22.13h Complications of Mechanical Ventilation

Endotracheal intubation is not without potential complications.

These include airway trauma, dental injury, laryngeal and vocal cord injury, tracheal injury, hypoxia, and esophageal intubation.

Accidental intubation of the right mainstem bronchus is not uncommon.

Aspiration rates are increased when intubation is performed without anesthesia.

Endotracheal tube cuff leaks allow air to enter or exit the respiratory tract around the endotracheal tube adversely affecting ventilation.

Lung injury that occurs as a result of mechanical ventilation—ventilator-induced lung injury (VILI)— is most commonly seen in patients with ARDS or COVID pneumonia.

It can result from volutrauma, atelectrauma, barotrauma, or a combination of these.

Volutrauma is a localized overdistention of normal alveoli and results from mechanical ventilation forcing air into the alveoli.

Positive-pressure ventilation forces air into the lungs, and the air typically follows the path of least resistance and flows into normal or relatively normal alveoli potentially causing overdistention (abnormal alveoli usually have increased resistance to airflow).

Overdistension of the alveoli causes some alveoli to be overstretched while other alveoli collapse (atelectasis).

These types of volutrauma can cause an inflammatory cascade that worsens the initial lung injury by causing additional damage to unaffected adjacent alveoli.

Lung injury created by alveoli that are next to each other collapsing and re-expanding is a called atelectrauma.

The rupture of alveoli due to pressure with resulting air leakage into the pleural space (pneumothorax) is a form of barotrauma.

Oxygen is necessary for life and can be lifesaving when used in hypoxic patients, but it is not without risk.

The oxygen concentration in atmospheric air is approximately 21 percent at sea level.

Oxygen supplementation is usually a part of mechanical ventilation, and many portable mechanical ventilators are oxygen driven.

Increased oxygen levels (hyperoxia), particularly in the setting of mechanical ventilation, can be harmful.

Typically, when mechanical ventilation is initiated, the oxygen delivery starts at 100 percent (FiO2 = 1.0).

As the patient starts to stabilize, FiO2 is reduced based on the SpO2 or arterial blood gasses and should be reduced to less than 0.50 as soon as it is clinically appropriate.

Continued exposure to hyperoxia can cause oxygen toxicity, also known as oxidative stress, resulting in the development of free radicals that can cause damage particularly to the lungs, eyes, and central nervous system that, in severe cases, can lead to seizures and even death.

Auto-PEEP occurs when pulmonary air flow does not return to zero at the end of exhalation.

Auto-PEEP most commonly occurs in patients with COPD during spontaneous breathing and asthma who require a prolonged expiratory phase of respiration.

These patients often have difficulty in totally exhaling the tidal volume delivered by the ventilator before the next breath is delivered.

This results in a portion of each subsequent tidal volume being retained in the patient’s lungs (a phenomenon sometimes referred to as “breath stacking”).

It can be avoided by allowing a longer expiratory phase on the I:E ratio.

Infections can develop as a result of mechanical ventilation.

Ventilator-associated pneumonia is the most common infectious respiratory complication in intensive care unit patients.

Other infections, such as sinusitis, can also occur.

Mechanical ventilation directly affects the cardiovascular system.

Positive-pressure ventilation, for example, increases the pressure within the chest and can decrease preload, stroke volume, and cardiac output.

Positive pressure in the chest can also decrease venous return from the head, increasing intracranial pressure.

Pressurized oxygen provides the energy source for many types of transport ventilators.

Ventilators require a large amount of oxygen to function and quickly deplete the available oxygen supply on ambulances and aircraft.

Because of this, EMS practitioners must carefully plan trips to ensure that adequate oxygen is available if an oxygen-driven transport ventilator is being used.

If a patient on a ventilator develops distress, as an EMS practitioner you can troubleshoot the situation in several ways.

If the ventilator can’t be fixed immediately, you must support the patient’s ventilation in some other way (i.e., by manual positive-pressure ventilation/BVM) until the ventilator can be fixed or—if a prompt repair cannot be arranged—until the patient can be transported to the hospital and transferred to the ED staff.

Ventilators have alarm systems to signal a problem.

Needless to say, when a ventilator alarm sounds, removing the ventilator does not fix the problem that activated the alarm.

For example, the most common alarm trigger is high airway pressure.

If you remove the ventilator, the alarm will stop, but the change in airway pressure that set off the alarm (perhaps a mucous plug or a developing pneumothorax) will still exist.

After turning off the ventilator, and if the patient does not improve with BVM ventilation, assess the patient and treat any problem you find (e.g., by suctioning the patient’s airway or decompressing a tension pneumothorax).