Does the exclusion criteria refer to oxygen at rest or exertion? What about nocturnal oxygen? There is also the concomitant medication criteria that specifies supplemental oxygen is permitted for use if at least 2 weeks prior to screening and can be continued throughout the study.
The only requirement is stability in use of oxygen. If a patient has been using oxygen intermittently at rest for more than 2 weeks then that’s fine, and if another patient has been using it on exertion for more than 2 weeks then that is also fine. What would not be permitted is for a patient to start using oxygen in the prior 2 weeks, or to switch from using it on exertion to use at rest in the prior 2 weeks. Similarly, switching from intermittent to continuous use would not be acceptable. A patient falling into these categories could come back after the 2 week stability period has passed.