Study of rainout effect on the heating of water-based humidifiers and related alarms

Abstract

The of this thesis project is to establish the consequences of the rainout effect on the performance of a MR850 humidifier using a mesh nebulizer and during non-invasive mechanical ventilation. A basic breathing circuit used for ICU patients consists of a ventilator, a heated humidifier and a nebulizer. While heated humidifiers (HH) used with nebulizers are important to prevent problerms in mechanical ventilators, thet can result in the ventilator circuit condensing as well, resulting in occlusion alarms.

Temperature, pressure and related alarms were studied with a non-invasive positive pressure ventilator the NIPPV 3+ at different pressure rated. The humidification system was a basic model of heated humidifier the MR850 (Fisher & Paykel, Auckland, NZ), which was a single heated circuit. The nebulization system was a piezoelectric nebulizer, the Aeroneb Pro (Aerogen, IE) which was tested in three nebulizer circuit positions. The circuit was completed with a standard test lung 6006832, Adult 190 (1 Liter) (Maquet, DE). The nebulizer was tested at three positions including at the dry side of the humidifiers, between the Y-piece and the circuit and finally the ventilator outlet. In general, the ressure rate did not dramaticallu affect the number of alamrs during trials. Deepending, on the placement of the nebulizer device, the prespective temperaute is affected and therefore the alarms. \placing the nebulizer far from the temperautre probe of the humidifier, developed significantly fewer alarms that placing it near them. Our results showed that the best position for the placement of the nebulizer is at the ventilator's outlet although the manudacturers do not recommend it. It should be noted, however, that these experiments were conducted in the laboratory and not in a cinical environment, where our findings remain to be confirmed.