Best of 2010
High Hopes for Low-Tech Ventilator
A simple, affordable, easy-to-maintain ventilator developed at Seattle Children’s could save 500,000 babies each year in the developing world.
The introduction of modern mechanical ventilators in the 1970s dramatically improved survival rates for newborn babies in respiratory distress. Constantly evolving with new technology, mechanical ventilators save the lives of many thousands of newborns every year.
Recently, a team at Seattle Children’s rolled out a new type of ventilator that could save even more lives – not because it’s more high-tech but because it’s less.
Respiratory distress claims the lives of a million newborns throughout the world every year. Many are premature infants who are not able to produce sufficient surfactant, a soap-like substance that reduces surface tension and keeps the lungs from collapsing when a person exhales. Providing these babies with even a small increase in air pressure above atmospheric levels helps stabilize the lung, reduces the work of breathing and can mean the difference between life and death.
The problem is that conventional mechanical ventilators are expensive and require specialized training to operate and maintain because they’re designed to deliver both basic and highly advanced care. Developing countries lack the resources to purchase and operate these complex machines, except on a limited basis. Many children who require only basic assistance with their breathing end up dying for lack of a simple, affordable alternative to conventional ventilators.
Fewer moving parts
The new ventilator is the brainchild of Dr. Tom Hansen, Children’s CEO and a practicing neonatologist and pulmonologist who continues to make time in his busy schedule for research. Three years ago, he challenged colleague Peter Richardson to create a simpler and more affordable ventilator. After brainstorming with members of Richardson’s team, Hansen suggested using columns of water, not electronics, to move air in and out of a baby’s lungs.
Conventional ventilator gauges describe the amount of airway pressure they produce in units of water pressure – akin to an automobile engine’s output being described as horsepower. Hansen’s “aha moment” came when he realized that if water could serve as a unit of measure for airway pressure, it also could be used to actually produce airway pressure. This is just the sort of low-tech/low-cost/low-energy approach needed in limited resource settings.
“We had some other ideas,” Richardson says, “but Tom’s idea was the best because, for one thing, it has fewer moving parts. And it requires very little power. You can run it off a laptop battery.”
Dubbed the Hansen Ventilator, the machine replaces the array of dials and gauges found in conventional ventilators with two knobs – one to control the respiratory rate and the other to control the inflation time. The simple design shrinks the cost of a Hansen Ventilator to a fraction of the $30,000 price tag for conventional ventilators. “We were able to buy most of the parts off the shelf from places like Home Depot,” Richardson says.
Many children who require only basic assistance with their breathing die for a lack of simple, affordable alternative to conventional ventilators.
New design outperforms conventional ventilators
Here’s how the Hansen Ventilator works: A blend of humidified air and oxygen flows through a tube to a pair of nasal prongs in the baby’s nose. A second tube conveys the gas from the nasal prongs to a pair of tubes submerged in water at different depths. A pinch valve – the only component that requires power – alternates the flow of gas between the submerged tubes. The tubes create different levels of positive airway pressure. When the valve is closed, gas flows through the deep tube, inflating the level of positive airway pressure and helping the baby inhale. When the valve is open, gas flows through the shallow tube, deflating the level of positive airway pressure and helping the baby exhale.
The bubbles emitted from the exhalation tube create oscillations that further improve the oxygen/carbon dioxide gas exchange in the baby’s lungs similar to the way bubble CPAP (continuous positive airway pressure) machines work. However, respiratory therapist Rob DiBlasi and engineer Jay Zignego made an important discovery as they tinkered with the Hansen Ventilator’s design. By bending the exhalation tube at a 135-degree angle (measured from vertical), they could amplify the oscillations to promote even greater gas exchange. Their discovery was quickly integrated into the Hansen Ventilator.
In 2010, DiBlasi, Zignego, Hansen, Richardson and Charles (Skip) Smith published a pair of papers in Pediatric Research that described results from two animal studies. The data showed that the Hansen Ventilator with amplified bubble CPAP did a better job of clearing CO2 than conventional ventilators and that amplified bubble CPAP alone produced higher blood oxygen levels than those produced by conventional ventilators on the same pressure settings. In addition, when subjects were supported with amplified bubble CPAP, they expended 50% less energy per breath than when supported with conventional bubble CPAP.
Envisioning a broader role
Despite its advantages, the Hansen Ventilator has some drawbacks compared to conventional ventilators. It delivers breaths at a scheduled rate that must be manually adjusted to match a baby’s changing breathing pattern and needs. Conventional, high-tech ventilators can automatically adjust to a baby’s breathing pattern.
The Hansen Ventilator also lacks advanced monitoring features that show how the lungs are responding to therapy and enable caregivers to increase or decrease support accordingly – an important feature when caring for babies with severe respiratory distress.
Still, many newborns in respiratory distress don’t need the additional features of conventional ventilators just as every illness doesn’t require treatment in the critical care unit. And this leads the Richardson lab to envision a role for the Hansen Ventilator beyond the developing world.
“Given all the concern about rising healthcare costs, it would make sense to use a less expensive ventilator whenever possible regardless of the setting,” says Richardson.
Partnering to bring ventilator to the field
The team is now working with PATH, a Seattle-based global health organization, to move the Hansen Ventilator out of the lab and into the field. The plan is to manufacture a series of prototypes in India and conduct clinical trials there while also seeking approval from the U.S. Food and Drug Administration.
DiBlasi visited clinics and hospitals in India and Vietnam to better understand the clinical needs for babies requiring respiratory assistance in the developing world. “A lot of donated ventilators sit in the corner gathering dust because no one knows how to use them or maintain them,” he says.
That shouldn’t happen with Hansen Ventilator. “In the long run,” Hansen says, “we think our ventilator can save a half-million lives a year.”