BACKGROUND: In patients receiving invasive mechanical ventilation through endotracheal tubes, the use of humidifiers is essential. OBJECTIVE: To evaluate temperature and relative humidity levels in the gas administered to patients undergoing mechanical ventilation by means of heated water humidifiers (HWH) and hygroscopic heat and moisture exchangers (HHME). METHOD: This was a prospective randomized study on 20 patients divided into two groups: one group using HWH (n=10) and the other using the Hygrobac "S" model of HHME, made by Mallinckrodt® (n=10). The variables analyzed were: temperature and relative humidity levels of the gas, minute volume (MV), tidal volume (V T) and condensation volume. RESULTS: It was found that HWH attained lower temperatures than did HHME (29.01 ± 1.33 °C versus 30.14 ± 1.24 °C; p<0.001). The relative humidity was higher in HWH than in HHME (97.45 ± 5.22% versus 89.87 ± 11.04%; p<0.021). The condensation volume in the ventilator circuit for the group using HWH was greater than for the HHME group (p<0.05). CONCLUSION: The results demonstrate that both systems (HWH and HHME) supplied absolute humidity that was below recommended values, while the HWH offered higher relative humidity. On the other hand, HHME produced better performance regarding gas heating.
humidifiers; hygroscopic heat and moisture exchangers; mechanical ventilation
