Study aim: This study want to determine the effect of intravenous magnesium sulfate in controlling the acute attack caused by chronic obstructive pulmonary disease (COPD) in patients referred to the emergency department of Imam Khomeini Hospital during a six-hour period. Design: Randomized, double blind, controlled with placebo, single-centered, phase 3 of trial Settings and conduct: Patients with chronic pulmonary obstruction with acute attack are examined at the time of admission, 45 minutes and 6 hours after intervention of primary outcomes and secondary outcomes, including respiratory rate and blood pressure in the emergency department of Imam Khomeini Hospital in Sari. Moreover, the standard treatment of the acute attack starts with intervention. Patients will not be informed about which group they are. Moreover, the pharmacist of the study will code the drugs (codes A, B) without the author's knowledge. Participants/Inclusion and exclusion criteria: Inclusion criteria: Patients who refer to the emergency department for chronic obstructive pulmonary disease caused by smoking Non inclusion criteria: Patients who have the need for intubation; Patients who have a history of heart disease;patients who have a low level of consciousness; patients who received intravenous magnesium sulfate within the last 24 hours Intervention groups: Interventional group:Magnesium sulfate 2% made by Obeidi pharmaceutical company is mixed with 200 ml normal saline and is administered using the peripheral vein through slow intravenous infusion within 20 minutes. Control group:Normal saline 0.9% (Obeidi factory) is given 100 cc once, under slow using the peripheral vein through slow intravenous infusion. Main outcome variables: Number of breaths