[Patient-noninvasive mechanical ventilation interaction]

Noninvasive mechanical ventilation is one more step in the treatment of patients with acute respiratory failure. In addition to gas exchange disorders, its primary indication to initiate it is the presence of signs of respiratory muscles fatigue. To assure successful mechanical ventilation, the ventilator and patient must be synchronized, that is, the effort the patient makes to start inspiration is recognized by the ventilator and it quickly delivers gas flow, that the flow provided by the ventilator adapts to the flow need of the patient during delivery of gas phase and that the ventilator recognizes the cessation of inspiratory activity by the patient, ends the delivery of gas and opens the expiratory valve to allow the patient expiration. This sequence of events, which seem so logical, is almost never achieved in the clinical practice, commonly observing some asynchrony in ventilated patients. The presence of patient-ventilator asynchrony leads to increased breathing work, which would lead to the failure of the main objective of ventilatory support, that is none other than decline in the patient's respiratory work.