Long-term supplemental oxygen therapy

INTRODUCTION — Long-term oxygen therapy (LTOT) increases survival and improves the quality of life of hypoxemic patients with chronic obstructive pulmonary disease (COPD) and is often prescribed for patients with other hypoxemic chronic lung disease [1-15]. Each year, approximately 1.5 million patients in the United States receive LTOT [13].

In this topic, the potential benefits and indications for LTOT and practical issues including reimbursement, documentation of need, and the process of prescribing LTOT are reviewed. High-flow nasal cannula, portable oxygen delivery, and oxygen conserving devices are discussed separately. (See "Continuous oxygen delivery systems for the acute care of infants, children, and adults" and "Portable oxygen delivery and oxygen conserving devices".)

BENEFITS — Five randomized trials have evaluated the effect of long-term oxygen therapy (LTOT) on mortality in patients with COPD.

●Two of the trials, the Nocturnal Oxygen Therapy Trial (NOTT) and the Medical Research Council (MRC) trial, demonstrated improved survival among patients that received LTOT (figure 1 and figure 2), including correlation between survival and the average daily duration of oxygen use [1,2].

●In contrast, three trials (nocturnal oxygen therapy [NOT], supplemental oxygen for moderate hypoxemia, and Long-Term Oxygen Therapy Trial [LOTT]), found no effect of LTOT on survival [4,16]. In NOT, oxygen supplementation did not improve mean pulmonary artery pressures, and in LOTT there were no between-group differences in time to first hospitalization, six-minute walk distance, or respiratory quality of life.

An important difference between these trials was the inclusion criteria [10]. The trials that demonstrated a survival benefit included patients with more severe resting hypoxemia (arterial oxygen tension [PaO₂] ≤60 mmHg [7.98 kPa]) or SpO₂ ≤88 percent than the trials that showed no benefit (PaO₂ <69 mmHg [9.18 kPa]), indicating that individuals with less severe hypoxemia may not derive a survival benefit from LTOT. One meta-analysis specifically examined the mortality benefit of nocturnal or continuous supplemental oxygen in 1002 patients with various definitions of moderate hypoxemia (PaO2 56 mmHg to 69 mmHg, SpO2 89 to 93 percent, exertional desaturations between 80 and 90 percent, and/or isolated nocturnal desaturations below 88 percent) [17]. Compared with placebo, long-term oxygen supplementation showed a small or absent benefit over three years of follow-up (20 versus 22 percent, relative risk 0.91, 95% CI 0.72-1.15) without evidence of heterogeneity among the studies.

LTOT may improve outcome measures other than mortality, including quality of life, cardiovascular morbidity, depression, cognitive function, exercise capacity, and frequency of hospitalization [3,5-9,18-22]. Improved quality of life was demonstrated in a prospective study that measured health related quality of life (using the St. Georges respiratory questionnaire [SGRQ]) before and after six months of LTOT delivered via a concentrator [21]. Prior to therapy, health related quality of life was worse among the patients with COPD who had hypoxemia (and had already been receiving LTOT for at least six months via a cylinder), compared to patients with COPD who were not hypoxemic. After six months of LTOT, health-related quality of life had improved and was similar in both groups. This suggests that LTOT may improve quality of life and the improvement is related, at least in part, to the time spent using supplemental oxygen, which also relates to the delivery system(s) used. The effect of combining concentrators and portable devices to improve mobility and further enhance quality of life has yet to be determined. Prescribing oxygen during exertion with highly portable lightweight devices without the support of a pulmonary rehabilitation program may or may not lead to a more active lifestyle, which also impacts quality of life.

All of the studies described above evaluated the impact of LTOT used during rest and exertion. Controlled trials have also evaluated the impact of supplemental oxygen when used during exertion only. Among patients who have COPD with a resting PaO₂ >60 mmHg (ie, are unlikely to derive a mortality benefit from LTOT), supplemental oxygen improved dyspnea and the distance walked during a five-minute walk test compared to supplemental air [23]. However, the results of this study do not support general application of long-term oxygen in this patient population. In a separate study, recovery time following exertion was shorter among the patients who received short burst oxygen [24].

