Inhaled gases humidification and heating during artificial ventilation with low flow and minimal fresh gases flow

Inhaled gas humidification and heating are necessary in patients under tracheal intubation or tracheostomy to prevent damage to respiratory system resulting from the contact of cold and dry gas with the airways. This study aimed at evaluating the effect of respiratory circle systems with carbon dioxide absorbers from Dräger's Cicero anesthesia machine (Germany) as to inhaled gases heating and humidification ability using low fresh gases flow (1 L min(-1)) or minimum flow (0.5 L min(-1)).

Participated in this study, 24 patients, physical status ASA I, aged 18-65 years, submitted to general anesthesia using Dräger's Cicero workstation (Germany) for abdominal surgery, who were randomly distributed in two groups: low flow group (LF) received 0.5 L min(-1) oxygen and 0.5 L min(-1) nitrous oxide, and minimum flow group (MF) received 0.5 L min(-1) oxygen only. Evaluated attributes were temperature, relative and absolute humidity of the operating room and of respiratory circuit gas.

There were no significant differences in inhaled gas temperature, relative and absolute humidity between groups, but they have increased along time in both groups, with influence of operating room temperature on inhaled gas temperature for both groups. Near optimal levels of humidity and temperature were reached as from 90 minutes in both groups.

There have been no significant differences in inhaled gas humidity and temperature with fresh gases low flow or minimum flow.