Introduction: In Neuro-Muscular Diseases (NMD) patients, weak muscles and poor cough lead to atelectasis and retained pulmonary secretions. Chest physiotherapy devices aim to reduce these progressive changes but lack evidence about efficacy. Aims: Prior to initiating a long term study, we conducted a pilot study to compare effects of 3 physiotherapy treatments on lung volume and cough flow in stable NMD patients: BiPAP assisted maximal inspiration (BAMI), mechanical insufflation-exsufflation (MI-E) and intrapulmonary percussive ventilation (IPV). Methods: We tested 40 subjects in 4, 3 day sessions. They underwent all 3 physiotherapy techniques, 1 a day. HR, SaO 2 , FVC, PEF, MIP and MEP were measured pre, immediately post treatment then 30 minutes later. All data was non-parametric so expressed as median (inter-quartile range (IQR)). Results: 38 patients; Duchenne muscular dystrophy largest group (n=17). M:F = 26:12. Age 15 years (11-21y); FVC 64% (46-82%). The effects of all 3 physiotherapy treatments on FVC and PEF are summarized in . While the median changes were small (only IPV9s effect on PEF was significant), the spread of results was unexpectedly wide. Conclusions: No physiotherapy modality showed consistent benefit but IPV may be worth studying long term in NMD children. Our study confirms the importance of gathering preliminary proof of concept data before conducting a long term study.