ADVERSE EFFECTS — Excess supplemental oxygen increases mortality among acutely ill hospitalized patients, so guidelines suggest specific target ranges in these patients to avoid the adverse effects of excess supplemental oxygen [25]. By following the recommendations for a target range for SpO₂ of 90 to 92 percent [25], tissue hypoxia may be prevented while minimizing any deleterious effects associated with oxygen therapy [26,27]. More definitive studies are required to better understand how enriched oxygen interacts with cells in the body, under a variety of different circumstances, especially when long-term oxygenation is required. Ideal oxygen targets are discussed below. (See 'Oxygen flow rate' below.)

Limited evidence suggests that low grade oxidative injury may occur with LTOT, but the clinical significance is uncertain and it should not preclude administration of LTOT when indicated. In one recent survey of patients on LTOT, adverse effects with the highest reported prevalence were reduced mobility or physical activity (70.9 percent), dry mouth (69.5 percent), congestion or nasal drip (61.6 percent), increased tiredness (57.0 percent), and dry nose (53.0 percent) [28]. However, reductions in mobility, physical activity, and poor sleep hygiene are associated with COPD disease progression and the additional impact of LTOT-induced oxidative injury on adverse effects needs further elucidation. These and other adverse effects of oxygen are discussed separately. (See "Adverse effects of supplemental oxygen" and "Adverse effects of supplemental oxygen", section on 'Adults on long-term oxygen'.)

INDICATIONS — Indications for continuous long-term oxygen therapy (LTOT) for patients with chronic lung disease include (table 1) [12,14,15,29,30]:

●Arterial oxygen tension (PaO₂) less than or equal to 55 mmHg (7.32 kPa), or a pulse oxygen saturation (SpO₂) less than or equal to 88 percent

●PaO₂ less than or equal to 59 mmHg (7.85 kPa), or an SpO₂ less than or equal to 89 percent, if there is evidence of cor pulmonale, right heart failure, or erythrocytosis (hematocrit >55 percent)

For patients with normal awake oxygenation, oxygen may be prescribed during sleep if any of the following occur during sleep: the PaO₂ is 55 mmHg or less, the SpO₂ is 88 percent or less, the PaO₂ decreases more than 10 mmHg (1.33 kPa), and/or the SpO₂ decreases more than 5 percent with signs or symptoms of nocturnal hypoxemia (eg, impaired cognitive function, morning headaches, restlessness, or insomnia). In this setting, portable oxygen would not be covered. (See "Sleep-related breathing disorders in COPD".)

Oxygen may be prescribed during exercise if there is a reduction of PaO₂ to 55 mmHg or less, or of SpO₂ to 88 percent or less during exercise. Additionally, oxygen may be warranted during exercise even in those patients who do not significantly desaturate during exercise, if they have dyspnea and ventilatory abnormalities during exercise that suggest supplemental oxygen may permit greater exertion [31]. This is supported by studies that found that hyperoxia increases exercise endurance in a dose-dependent manner, up to an inspired oxygen fraction of 50 percent or a flow rate of 6 L/min [32].

The use of supplemental oxygen in the palliative treatment of dyspnea in non-hypoxemic patients is not well supported by the literature. A randomized trial and systematic reviews have found that supplemental oxygen provides no symptomatic benefit beyond room air for patients with dyspnea, but not hypoxemia, due to advanced heart failure or end stage cancer. At this advanced stage, pharmacological management assumes a central role [33]. (See "Assessment and management of dyspnea in palliative care", section on 'Non-hypoxemic patients'.)

