Pain During Chest Tube Withdrawal: Evaluation Using Pan Monitor

Inclusion Criteria: * patients undergoing removal of a chest tube after lung surgery, * patients able to indicate the pain score. Exclusion Criteria: * pregnancy, lactation , * insulin-dependent diabetes with dysautonomia, * central or peripheral neurological disease, agitation, * inability to understand the protocol, * inability to use the Pain Monitor: skin abnormalities at the site of measurement, pacemaker or implantable defibrillator, condition affecting the sympathetic nervous system, tremor of the extremities, * contra-indication to oral morphine , * respiratory failure, severe hepatic insufficiency, intracranial hypertension, epilepsy associations * recent administration of neostigmine or of atropine.