A patient support includes a cover defining an interior region, an air permeable first layer located in the interior region, at least one air supply coupled to the first layer to provide air flow through the first layer, a support layer located beneath the air permeable first layer, a pressure sensing layer located underneath the support layer, and a controller coupled to the air supply and to the pressure sensing layer. The controller controls air flow through the first layer in response to a signal from the pressure sensing layer.