PRESCRIBING OXYGEN — Responsibilities of the clinician prescribing long-term oxygen therapy (LTOT) include (table 2):

●Determine the need for LTOT and goal for therapy

●Ascertain the oxygen flow rate for each condition (ie, the required flow rate may be different during sleep, exercise and sedentary wakefulness)

●Assure the selection of a qualified durable medical equipment supplier

●Complete the Certification of Medical Necessity (eg, CMS 484) for Medicare patients

●Provide a prescription for ambulatory oxygen if required

●Test patients using the portable oxygen system (typically with an oxygen conserving device) provided during typical exercise to assure adequate oxygenation

●Reassess the need for LTOT for prescription renewal and/or modification

●Educate patients about goals of therapy and safety issues [34,35]

Determining need — Long-term oxygen therapy (LTOT) should be prescribed only when there is evidence of persistent hypoxemia in a clinically stable patient who is receiving otherwise optimal medical management. Patients who are clinically unstable or whose medical management is not optimized should be prescribed oxygen therapy and reassessed later for their long-term oxygen needs.

There are specific requirements for determining a patient's need for LTOT that must be met for LTOT in order to be reimbursed:

●Arterial blood gas analysis or measurement of pulse oxygen saturation (SpO₂ by pulse oximetry) must be performed by a physician or by a qualified laboratory. The intent of this requirement is to prevent the oxygen provider from also being involved in certifying the medical necessity, since this could represent a conflict of interest.

●The arterial blood gas or SpO₂ measurement must be obtained within two days of discharge if the oxygen is prescribed at the time of hospital discharge. When arterial blood gas and oximetry studies are both used to document need for supplemental oxygen and the results are conflicting, arterial blood gas results become the preferred source for documentation of medical necessity.

Oxygen flow rate — Although not required by payers, we believe that arterial blood gas measurements should be the standard for consideration of accuracy and to fully assess the arterial tension of carbon dioxide (PaCO₂) and acid base status. Performed along with pulse oximetry, ABGs will help to confirm the accuracy of the SpO₂ measurement.

●Flow rate during rest – The flow of oxygen needed to correct hypoxemia should be determined by measurement of PaO₂ or SpO₂ when LTOT is initiated (table 3). The threshold PaO₂ or SpO₂ that optimally improves survival and quality of life is not known. A PaO₂ of 60 to 65 mmHg (7.98 to 8.65 kPa) or SpO₂ of 90 to 92 percent is generally considered to be an acceptable target [25]. This represents clinically "adequate" correction of hypoxemia for most patients and is unlikely to cause significant CO₂ retention. High flow oxygen may cause CO₂ retention and possible oxygen toxicity [27]. Based on studies in hospitalized patents, efforts should be made to avoid SpO₂ >96 percent [25]. (See 'Adverse effects' above and "The evaluation, diagnosis, and treatment of the adult patient with acute hypercapnic respiratory failure".)

One of the early studies that demonstrated increased survival among patients with chronic obstructive pulmonary disease (COPD) who received LTOT raised the mean PaO₂ to 71.3 mmHg (9.48 kPa) [36]. In the Nocturnal Oxygen Therapy Trial (NOTT), the investigators attempted to maintain the PaO₂ between 60 and 80 mmHg (7.98 to 10.64 kPa) [1].

●Flow rate during exercise/exertion – It is common for patients with COPD who qualify for LTOT and experience hypoxemia at rest to desaturate further during usual activities of daily living, such as walking. As a result, higher oxygen flows are often necessary during exertion. It is therefore important to determine the exercise oxygen prescription while the patient is walking and to include this information in the oxygen prescription. The difference in oxygen flow necessary to correct hypoxemia at rest and during exercise may be magnified when some of the oxygen conserving devices are being used, especially those that utilize an oxygen pulsing device delivering oxygen intermittently [37,38]. An additional consideration is the use of hyperoxia to improve ventilation, reduce dyspnea, and enable the patient to exercise longer or at higher intensity during training programs [31,39]. Therefore, not only should patients be evaluated for desaturation (hypoxemia), but other outcomes such as dyspnea and exercise improvement during exercise on various O₂ liter flows regardless of a desaturation response. (See 'Exercise training' below.)

