A ventilator is a machine that helps you breathe or takes breaths for you. It can be a lifesaver if you have a health condition that causes you to struggle to get air.
You may know about the type of ventilator that pumps oxygen into your lungs. It’s called a “positive pressure ventilator.” That’s the main kind of ventilation that doctors use today. But there’s also a type that’s not used as often, called a negative pressure ventilator (NPV).
Many hospitals used NPVs during the polio pandemic in the early 1950s. More recently, a 2021 study found that researchers have studied – and some doctors have used – NPVs as an alternative ventilator for people with severe cases of COVID-19.
Negative pressure ventilation has also been used to help treat problems like COPD and certain disorders that affect muscles.
How Does a Negative Pressure Ventilator Work?
In general, an NPV lowers the air pressure around part of your body, making the pressure “negative.” This creates a vacuum effect that expands your lungs and chest, pulling air into your lungs. Then the machine removes that lower pressure to let your lungs and chest contract, helping you exhale.
What Are Some Types of Negative Pressure Ventilators?
Just a few kinds of NPVs are:
Iron lung. You lie down in this cylinder-shaped, tank-like machine, and it seals in most of your body, except for your head.
Iron lungs mainly helped people with polio breathe during the early and mid-1900s. Since then, newer breathing machines have replaced them. But a small number of people with polio still use them.
A 2021 study also found that in some parts of the world, manufacturers tried to make smaller, less expensive iron lungs as substitutes for positive-pressure ventilators during the COVID-19 pandemic.
Cuirass ventilator. This is one of the simpler and much smaller NPVs developed after the iron lung. The cuirass ventilator is a shell-like machine encloses just your rib cage and belly. Some researchers consider it a much smaller version of the iron lung.
The cuirass has been used to treat babies with a rare chronic disease called bronchiolitis obliterans, also known as popcorn lung. They’ve also been useful for children with certain neuromuscular disorders, which affect how your muscles work due to problems with nerves and muscles.
Some researchers say cuirass ventilators can help in emergency situations when someone has a serious lung condition called acute respiratory distress. Other researchers say a type of cuirass ventilation with a few changes showed promise as alternative to more commonly used ventilators during the COVID-19 pandemic.
“Jacket” ventilator. This is an airtight, lab-made garment lined inside with a plastic or metal grid, a suction pump, and a back plate that goes to your hips. You’re more likely to use it at home than in the hospital.
Why Is Negative Pressure Ventilation Used Less Often?
Some researchers say it had disadvantages compared to positive pressure ventilation, including:
- It’s less convenient to use.
- It’s less portable.
- It has a higher risk of causing upper airway blockages.
Researchers say that these upper airway obstructions outside the chest are the biggest risk of using negative pressure ventilation. Once a doctor spots this problem, they can treat it by adding a CPAP (continuous positive airway pressure) device or using different type of ventilator.
If a doctor puts your loved on negative pressure ventilation, you could ask things like how long your loved one will need it, how it might help them, and what side effects it could have. If the doctor recommends an NPV device to use at home, follow their directions exactly on how to use it and how to notice any problems that could happen.