Noninvasive Ventilation in Moderate-to-severe COVID-19-associated Acute Respiratory Distress-syndrome

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. The objective of the study is to evaluate the ability of non-invasive ventilation guided with expanded respiratory monitoring to decrease the intubation rate in in moderate-to-severe COVID-ARDS. Investigators will set IPAP as a point of the balance between minimal work of breathing (minimum point of W.Patrick scale for assessment of the accessory respiratory muscles, and minimum diaphragm thickening fraction) and minimum tidal volume, and respiratory rate. Investigators will set expiratory pressure at 8-10 cm of water and the inspiratory oxygen fraction (FiO2) to reach oxygen saturation by pulse oximetry (SpO2) 95%. All gas exchange measurements will be set at IPAP level. For gas exchange assessment investigators will measure partial oxygen tension in the arterial blood (PaO2), partial carbon dioxide tension in arterial blood (PaCO2), end-tidal carbon dioxide tension (PetCO2), then will calculate PAO2/FiO2, alveolar dead space (Vd alv) and ventilatory ratio (VR). Investigators will measure expiratory tidal volume (VT), respiratory rate (RR), peak inspiratory flow (PIF) and inspiratory time at 3 levels: at the set IPAP, at IPAP+4 cm of water and at IPAP-4 cm of water. Measurements will be repeated on day 1, 3, 5, 7, 14 and 21 of NIV. NIV failure is determined as one of the following at set IPAP 26 cm of water and FiO2 100%: fatigue, Patrick scale 5 points, SpO2\<92%, apnoea, hemodynamic instability or Glasgow coma score \<14 points. In patients with NIV failure after intubation and every 7 day after intubation investigators will measure plateau pressure and calculate the driving pressure at PEEP 8-10-12-14 cm of water and VT 6 ml/kg predicted body weight (PBW), and VT+100 ml and VT+200 ml at PEEP 8 cm of water, plot static pressure volume-curve at positive end-expiratory pressure (PEEP) 5 and 14 cm of water, and perform electro impedance tomography. This study is an observational trial in the ICU of the University hospital.