Strategies for Ventilator Management

There are six major types of ventilator support including continuous mandatory ventilation to noninvasive ventilation.

Intubation is a procedure performed when the patient is unable to breathe by themselves. It may be a life-saving procedure in the emergency room (ER) or planned during the surgery when the patient is under general anesthesia. 

The doctor inserts a tube through the nose or mouth into the throat and trachea (windpipe). The tube facilitates air entry into and out of the lungs. The tube is connected to a machine called a ventilator that pumps air containing an increased concentration of oxygen compared with atmospheric air. The machine then helps in exhaling air containing carbon dioxide (CO2). 

The ventilator maintains normal oxygen and CO2 levels in the body. This is called mechanical ventilation. During mechanical ventilation, cardiac function, blood pressure, and oxygen saturation/levels in the body are monitored continuously.

Most ventilators can be set to apply a custom amount of air based on the individual patient’s lungs and breathing function. This is called delivered tidal volume (the total volume of air that is inspired and expired in one cycle of breathing/respiration), and a respiratory therapist can adjust the delivered tidal volume . Ventilators deliver air via two basic settings:

• Control mode: In a control mode, the ventilator delivers a preset tidal volume once it is triggered irrespective of patient’s effort.
• Support mode: In a support mode, the ventilator provides assistance during inspiration with the help of an assist pressure. The ventilator detects inspiration by the patient and supplies an assist pressure during inspiration. The assist pressure is terminated when it detects expiration. The support mode requires the patient to have an adequate respiratory drive.

There are six major types of ventilator support:

• Continuous mandatory ventilation: Breaths are delivered at preset intervals, irrespective of the patient’s effort. This mode is usually used in patients who are paralyzed with no respiratory effort of their own. It can increase the breathing rate if respiratory effort is present; hence, it is not be used in patients with adequate respiratory drive. 
• Assist-control ventilation: The ventilator delivers a preset number of breaths. This is used in co-ordination with the patient’s irregular spontaneous attempts at breathing.
• Intermittent mandatory ventilation (IMV): The ventilator delivers breaths at preset intervals, and spontaneous breathing occurs between the ventilator-administered breaths. 
• Synchronous IMV: The ventilator delivers preset breaths in coordination with the respiratory effort of the patient. Spontaneous breathing occurs between the ventilator breaths.  Synchronization between preset mandatory breaths with the patient’s spontaneous breaths reduces the risk of ventilator-related trauma to the chest. 
• Pressure support ventilation: This type of ventilation is for people who are able to breathe some on their own. It reduces the risk of ventilator-related trauma to the chest and the effort of breathing. The airway pressure support is maintained till the patient's inspiratory flow drops. There is better patient comfort, reduced risk to the heart, reduced risk to the chest and better gas distribution.
• Noninvasive ventilation: Mechanical ventilatory support is provided through a mask instead of a tube. This is common in emergency departments. It is used in patients with mild-to-moderate respiratory failure, and the patient should be alert.

The main purpose of mechanical ventilation is to protect the airway and manage respiratory failure. Patients with respiratory failure in the emergency room are usually clinically diagnosed. The decision to intubate and mechanically ventilate or use noninvasive ventilation support is based on clinical assessment by the physician, without delay for laboratory results.

It is also indicated for the treatment of critical, life-threatening conditions such as salicylate intoxication, major head injury with elevated intracranial pressure, or antidepressant toxicity.

Pulmonary (lung) complications

• Barotrauma (damage to the lungs due to pressure differences) may result in the following:
• Pneumomediastinum (air in the space between the two lungs)
• Pneumoperitoneum (presence of air in the abdomen)
• Pneumothorax (air in the space between the lungs and chest wall)
• Infection of the lungs
• Atelectasis (collapse of the lungs)

Cardiovascular (heart and blood vessels) complications

The heart and major blood vessels in the chest cavity are subjected to the increased pressure from mechanical ventilation. This may decrease cardiac function, leading to ischemia (decreased oxygenation in the body).