Investigators developed a test to assess the bronchodilator effects in mechanically ventilated chronic obstructive pulmonary disease patients by comparing the change of airway resistance. No matter whether patients respond to bronchodilator or not, they are randomized assigned to bronchodilator 3-4 times per day group and no bronchodilator group. Then investigators could objectively decide whether individual patients need or benefit from bronchodilator administration.

Bronchodilator is commonly used in mechanical ventilated chronic obstructive pulmonary disease patients. It is assumed that patient's response to bronchodilator is the same during acute exacerbation or when stable whether on mechanical ventilation or not. Decision to treat is often independent of response and the patient's response to the medicine is not precisely evaluated. Investigators developed a test to assess the bronchodilator effects in mechanically ventilated chronic obstructive pulmonary disease patients by comparing the change of airway resistance. No matter whether patients respond to bronchodilator or not, they are randomized assigned to bronchodilator 3-4 times per day group and no bronchodilator group. Then investigators could objectively decide whether individual patients need or benefit from bronchodilator administration.

Inclusion Criteria:

should meet all the criteria:

1. Acute exacerbated chronic obstructive pulmonary disease
2. Invasive mechanical ventilation with intubation outside ICU no more than 48 hours

Exclusion Criteria:

Meet any of the criteria:

1. Asthma
2. Tracheotomy
3. Prolonged Mechanical Ventilation (Have been mechanical ventilated for more than 21 days)
4. Unstable hemodynamic status
5. Severe pneumonia
6. Contraindication for bronchodilator
7. Contraindication for sedation
8. Refusal to participate in study
9. Re-intubation in 48 hours
10. Mental disorder, could not understand and accomplish pulmonary function test