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: Closed suction catheters are commonly used with pressurized metered-dose inhalers (pMDIs) in ventilator-dependent patients receiving bronchodilator therapy. Although heated/humidified circuits result in a decrease in drug delivery, no studies have investigated the impact of a closed suction catheter with a pMDI on aerosol delivery during mechanical ventilation. We sought to quantify aerosol delivery with a variety of closed suction catheters and pMDI adapters in a simulated ventilator-dependent adult lung model with and without exhaled humidity.

METHODS: A ventilator (tidal volume 450 mL, PEEP 5 cm H₂O, breathing frequency 15 breaths/min, peak flow 60 L/min, and bias flow 2 L/min) was attached to 3 closed suction catheter designs (T-piece, double swivel elbow, and a multi-access port) with pMDI adapters (small- and large-unidirectional adapters, a bidirectional adapter, and a built-in port) connected to an endotracheal tube (ETT) with a collecting filter and a passive test lung. To simulate exhaled humidity, a heated humidifier was placed between the collection filter and the distal tip of the ETT, set at 36°C. Experiments without exhaled humidity were performed with no heat and humidification. For each test, 4 puffs of albuterol sulfate (432 μg) were administered. The drug was eluted from the collecting filter and analyzed via spectrophotometer (276 nm). Each experiment was run 3 times.

RESULTS: Delivery efficiency of the bidirectional adapter was greatest compared to other adapters tested in this study (P = .01). Aerosol deposition obtained from the combination of the T-piece closed suction catheter and the bidirectional adapter was more than that from the multi-access port (P = .42) and double swivel closed suction catheter (P = .27). Drug delivery without exhaled humidity exceeded values with exhaled humidity by 20–90% using the small unidirectional, large unidirectional, and bidirectional adapters (P = .01, P = .02 and P = .02, respectively).

CONCLUSIONS: Closed suction catheter, pMDI spacer/adapters, and exhalation conditions have an impact on drug delivery during simulated adult mechanical ventilation. Aerosol delivery without exhaled humidity appears to report unrealistically high values in comparison to the more accurate values with simulated exhalation humidity.