Vol. 18 •Issue 21 • Page 21
High-Flow Oxygen Defined
Therapy Carries Many Names Today
About two-thirds of the human body is oxygen. So is nine-tenths of water. Without this colorless, odorless and tasteless gas, we would die. Giving oxygen, in a metaphysical sense, could be construed with giving life. It is when we talk about giving oxygen in the practical sense that things get a little more complicated.
As RTs, we like to think we have cornered the market in the oxygen delivery world. But we haven’t; and increasingly, the lines are getting blurred as to what we are giving and even how we are giving it.
Nowhere is this more evident than in the emergency department.
Within the walls of our hospitals, therapists can pretty much control what goes on. We determine the policies and procedures, so we generally are not surprised by some new-fangled oxygen system spontaneously popping up on a unit somewhere. But in the ED, we must face whatever rolls in the door.
When it comes to oxygen delivery systems, this can be a challenge. A patient can be brought in on a “high-flow oxygen system.” The problem is there is no clear cut, uniform definition of what this means.
Shapiro defines a high-flow system as a “system in which the flow rate and reservoir capacity are adequate to provide the total inspired atmosphere.” By this definition, most venture masks and non-rebreathers meet these criteria. Traditionally a nasal cannula does not.
But now there are high-flow nasal cannulas (HFNC). A study published in Chest last year compared the effects of high-flow, humidified oxygen to conventional low-flow oxygen delivery via a cannula at rest and during exercise in patients with COPD.
In that study, 10 patients with stable COPD underwent rest and baseline assessments of work of breathing and ventilatory parameters and exercised on a cycle ergometer for up to 12 minutes. Patients exercised using a low flow first, rested and then repeated the exercise using the high-flow system set at 20 L/min.
Researchers found the high-flow system permitted the patients to exercise longer (10.0 ± 2.4 minutes vs. 8.2 ± 4.3 minutes) with less dyspnea and have a more comfortable breathing pattern overall. When FiO2s were comparable, the oxygenation was higher while patients received high-flow oxygen at rest and during exercise than when they were on the low-flow system.
Topical vs. Hyperbaric Oxygen
There has been a growing interest in the application of topical “high-flow” oxygen, particularly for the treatment of chronic wounds such as the kind often seen in diabetics. There is not a great deal of published literature to support this therapy. Topical therapy involves placing an airtight plastic or polyethylene bag over the affected area and then adding “high-flow oxygen” (about 10 lpm) to the bag.
The goal is to raise the pressure in the bag to 1.0 atmospheres absolute (atm abs). Higher pressure than that can restrict capillary blow flow and perhaps cause more harm than good. Proponents of the therapy say the diffusion of oxygen into the wound enhances healing and is safer and less expensive than hyperbaric oxygen. At the same time, the procedure can be easily performed in any setting.
Advocates further note that when compared to traditional hyperbaric therapy, topical therapy has a lower incidence of free radical formation and more efficient delivery of oxygen to the wound surface.
Because this therapeutic method is so new, it has not been officially named. In additional to being called “topical oxygen therapy,” it has also been dubbed “topical hyperbaric oxygen therapy” and simply “hyperbaric oxygen therapy.”
This has created some confusion in what little literature has been published to date, not to mention befuddling third-party payers.
Collagens and Fibroblasts
Studies have shown that collagen production and fibroblast proliferation (markers of improved healing) are both enhanced with hyperbaric oxygen therapy. Yet decreased collagen production and fibroblast inhibition in wounds has been anecdotally reported in some cases.
Perhaps the most telling point is that the Centers for Medicare and Medicaid Services will reimburse for hyperbaric oxygen therapy under certain limited circumstances, but CMS will not reimburse for topical oxygen therapy for wound care.
From our perspective, it is interesting to note that “topical oxygen therapy” is being billed as portable therapy that can be done anywhere using “high-flow oxygen.”
Who is to say this therapy will not be requested by an ER physician in an exam room or by a discharging physician as part of a patient’s home care in the future? Are we prepared to provide this service?
When all is said and done, respiratory therapists are usually the ones called on to deliver oxygen therapy. But we need to remember the definitions we grew up with and accepted as truths are being challenged by newer technologies and procedures. This isn’t necessarily a bad thing. But before the water becomes any murkier, perhaps we should take a look at how we title things. We should also take the time to educate our colleagues and ourselves on these new practices, especially before one shows up unannounced in the ED where we work.
Margaret Clark is a Georgia practitioner.