Changes in ventilation during use of heat and humidity exchangers

The Authors studied in 10 patients during mechanical ventilation the effects of the application of heat and moisture exchanger (HME) in the presence of constant TV and frequency. They observed an increase of PaCO2 and PE, CO2 during the use of HME; this is due to Vd/Vt increase. The Authors conclude that it is mandatory to increase the total ventilation when using HME to avoid dangerous levels of hypercapnia.