Acute hypoxia and impaired carbon dioxide gas exchange due to respiratory arrest or inadequate ventilation. Severe hypoxemia caused by a huge intrapulmonary shunt, where external oxygen supply fails to achieve adequate inspired oxygen concentrations. Prophylactic brief ventilatory support after major surgical procedures (e.g., cardiac, thoracic, or upper abdominal surgery) to prevent postoperative respiratory dysfunction. In certain neurological and muscular disorders, mechanical ventilation may be applied to increase ventilation to avoid pulmonary atelectasis and secretion retention due to limited lung capacity to produce effective voluntary respiration. The following indicators can be used as criteria for the application of invasive mechanical ventilation. Respiratory rate >30 breaths/min; spirometry <10-15 ml/kg; maximal inspiratory pressure <25 cmH2O (2.35 kPa) PaO2 <60 mmHg (in mask oxygen inhalation), PaCO2 >55 mmHg (in acute respiratory failure).