<prompt> All of the following are causes of hypercarbic resiratory failure EXCEPTMyasthenia gravisAmyotrophic lateral sclerosisChronic obstructive pulmonary diseasePneumonia  <response>: Type ll respiratory failure is characterised by hypoxia and hypercapnia.Mechanisms by which this occurs are categorized by impaired CNS drive to breath;impaired strength with failure of neuromuscular function in the respiratory system increased load on the respiratory system.Reasons for diminished CNS drive to breathe include drug overdose,brain stem injury,sleep- disordered breathing,and hypothyroidism.Reduced strength can be due to impaired neuromuscular transmissioneg.,myasthenia gravis,Guillen-Barre syndrome,amyotrophic lateral sclerosis,phrenic nerve injury or respiratory muscle weaknesseg.,myopathy,electrolyte derangements,fatigue.The overload on respiratory system can be due to increased resistive loadsbronchospasm in asthma,COPD,reduced lung compliancealveolar edema,atelectasis,reduced chest wall compliance pneumothorax,pleural effusion due to increased minute ventilation requirementseg.,pulmonary embolus with increased dead space fraction,sepsis Ref:Harrisons medicine-18th edition,page no:2200. 