Adequate humidification is essential for intubated patients because dry medical gases can cause thick secretions and dangerous endotracheal tube blockages. A clear correlation exists between exhaled and inhaled humidity delivered by heat and moisture exchanger. The objective of this study is to measure the temperature of exhaled gases in intubated patients in order to accurately calculate the absolute humidity during the expiratory phase. These data will allow for a more accurate reproduction of real clinical conditions during bench testing and will improve the assessment of heat and moisture exchanger performance device evaluation.