Invasive mechanical ventilation refers to the administration of ventilation directly in the trachea via an endotracheal tube or tracheostomy.
1. Breath control: This refers to the method by which the mechanical breath is delivered. If the tidal volume and inspiratory flow are designated, the breath is classified as volume controlled (VC). Conversely, if the breath is delivered based on a preset inspiratory pressure, the breath is pressure controlled (PC).
2. Breath sequence: Spontaneous and mandatory are the two types of breaths. A mandatory breath is started (triggered) or ended (cycled) by the machine; ventilators may also be set to allow triggering of a mandatory breath coordinated with patient inspiratory effort. If the breath is both triggered and cycled by the patient, it is a spontaneous breath. By definition, a mandatory breath is always assisted (that is, the machine does some portion of the work of breathing), but a spontaneous breath may or may not be assisted. Therefore, there are three breath sequences:
Continuous mandatory ventilation (CMV): All breaths are mandatory. A preset frequency represents the minimum number of mandatory breaths per minute; the patient may trigger breaths at a higher frequency.
Intermittent mandatory ventilation (IMV): Spontaneous breaths are allowed between or during mandatory breaths. A preset frequency represents the maximum number of mandatory breaths per minute.
Continuous spontaneous ventilation (CSV): All breaths are spontaneous.
Titrate the ventilator settings to acceptable physiological parameters (i.e., some degree of hypoxemia and hypercapnia is okay.
Use low tidal volumes to avoid ventilator-induced lung injury.
Use the lowest fraction of inspired oxygen (FIO2) to maintain oxygenation at 90%-92%. Positive end expiratory pressure (PEEP) can recruit collapsed lung units and improve oxygenation.
Note: If the patient’s respiratory status acutely decompensates or the ventilator is sounding an alarm or malfunctioning, you can always disconnect the patient from the ventilator and manually ventilate with a bag valve mask while you troubleshoot.
Patients should be assessed daily for their readiness to be weaned from mechanical ventilation by withdrawing sedation and performing a spontaneous breathing trial.