Individualized Dosing Schedule of Inhaled Bronchodilator for Endotracheally Intubated Chronic Obstructive Pulmonary Disease Patients

*Study Design

• This is an open-label, randomized controlled study comparing individualized versus fixed bronchodilator dosing schedule for patients with COPD with acute respiratory failure.

*Patients Enrollment

• We will collect 100 patients just admitted to the intensive care unit of Changhua Christian Hospital (Changhua, Taiwan) due to COPD with acute respiratory failure.All participants will be randomly assigned to either group according to a computer-generated allocation sequence in block size of 4 patients.

*Airway Resistance (Raw) Determination

• Enrolled patients will be ventilated by either AVEA (CareFusion, Yorba Linda, CA, USA),e500 (Newport Medical Instrument Inc. CA, USA) or Eivta 4 (Drager) ventilator. When evaluating Raw, the ventilator settings will be transiently switched to volume control mode with fixed tidal volume (500 ml) and constant flow (with a rate of 60 L/min). Plateau pressure is measured by manually controlled end-inspiratory pause12. Every effort will be exercised to avoid excessive airway secretion or patient agitation during measurement. Each measurement will be repeated three times with an interval of at lease 1 minute and calculate their average. Raw will be calculated by an equation of (peak inspiratory pressure - plateau pressure)/flow. After each measurement, the ventilator will soon be reverted to its usual settings. Raw will be routinely determined every 8 hours for 28 days if the ventilator is not discontinued.

*Technique of Metered Dose Inhaler (MDI) administration through endotracheal tube

• The technique basically follows the recommendation of Dhand and Guntur. Airway secretions should be sucked out before drug administration. Heat moisture exchanger, but not humidifier, is removed. After shaking and warming MDI to hand temperature, the canister is connected to an AeroChamber HC MV spacer (Trudell Medical International, London, Canada) placed in the inspiratory limb of ventilator circuit 15 cm away from the endotracheal tube. Actuation is synchronized with the initiation of inspiration. Each actuation is at least 15 second apart.