Long-Term Oxygen Therapy in COPD: Factors Affecting and Ways of Improving Patient Compliance

Abstract

Long-term oxygen therapy (LTOT) is the cornerstone mode of treatment in patients with severe chronic obstructive pulmonary disease (COPD) associated with resting hypoxaemia. When appropriately prescribed and correctly used, LTOT has clearly been shown to improve survival in hypoxemic COPD patients. Adherence to LTOT ranges from 45% to 70% and utilization for more than 15 hours per day is widely accepted as efficacious. Although several studies have addressed the level of patients' adherence to LTOT, few have suggested or evaluated interventions that conduce to compliance enhancement. The lack of sufficient data regarding COPD patients following oxygen prescription is an enormous void that must be duly confronted to augment clinical effectiveness and cost containment for the long term use. The present review article highlights factors influencing the compliance of patients using LTOT and emphasizes novel strategies and interventions that may prove to be of significant benefit given the remarkably little current research appraising this issue. Therefore, additional research should be promptly performed to verify the efficacy of newly designed approaches in improving the outcomes of patients receiving LTOT.

1. Introduction

It is well established that long-term oxygen therapy (LTOT) is the only therapeutic modality proven to alter the late course of chronic obstructive pulmonary disease (COPD). Particularly, two landmark studies, the Nocturnal Oxygen Therapy Trial (NOTT) and the British Medical Research Council (MRC) conducted in the late 1970s have explicitly demonstrated that LTOT (when used for more than 15 hours/day) improves survival rates in patients with severe COPD associated with resting hypoxemia. In terms of maximum benefit, continuous oxygen administration (≥15 h/d) is superior to intermittent or nocturnal use. There is also accumulating evidence that LTOT has favourable effects on other outcome measures, including depression, cognitive function, quality of life, exercise capability, and frequency of hospitalization. Moreover, it stabilizes and sometimes reverses the progression of pulmonary arterial hypertension and it diminishes as well cardiac arrhythmias and electrocardiographic findings indicative of myocardial ischemia.

The effectiveness of LTOT in improving survival has been substantiated only in stable COPD patients with severe chronic hypoxemia (PaO2 less than 55 mmHg (7.3 kPa) or PaO2 ranging from 56 to 59 mmHg (7.4–7.8 kPa) in presence of signs of cor pulmonale, hematocrit > 55%) . The resultant clinical benefits of LTOT are contingent on the treatment compliance, the treatment duration, and the adequate correction of hypoxemia.

Despite the generally recommended daily duration of oxygen use (>15 h/day) to achieve its goals, the adherence to LTOT seems to be poor according to the existing literature. Furthermore, this therapy incurs great expenses to the healthcare systems worldwide because of several hundred of thousands of COPD patients receiving supplemental oxygen and the high expenditures pertinent to durable delivery oxygen equipment. In particular, it is estimated that 1 million patients receive LTOT in the USA with total Medicare reimbursements for costs related to O2 exceeding $ 2 billion/year. It is likely that a great deal of money is dissipated since several studies report inadequate adherence rates to this treatment.

2. LTOT for severely hypoxaemic COPD patients

The actual current guidelines are in strong agreement in recommending LTOT for severely hypoxaemic COPD patients (PaO2 < 55 mmHg, < 7.3 kPa), whereas some differences have been observed in patients with moderate hypoxaemia (55 < PaO2 < 60 mmHg, 7.4 < PaO2 > 8 kPa) regarding the criteria which should be associated with PaO2 values.

Much of the initial research for LTOT addressed the precision of the prescription. In particular, the prescription of oxygen administration for at least 15 h/day is considered to be adequate and it represents one variable that is associated with effective usage. Howard et al. reported that physicians “varied widely in their prescribing habits”. 36% out of LTOT patients were prescribed less than 15 hours per day thus reducing optimal dosage. Walshaw and coworkers concluded that an effective prescription and compliance was associated with a respiratory physician more often than a family doctor. Granados et al. mentioned that 58% of the selected sample met the criteria for oxygen therapy, of these 80.5% (29/36) were correctly prescribed with corrected hypoxemia. Another study found that 55% of patients had not received thorough written instructions regarding the use of LTOT by their physician and 63% were not aware of LTOT importance in the therapeutic management of their disease. The lack of explicit prescription instructions and prescription review does limit patient adherence.

3. LTOT Adherence

The minimum recommended duration of LTOT is 15 h/day thus representing an adequate oxygen adherence, as it has been established and defined by international guidelines on domiciliary LTOT. Several studies have evaluated compliance to LTOT showing rates ranging from 45 to 70%. These clinical trials have determined the extent of patients’ oxygen use as well as identified problems. Annotations from these studies indicate potential research direction such as patient and oxygen provider education and/or postprescription support. Suboptimal adherence has been reported as an independent modifiable risk factor of frequent COPD exacerbations necessitating hospital admissions thus increasing health care costs.

4.Risk Factors for LTOT Noncompliance

Disease severity can adversely affect LTOT adherence. COPD in its late stages is a debilitating disease leading to notably poor quality of life. Some reported that poor functional status for patients is related to depression and feelings of minor support which may translate to inadequate compliance. Symptom management, mainly dyspnea might affect adherence, according to study findings. Several participants could tell little difference in how they felt whether they were using oxygen or not. This group of patients, who felt little but immediate benefit in symptom alleviation, struggled more with the role of oxygen in their lives.

Additionally, poor adherence to LTOT prescriptions may result from associated mental confusion or misunderstanding of the correct prescription. COPD patients with low educational level may be noncompliant with LTOT. Illiteracy to incomprehensible written medical instructions containing scientific terms may lead to inadequate oxygen usage. Accordingly, prescribing physicians should simplify their instructions on LTOT in illiterate patients. Moreover, old age, portable oxygen systems to mobile patients, high PaO2 values on room air, and smoking habits comprise potential factors with negative influence on LTOT compliance. COPD hypoxaemic patients, who are active smokers, prefer keeping on smoking to using advisable oxygen therapy resulting in detrimental health consequences.

5. Conclusion

It is well substantiated that suboptimal adherence with long-term oxygen therapy is common and causes significant morbidity as well as great expenses to healthcare systems universally. When prescribing medication, it may be important to consider the complexity of the regimen in addition to the efficacy of the intervention. Oxygen is a controller medication, according to the international pharmacopoeia grade, and should be dispensed only upon the written order of a licensed physician. Inappropriate use of oxygen and oxygen-delivery equipment has the potential to result in real harm or injury to the public and cause economic implications. Clinicians involved in LTOT need to be aware and work with the patients to facilitate their use of oxygen. Improving adherence to oxygen therapy and minimizing the negative impacts of the therapy require understanding the subjective experience of the therapy. Exploring patients' concerns and prejudices about oxygen therapy can assist with the development of new interventions and management strategies. Moreover, worthwhile goals for future research include the development of better strategies for patient education and more tolerable methods for oxygen delivery (e.g., oxygen-conserving systems, nondelivery long-term oxygen systems), together with testing of these approaches to verify their effectiveness in improving the outcomes of patients receiving LTOT.