Choosing the best type of oxygen therapy
Oxygen is one of the most important treatments available to patients with cardiopulmonary disease. Here’s an updated guide to the equipment.
As primary-care providers have become increasingly adept at recognizing patients with lung disease, and pulse oximetry has simplified the detection of hypoxemia, the use of long-term oxygen therapy for adults has been on the rise. In the appropriate clinical setting, oxygen administration may be one of the most beneficial therapies available to patients with cardiopulmonary disease. Nurse practitioners and physician assistants are the ideal patient advocates for directing oxygen therapy for those with hypoxemia.
Long-term oxygen therapy has been shown to improve survival among patients with severe hypoxemia. Other proven benefits include improvement in quality of life, cognitive function, and exercise capacity. A reduction in the frequency of hospitalizations for hypoxemic patients with chronic obstructive pulmonary disease (COPD) has also been noted with oxygen therapy. Many patients welcome measures directed at improving cognitive function or memory. Obviously, the merits of long-term oxygen therapy outweigh the negative effects, and clinicians should not let the intrusive technologies interfere with prescription of oxygen in appropriate patients.
The most common chronic diseases requiring assessment of oxygenation and consideration of oxygen prescription include COPD, interstitial lung disease (pulmonary fibrosis), cystic fibrosis, bronchiectasis, and pulmonary neoplasms. Other diseases that may present with hypoxemia include pulmonary hypertension, obstructive sleep apnea, and congestive heart failure. Practitioners should be aware of the chronic disease states that may present with hypoxemia and monitor them accordingly.
It is important for clinicians and patients alike to remember that oxygen therapy relieves hypoxemia and prevents the complications associated with chronic tissue hypoxia. However, symptoms of breathlessness and dyspnea do not go hand in hand with hypoxemia. The mechanisms of dyspnea are little related to oxygen levels. Patients can have significant hypoxemia without major dyspnea, or conversely, they may have severe dyspnea with completely normal oxygenation. Patients should be aware that they cannot judge their need for oxygen simply by shortness of breath—they require guidance from measurements of oxygenation.
Making the diagnosis of hypoxemia is relatively easy. Either pulse oximetry or arterial blood gas analysis is sufficient. Pulse oximetry is markedly easier on the patient and can provide adequate data to diagnose hypoxemia. If you suspect that a patient may have hypercarbia (high carbon dioxide in the blood stream), an arterial blood gas is the only option for analysis.
Pulse oximetry measures the light absorption of the hemoglobin in the RBCs, with the absorption changing as the oxyhemoglobin content changes. If pulse oximetry is measured by light absorption through fingernail beds, there should be no nail polish. Nail polish (especially red) can falsely elevate saturation measurements. However, rotating the oximeter clip 90° sideways on the finger obviates the need to remove nail polish to measure the correct saturation. Also be mindful that cold hands can throw off results—a situation easily remedied by gently warming the hands prior to measurement. Low cardiac output states may also make it difficult to obtain an adequate saturation level.
Individuals with suspected hypoxemia can be tested in various ways. During a routine office visit, you can measure pulse oximetry when the patient is either at rest or walking. A patient who has a normal oxygen saturation at rest may have hypoxemia with exertion; this patient may benefit from oxygen administration during exercise. Patients can also have oxygen saturation measured during exercise at pulmonary or cardiac rehabilitation.
Finally, if you suspect that your patient needs supplemental oxygen, testing oxygen saturation at night may be helpful. Frequently, nocturnal hypoxemia can be documented with simple nocturnal oximetry. If your office or clinical practice does not have this device, some durable medical equipment (DME) companies offer the service. A formal sleep study will not be needed unless you suspect a sleep-related breathing disorder, such as obstructive sleep apnea. Nocturnal oxygen therapy is usually a more accepted form of oxygen to patients, since the embarrassment of wearing oxygen equipment in public is avoided. The Medicare indications for long-term oxygen therapy are shown in Table 1.
The most common delivery device for oxygen therapy is a nasal cannula. This device is usually well tolerated by patients and delivers oxygen at prescribed levels. Patients who breathe through their mouths may worry about receiving adequate oxygen. You can reassure these patients that adequate oxygen levels are achieved with the cannula in the nose. As a breath is taken through the mouth, the inspiratory effort pulls the oxygen from the nares into the oropharynx and into the rest of the respiratory system. Those with severe hypoxemia can eat, drink, and even shower with a nasal cannula in place.
Remind patients to prevent their nasal cannula from becoming stiff and uncomfortable by replacing it routinely. There are even glasses (with or without prescription lenses) that incorporate a nasal cannula without calling attention to this delivery device (for more information, visit www.oxyview.com).
Nasal dryness is a common problem associated with the use of nasal cannulas. The first solution is to add a water bottle humidifier to the oxygen source at home. Patients should be careful to keep this humidifier clean and refill it as needed. Another helpful approach is to moisturize the nasal passages with an OTC balanced saline nasal spray. Patients may use this spray as often as necessary without the worry of its interacting with other medications.
A subset of patients need high-flow oxygen or may be unable to tolerate long-term oxygen therapy via nasal cannula for an extended length of time. A transtracheal catheter is one option for these individuals. A minor surgical procedure to insert a transtracheal catheter can be performed by a qualified physician. After the site has healed, the patient or caregiver is taught how to clean and change the catheter daily. This minimally invasive technique is underutilized.
