Aim: Hybrid mattresses are increasingly being used in UK healthcare due to their ability to be rapidly switched from a reactive mode to providing active alternating therapy. This study investigated a new hybrid mattress designed to automatically switch from its reactive to active mode where a person remains immobile for at least 60 minutes. Methods: Healthy volunteers rested upon the test mattress for 90 minutes remaining relatively immobile for the first hour. After 61 or 62 minutes of immobility the mattress switched to its active mode for each volunteer. Pressure measurements were performed using a pressure map during the 90-minute session. Results: We recruited 10 healthy volunteers. These data were heterogeneous, and in the absence of a control mattress surface challenging to interpret. The two volunteers with the highest body mass index (BMI) >30 both experienced malfunctions of the pressure map system. Conclusion: The link between BMI and the functioning of the pressure map requires further investigation.