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.