The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

Effect of Nebulization through Humid-HeatT on Bronchodilator Effect of Albuterol in Stable Asthmatics

David C. Willms MD, Melissa K. Brown BSRT, RRT-NPS, Jim Spinharney RCP, Marc Tappen RRT, Jodette Brewer RRT, Sharp Memorial Hospital, San Diego, California.

Background: The Humid-HeatT, is a heat-moisture exchanger (HME) modified to incorporate additional water and heat into the appliance. Typical practice precludes giving nebulized medications through an HME, out of concern that nebulized medication will be trapped, and not reach the patient.  Bench tests performed by the manufacturer, Gibeck, demonstrated that significant concentrations of nebulized material did cross over the Humid-HeatT HME in a laboratory study (Hans Lambert, unpublished study). The ability to administer nebulized medications on the inspiratory side of such a device would be a significant advantage, in that it would avoid the need to interrupt the circuit for each treatment (infection risk), or to place an adapter 'downstream" from the HME (increase circuit dead space). Demonstration of a biological effect from bronchodilators delivered through the Humid-HeatT HME would be useful. Due to the difficulty of demonstrating bronchodilator effects on mechanically ventilated patients, the current study involves stable spontaneously breathing outpatient asthmatics.

Methods:
Baseline spirometry was obtained before and after administration of Albuterol, using standard American Thoracic Society technique. If the subject demonstrated a significant bronchodilator response (defined as a 15% and >300 ml in FEV1) the subject was asked to participate in the Humid-HeatT portion of the study. Spirometry was repeated 1-2 days later, with the bronchodilator given by nebulizer (same dose and technique), in this case with a Humid-HeatT device interposed between the nebulizer output and the patient. The Humid-HeatT was turned on and the subject allowed to breathe through the device for 5 minutes before beginning nebulization of Albuterol. This is to permit the saturation of the Humid-HeatT wick. Values for pre and post spirometric functions were analyzed to determine if the bronchodilator response was similar through the Humid-HeatT device.

Results: Two female subjects were studied age 41 and 58 years. Subject #1 demonstrated a 26% increase in FEV1 post bronchodilator and a 44% increase in FEV1 post bronchodilator in conjunction with the Humid-HeatT device. Subject #2 demonstrated a 22% increase in FEV1 post bronchodilator and a 15% increase in FEV1 post bronchodilator in conjunction with the Humid-HeatT device.

Subject #1 FEV1 Pre FEV1 Post % Change in FEV1 ml Change in FEV1
Baseline 2.32 2.93 26% 610 ml
HumidHeatT 2.14 3.06 44% 920 ml

Subject #2 FEV1 Pre FEV1 Post % Change in FEV1 ml Change in FEV1
Baseline 2.36 2.88 22% 520 ml
HumidHeatT 2.46 2.82 15% 360 ml

Conclusions: This pilot study demonstrates a positive bronchodilator response in two patients with traditional medication delivery, as well as through the Humid-HeatT device. Further research is needed to ascertain the output of particles in the respirable range as well as the clinical effectiveness of delivering nebulized medications through the Humid-HeatT device.

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