Used correctly, the Ultrabreathe can be used by almost anyone and has no harmful side effects.
Very occasionally however, there may be instances in which the creation of a large negative pressure in the chest may exacerbate an existing condition. If this happens advice should be sought from your doctor. If you are on any form of medication, suffer from a medical condition, (Asthma for example), or are uncertain as to whether the Ultrabreathe is appropriate for you, then you should consult your doctor prior to commencing breathing training. Above all, unless advised by your doctor, you should NOT stop taking any medication - the Ultrabreathe is intended to complement existing treatments, not to replace them.