Life Support: When Machines Do the Breathing

by Food and Drug Administration (FDA)

The idea that life support is only for the critically ill, comatose or moribund person was quickly dispelled during a Barbara Walters' interview with actor Christopher Reeve in 1995. At that time, he was in rehabilitation for a riding accident that left him paralyzed from the neck down.

Viewers saw a person that to this day continues to lead an active life, directing movies, speaking at various functions, and chairing a group for paralyzed Americans — even though he depends almost entirely on a medical device called a ventilator to do his breathing for him.

Though more commonly known as life-support devices, ventilators today do more than merely keep patients alive: They promote patient comfort, aid recovery from surgery and other medical conditions, prolong life for people with certain neuromuscular diseases (such as Lou Gehrig's disease), and, in cases such as Reeve's, allow patients to live at home and lead as nearly normal lives as possible.

Ventilators are used by people of all ages, from premature infants to adults, who have any number of health problems that for one reason or another impair their ability to breathe normally. Though most ventilators are used in hospitals and other health-care settings, an increasing number are being used in the home setting. These include the noninvasive ventilators that aid breathing without requiring inserting a tube into the patient's body to create an artificial airway. Frost & Sullivan, an international marketing, consulting and training company, estimates that ventilator home care will grow to represent more than 40 percent of the ventilator market by 2006.

The Food and Drug Administration regulates most ventilators as class II devices. This means that manufacturers must notify FDA about new ventilator designs. FDA can then determine whether the new devices function similarly to currently marketed ventilators before the new devices are offered for sale.

The agency also requires ventilator manufacturers to maintain records of each unit intended for transport or home use — called medical device tracking — so that devices can be quickly located and recalled from patient use if a problem that threatens patient safety is identified.

Complex Function

Ventilators perform one of the most complex functions of the body — ventilation, a process in which the lungs take in and disperse oxygen the body needs and gather up and expel the carbon dioxide created as a result of body functions. In healthy people, this gas exchange takes place in the small air sacs of the lungs, called alveoli, and, in the course of one day, normally involves 8,000 to 9,000 liters of air breathed in through the nose or mouth and 8,000 to 10,000 liters of blood pumped through the lungs by the heart.

The idea of mechanical ventilation is not new: Earnest efforts date to the mid-1800s, when devices resembling steam cabinets and phone booths were used to maintain breathing by decreasing the air pressure inside the machine. A well-known device that applied this "negative-pressure" principle was the iron lung, which was widely used in the United States from the late 1920s into the 1950s, particularly for polio patients. However, these devices were large, and they greatly restricted patient movement.

In the late 1950s, "positive pressure" ventilators, which force air into the lungs, were introduced.

Like their predecessors, modern ventilators function to deliver breaths of oxygen-enriched air to the body and remove carbon dioxide. But unlike in the past, most ventilators today are computer-controlled, functioning in complex ways to produce positive-pressure ventilation that more closely matches patients' breathing needs.

Until about the early 1990s, modern ventilators required an artificial airway, usually a tube placed through a hole surgically created into the patient's throat or a tube passed through the patient's nose or mouth.

More recently, noninvasive positive-pressure ventilators that allow for gas exchange through a face or nose mask have become popular.

Dan Van Hise, marketing manager for Siemens Medical Systems Inc. and a registered respiratory therapist who worked in patient care for a number of years, says that already in the span of his career, he's seen vast improvements in ventilators.

"The older vents — like the ones of the early 1980s — required a lot of respiratory work on the patient's part," he says, referring to the increased workload of the muscles that assist with breathing. "Today, it's not nearly the same. [Using a ventilator] is almost effortless.

"One of the biggest misconceptions from the general public is that it looks uncomfortable for the patient," he adds. But, he says, because of advancements in technology — such as computerization of ventilators, improved communication devices for patients whose speech is hampered by some medical equipment, and improved medicines for alleviating the discomfort of tubes inserted into the body — that's not always true anymore. "[Ventilator] patients are much more comfortable."

Different Designs Meet Different Needs

FDA classifies ventilators into three groups: hospital, transport and home-use ventilators. The hospital units typically are sophisticated devices that offer such features as central monitoring, which sends patients' respiratory data directly to the nurse's station. The units generally come with a number of built-in alarm systems to alert care-givers to act on impending or immediate life-threatening changes in patients' respiration.

Transport devices are designed to withstand excessive shock or vibration that can occur in rescue vehicles or higher levels of electromagnetic interference from electronic sources, such as two-way radios used for communications.

According to marketing and respiratory care-givers, manufacturers are increasing development and production of ventilators for "step-down" areas of hospitals — that is, noncritical patient care areas. While these patients still require full or partial ventilatory support, their conditions have otherwise stabilized, making the continuous monitoring of intensive care unnecessary. Some health-care providers are even opening "subacute" care facilities for long-term patients who no longer need round-the-clock care but still require a high degree of medical support.

Ventilators for subacute ventilator-assisted patients offer full ventilation capabilities but don't come with all the specialized features of full-conventional ventilators; for example, they might offer fewer alarms.

The goal of these ventilators is to provide patients with necessary ventilatory support while lessening care-givers' workload, says Steve Tunnell, a registered respiratory therapist and director of marketing for the Puritan Bennett ventilator division of Mallinckrodt Inc. "Efficient tools are what [care-givers and hospitals] need most," he says.

Portable ventilators operate similarly to those designed for subacute care but are smaller and lighter. Many, like the one Reeve depends on, can fit on a wheelchair and are battery operated. They also tend to be less expensive, ranging from $5,000 to $12,000 per unit, compared with $15,000 to $35,000 for a hospital unit.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.