The main variables such as age, sex, vital signs parameters: heart rate, respiratory rate, saturation of peripheral oxygen (SpO2) at the time of admission (T0), 1 hour (T1), 6 hours (T2), 12 hours hours (T3), 24 hours (T4), 48 hours (T5), 72h hours (T6) after IPV; arterial blood gas indices such as pH, PaCO2, PaO2, HCO3 - at the time of T0, T2, T4, T5, T6.