PHPN: O2 Trials and Tribulations
Many caregivers are regularly challenged with questions regarding portable oxygen. There are more options available than ever and one would assume that would simplify things. However, there is more mainstream marketing directed at patients, and some systems are simply not sufficient for patients' needs.
LOOKING BACK
Forty years ago the only existing “home oxygen” option available was when an industrial supplier of medical gases would deliver a series of “H” cylinders (with brass regulators) to a patient's home. Times have changed. Today's choices include home oxygen concentrators, portable oxygen concentrators (POCs), aluminum portable (lighter and smaller) tanks, oxygen conserver (demand) devices, portable liquid oxygen (LOX), and “self-fill” home systems. In this article, we will briefly discuss some of the newer systems and how they work.
DEMAND AND PULSE OXYGEN CONSERVER
While conservers were initially introduced as a way for portable oxygen tanks to last longer, manufacturers have added this technology to some liquid delivery systems and portable concentrators, as well. The basic operating systems of these conservers are either electric or pneumatic.
Electric conservers can operate on an intermittent-breath or every-breath basis. The “smart” technology senses the negative pressure generated at the beginning of inhalation. With an “every-breath” conserver, the solenoid of the conserver opens every time the sensor signals. The length of time it remains open depends on the pulse setting. The higher the pulse setting, the longer the solenoid remains open, thereby increasing the flow. The volume of the pulse is based on the number on the dial, which manufacturers compare to liters per minute (lpm), but it is actually not delivering lpm when in pulse mode. Instead, it is delivering milliliters per breath.
The intermittent-breath conserver senses the breath initiation and fires based on its setting. If the device is set at number 1, it will deliver 1 pulse of a fixed volume of oxygen for every 4 breaths sensed; number 2 will deliver a pulse of oxygen every other breath; number 3 would deliver a pulse of oxygen on 3 out of 4 sensed breaths; and number 4 would deliver it every breath.
A pneumatic conserver senses the initial negative pressure then delivers a fixed pulse of oxygen followed by continuous flow until it senses the beginning of exhalation. For that reason, some pneumatic conservers have a dual cannula (one is attached to the “sensing” port and the other to the “oxygen” port).
Oxygen suppliers stock a variety of systems and it would be very difficult to keep up with the newest developments. When a patient inquires about the eligibility of a conserving device (or a smaller tank), one option is to write a prescription to “titrate and evaluate a patient for a conserver device.” The oxygen company would then assess the patient with the conserver that they supply. After documentation is received identifying the patient's precise oxygen saturations on that device, the conserver prescription can be approved or denied.
A recurrent challenge with “pulse” dosing is that a patient (when short of breath) will sometimes breathe through their mouth to “catch up.” While “mouth breathing,” the sensor does not always recognize the inspiration and therefore will not fire. Lack of oxygen flow further decreases a patient's oxygen level and increases shortness of breath (thereby perpetuating the problem). The same may be true at night when a patient does not generate sufficient pressure to trigger the demand device.8 Each conserver has specific pros and cons. Instructing the home oxygen company to test the patient on the actual conserver provided is the safest option.
CONSERVER TECHNOLOGY HAS BEEN INTEGRATED WITH VARIOUS CURRENT OXYGEN OPTIONS
Liquid Oxygen
Liquid oxygen (LOX) is one of the only viable home oxygen options for patients on liter flows greater than 10 lpm. There are several variations of setups for high-flow patients. Some patients utilize a concentrator for their home and LOX for portability. If a patient requires a flow between 10 and 15 lpm, patients can receive their home flow from a flow-meter attached to a liquid reservoir. The major drawback to LOX is cost and storage of the refill reservoirs. Each standard home reservoir holds about 20 liters of LOX and weighs between 100 and 160 pounds. Smaller reservoirs hold 10 liters and are usually less than 60 pounds (full). The smaller units are the perfect size for travel and can easily be transported in mid- to large-sized automobiles (as long as the home oxygen company will allow it). How often the oxygen company refills the patient's reservoir depends on liter flow and the rate of evaporation. Consider LOX if your patient requires high flows.
Self-Fill Systems
In recent years reimbursement for home oxygen has decreased, and it has become more fiscally challenging for oxygen companies. With home oxygen companies trying to find more ways to deliver care with fewer deliveries and less upkeep, a new product was developed in 2000, enabling home oxygen patients to fill their own portable gas cylinders from their oxygen concentrator. The key with this system is that a cylinder filled with a concentrator will not contain 100% oxygen. A properly functioning concentrator can produce an oxygen concentration as low as 88%; therefore, that would be the percentage of oxygen filling the patient's portable tank. While there have been studies citing this as clinically inconsequential, it should be noted, particularly if your patient needs liter flows >4 lpm.
Portable Oxygen Concentrator
The newest addition to the oxygen world is the POC. There are several factors to consider with each option, keeping in mind all of the particulars discussed previously. Since the 2005 landmark decision by the Federal Aviation Administration to allow POCs on commercial aircraft,1 there have been a host of new POCs introduced. While 5 portable concentrators have the ability to provide continuous flow and they are limited to a maximum of 3 lpm, the majority of POCs deliver oxygen by pulse flow only. Considerations for selection of a POC include: weight, size, battery life, maximum oxygen capacity, sound level, and oxygen hose length. POC weights with a single battery range from 2.3 to 19.9 pounds. In general, lighter units have shorter battery life and lower maximum oxygen capacities. Battery life varies by POC unit and flow rate used, ranging from <1 hour to 6 hours. Utilizing extra batteries can extend the time between charges.5 The more details we learn about how portable concentrators work, the more we can appropriately gauge which patients may benefit most from this technology. Different options are constantly emerging.
When initiating oxygen therapy, it is wise to discuss the patient's expectations and lifestyle. Some patients have frequent travel plans and should select a company that can and will accommodate those needs. The world of oxygen systems is ever changing and new developments must be addressed. The focus should center on developing individualized patient oxygen therapy plans as new options emerge.
An important tool in the arena of patient self-monitoring is the portable pulse oximeter. In recent years, the portable pulse oximeter has become increasingly affordable. While it is not a perfect tool, a home pulse oximeter can be very helpful for a patient to report their oxygenation while in the home setting. This is especially true in monitoring patients with exercise-related dyspnea and for titrating oxygen flow for patients on long-term oxygen therapy, provided their disease is stable and they have good circulation. In general, the goal should be to maintain oxygen saturation >90% during all activities.
Pulse oximeters can overestimate oxygen saturation, particularly in those with darkly pigmented skin. Additional cautions should be noted if the patient has:
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Poor perfusion due to systemic hypotension, Raynaud's, hypovolemic shock, cold environment, or cardiac failure—it may result in the machine not providing a reading (or an inaccurate reading)
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Anemia—oxygen delivery to tissues is inadequate due to lack of hemoglobin for oxygen to bind to, but oxygen saturation is normal
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Carbon monoxide poisoning—carbon monoxide binds to hemoglobin, resulting in inadequate oxygen transport despite normal pulse oximeter readings. The pulse oximeter cannot distinguish what gas is binding to the hemoglobin (only that a gas is attached).
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Movement, shivering patient, heart arrhythmias—oximeter may not be able to identify an adequate pulse signal due to movement intolerance
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Nail polish, dirt, artificial nails—can cause false low readings or prevent readings altogether
It is difficult to predict whether a patient will be appropriately oxygenated with a particular system, but by working closely with patients and home oxygen providers, patients can truly live life to its fullest.
Contributor Notes