Inclusion Criteria:  Patients with neuromuscular disease(NMD) Age ≥18  Exclusion Criteria:  Unable to comply with protocol Unable to give informed consent Evidence of obstructive airways disease FEV1:FVC <0.7 Patients with a history of: Un-drained pneumothorax Severe bronchospasm Head injury with ICP > 25mmHg Severe arterial hypotension Trache-oesophageal fistula Significant haemoptysis Facial fractures Vomiting Flail segment Epistaxis within two weeks