Characteristics and Outcomes of Patients With COVID-19-related Acute Respiratory Failure Treated With High-flow Nasal Oxygen and Awake-prone Position

Objective. To evaluate the clinical results of the simultaneous application of high-flow nasal oxygen therapy HFNO and awake-prone position in a cohort of patients with severe respiratory failure secondary to COVID-19 on relevant clinical outcomes, and to assess risk factors of treatment failure defined as requirement of invasive mechanical ventilation.

Design: Prospective multicenter cohort study conducted at 5 ICUs of 5 centers in Argentina. The Internal Review Board from the 5 centers approved the study including waived informed consent. The interventions carried out were part of the usual practice at each center and confidentiality of participants was guaranteed.

Population. Patients older than 18 years admitted to the ICU with a confirmed diagnosis of COVID-19 (real-time PCR) and receiving HFNO for at least 4 hours. Patients received HFNO when any of the following criteria were present: a) peripheral oxygen saturation (SpO2) < 92% with oxygen > 4 liters/minute; b) increased work of breathing with use of accessory respiratory muscles, and a respiratory rate > 30/min; c) partial pressure of oxygen /Fraction of inspired oxygen (PaO2/FiO2ratio) < 200 mmHg. Patients with respiratory failure secondary to a different etiology, decreased level of consciousness, presence of shock requiring vasopressors, immediate need for intubation, use of positive-pressure ventilation prior to HFNO, and with do-not intubate orders were excluded.

Procedures.Immediately after admission to the ICU, the inclusion criteria regarding oxygenation and/or work of breathing are checked. Then a high-flow nasal cannula sized according to the nares size is placed, and connected to a specific device for the provision of high-flow O2. The initial flow is 50-70 L/min, with the fraction of inspired oxygen (FiO2) necessary to obtain an SpO2 > 92%. No maximum FiO2 limits is established. Once therapy with HFNO is started, participants are encouraged and assisted by the health-care team to rotate from supine to prone position for as long as possible, taking breaks for personal hygiene and eating. No maximum time limits for prone position are established. Patients who tolerated HFNO for the next 4 hours are included in the study. These interventions are maintained during the study period until one of the following criteria was met: maintenance of SpO2 > 92% with FiO2 ≤ 40%, and flow ≤ 40 L/min for a period > 12 hours in the supine position; or endotracheal intubation. Analgesic drugs (opioids, paracetamol) or light sedation (dexmedetomidine) was allowed and indicated according to the criteria of the health-care team.

Variables and measurements. The following variables are collected: demographics (age, sex, body mass index [BMI]), comorbidities, severity scores upon ICU admission (APACHE II and SOFA), chronology of the disease (time from the onset of symptoms to hospital admission and ICU admission), vital signs, laboratory parameters, Respiratory rate Oxygenation index (ROX index) [7] , and chest computed tomography score (CT score) determined as the sum of lung involvement, ranging from 0 -no involvement- to 25 -maximum involvement [8].