CPAP Therapy Through a Helmet or a Full Face Mask in Patients With Acute Hypoxemic Respiratory Failure: Cross-over Study

Observational and randomized trials have demonstrated the high effectiveness of non-invasive helmet ventilatory support, demonstrating a reduction in intubation rate mortality compared with high-flow and standard oxygen therapy. Some pilot physiological studies have shown physiological benefits of helmets compared to the oronasal mask for non-invasive ventilation. The purpose of the study is to compare markers of patient self-inflicted lung injury (P-SILI), patient's comfort, work of breathing, gas exchange, and hemodynamics in patients with acute hypoxemic respiratory failure (AHRF) during non-invasive ventilation (NIV) in continuous positive pressure (CPAP) mode during an oronasal mask ventilation or a combination of a helmet with high-flow oxygenation as an air flow generator.

In December 2019, an outbreak of a novel coronavirus emerged in Wuhan, China and rapidly spread worldwide. The World Health Organization (WHO) declared the outbreak a pandemic on March 11th, 2020. The clinical disease (COVID-19) results in critical illness in about 5% of patients with predominant acute respiratory failure. Observational and randomized trials have demonstrated the high effectiveness of non-invasive helmet ventilatory support, demonstrating a reduction in intubation rate mortality compared with high-flow and standard oxygen therapy. Some pilot physiological studies have shown physiological benefits of helmets compared to the oronasal mask for non-invasive ventilation.

The purpose of the study is to compare markers of patient self-inflicted lung injury (P-SILI) (measuring esophageal pressure, transpulmonary pressure during inspiration and expiration), the patient's work of breathing (assessment of accessory muscles work) patient's comfort by visual-analog scale, gas exchange (by PaO2/FiO2 and Respiration Oxygenation Index (ROX-index), and hemodynamics in patients with acute hypoxemic respiratory failure (AHRF) during non-invasive pulmonary ventilation (NIV) in continuous positive pressure (CPAP) mode during an oronasal mask ventilation or a combination of a helmet with high-flow oxygenation as an air flow generator.

Eligibility Criteria:
Inclusion Criteria:

* Patients with acute hypoxemic respiratory failure due to community-acquired pneumonia or COVID-19
* The ratio of the partial pressure of oxygen in arterial blood to the inspiratory fraction of oxygen (PaO2/FiO2) is less than 250 mm Hg while breathing atmospheric air
* Respiratory rate more than \> 25 per minute.
* Written informed consent

Exclusion Criteria:

* Patients who achieve the following target parameters with only low-flow oxygen therapy (flow up to 15 l/min): SpO2 \> 93%, the patient does not have a subjective feeling of fatigue, there is no visible work of the auxiliary respiratory muscles of the neck,
* Unstable hemodynamics (systolic blood pressure \<90 mm Hg or mean arterial pressure \<65 mm Hg) and/or lactic acidosis (lactate \>5 mmol/l and/or clinically diagnosed shock) and/or life-threatening arrhythmia,
* Metabolic acidosis (pH \<7.30);
* Patients who were in the ICU for less than 24 hours for any reason
* Primary or secondary lung diseases (exacerbation of chronic obstructive pulmonary disease (COPD), bronchial asthma, interstitial lung diseases, metastatic lung disease)
* Cardiogenic pulmonary edema,
* Chronic diseases in the stag e of decompensation with the development of extrapulmonary organ dysfunction (liver cirrhosis, progression of cancer, CHF),
* Glasgow Coma Scale score \<14 points,
* Swallowing disorders
* Hypercapnia (PaCO2\>45 mmHg),
* The need for urgent tracheal intubation for any reason,
* Recent head surgery or anatomy that prevents the placement of a helmet or full face mask on the patient,
* Pregnancy,
* Inability to cooperate with staff