There are many kinds of medication for asthma, some of which break the fast and some do not. The most well known of these medicines and treatments are puffers , oxygen, vaporizers and capsules.
The puffer uses a compressed gas that is used by the patient, which reaches the lungs via the trachea to expand the lungs. It is not food or drink or anything resembling them. The scholars of the Standing Committee have ruled that the fast is not broken by using this kind of medicine. This is also the ruling of Shaykh Ibn ‘Uthaymeen and most of our scholars.
With regard to oxygen, it too is neither food nor drink. Based on this, it may be used when fasting with no problems.