What Is A Ventilator, Anyway?

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As we all know, ventilators are in short supply in hospitals around the world—and patients who go into respiratory failure as a result of the coronavirus may not be able to get the help that they need to breathe.

The number of COVID-19 patients who require aggressive breathing assistance is still relatively small compared to the total number of infections, but the US and other countries are preparing to ration the machines, asking manufacturers to rush their production, and even creating makeshift ventilators out of scuba masks. Some hospitals are figuring out how to share a single ventilator between multiple patients.

So what is a ventilator, and how sick do you have to be to need one?

Ventilators 101

A healthy person can inhale oxygen and expel carbon dioxide at a normal rate to keep the body functioning. But a person with sick or damaged lungs cannot breathe in regular air fast or hard enough to support their body’s oxygen needs. A ventilator does this work by creating pressure to open the lungs, delivering oxygen to the lungs through a tube, and removing the carbon dioxide the lungs create.

When you breathe, your diaphragm and other muscles in your chest contract, which expands your chest and creates negative pressure to pull oxygen-rich air into the lungs. You exhale carbon dioxide when these muscles relax and your chest returns to its normal size. If your body can’t create that negative pressure on its own, a ventilator can be used to create positive pressure—pushing air in instead.

Mechanical ventilators used in critical care settings are large, complex devices that run on power and are connected to a central oxygen source. The bulk of the machine is a monitor with dials, displays, and settings options that can be adjusted to each patient’s breathing needs.

Inside the housing is a bellows that—like an Ambu bag you’ve seen paramedics use on TV—pushes oxygenated air through a series of tubes and into the lungs.

Before it reaches the patient, the air runs through a humidifier, which warms and moistens it. From there, the oxygenated air is pushed through a tube that delivers it to the lungs and removes the resulting carbon dioxide.

Patients on mechanical ventilation are generally intubated—meaning they have a tube inserted through their mouth and into their airway. Once an endotracheal tube is in place, the end balloons out to seal off the airway, which prevents any gas or fluid from leaking backward as air is pushed into the lungs.

Intubated patients are also at least mildly sedated for part or all of their time on mechanical ventilation. Beyond the discomfort of having a tube shoved down your throat, it can feel like you’re choking, suffocating, or drowning.

There are less invasive types of breathing assistance, such as oxygen delivered through a mask, but for a COVID-19 patient, supplemental oxygen may not be enough.

COVID-19 affects the respiratory system, so people with preexisting lung conditions are already a half-step behind, said Dr. Brian Redmond, an anesthesiologist in Savannah, GA. Smokers, older adults, and patients with other respiratory problems have less efficient lungs and may be hit harder by breathing issues resulting from the virus.

Why the ventilator shortage?

When there’s not a global pandemic, there are still patients on ventilators. But many of those people require machines for only a few hours (during surgery, for example) or a few days, and then they’re passed on to the next patient. COVID-19 patients in respiratory failure often need mechanical ventilation for a week or more, so machines aren’t freed up at the same rate.

“The reason there’s a bottleneck is because there are too many sick patients, and when they go on they stay on a long time,” Redmond said.

Plus, a ventilator is not a set-it-and-forget-it device. It requires constant monitoring and frequent fine-tuning to balance the pressure, the volume, the oxygen percentage, and the breathing rate for each individual patient—which means that having lots of people on ventilators taxes the resources of already-busy hospitals, nurses, and doctors.

An additional hurdle with COVID-19 is that medical staff have to be dressed in personal protective equipment—gowns, masks, gloves, goggles—each time they interact with a patient. That means they can’t just walk in and turn a dial to adjust the machine, Redmond said. There’s also a risk of exposure to the virus during intubation.

There are risks to patients who stay on mechanical ventilation long-term as well, but Redmond says that’s not a leading concern for coronavirus.

“We’re just trying to get these people to survive,” he said.


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