The Science Journal of the American Association for Respiratory Care
BACKGROUND: Aerosolized albuterol (ALB) is commonly administered to mechanically ventilated neonates with chronic lung disease. Treatment with a metered dose inhaler (MDI) and spacer is more efficient and less costly than nebulization; however, prolonged use of large-volume spacers in neonates may result in CO2 retention due to mechanical dead space. To minimize this risk, some institutions limit the time that spacers remain in-line to < 30 seconds. However, this strategy may also limit ALB delivery. The objective of this bench study was to determine the relationship between the time that a spacer is left in place following each MDI actuation and the efficiency of ALB delivery in a neonatal ventilator-lung model.
Methods: The model consisted of a Bird VIP ventilator in a time cycled, pressure-limited, continuous flow mode with settings to simulate a 1-kg infant with moderate lung disease. The circuit was attached to a 3.0-mm endotracheal tube (ETT) and a neonatal test lung. Ventilator settings: Vt = 6.5-6.7 mL, flow 9 L/min, pressure 25/4 cm H2O, rate 30, FiO2 0.4, and gas conditioned to 34
Results: Mean (SD) ALB delivery (%) is presented below. Thirty manual breaths after each actuation increased ALB delivery by 44% and 118% as compared to 15 and 5 manual breaths, respectively. Inserting the spacer in-line and waiting 60 seconds after each actuation improved ALB delivery by 59% as compared to 5 manual breaths after each actuation.
|Method of Administration||% ALB Delivery (n=10)|
|5 manual breaths (10 sec) after each actuation||2.34 (0.5)|
|15 manual breaths (30 sec) after each actuation||3.55 (1.77)|
|30 manual breaths (60 sec) after each actuation||5.11 (1.27)*|
|In-line spacer placement - 30 sec after each actuation||3.69 (1.32)|
|In-line spacer placement - 60 sec after each actuation||3.73 (0.64)?|
|*p<0.05 as compared to 5 and 15 manual breaths; ? p<0.05 as compared to 5 manual breaths. (ANOVA with Tukey all-pairwise comparison).|
CONCLUSION: Manually ventilating for 30 breaths after each actuation resulted in a superior ALB delivery as compared to 15 breaths and 5 breaths. Similar results can be achieved by leaving the spacer in-line for 30-60 seconds after each actuation.