Abstract Background When ventilating extremely low birth weight infants, clinicians face the problem of instrumental dead space, which is often larger than tidal volume. Hence, aggressive ventilation is necessary to achieve CO 2 removal. Continuous tracheal gas insufflation can wash out CO 2 from dead space and might also have an impact on O 2 and water vapor transport. The objective of this bench study is to test the impact of instrumental dead space on the transport of CO 2 , O 2 , and water vapor and the ability of continuous tracheal gas insufflation to remedy this problem during small tidal volume ventilation. Methods A test‐lung located in an incubator at 37°C was ventilated with pressure levels needed to reach different tidal volumes from 1.5 to 5 mL. End‐tidal CO 2 at the test‐lung exit, O 2 concentration, and relative humidity in the test‐lung were measured for each tidal volume with and without a 0.2 L/min continuous tracheal gas insufflation flow. Results CO 2 clearance was improved by continuous tracheal gas insufflation allowing a 28%–44% of tidal volume reduction. With continuous tracheal gas insufflation, time to reach desired O 2 concentration was reduced from 20% to 80% and relative humidity was restored. These results are inversely related to tidal volume and are particularly critical below 3 mL. Conclusion For the smallest tidal volumes, reduction of instrumental dead space seems mandatory for CO 2 , O 2 , and water vapor transfer. Continuous tracheal gas insufflation improved CO 2 clearance, time to reach desired O 2 concentration and humidification of airways and, thus, may be an option to protect lung development.