The Science Journal of the American Association for Respiratory Care
Background: Heated humidity during mechanical ventilation (CMV) reduces aerosol delivery from a metered dose inhaler (MDI). We previously reported less aerosol loss from impaction in the endotracheal tube (ETT) than the ventilator circuit, under both ambient (dry) and humidified conditions (Am J Respir Crit Care Med 1999; 159:63-68). The the right angle elbow adapter may be a factor reducing aerosol delivery.
Methods: To determine the effect of an elbow adapter on aerosol delivery, four puffs of albuterol (360
Results: With the elbow adapter more aerosol was deposited to the bronchi under dry conditions (25.31.1%) than with humidity (19.21.1%; p<0.01). Removing the elbow adapter, albuterol delivery to the bronchi was similar under dry (26.1 0.9%) and humid (26.30.1%) conditions.
Discussion: Our findings suggest that the elbow adapter reduces aerosol delivery during humid but not dry conditions. Without the elbow adapter there was no difference in aerosol delivery between dry and humidified conditions. Previous reports of reduced delivery of aerosol during CMV with humidity utilized elbow adapters between the ventilator circuit and endotracheal tube. Redesign of the ventilator circuit/ETT interface may result in more efficient aerosol delivery during CMV. Further research is warranted to determine if our findings pertain to other ventilator circuit and MDI spacer configurations.
Conclusion: The elbow adapter did reduce aerosol delivery during CMV under humidified conditions.