With increased availability of finger pulse oximeters, it is commonly recommended that patients titrate their own oxygen flow setting to a target SpO₂. Considering that some inexpensive oximeters may provide inaccurate readings, it is important that the oximeter purchased is accurate and calibrated against arterial blood gases. This is easily accomplished by having the patient bring the oximeter with them to the clinic and validating against clinic measures (eg, the clinics oximeter or preferably arterial blood gas measures).

●Flow rate during sleep – Among patients prescribed LTOT for daytime hypoxemia, clinicians should determine if higher flows of oxygen are necessary to prevent nocturnal oxygen desaturation. The importance of nocturnal desaturation is uncertain since some persons have oxyhemoglobin desaturation during sleep without daytime sequelae. Nevertheless, most clinicians managing patients who qualify for LTOT because of daytime hypoxemia adjust the flow rate to prevent hypoxemia during sleep. As an example, the oxygen flow was routinely increased by one L/min during sleep in the NOTT trial [1].

Some patients who do not qualify for oxygen when awake may require oxygen therapy during sleep. As many as 30 percent of patients with COPD who have no daytime hypoxemia experience desaturation during sleep [40,41]. In those patients with COPD who have cor pulmonale, right heart failure, or erythrocytosis without evidence of hypoxemia while awake, any period of prolonged desaturation during sleep may potentially be detrimental. Thus, nocturnal monitoring of hypoxemic events and titration of supplemental oxygen are advised. Some patients may have obstructive sleep apnea (OSA) in addition to their COPD, as a cause of nocturnal desaturation. Overnight polysomnography can help clarify whether OSA is playing a role, and affected patients should be treated for their OSA. (See "Pulmonary hypertension due to lung disease and/or hypoxemia (group 3 pulmonary hypertension): Epidemiology, pathogenesis, and diagnostic evaluation in adults" and "Clinical presentation and diagnosis of obstructive sleep apnea in adults".)

Equipment selection — The clinician should also be familiar with the durable medical equipment (DME) providers in the area and encourage the use of those providers who are willing and able to provide the best service and equipment (particularly portable) and to fill the prescription appropriately.

Every attempt should be made to provide portable or wearable oxygen systems in support of patients striving for an active lifestyle [34,35]. For highly active and mobile patients, the clinician should order ambulatory liquid oxygen, a lightweight aluminum or fiber-wrapped ambulatory cylinder, or a portable oxygen concentrator. Oxygen concentrators are typically less expensive than other forms of LTOT.

Each of these systems may be combined with an oxygen conserving device or transtracheal catheter to substantially increase the functional time and reduce the size and weight of the unit that the patient carries [34,35]. This requires the clinician to order portable oxygen with or without an oxygen conserving technology, in addition to a stationary LTOT system, although in some cases a portable oxygen concentrator will serve as the stationary as well as the portable system. The proper prescription depends on the individual needs of the patient. The DME supplier might not provide patients with the best available technology unless the clinician has the knowledge and ability to prescribe it. (See "Portable oxygen delivery and oxygen conserving devices".)

Portable oxygen is reimbursed if the Medicare patient is mobile in the home and regularly goes beyond the limits of a stationary oxygen delivery system with 50 feet of tubing. The Center for Medicare and Medicaid Services (CMS), in the United States, does not consider travel outside of the home in making this determination and also does not recognize a distinction between portable and ambulatory oxygen. The distinction made by the pulmonary community is that ambulatory oxygen delivery systems should weigh less than 10 pounds (4.5 kg) and be easily carried by the patient [42]. This 10 pounds limit is high enough to encompass the use of several portable oxygen concentrators; several portable gas, concentrator, and liquid systems weigh less than 5 pounds. These units should be provided for patients who are highly mobile and active.

Patients who are ambulatory outside the home and require >3 L/minute of continuous flow oxygen may benefit from liquid oxygen [14]. Portable liquid oxygen devices provide continuous-flow oxygen up to 15 L/minute via a lighter and longer-duration device than oxygen concentrators.

