Secretion Mobilization Capabilities of Two Airway Clearance Devices

Abstract

Background:

Secretion clearance is one of the most important tasks for respiratory therapists and patients. We tested two high frequency airway clearance devices to determine which device is more efficient at mobilizing secretions in a bench model. The null hypothesis is that there will be no difference in secretion mobilization between the IPV (Model IPV-1C, Percussionaire, Sandpoint, ID) and MetaNeb System (Hill-Rom, St. Paul, MN).

Methods:

An Ingmar Medical ASL 5000 lung simulator was set to mimic a chronic bronchitis patient with a compliance of 60 mL/cm H₂O and resistance of 18 cm H₂O/L/s. The simulator was then programmed to produce a tidal volume of 500 mL, respiratory rate 15, and I: E ratio of 1: 3. A section of Tygon tubing with a length of 33. 2 cm and internal diameter of 13 mm was used to simulate an airway. Using appropriate adaptors, the airway was then connected directly to the ASL 5000. The two devices were then connected to the distal end of the airway which was lubricated with a silicone lubricant. A mucous simulant was created by crosslinking 100 mL of a locust bean gum solution (0.38 mg/100mL) with 3 mL of sodium tetra borate (19 mg/L). Using a syringe, 2 mL of mucous simulant was injected into the end of the tubing closest to the ASL 5000. To determine mucus velocity, a ruler was placed next to the tubing and the leading edge of the mucous was noted. After each device was allowed to run for a period of two min, the leading edge of mucus was again noted and the velocity was calculated. The tubing was cleaned, dried, and lubricated after each run. This procedure was repeated three times at both the high and low frequencies on the MetaNeb as well as the highest and lowest frequency settings on the IPV.

Results:

The IPV set on the highest frequency produced a mean positive velocity of 3.98 cm/min. The IPV set on the lowest frequency produced a mean negative velocity of 1.02 cm/min. The Metaneb produced a velocity of zero on both the high and low frequency settings.

Conclusions:

The MetaNeb produced no net movement of secretions. The high frequency setting of the IPV produced secretion mobilization away from the ASL or cephalad. On the low frequency setting, the IPV moved secretions toward the ASL or caudad. When using the IPV for secretion clearance, the best results will be obtained when it is set on the on the highest frequency.