Figure 2 -.

Effect of tidal volume (200, 500 and 1000 mL) in the context of %RAH. The dead-space volume for each HME is shown in parentheses and the HME units are listed in order of increasing dead-space volume. Overall, the HME models differed slightly in terms of their ability to maintain absolute humidity levels, except when a high tidal volume was delivered. There was an inverse relationship between the efficiency of humidification and tidal volume. Hygrobac S was the HME model with the greatest %RAH.