Affiliations: University of Toronto
Hamilton, Ontario, 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: email@example.com
To the Editor:
We read with interest the article by Dr. Guyatt
and coworkers in a recent issue of CHEST (November
2000)1regarding 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
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
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
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
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.
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
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.2We 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.
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