1. Sedation, analgesia, paralysis: Adequate sedation and analgesia are necessary during mechanical ventilation regardless of tidal volume. Factors such as agitation, delirium, metabolic acidosis, drug withdrawal, septic encephalopathy, and pain need to be considered. Neuromuscular blocking agents should be considered in the 48 h following intubation in patients with severe lung injury, otherwise, paralysis should only be used to achieve patient-ventilator synchrony if sedation and analgesia are insufficient and when other methods described here have been exhausted.
2. Respiratory rate: An increase in respiratory rate setting on the ventilator may match the breathing pattern of the patient to the ventilator, thereby enhancing synchrony. Increasing the respiratory rate setting decreases work-of-breathing and increases patient's comfort. During transition to lower tidal volume ventilation, the respiratory rate should be increased as tidal volume is decreased to maintain constant minute ventilation.
3. Tidal volume: An increase in VT, if accompanied by an increase in alveolar ventilation, decreases respiratory drive. The ARDSNet protocol allows tidal volume to be increased to 8 mL/kg IBW in the case of asynchrony and severe dyspnea, provided plateau pressure is ≤ 30 cm H2O.
4. Trigger sensitivity: Set trigger as sensitive as possible without causing autotriggering.
5. Auto-PEEP: Minimize auto-PEEP.
6. Inspiratory flow: An increase in inspiratory flow may better meet the flow demand of the patient and improve patient's comfort. A higher inspiratory flow also decreases neural inspiratory time, which results in a greater spontaneous breathing frequency and may further contribute to asynchrony.
7. Inspiratory time: A shorter inspiratory time (higher inspiratory flow during VCV) may improve patient-ventilator synchrony. If the inspiratory time setting on the ventilator is less than the neural inspiratory time, however, double triggering and worsening asynchrony may occur. In this case, a longer inspiratory time may be appropriate.
8. Flow waveform: Asynchrony may improve with a descending flow waveform in some patients. For the same peak flow, inspiratory time is longer with a descending flow, which may achieve the goal of better synchrony because of the higher flow while avoiding double triggering secondary to an inspiratory time that is too short.
9. PCV: PCV achieves the goals of a descending flow waveform and an adjustable inspiratory time independent of flow. PCV may result in better synchrony in some patients. A limitation of PCV is the possibility that transpulmonary pressure (an important determinant of volutrauma) may increase because of the generation of high negative intrapleural pressure swings, consequently increasing delivered tidal volume. For the same tidal volume and inspiratory flow, work-of-breathing is likely the same for PCV and VCV.
10. Pressure rise time: With PCV, the clinician can adjust the rate of rise in pressure at the onset of the inspiratory phase. If the pressure rises more quickly, flow is higher at the beginning of inhalation, which might affect work-of-breathing and patient's comfort.