There has been much public discussion about ventilators amidst the COVID-19 pandemic. It is humbling to consider that we, or someone we love, might require one. Most people know something about the benefit of a ventilator when needed; but how well do we really understand the functions and risks of mechanical ventilation? The pandemic presents an opportune time to learn about this. So I posed a series of questions about these machines and the processes involved in using them to a physician, who is a specialist in using ventilators to treat very ill patients. Those questions, and her answers, follow.
1) Please introduce yourself to our readers.
Meredith Pugh, MD, MSCI. I am a wife, mother, and pulmonary and critical care physician that works in a tertiary care center medical intensive care unit.
2) Generally, when does one need a ventilator? That is, what are the benefits of mechanical ventilation?
A ventilator is a machine that provides breathing support. A ventilator can be connected to a patient through either a mask (i.e., covering the nose, mouth, or face; this is commonly referred to as a non-invasive ventilator) or a tube that enters the windpipe (called an endotracheal tube; this is commonly called an invasive mechanical ventilator). Ventilators can be used to support breathing for healthy lungs, like during surgery when under general anesthesia. Ventilators can be used at home, but most commonly and for the purposes of this discussion, we think about ventilators as devices utilized to support breathing in the context of a severe or critical illness. In the intensive care unit, we frequently use ventilators to support breathing in the setting of lung injury or lung disease when the lungs have difficulty getting sufficient oxygen into the body, and/or difficulty removing carbon dioxide from the body. There are devices that can be used to provide oxygen, even high amounts of oxygen, that are not ventilators—these are things like nasal cannula oxygen, or high-flow nasal cannula. There are also machines that circulate blood outside the body and provide oxygenation to the blood (i.e., extra-corporal membrane oxygenation or ECMO)—that device is not typically considered a ventilator.
There are several reasons when one might need a ventilator:
- When the muscles that power breathing are not working properly. An example of this might be a patient with a high spinal cord injury. In this case the lungs may be normal, but the ventilator provides the power to breathe.
- When a person is unresponsive due to a medical process, or drug effect. An example of this would be when a ventilator is used to support the lungs during anesthesia or sedation for a procedure.
- When the lungs are diseased and cannot get sufficient oxygen into the blood. An example of this would be pneumonia or pulmonary edema.
- When the lungs cannot get carbon dioxide out of the body. This can be seen in chronic lung disease and also severe pneumonias.
- When there is a blockage or obstruction in the upper airway. Then a tube can be used to bypass this blockage, and often the tube is connected to a ventilator, at least temporarily.
Especially in the intensive care unit setting, ventilators should be considered as support devices—they help support the body while we wait for other treatments directed at the underlying issue to improve lung function. These other treatments might be antibiotics (in the setting of a bacterial lung infection), anti-viral medications, anti-inflammatory medications, and/or time.
The benefits of ventilators:
- High amounts of oxygen can be delivered to the lungs to try to enhance oxygen levels in the body. In the setting of severe lung disease, we often must use high amounts of oxygen to overcome the diseased lung.
- Use of pressure can help open up areas of the lung to improve gas exchange in diseased lung (i.e., application of positive end-expiratory pressure or PEEP).
- Ventilators can provide some “rest” for the muscles of breathing, and this can be beneficial for patients who have been working hard to breathe. Ventilators also allow clinicians to give sedating medicines and even medicines that relax or paralyze muscles to try to improve oxygen levels in the blood.
- Ventilators are invaluable tools to helping very sick patients survive severe lung injury like ARDS (acute respiratory distress syndrome, caused by Sars-CoV-2 or other causes).
3) What are some of the risks of mechanical ventilation? More to the point, are there short-term or long-term changes mechanical ventilation can produce in patients’ pulmonary (or other) systems?
- Normal breathing is what we call “negative pressure” breathing. Most ventilators use “positive pressure”—meaning air is pushed into the lungs. It is worth noting that the first ventilator, the iron lung, was a negative pressure ventilator, but from an engineering perspective, positive pressure ventilators are most commonly used now as they are much smaller and easier to manipulate. High amounts of pressure in the lung can lead to lung injury—even lung rupture or collapse (i.e., pneumothorax). In addition, there is research that suggests that even mildly high lung pressures can lead to inflammation not only in the lungs, but also release of inflammatory markers in the body that can affect other organs and lead to injury.
- Patients on ventilators are at risk for pneumonia—the tubes used for mechanical ventilators can get colonized with bacteria, and the longer a patient is on the ventilator, the higher the risk of infection.
- In general, being on a ventilator is not very comfortable, especially with an endotracheal tube in place. So many patients on ventilators require sedation and/or pain medications to remain comfortable and calm while they require the ventilator. These medications can have side effects including sedation, lower blood pressure, and even delirium—or altered consciousness and awareness of one’s surroundings that can linger for some time. For extremely ill patients, we sometimes use paralytic medications to help relax muscles to enhance oxygen delivery though the ventilator, and these medications can lead to muscle weakness.
- An endotracheal tube, entering through the nose or mouth and passing through the vocal cords into the trachea, can lead to injury or scar tissue in the larynx or trachea, which can lead to problems after a patient survives critical illness.
4) Specifically, when are ventilators used in patients with COVID-19? At first, the advice seemed to be “intubate early”; now there appears to be a change from that advice.
In our ICU, we have relied on decades of research and best practice for severe pneumonias and ARDS to help inform our management of ARDS in COVID-19 patients. While every patient and situation can be different, in general we utilize non-invasive types of oxygen devices as much as possible, but if these devices are not sufficient to maintain oxygen levels, or if a patient’s level of consciousness is altered to the point where they are not breathing efficiently, the patient is intubated and placed on a mechanical ventilator.
5) There has been much conversation about a possible shortage of ventilators for COVID-19 patients. Where are we regarding that in Tennessee? Is this a problem? Why or why not?
I am thankful that I work for a health system that has been working hard to ensure an adequate supply of ventilators so that we are equipped to serve patients in our region. I know that there are many people, across lots of different health systems in Tennessee, who have come together to work on this issue specifically. I think it has really been a teamwork approach across different health systems and in different regions. I am so thankful for all of these efforts, and these health system leaders deserve kudos! At least here in Middle Tennessee, so far our COVID-19 patient numbers have been within a range where we have been well-equipped to care for patients without any shortages of ventilators or critical supplies. We have many contingencies in place, but hopefully the numbers will remain stable.
6) Are there particular risks of mechanical ventilation for COVID-19 patients?
I think the risks for COVID-19 patients are similar to all patients with severe ARDS who require mechanical ventilation. Patients may spend several days to weeks on the ventilator, so they are at risk for all the potential complications of a long ICU stay including secondary infections (like a secondary bacterial pneumonia), deep venous thrombosis and pulmonary emboli, ICU-acquired weakness, delirium, pneumothoraces, and other lung injury. There are concerns that the incidence of blood clotting complications may be higher in COVID-19 patients than in the general ICU population.
7) Is there anything you’d like especially for our readers to know?
I am sure there are things that we are doing now in the care of COVID-19 patients today that might look different in one month, or six months, or two years from now. The pace of the disease, and the rapid dissemination of data about the disease has presented unique challenges and opportunities.
