11/02/2021 Chicago
05/02/2022 UPDATE - DIMAR CPAP and NIV helmets received FDA EUA approval on April 20th.
Helmets for non-invasive ventilation may be new to the United States, but in Italy, manufacturers like DIMAR have been making them for decades. The COVID-19 global pandemic means DIMAR’s helmet production is even more important to the countries and hospitals using these life-saving devices.
Company owner Maurizio Borsari has 35 years of experience in the respiratory critical care field. He founded DIMAR in 2002 to produce and market biomedical devices for the treatment of Acute Respiratory Failure, or ARF, and non-invasive ventilation, or NIV, technologies. According to its website, DIMAR supplies about 750 departments in 250 Italian hospitals and 50 national distributors, which serve hundreds of hospitals in Europe and not only. The company has increased production size seven times and will double its laboratory space this fall.
Yet, during a tour of the facility, company export manager Riccardo Lambertini noted it’s still a small enough company that many workers do multiple jobs, from research and development to testing and production.
Two kinds of helmets
DIMAR manufactures two types of helmets: CPAP, which stands for continuous positive airway pressure, and NIV, or non-invasive ventilation (Pressure Support Ventilation and bilevel ventilation).
The CPAP helmet has no interaction between patient and machine, Lambertini explained. The airflow runs inside the helmet regardless of what the patient is doing. It’s continuous, and “the patient just takes what he needs from inside the helmet; pressure inside the interface remains stable and diaphragm works physiologically,” he said.
The NIV helmet is connected to a ventilator, and as the patient inhales, the ventilator pushes air into the lungs. “If you move to NIV, it is obvious there’s a kind of communication/interaction between the patient and the ventilator,” Lambertini said.
The CPAP helmet DIMAR produces is made from flexible biomedical plastic film and has a zipper across the lower front area. It includes a number of connectors to attach oxygenated airflow, a PEEP valve, filters, a manometer, or other devices to measure temperature, pressure, or flow inside the helmet. The neck collar is stretchy and unbreakable but provides a tight seal during use.
DIMAR’s NIV helmet is made from stiffer biomedical plastic film with a thicker and more rigid neck collar. It is designed to be less compliant and limit the balloon effect, which you don’t want with a ventilator, Lambertini said. The rigid ring stabilizes the structure and connectors so they don’t move up and down during breathing, which could cause patient-ventilator asynchrony.
But where DIMAR has created two helmets – one for each kind of use, CPAP or NIV – the US only has one helmet design approved for use with COVID patients.
Lambertini said three things make a helmet a good interface:
Patient comfort and easy management for long term treatment
Absence of air leaks
Dilution of carbon dioxide, or CO2
Comfortable and easy to use
Helmets are more comfortable than full-face masks. They have a universal fit so the patient's facial shape is not an issue during helmet-based ventilation because nothing is touching their face. On the other hand, the mask puts lots of pressure on the face and head, which makes long-term use very difficult to maintain. Mr. Borsari demonstrated different pressure points using a water bottle. The same weight distributed in different ways will create more or less pressure. But even a light touch of your finger on your hand after an hour can result in a bruise.
DIMAR’s helmets have straps that go under the patient’s arms to help create a good seal around the neck and keep the helmet from rising up or bobbing up and down during breathing. The helmets also have plastic loops at the top to add straps connected to weight to push the helmet down from the top in addition to the underarm straps. It releases pressure from under the arms for long-term helmet users, Lambertini said, offering greater patient comfort.
The zipper can be opened by the patient or clinician to allow easy access to eat or put on glasses to read, for example. Even if the helmet needs to stay in place, the connectors allow for a straw to be inserted to get a sip of water, perform oral care or suction. DIMAR also offers a nebulizer attachment that fits the helmet interface.
The clear plastic helmet allows the patient to see out all sides, zip opening doesn’t limit the 360° surrounding view. Adding filters to the airflow inlet and outlet protects from pathogenic agent aerosolization and greatly reduces noise in the helmet so patients can hear and speak easily. Patients also can talk while using the helmet, something that’s not possible with a face mask interface.
In less than five minutes, Lambertini and a colleague placed a CPAP helmet on Aurika Savickaite to demonstrate how easy it is to use. They checked the helmet, put it on her, and connected it to a venturi system. After a few minutes, Lambertini and Savickaite switched it to wall air and then added oxygen, showing the flexibility of its uses.
Removing the helmet also requires two people to stretch the neck collar to the sides and gently take off the patient’s head. But once it’s in place, only one person is needed to adjust the airflow, oxygen, pressures and attach any other accessories.
Absence of air leaks
Face masks don’t fit perfectly on some people’s faces, which means there are air leaks that can affect the delivery of oxygen and pressure to the patient’s lungs.
DIMAR’s helmets are designed to have no air leaks. They are tested by inflating them under 100 centimeters of water pressure to make sure there are no leaks in the interface. This is why the helmet will inflate instantly when connected to the airflow or the ventilator.
In a COVID environment, the CPAP helmet isn’t a protective device, Lambertini said, but it is less polluted. Placing a “filter before the PEEP valve can protect the environment from pathogenic agent actualization, which is something really problematic with a high-flow nasal cannula or with a face mask,” he said.
Washing out CO2
Patients exhale carbon dioxide, which can cause problems if it’s rebreathed or allowed to build up.
“When the helmet was invented, we thought – they thought – the CO2 was higher around the neck or around the head of the patient,” Lambertini said. “So having the connection in this position,” he said as he pointed to his face, “helped the washout. But now we know the CO2 is in this area (bottom) of the helmet, so having the connectors here is better,” he said pointing to his shoulders.
DIMAR’s CPAP helmet has more than two connections to separate inspiration and expiration. “It is much easier for the gas flow to enter and leave the interface, and this setup can generate a better washout,” Lambertini said. The additional connector ports are also used to create intentional air leakage to increase the CO2 washout.
The volume of a helmet is greater than a face mask, so the patient will inhale more CO2 from a mask than a helmet, in case the airflow is lost, Lambertini said. Because, each minute, 100 to 300 milliliters of CO2 can be diluted faster in a six-liter helmet.
There’s no contraindication for using filters, Lambertini added. Just keep in mind that a filter will add 3-4 centimeters of pressure, which will affect the PEEP, or positive end-expiratory pressure, in the helmet CPAP. “If you put the filter in the line with the PEEP valve, the value you set is lower than actual pressure in the helmet. Trust the manometer, not the indication on the PEEP valve” when using a helmet for CPAP setup, he said.
Understanding how it works
There’s a hesitancy among some clinicians and patients to use helmets. Lambertini said people have been told not to put a plastic bag over their heads, so they are worried about being able to breathe in a plastic helmet. Even some nurses say they would rather use a face mask than a helmet with their patients, he added. Despite the fact that they have never tested it personally, they make assumptions without looking into the physics, design features, testings, and studies that have been conducted on the safety and positive outcomes of using helmets for non-invasive ventilation.
“It’s really a matter of being able to explain how it works and why it’s safe. That’s the key point. If you have some doubts, sometimes it’s difficult to make the patient comfortable,” Lambertini said.
“This is what we mean when we say that you need to be confident with the machines you are using, with the devices and the interfaces, because when you understand how it works, you can do whatever you want and switch from one device to the other very easily, being confident with what you are doing.”