[Patient-ventilator interaction]

Mechanically ventilated patients interact with ventilator functions at different levels such as triggering of the ventilator, pressurization and cycling from inspiration to expiration. Patient ventilator asynchrony in any one of these phase results in fighting with ventilator, increase in work of breathing and respiratory muscle fatigue. Patient ventilator dyssynchrony occurs when gas delivery from the ventilator does not match with the neural output of the respiratory center. The clinical findings of patient-ventilator asynchrony are; use of accessory respiratory muscle, tachypnea, tachycardia, active expiration, diaphoresis and observation of asynchrony between patient respiratory effort and the ventilator waveforms. Among the patients with dynamic hyperinflation such as chronic obstructive pulmonary disease the most frequent causes of patient-ventilator asynchrony are trigger and expiratory asynchronies. In acute respiratory distress syndrome patient-ventilator asynchrony may develop due to problems in triggering or asynchrony in flow and inspiration-expiration cycle. Patient-ventilator interaction during noninvasive mechanical ventilation may be affected by the type of masks used, ventilator types, ventilation modes and parameters, humidification and sedation. Among the different patient groups it is important to know causes and solutions of patient-ventilator asynchrony problems. By this way patient will adapt ventilator and then dyspnea, ineffective respiratory effort and work of breathing may decrease subsequently.