Patient eligibility. The study is open to children with neuro-muscular diseases of any type, who are enrolled in the NMD clinic at children's hospital. The main end points will be lung function measurements so children will need to be old enough to perform the testing process. For cognitively normal children this is usually 5 to 6 yrs of age. All of the three treatments are administered by a face mask so, apart from lack of consent and clinical instability, the only other exclusion criteria will be factors that limit the use of a face mask. Those children with a poor mask seal due to facial structural abnormalities, or those with tracheostomies will be ineligible for the study