Twenty-pound E cylinders with their two-wheeled strollers cannot be carried by the patient and are difficult to maneuver on stairs and on public or private vehicles of transportation. These E cylinders may be prescribed for patients who are less mobile and leave the home only occasionally, or who require the higher storage capability of these cylinders. Additionally, E-cylinders are typically placed in the patient's home as an emergency backup in the event the primary O₂ delivery system fails.

Oxygen is reimbursed on a prospective payment basis by CMS, and there is no Medicare requirement concerning the type of equipment being provided by the home oxygen supplier. CMS considers all oxygen delivery systems to be equal and "modality neutral" for the purpose of reimbursement. For patients who require portable systems, there is a small additional reimbursement for a "portable add on" device, which must be ordered by the clinician. The portable device provided to the patient will be tested during ambulation by an independent respiratory therapist or physician to assure adequate oxygenation during activity by that device.

Certification of medical necessity — Medicare and most third party carriers will cover home oxygen and oxygen equipment under durable medical equipment benefits when oxygen is considered reasonable and necessary for patients with significant hypoxemia who satisfy all medical documentation, laboratory evidence, and health conditions specified by the Social Security Administration [13]. The need for oxygen must be determined after optimal medical management is implemented (eg, medical and physical therapy directed at secretions, bronchospasm, and infection).

The clinician or a member of his or her staff must complete a Certification of Medical Necessity (CMN) and only the clinician can sign the form (Certificate of Medical Necessity CMS form 484). The requirement for the clinician to sign the CMS Form 484 was recommended by the Office of the Inspector General of the United States after a five–state survey indicated that the clinician's knowledge of home oxygen therapy and involvement in writing the prescription were often inadequate [43]. In many cases, the home oxygen supplier was determining the need for therapy and also supplying the equipment without adequate clinician input. This requirement is intended to assure the clinician's involvement in the prescribing and administration of long-term oxygen therapy (LTOT). Further, the same form CMS-484 is used for recertification [44].

In addition to the CMN, a separate written prescription must be provided to the home oxygen supplier when oxygen is ordered and prior to completion of form 484 (figure 3).

Ongoing assessment — With the aid of the durable medical equipment (DME) provider, the clinician should monitor the use of the oxygen by the patient and the environment in which the oxygen is being used. Patients who continue to smoke or use e-cigarettes while using oxygen create a hazard to themselves, their families, and other occupants of buildings where they live [45].

Patients should be asked about their patterns of oxygen use to determine whether they are adhering to the oxygen prescription. Some patients may discontinue LTOT because they feel that they are doing better, do not want to become "addicted" to oxygen, or do not want to be seen using their supplemental oxygen. Reassurance can be provided regarding the benefits of LTOT in the setting of hypoxemia and the absence of "addiction" to oxygen. Patients sometimes adjust their oxygen use or flow rate based on symptoms. As the presence or absence of dyspnea is not a good substitute for measurement of pulse oxygen saturation, patients should be encouraged to use LTOT as prescribed.

Oxygen should not be continued if the patient is unwilling to use it, and advanced ambulatory equipment should not be supplied if the patient is unwilling or unable to be physically active. All patients receiving LTOT must be recertified every 12 months; retesting of PaO₂ or SpO₂ is not required by Medicare but may be required by other third party payers.

REIMBURSEMENT — In the United States, the Center for Medicare and Medicaid Services (CMS) does not pay for oxygen as medication. Rather, CMS classifies oxygen and oxygen delivery equipment as durable medical equipment (DME); this definition allows oxygen to be reimbursed as a form of "medical equipment." As a result, a specific Certificate of Medical Necessity (CMN, CMS 484.5) must be completed by the clinician in order for oxygen therapy to be reimbursed at a level of 80 percent of the Medicare allowable charge. The patient or the supplemental insurance provider is responsible for the remaining 20 percent of the cost. For patients not requiring oxygen at rest but prescribed ambulatory oxygen, the clinician must document three SpO₂ readings: on room air at rest, with exercise, and on the prescribed oxygen setting during exertion.

