Respiratory therapy has progressed far from the days of the polio epidemic, when iron lungs were the standard of care for patients needing ventilation. Today, smaller and increasingly sophisticated ventilators allow sicker patients with a greater variety of lung conditions to be treated at home. However, issues remain, and for all the new “bells and whistles” on modern home ventilators, there is little comparative data on how each ventilator works and how each responds to different lung conditions.

To begin to understand modern home ventilation, it is helpful to look back at the early days of ventilation when iron lungs were the norm. Iron lungs were effective, but very cumbersome to work with, for both the patient and the caregiver. One advantage of this type of ventilation, however, was that the therapy was provided noninvasively, preventing complications associated with an endotracheal tube. Interestingly, modern home ventilation has come around to noninvasive once again, yet we still have issues with masks used for the patient interface.

The next major advance in ventilators came with the invention of microprocessors, which made ventilation more sophisticated for hospital-based patients. The microprocessors allowed for a multitude of control over ventilation and monitoring of both machine and patient parameters.

As patients migrated to the home setting, engineers were challenged to develop a durable, reliable, and portable ventilator. In the mid 1980s, manufacturers developed three ventilators that met these requirements of home ventilation. These units were durable—being made out of cast aluminum—and simple to operate, and met the needs of basic ventilation. More complex ventilation was out of reach for these devices, but this did not matter because, at that time, patients who were discharged to the home were typically stable and incapable of weaning from the ventilator. Few saw much need for further sophistication in home ventilation, so advancements in ventilator technology were minimal.

That changed in the late 1990s when hospitals started discharging more pediatric patients still on ventilation. These patients were capable of breathing with the ventilator and ultimately weaning from the ventilator, which meant that home devices had to become sophisticated enough to adapt to varying lung conditions and would require features necessary for spontaneously breathing patients.

Devices Differ
Today, as hospitals are discharging sicker patients, there is a greater variability of lung conditions being treated in the home. A patient with a high lung resistance and low lung compliance can challenge a ventilator’s ability to maintain pressure and flow. When a patient is not responding to a ventilator change, is it due to the patient’s disease or the limitations of the ventilator? It is often assumed that each ventilator performs in a similar fashion, yet initial investigations have shown that there are differences.

Flow generation is the heart of a ventilator. Currently, there are three methods of generating flow for the popular ventilators found in the home.

1) Large piston-driven ventilators, which have been the standard for many years and are considered the old guard of durable ventilators.

2) The dual piston ventilator, which entered the market only recently and offers both reduced unit size and longer battery life than the large piston-driven ventilators.

3) Turbine-based ventilators, which are popular due to their small size and continuous flow capabilities.

Knowing the capabilities and limitations of each ventilator gives clinicians the ability to exercise their skill and knowledge to adapt to challenges when they arise.

For a ventilator to be considered portable, it should be moveable. New ventilators are much smaller and lighter than a generation ago, which allows for ease of use related to lifting and positioning. Also, for true portability, a home ventilator needs to have a battery life that allows it to be away from a stationary power source long enough to be practical for the user. Therefore, the driving factor in ventilator engineering today is striking the right balance between smallest possible size, longest possible battery life, and lowest practical cost.

Clinical Consideration
New ventilators are small and sophisticated, yet sacrifice durability in some cases. Therefore, many seasoned home health care respiratory therapists still prefer the “tank” ventilator that can fall down a flight of stairs and keep working. The ideal home ventilator may prove to be somewhere in the middle of durable and sophisticated.

Home ventilation is a respiratory therapist’s area of expertise. Therapists are trained to observe, assess, and respond to lung conditions—and this is put to the test in the home setting where there are multiple variables. For example, the patient’s living environment, family support, and insurance coverage can make each patient situation different. Home nurses, health care aides, and family caregivers all depend on the therapist to understand the disease, the technology, and the options available.

It is therefore important to remember that while home ventilators are entering the market with sophistication and features that improve the mobility of the patient, there may be some trade-off for these new features. The therapists should be aware of the differences and capabilities of each ventilator they use so that when a challenge arises, they can distinguish between a limitation of the ventilator and a change in the patient’s clinical condition.

For example, a recent bench study on how home ventilators respond to identical lung conditions found that different ventilators produced different results even when the test lung consistently repeated the same lung situation and each ventilator was set to the same parameters for comparison. The ventilators were all effective, but their capabilities were somewhat different and should be understood by clinicians so they can make appropriate adjustments. If a ventilator is not able to be adjusted to meet a specific patient’s needs, then that ventilator has a limitation for that situation and should not be used on that patient.

Robert McCoy, BS, RRT, is managing director of Valley Inspired Products, an Apple Valley, Minn-based consulting firm providing market and design services to the respiratory device industry. Contact him at (952) 891-2330 or bmc coy@inspiredrc.com.