Exercise-induced oxygen desaturation is common in people with chronic obstructive pulmonary disease (COPD).1–3 One Australian study reported that 47% of patients with COPD referred to pulmonary rehabilitation had a fall in oxygen saturation (SpO2) of more than 4% to a SpO2 of less than 90% during a six-minute walk test.1 Availability of supplemental oxygen is recommended for provision of a pulmonary rehabilitation program4,5 as it may be required during exercise testing or training in people with COPD who demonstrate oxygen desaturation or in case of an emergency. The rationale for use of oxygen is based on laboratory studies that have shown that oxygen administration during a single bout of exercise reduces minute ventilation at equivalent work rates and delays the onset of dynamic hyperinflation and the associated dyspnea in people with COPD who had severe disease.6,7

While there have been a number of national pulmonary rehabilitation surveys conducted in Australia,8 New Zealand,9 United States of America,10 United Kingdom11 and Canada,12 these surveys have focused on reporting current practice in terms of setting, access, structure, and the outcome measures from pulmonary rehabilitation programs. Information on how and why supplemental oxygen is utilized during programs for both exercise testing and exercise training is lacking. The National Canadian Survey reported that most pulmonary rehabilitation programs (90%) had supplemental oxygen available but no information was provided on whether SpO2 was monitored during exercise testing or how or why supplemental oxygen was prescribed during exercise training.12 The national pulmonary rehabilitation audit in the United Kingdom11 did not report supplemental oxygen availability but did report that 9% of pulmonary rehabilitation attendees used supplemental oxygen during exercise training.11 The report did not specify if these attendees were people on long-term oxygen therapy or were people who experienced exercise-induced oxygen desaturation and were provided with supplemental oxygen during exercise training.

The aims of this study were to determine, in Australian pulmonary rehabilitation programs for people with COPD: (1) whether oxygen saturation (SpO2) was monitored during exercise testing; (2) whether supplemental oxygen was available during exercise testing and/or training; (3) whether oxygen was prescribed during exercise training; and the reason for providing oxygen; (4) whether a protocol was available for supplemental oxygen prescription during exercise training.

Data were collected between November 2015 and April 2016. Of 261 email invitations sent, 148 surveys (57%) were returned. Six surveys were discarded due to incomplete information and 142 surveys were included in the analysis.

This is the first study to investigate the use of supplemental oxygen during exercise testing and training in Australian pulmonary rehabilitation programs. The main findings of the study indicate that SpO2 was commonly measured before, during, and after exercise testing and that supplemental oxygen was readily available in most pulmonary rehabilitation programs during exercise testing and training. The rationale for supplemental oxygen prescription during exercise training was wide-ranging with the most common reasons being to maintain SpO2 over a certain threshold, to ensure safety, and to reduce symptoms of dyspnea and fatigue during training. Only 32% of programs had a protocol in place for supplemental oxygen prescription during exercise training.

Oxygen saturation was commonly monitored during exercise testing, confirming that the majority of programs would be able to identify people who had exercise-induced oxygen desaturation during exercise testing. Monitoring oxygen saturation every minute during field walking tests is recommended.4 Based on the survey results, the majority (85%) of Australian pulmonary rehabilitation programs are meeting this recommendation.

Sixty-two percent of respondents indicated that a rest would be imposed if SpO2 fell below a certain threshold, however the threshold varied greatly between programs and the rationale for choosing such differing thresholds remains unknown. In addition, there were higher odds of inexperienced clinicians imposing a rest during the 6MWT when SpO2 ≥85%. Although no studies have examined appropriate SpO2 levels for test termination during field walking tests, a recent study indicated that desaturation to less than 80% during a 6MWT was not associated with adverse event in a large cohort of patients referred to pulmonary rehabilitation (n=549) including 384 participants with COPD.14 Such findings are consistent with other study that also found no adverse events associated with substantial exertional hypoxemia (SpO2 <85%) during a 6MWT in people with chronic lung diseases.15 This suggests that a clinician-imposed rest during a 6MWT may not be required when patients with COPD desaturate during the test. However, a clearer recommendation for test termination based on oxygen desaturation during exercise testing in people with COPD is necessary in any future guideline for field testing, especially for clinicians with less experience.

Although supplemental oxygen was readily available in most programs, 14% of programs did not have supplemental oxygen available during either exercise testing or training. This is higher than the 10% reported from the Canadian data12 and could be due to a higher percentage of programs being held in community centers in Australia compared to Canada (37% vs 8%). While the technical standards for field walking tests for people with chronic respiratory disease4 recommends that supplemental oxygen should be available in case of an emergency during a walk test, very few adverse events have been reported during a 6MWT in people with chronic lung disease,1,14 making the need for supplemental oxygen equivocal.

The rationale given by respondents for their prescription of supplemental oxygen during exercise training for people with COPD was wide-ranging. The differences in responses may relate to the different levels of workforce training for those providing pulmonary rehabilitation, which may have resulted in different degrees of understanding of the role supplemental oxygen may have during exercise training. Another reason for this variation may relate to conflicting recommendations for oxygen prescription making it difficult for those conducting pulmonary rehabilitation programs to formulate an oxygen protocol. A previous randomized controlled trial of cycle-based training in people with COPD without exercise-induced oxygen desaturation showed that supplemental oxygen allowed participants to achieve higher training intensities and obtain greater improvements in exercise capacity following training.16 In contrast, a few randomized controlled trials have demonstrated no difference in exercise capacity and symptoms when comparing the effect of supplemental oxygen versus air following training in people with COPD who experience exercise-induced oxygen desaturation.17–19 The quality of these trials was moderate due to lack of blinding and small sample size.17–19 A recent large, double blinded, multi-centered randomized controlled trial has confirmed that there was no added benefit from training with supplemental oxygen compared with medical air on exercise capacity and health-related quality of life for people with COPD who experience exercise-induced oxygen desaturation.20 Such findings demonstrate that exercise training for people with COPD who experience exercise-induced desaturation can be provided safely and with benefits in exercise capacity and health-related quality of life in venues where supplemental oxygen is not available.

A limitation of this study was that the response rate was only 57% despite three reminder emails being sent to the program representatives. The relatively low response rate could be due to the way the participants were recruited. All pulmonary rehabilitation programs were emailed by the Lung Foundation Australia based on their confidential list of programs, and surveys were submitted anonymously. Therefore, it was not possible to identify programs which had not responded to send follow-up emails directly. Despite this, the sample of programs that were included in this study represented programs of different sizes and settings across Australia, thereby providing a reasonable overview of current clinical practice with respect to supplemental oxygen use in pulmonary rehabilitation programs in this country.

In conclusion, SpO2 is commonly monitored during exercise testing and supplemental oxygen is available in most Australian pulmonary rehabilitation programs. However, protocols for the prescription of supplemental oxygen during exercise training have not been widely developed. As more robust evidence is emerging about the lack of value of supplemental oxygen during an exercise training program for people with COPD who experience exercise-induced oxygen desaturation but are not on long-term oxygen therapy, evidence-based protocols will be important.

This work was supported by National Health and Medical Research Council, Australia [grant number: APP1019989].

The authors declare no conflicts of interest.