Abstract: A patient support device includes a patient support surface formed of chambers continuously inflated with air from a blower. A sensor in the form of either a tubular member or pressure sensitive switch is configured to be disposed at the base of at least one of the individual inflatable chambers of the patient support device and can be configured to be disposed in the interstice between two adjacent chambers in a manner so that normal support of the patient's body on the chamber(s) does not put the patient's body in contact with such sensor or deform the adjacent chamber(s) sufficiently to cause such chamber(s) to apply pressure to such sensor. The flow of air exhausted from the chambers can be varied by a variable flow valve or by a flexible gasket that variably engages an outlet tube. The flow permitted through the valve or by the gasket can be controlled by a controller based on signals from the sensor. The controller also can control the speed of the blower based on signals from the sensor.