Mechanical Ventilation

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Some of you may remember back in early 2020 when cases of and hospitalizations for COVID-19 were skyrocketing, political leaders scrambled to make sure there were enough ventilators. So, let’s take a closer look at mechanical ventilation, which is the process of using a machine to assist with the work of breathing. Ventilators are frequently used for conditions that cause low oxygen levels (hypoxia, as seen with pneumonia) or high carbon dioxide levels (hypercapnia, as seen with COPD).

Mechanical ventilation can be either noninvasive or invasive. Noninvasive mechanical ventilation involves the use of a machine that supplies oxygen and removes carbon dioxide through an external device such as a face mask. It is most commonly used for patients who have mild to moderate breathing difficulty due to an acute or chronic medical condition.

Noninvasive ventilation is used to help prevent the patient’s breathing difficulty from worsening. Should breathing difficulty worsen, invasive ventilation becomes necessary. This involves the insertion of an endotracheal tube through the mouth or nose into the upper part of the airway, or the trachea, a process known as intubation, usually performed by an anesthesiologist. The endotracheal tube is connected to a machine, or ventilator. Ventilators have multiple adjustments for respiratory rate, tidal volume (the volume of air in each breath), oxygen level, and other variables. The lower end of an endotracheal tube has an inflatable balloon. Once inflated, the balloon seals the airway, both preventing air leaks and protecting the airway from aspiration of oral secretions which could cause pneumonia. Since having a tube inserted in the airway can be very uncomfortable, most intubated patients are sedated to keep them comfortable and to prevent them from pulling out the tube. Patients undergoing surgery with general anesthesia are usually intubated and placed on a ventilator to maintain proper breathing and protect the airway during the procedure.

Once the patient’s condition improves sufficiently, the process of weaning off mechanical ventilation begins. Usually, the set respiratory rate is decreased or set to zero and the patient is monitored to ensure he/she can breathe on their own and maintain sufficient oxygen levels. If weaning is successful, the tube is removed (extubation). If weaning is unsuccessful, after about seven to 10 days of being intubated, an alternate means of respiratory support must be used which usually involved the placement of a tracheostomy tube (surgical insertion of a tube in the neck). The reason for this is that prolonged use of an endotracheal tube can damage the trachea and cause narrowing of the trachea, known as tracheal stenosis.

Patients who cannot breathe on their own after a period of time may opt (themselves or family members) to have the ventilator removed and allow natural death to occur. Removing the ventilator can be a very emotionally difficult time for family members which is why, should a patient have an advanced directive (i.e., living will and/or health care proxy) that specifies that the patient does not want to receive mechanical ventilation, it is important to prevent initial intubation. In addition, the process of removing a ventilator from a patient who does not have any advanced directives can be legally and ethically challenging.

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By Peter Galvin, MG

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