All of the following are causes of hypercarbic resiratory failure EXCEPT

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 transmission(eg.,myasthenia gravis,Guillen-Barre syndrome,amyotrophic lateral sclerosis,phrenic nerve injury) or respiratory muscle weakness(eg.,myopathy,electrolyte derangements,fatigue).The overload on respiratory system can be due to increased resistive loads(bronchospasm in asthma,COPD),reduced lung compliance(alveolar edema,atelectasis),reduced chest wall compliance (pneumothorax,pleural effusion) & due to increased minute ventilation requirements(eg.,pulmonary embolus with increased dead space fraction,sepsis) Ref:Harrison's medicine-18th edition,page no:2200.