After you have identified the at-risk patient and diagnosed hypoxemia, how do you prescribe oxygen therapy? Currently, a certification of medical necessity needs to be completed (only a physician can sign this form). Important aspects to consider when prescribing oxygen therapy are how the patient will be utilizing the oxygen (continuous, with exercise only, nocturnal only), the required flow rate in liters, and the type of delivery device that will be prescribed. Nonadherence to oxygen therapy is common. Clinicians can increase adherence (and the benefits of preventing hypoxemia) by being knowledgeable about oxygen therapy and the delivery devices available. Simple changes in oxygen devices can greatly improve your patients’ quality of life.
The three forms of oxygen
Oxygen can be delivered in three basic ways: via concentrator, compressed oxygen gas, and liquid oxygen. The least expensive and most efficient method to deliver oxygen therapy at home is via an oxygen concentrator. This device uses electricity to extract nitrogen from room air and delivers oxygen that is 95%-96% pure. Concentrators are reliable and rarely require service (except for cleaning the filter). Extended cords for the nasal cannula can be added to allow the patient to use this device throughout the home.
At times, concentrators can be loud, so the patient may want to put the device in a room other than the bedroom if it disturbs sleep. Electrical power outage is a potential drawback. Patients frequently keep a tank of compressed oxygen at their home for emergency use. Some concentrator units allow patients to fill their own portable oxygen tanks. Alternatively, portable oxygen tanks can be home-delivered by the DME company. Some patients have only a large gas cylinder for their primary oxygen source at home, which must be replaced by the DME company as necessary.
Liquid-oxygen systems operate by cooling oxygen to -183°C and forcibly compressing it so it becomes a liquid. A large liquid-oxygen container is required, which the DME company refills on a scheduled basis. From this large container, a liquid portable system can be filled by the patient or family member. All oxygen-delivery systems are reliable; insurance coverage and personal preference guide the selection and prescription. DME companies can only provide what is prescribed; this is when knowledge about the different oxygen systems becomes so important.
Portable systems are critical for maintaining independence and quality of life for hypoxemic patients. Several good options are available, such as portable gas cylinders or liquid-oxygen systems. By using pulses of oxygen rather than continuous flow, conserving devices on portable systems make oxygen supplies last longer. Pulse devices deliver oxygen on every breath or on alternate breaths at a fixed volume. By comparison, demand devices deliver oxygen only with each inhalation. Demand devices vary delivery with the patient’s inspiratory effort and duration, whereas pulse devices deliver at a preset volume and rate. Conserving units may be pneumatically driven or require batteries for delivery. Before selecting one of these devices, make sure the patient’s inspiratory effort is sufficient to trigger the demand valve.
Demand for oxygen varies with activity. Test the oxygen saturation at rest, with exercise, and during sleep to ensure adequate oxygenation. For example, a patient may require oxygen at 1 L/minute at rest, 3 L/minute with exercise, and 2 L/minute at night. A desirable oxygen saturation level is usually in the low 90s or higher.
How long portable oxygen tanks with conserving devices will last depends on the patient’s prescribed flow rate and the size of the tank. The optimum tank should be lightweight with a conserving device and fit into a shoulder bag for portability. Patient outings and oxygen consumption should be planned for accordingly.
There are several liquid-oxygen systems available, but two stand out above the rest. Both have been praised by patients for ease of use and facilitating independence.
The Helios system (www.heliooxygen.com) offers two models: the Helios Plus and the Helios Marathon. The Helios Plus is only 10 inches tall, weighs 3.6 lb when filled, and lasts approximately 10 hours on demand flow. The Helios Marathon is 15 inches tall, weighs 5.6 lb when full, and can last up to 20 hours. Each model provides either continuous or demand flow depending on the patient’s needs. Both come with a belt clip or can be carried by backpack or shoulder bag.
The EasyMate, manufactured by Precision Medical (www.precisionmedical.com), is 8.2 inches high, weighs 3.6 lb when filled, and lasts approximately eight hours. It is quite durable and also comes with a form-fitting carrying bag.
Portable oxygen concentrators are now commercially available. The three units available at this time are the Inogen One (www.inogenone.com), the EverGo by Respironics, and the SEQUAL Eclipse by SeQual. These portable devices run on batteries, or they can be plugged into an electrical wall outlet or DC car adapter. The Inogen portable concentrator weighs 9.8 lb, and the rechargeable battery lasts for three hours.
These units are fairly expensive and may not be covered by insurance. One of the biggest advantages of a portable concentrator is that it can be used for travel, including on most airlines. By federal law, if an airline allows oxygen in flight, a portable concentrator may be utilized by the hypoxemic individual.
Currently, patients cannot use or carry portable tanks or liquid oxygen systems on flights. All arrangements for oxygen therapy must be approved by the airline well before the flight; additional costs are paid by the patient. Several DME companies rent portable oxygen systems for travel and other special situations.
Oxygen therapy clearly improves quality of life for hypoxemic individuals. To optimize therapy, clinicians must participate in designing the most appropriate system for each individual patient.