It was well known that long term intubation caused a various kind of abnormal presentations of dysphagia such as the increased aspiration risk, the decreased gag reflex, mucosal pathology, the airway stenosis and so on. It was thought that the freezing and impaired proprioception to be developed as a result of dis-use around the pharynx and the larynx while intubation was one of the reason.

Preemptive swallowing manual stimulation applied on the oral cavity to avoid the vicious cycle of dis-use was reported to improve dysphagia after extubation.

Neuromuscular electrical stimulation have been utilized for a wide variety of dysphagia of multiple causes of neuro-muscular disorder.

Supposing that preemptive transcutaneous neuromuscular electrical stimulation to be delivered to the muscles of being involved in swallowing could decrease the degree of dis-use during intubation so that it could reduce the occurence and severity of dysphagia developed after extubation, the investigators plan to perform randomized prospective double blind placebo controlled clinical interventional study.

Inclusion Criteria:

• patients to be admitted to the ICU due to the respiratory failure and intubated for at least 48 hours

Exclusion Criteria:

• Past history of intubation
• Past history or current status of traumatic brain injury
• Past history or current status of symptomatic stroke
• Past history or current status of injury of cranial nerves
• Past history or current status of neuromuscular disorder
• Patient not to be expected to be extubated
• Patient to reject the participation
• current usage of neuro-muscular blockers