Study objective: To compare aerosol delivery to the lungs in ventilated patients from two devices with holding chamber and two devices without holding chamber.
Design: A controlled clinical trial with randomization to one of four delivery devices.
Setting: An academic university-affiliated Canadian ICU.
Patients: Forty-eight patients undergoing mechanically assisted ventilation for a variety of clinical reasons and each judged to require inhaled bronchodilator therapy by the attending physician.
Interventions: Patients received 4 puffs of fenoterol labeled with technetium 99m pertechnetate delivered by metered-dose inhaler via 1 of the following: A, a 167-ml chamber device; B, a 700-ml chamber device; C, a nonchamber device (A, B, and C, all in the ventilator inspiratory line); and D, a nonchamber device on the end of the endotracheal tube.
Measurements and results: One-minute images of the thorax were made by a portable gamma camera at the bedside. Deposition of radioactivity in the lungs (uncorrected for tissue absorption and calculated as a percentage of the radioactivity delivered from 4 puffs) was 5.53 +/- 0.72 (mean +/- 1 SEM), 6.33 +/- 1.16, 1.67 +/- 0.43, and 3.89 +/- 0.52 percent for devices A, B, C, and D, respectively (p = 0.004). Subgroup analysis showed a statistically significant difference in delivery between devices A and C and between devices B and C only.
Conclusion: There were statistically significant differences between delivery from both chamber devices and the inline nonchamber device, but not between delivery from other devices. Further work will be necessary to determine the effect of device position in the ventilator circuit on aerosol delivery.