPS II score ≥ 33 and serum lactate dehydrogenase ≥ 405 units/L represent the population with the greatest risk.

Background: Although widely applied, noninvasive ventilatory support (NIVS) efficacy in COVID-19 disease is unknown. Early identification of treatment failure is warranted to avoid delays in endotracheal intubation and protective ventilation. We conducted a study to determine the rate of and factors associated to NIVS failure in critically ill patients with COVID-19 disease, and to compare NIVS failure rate in COVID-19 patients to that of a matched cohort with hypoxemic respiratory failure of other origins. Methods: All consecutive patients receiving first-line treatment NIVS for hypoxemic respiratory failure due to COVID-19 in the ICU of a University Hospital in Italy up to April 20th, 2020, were studied: laboratory data were collected on arrival, 28-day outcome was recorded. After one-to-one propensity score matching based on simplified acute physiology (SAPS) II score, age, PaO2/FiO2 and PaCO2 at arrival, NIVS failure rate in COVID-19 patients was compared to a previously published cohort who received NIVS during hypoxemic respiratory failure from other causes. Results: Eighty-five patients received first-line treatment with NIVS, mainly with helmet noninvasive ventilation and high-flow nasal cannula. Fifty-two patients (61%) needed endotracheal intubation. Independent predictors of NIVS failure were SAPSII score (adjusted hazard ratio 1.039 [1.018-1.061], Conclusions: COVID-19 patients receiving first-line NIVS are burdened by high risk of needing endotracheal intubation: this appears greater than that of patients affected by hypoxemic respiratory failure of other origins. In order to not delay endotracheal intubation, if logistically sustainable, NIVS use in the intensive care unit should be avoided in severe patients (SAPSII score≥33) with serum lactate de-hydrogenase≥405 Units/Liter.