Table 1

Eligibility criteria

Inclusion criteria

  1. Suspected or confirmed COVID-19.*

  2. Aged ≥14 years old. ICUs that use other age cut-off for adult patients will adhere to their local standard (16 or 18 years).

  3. Acute hypoxaemic respiratory failure based on PaO2:FiO2 ratio of <200 despite supplemental oxygen with a partial or non-rebreathing mask at a flow rate of >10 L/min or higher.

  4. Intact airway protective gag reflex.

  5. Able to follow instructions.

Exclusion criteria

  1. Prior intubation during this hospital admission.

  2. Cardiopulmonary arrest.

  3. Glasgow Coma Scale score of <12.

  4. Tracheostomy.

  5. Upper airway obstruction.

  6. Active epistaxis.

  7. Requirement for more than one vasopressor to maintain mean arterial pressure of >65 mm Hg.

  8. Pregnancy.

  9. Imminent intubation.

  10. Patients with do-not-intubate orders (or equivalent).

  11. Enrolled in another trial for which coenrolment is not approved, including trials on mechanical ventilation.

  12. Patients already treated with helmet.

  13. Patients with chronic carbon dioxide retention (PaCO2 >45).

  14. Previous enrolment in this trial.

  15. The primary cause of respiratory failure is not heart failure as judged by the treating team.

Eligible non-randomised

  1. Patient or substitute decision maker declines consent.

  2. ICU physician or other treating clinician declines consent.

  • *A suspected/probable COVID-19 case is defined as at least two of the following symptoms: fever (measured or subjective), chills, rigours, myalgia, headache, sore throat, new olfactory and taste disorder(s) or at least one of the following symptoms: cough, shortness of breath or difficulty breathing, or severe respiratory illness with at least one of the following: clinical or radiographical evidence of pneumonia or ARDS and no alternative more likely diagnosis. A confirmed COVID-19 case is defined as detection of SARS-CoV-2 RNA in a respiratory specimen using a molecular amplification detection test such as RT-PCR (https://wwwn.cdc.gov/nndss/conditions/coronavirus-disease-2019-covid-19/case-definition/2020/).

  • ICU, intensive care unit; PaO2:FiO2, ratio of arterial oxygen partial pressure to fraction of inspired oxygen; RT-PCR, reverse transcription PCR.