Putting Renewed Focus on Negative Pressure Ventilation

By Keith Gillogly

But for many patients, negative pressure ventilation could be a viable alternative, says Geovanny Perez, MD, clinical associate professor and chief of the Division of Pulmonology and Sleep Medicine in the Jacobs School of Medicine and Biomedical Sciences Department of Pediatrics.

“The natural way that we breathe involves negative pressure,” Perez says. Negative pressure ventilation works by expanding and contracting the chest cavity, steadily drawing air into the lungs.

Now, Perez and his colleagues are working to grow use of negative pressure ventilation and to help define the indicators of its use. In October, the Jacobs School hosted a day-long “Expert Summit on Negative Pressure Ventilation” conference providing an overview on clinical use of negative pressure ventilation.

Negative pressure ventilation is typically used in hospital settings to support patients’ breathing during respiratory failure, which can result from a viral infection of the lungs, bronchitis, and many other causes. The “cuirass,” an external plastic shell-like encasement around the torso, is the most commonly used negative pressure ventilation device, Perez says.

At the October conference, physicians, respiratory therapists, and other health care providers from the region and beyond shared and discussed best practices, research, and systems of care for negative pressure ventilation.

Presentations and discussion centered on pediatric respiratory care, acute respiratory failure, the cardiac ICU, neuromuscular disorders, and end-of-life care, among other topics.

In addition to physicians from the Jacobs School and affiliated UB hospitals, the conference included presenters from Duke University, the University of Rochester, Children’s National Hospital, and other institutions.

The conference even involved demonstration of the cuirass devices, where respiratory technicians from Oishei Children’s Hospital set up the equipment for participants to wear and experience how it feels.

Participants also discussed research gaps and future directions, as Perez says he’s hoping the conference becomes an annual event. Sponsors included Hayek Medical, the Muller Family Fund, the Department of Pediatrics, and UB’s Child and Maternal Health Research Institute, which also organized the event.

Perhaps the most powerful moment, Perez recalls, came when a former Buffalo ICU chief shared a story about how negative pressure ventilation saved his own child from respiratory failure and prevented need for intubation. 

Negative pressure ventilation isn’t new. It’s been a therapy as far back as the early 20th century. During the polio epidemic mid century, the iron lung became the most famous and feared example of negative pressure ventilation.

Consisting of a long cylindrical tube that encased the body from the neck down, the iron lung kept polio patients breathing but confined them permanently to the metal enclosure.

The modern cuirass shell, conversely, is lightweight and transparent, leaving the arms open for IV access and does not require a mask. A seal around the openings creates a vacuum, and a tube connects the shell to an external pump or ventilator.

Negative pressure ventilation devices are readily available, Perez says, and the manufacturer provides substantial training and instruction on use.

When positive pressure ventilation emerged, it largely replaced use of negative pressure, Perez says, but it still has drawbacks.

Positive pressure therapy using a ventilator requires an endotracheal tube and sedation, and even short-term ventilation use can weaken the diaphragm, Perez says.

The breathing masks used with CPAP machines, which also use positive pressure, can cause claustrophobia, skin irritation, and restrict functions like eating.

The cuirass is much less invasive, Perez says, and is particularly well suited to patients with certain neuromuscular disorders, airway obstructions, or others who cannot be intubated.

But the goal is not to overtake positive pressure ventilation. Rather, Perez and his colleagues hope to figure out precisely how and when negative pressure ventilation is best applied. Some cases can even involve using both types of therapies at different stages, he adds.

The COVID-19 pandemic highlighted the need for different approaches to breathing therapies, Perez says. As more and more patients occupied ICUs across the country, the shortage of ventilators worsened.

Further, intubating patients invariably exposed medical teams to expelled coronavirus.  Patients using a cuirass device, however, could still potentially wear face coverings.

Perez also points to palliative care and how intubation can restrict patients.

“When you’re providing respiratory support at the end of life, you have a tube going through your throat, you’re unable to communicate with your family, you’re sedated,” he says, highlighting an example clinical scenario that could benefit from alternative breathing therapies.    

Buffalo, Perez says, has been a leader in negative pressure ventilation since the therapy was first introduced in its hospitals.

“Buffalo has plenty of experience. The PICU in particular is perhaps the center with the most experience in the country with use of negative pressure ventilation,” he says, drawing from a recent analysis of ICU data from across the country.

But Perez says scaling up use of negative pressure ventilation will require more data on who should receive negative pressure ventilation, for how long, and under which specific conditions.

He hopes to potentially help develop a scoring system and more structured guidelines that dictate best clinical practices for both standard cases and for patients with complex cardiac conditions, neuromuscular disorders, and many other scenarios.

“In a lot of places, they don’t use the device because of lack of knowledge and lack of expertise,” he says.

Over time, and with Buffalo leading the way, Perez hopes to change that.