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University of Toronto Toronto, Canada
Correspondence to: Charles K. N. Chan, MD, FCCP, Respirology—10EN 220, University Health Network/Mt. Sinai, 200 Elizabeth St, Toronto, ON, M5G 2C4 Canada; e-mail: charles.chan{at}uhn.on.ca
To the Editor:
We read with interest the article by Dr. Guyatt and coworkers in a recent issue of CHEST (November 2000)1 regarding the appropriateness of domiciliary oxygen delivery. Their study found that 32.1% of patients receiving long-term oxygen therapy (LTOT), all of whom would have had to meet the arterial blood gas criteria outlined in the continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease (NOTT) trial2 to qualify for funding, did not continue to meet the same criteria when evaluated in their study. Based on these findings, they suggested that these patients should be denied further funding for LTOT to achieve economic savings for the health-care system. We have concerns with respect to their conclusions and recommendations.
First, in the NOTT and the long-term domiciliary oxygen therapy in chronic hypoxic cor pulmonale complicating chronic bronchitis and emphysema trials,3 hypoxic patients were randomized to their respective study arms, in which they remained for the duration of the trials. Although PaO2 levels were monitored throughout both trials, they were not used to deny or offer patients oxygen therapy. Since these trials provide the strongest evidence of a mortality benefit for patients with hypoxic lung disease who are receiving LTOT, further studies would be needed to determine whether this benefit is maintained if LTOT is stopped in response to an improved PaO2.
Second, Guyatt et al dismissed a physiologic argument that we think may have some validity. They dismissed the possibility that oxygen therapy may result in cardiopulmonary vascular changes that improve ventilation/perfusion matching and result in subsequent improvement in blood gas levels while the patient is at rest. While evidence supporting this specific phenomenon is limited,4 there is convincing evidence demonstrating that cardiovascular parameters in general are substantially improved with oxygen therapy.2 3 5 This suggests that more study in this area may reveal that LTOT does lead to an improvement of PaO2 while the patient is breathing room air.
Third, in order to determine whether real economic savings will be achieved by discontinuing funding for patients with advanced lung disease who no longer qualify for LTOT, one needs a proper study to assess the health consequences of this action. For example, such patients who have stopped receiving LTOT may have more exacerbations requiring additional medical assessments, therapeutic interventions, and hospitalizations. In the absence of an overall health economic study, the cost savings suggested are purely related to the cost of the LTOT alone.
Last, Guyatt et al suggested that the discontinuation of LTOT when patients no longer meet qualifying criteria may improve quality of life. We wonder whether patients’ sentiments contributed to this hypothesis. Did they ask the subjects who participated in their study whether they would be willing to stop using LTOT if they were found to have an improved PaO2 level? Did they ask them whether they felt that stopping LTOT would improve their quality of life? Based on our experience with similar patients, we think that the majority would be deeply concerned about discontinuing LTOT. Specifically, we think they would be worried about experiencing a reduction in their exercise tolerance and being unable to maintain an optimal level of activity.
As recommended by all the published guidelines, we agree that patients being evaluated for LTOT should be required to meet qualifying criteria when they are medically stable. However, we feel it would be wrong to use this recent study to justify the disqualification of recipients who have experienced improvements in their PaO2 levels from receiving LTOT in order to achieve economic savings.
References
McMaster University Hamilton, Ontario, Canada
Correspondence to: Gordon H. Guyatt, MD, McMaster University, Health Science Center, Room 2C12, 1200 Main St West, Hamilton, Ontario, Canada L8N 3Z5
To the Editor:
Drs. Gershon and Chan make a number of thoughtful and interesting points about our article (November 2000).1
With respect to the Nocturnal Oxygen Therapy Trial design, they are correct that oxygen was not discontinued if patients no longer met the blood gas criteria. The Nocturnal Oxygen Therapy Trial investigators were, however, careful to ensure that patients were stable at baseline. The explanation for the very high incidence of patients not meeting the criteria in our study is likely to be that initial measurements were made while patients were in the process of recovering from an exacerbation.
It is theoretically possible that oxygen could lead to improved ventilation/perfusion relationships. The evidence supporting this phenomenon is very weak. We remain skeptical.
We agree that it is possible that patients who no longer meet the criteria for home oxygen therapy, and in whom oxygen is discontinued, will use other health services more frequently than if their oxygen therapy were continued. As Gershon and Chan imply, the study required to determine whether this occurs would be a randomized trial in which the use of all important health-care resources would be monitored. Indeed, we made this statement in our article: "Definitively resolving this issue would require a randomized trial of alternative organizational systems of oxygen delivery that would include health services utilization among the outcomes." Such a trial would be a very important contribution to the understanding of the optimal use of home oxygen therapy.
Gerson and Chan suggest that many patients would be reluctant to discontinue home oxygen therapy because of fears of reduced exercise tolerance. We agree. However, the evidence that patients who do not meet criteria for life-prolonging oxygen therapy increase exercise tolerance in their daily lives with the use of home oxygen is extremely weak. Indeed, the best study on the subject suggests that they do not.2 We suspect that oxygen is a very powerful placebo, and patients’ reluctance to discontinue home oxygen therapy, despite its burden of inconvenience, is a testimony to this effect. Demonstrating to patients that oxygen does not improve their exercise tolerance may require an N-of-1 randomized trial.3
Finally, we agree that the mechanism of dealing with the problem that we identified, which we believe is due to patients being tested for home oxygen therapy while unstable, is not to cease funding for oxygen in those who were in stable conditions when initially tested. Rather, we advocate more rigorously ensuring stability before committing a patient to long-term domiciliary oxygen.
References
This article has been cited by other articles:
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  J. C. Chaney, K. Jones, K. Grathwohl, and K. N. Olivier Implementation of an Oxygen Therapy Clinic to Manage Users of Long-term Oxygen Therapy Chest, November 1, 2002; 122(5): 1661 - 1667. [Abstract] [Full Text] [PDF]
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