Most third party payers also utilize the requirements for medical necessity established by CMS. These requirements are based primarily on the parameters for entry into the multicenter Nocturnal Oxygen Therapy Trial (NOTT) sponsored by the National Institutes of Health [1]. Indications and guidelines for therapy have been further refined by six national consensus conferences on long-term oxygen therapy (LTOT) [34,42,46-49] and the 2020 American Thoracic Society guidelines [14]. These guidelines apply not only to hypoxemic patients with COPD, but also to patients whose hypoxemia is due to other disorders, such as chronic interstitial lung disease, chest wall disease, lung cancer, and cardiac disease [14,50].

Within these guidelines, it is the clinician's responsibility to be involved in selection of appropriate equipment and provision of an individualized prescription that must be transmitted to the DME provider (figure 3). The prescription must contain several required elements including a specified diagnosis of the disease requiring supplemental oxygen, liter oxygen flow and any changes that may be required for sleep, exercise or other condition, frequency and duration of use, and/or the issuance of portable oxygen devices. "Oxygen PRN" or "Oxygen as needed" do not qualify. The clinician is now instructed not to sign the CMS form (484.5) unless the provider has correctly restated the prescription in Section C. Periodically, the clinician will need to recertify the patient for supplemental oxygen and this recertification must be completed within a specified period of time to ensure that oxygen is provided without interruption.

CLINICAL TRIALS APPROVED BY CMS AND SPONSORED BY THE NATIONAL HEART, LUNG, AND BLOOD INSTITUTE (NHLBI) — The Centers for Medicare and Medicaid Services (CMS) will cover the home use of oxygen as outlined in Section 240.2 of the CMS National Coverage Determinations Manual for beneficiaries with a PaO₂ from 55 to 65 mmHg or an oxygen saturation at or above 89 percent when they are enrolled in clinical trials sponsored and approved by CMS and co-sponsored by the National Heart, Lung, and Blood Institute (NHLBI).

ADDITIONAL CONSIDERATIONS — Adjustment of the oxygen prescription may be required for exertion, sleep, and air travel, as well as, during acute exacerbations of the disease.

Exercise training — Hypoxemic patients are prescribed oxygen in order to prevent exertional desaturation as described above. (See 'Oxygen flow rate' above.)

The role of short-term supplemental oxygen therapy in patients who are not hypoxemic at rest, but desaturate during exertion is unclear [51]. In a systematic review of trials in patients with interstitial lung disease [51], two trials that examined the effect of supplemental oxygen during exertion found no benefit in exercise capacity or dyspnea [52,53], while a third found an increase in endurance time [54]. However, oxygen saturation was not always monitored during exercise. A trial of supplemental oxygen during cycle ergometry in patients with COPD and exercise-hypoxemia reported that oxygen during exercise enabled patients to tolerate higher training intensity and increased exercise tolerance [39]. The 2020 ATS Guidelines support emerging evidence that ambulatory oxygen may improve health-related quality of life (HRQL) in patients with interstitial lung disease [14,29]. The exact role of oxygen as a rehabilitative adjunct remains to be delineated [11,31,51].

Nocturnal desaturation — For patients with nocturnal desaturation, a clinical evaluation for sleep-disordered breathing and overnight polysomnography are often appropriate. (See "Sleep-related breathing disorders in COPD" and "Clinical presentation and diagnosis of obstructive sleep apnea in adults".)

Air travel — During air travel, ambient air pressure in the cabin decreases (not pressurized to sea level), leading to a decrease in the oxygen tension (also known as the partial pressure of oxygen) of inspired air, which can lead to hypoxemia in patients with lung disease. Patients with a resting room air pulse oxygen saturation (SpO₂) <92 percent at sea level are candidates for supplemental oxygen during air travel. Patients with a resting room air SpO₂ between 92 and 95 percent at sea level need further assessment to determine the need for oxygen in-flight. The evaluation of patients for potential in-flight hypoxemia and the prescription of supplemental oxygen for air travel are discussed separately. (See "Evaluation of patients for supplemental oxygen during air travel".)

