The Effect of Different Closed Suction Catheter Designs
The Effect of Different Closed Suction Catheter Designs and pMDI Adapters on Aerosol Delivery in Simulated Adult Mechanical Ventilation With and Without Exhaled Humidity
Background: In ventilator-dependent patients receiving bronchodilator therapy, closed suction catheters are often used in conjunction with pressurized metered-dose inhalers (pMDI). Although the heating/humidification circuit leads to a decrease in drug delivery, no studies have investigated the effect of closed suction catheters with pMDI on aerosol delivery during mechanical ventilation. We tried to quantify the delivery of aerosols using a variety of closed inspiratory catheters and pMDI adapters under the simulated ventilator-dependent adult lung model (with or without exhaled humidity).
Method: Connect the ventilator (tidal volume 450 mL, PEEP 5 cm H2O, respiratory rate 15 breaths/min, peak flow 60 L/min, bias current 2 L/min) to 3 closed inspiratory catheter designs (T type, Dual swivel elbow and a multi-channel port) with pMDI adapters (small and large unidirectional adapters, bidirectional adapters and built-in ports), connected to the endotracheal intubation (ETT) lungs through collection filters and passive testing. To simulate the exhaled humidity, a heated humidifier was placed between the collection filter and the distal end of the ETT, and the temperature was set to 36°C. The experiment without exhaled humidity was conducted without heating and humidification. For each test, 4 grams of salbutamol sulfate (432μg) were taken. The drug is eluted from the collection filter and analyzed by a spectrophotometer (276 nm). Each experiment was performed 3 times.
Results: Compared with other adapters tested in this study, the two-way adapter has the highest transmission efficiency (P = 0.01). The combination of the T-shaped closed suction duct and the two-way adapter produced more aerosol deposition than the multi-inlet (P = .42) and double-turn closed suction duct (P = .27). Using small one-way, large one-way and two-way adapters (respectively P = .01, P = .02 and P = .02), drug delivery without exhaled humidity will exceed the value of exhaled humidity by 20-90%.
Conclusion: Closed suction catheters, pMDI spacers/adapters, and exhalation conditions have an impact on drug delivery during simulated adult mechanical ventilation. Compared to more accurate values with simulated expiratory humidity, aerosol delivery without expiratory humidity reports unrealistically high values.