Transtracheal oxygen — Transtracheal oxygen therapy (TTO) refers to transcutaneous placement of a specialized catheter to deliver oxygen directly into the trachea. Compared to LTOT delivered by nasal cannula, TTO offered several potential benefits, including reduced dyspnea, improved mobility, improved comfort, increased exercise capacity, and fewer days of hospitalization [55-62]. Although TTO was a more invasive alternative, patients who chose this approach had excellent compliance with oxygen therapy [55]. The catheters and procedure kits have not been manufactured since 2021, so this therapy is no longer available.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Supplemental oxygen".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Beyond the Basics topic (see "Patient education: Supplemental oxygen on commercial airlines (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Indications – There are several indications for continuous long-term oxygen therapy (LTOT) for patients with chronic lung disease (table 1). (See 'Indications' above.)

There is strong evidence of benefit in the following patient groups:

•Resting arterial oxygen tension (PaO₂) ≤55 mmHg (7.32 kPa), or a pulse oxygen saturation (SpO₂) ≤88 percent

•PaO₂ ≤59 mmHg (7.85 kPa), or an SpO₂ ≤89 percent, if there is evidence of cor pulmonale, right heart failure, or erythrocytosis (hematocrit >55 percent)

Patients with PaO₂ ≤55 mmHg (7.32 kPa), or an SpO₂ ≤88 percent during exercise or sleep may benefit from administration of supplemental oxygen during those activities, but the evidence for benefit is less clear.

●Determining appropriate flow rate – When determining the flow rate of supplemental oxygen for LTOT, a goal PaO₂ of 60 to 65 mmHg (7.98 to 8.65 kPa) or an SpO₂ of 90 to 92 percent is generally considered to be acceptable. There is no advantage to SpO₂ >92 percent at rest and there may be disadvantages in giving a higher FiO₂. In particular, avoidance of SpO₂ >96 percent at rest is recommended. Higher flows may be advantageous as part of exercise training, although further study is needed. (See 'Oxygen flow rate' above and 'Exercise training' above.)

●Equipment selection

•Every attempt is made to provide portable or wearable oxygen systems for patients striving for an active lifestyle. Ambulatory oxygen and portable oxygen concentrators weigh less than 10 pounds (4.5 kg) and are preferred for more active patients. (See 'Equipment selection' above.)

•Use of oxygen conserving devices, such as reservoir cannulas, oxygen pulsing devices, or transtracheal oxygen delivery may enable improved efficiency, a lighter weight system, and a longer oxygen supply when away from home. (See 'Equipment selection' above and "Portable oxygen delivery and oxygen conserving devices".)

●Typical adjustments to oxygen therapy – Adjustment of the oxygen prescription may be required for exertion and sleep, as well as during acute exacerbations of the disease.

•Activity – Patients on portable oxygen systems should be tested using the device provided while performing a typical level of exercise to assure adequate oxygenation. (See 'Oxygen flow rate' above.)

•Sleep – For patients with nocturnal oxygen desaturation, clinical evaluation for sleep-disordered breathing and polysomnography are often appropriate. (See 'Nocturnal desaturation' above.)

•Air travel – If the patient is ambulatory and desires to travel, special considerations for optimizing oxygen deliver should be considered, as well as oxygen/device availability and support. (See 'Air travel' above.)

●Safety and ongoing assessment – Patients should be encouraged to use their oxygen and reassured regarding its benefits and lack of addictive potential. Patients who continue to smoke or use e-cigarettes while using oxygen create a hazard to themselves, their families, and other occupants of buildings where they live. Oxygen should not be continued if it is unsafe or if the patient is unwilling to use it, and advanced ambulatory equipment should not be supplied if the patient is unwilling or unable to be physically active. (See 'Ongoing assessment' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Brian L Tiep, MD (deceased), who contributed to earlier versions of this topic review.