An apparatus for applying negative pressure therapy, comprising: a housing comprising a source of negative pressure, the source of negative pressure including a pump configured to be in fluidic communication with a wound dressing via a fluid flow path; and a controller configured to operate the source of negative pressure, the controller further configured to: determine a level of activity of the pump, maintain a value in a memory responsive to the level of activity of the pump, the value being saturated when the level of activity of the pump is at or below a threshold level of activity and the value is unable to be further increased or decreased even though the value should further change responsive to the level of activity of the pump according to the function which is used to adjust the value, detect presence of a blockage in the fluid flow path using the level of activity of the pump and without using a pressure in the fluid flow path, and in response to detecting presence of the blockage in the fluid flow path, provide an indication of the blockage in the fluid flow path, wherein the controller is configured to detect the presence of the blockage in response to determining that the value is saturated wherein a clamped state has been reached. a housing comprising a source of negative pressure, the source of negative pressure including a pump configured to be in fluidic communication with a wound dressing via a fluid flow path; and a controller configured to operate the source of negative pressure, the controller further configured to: determine a level of activity of the pump, maintain a value in a memory responsive to the level of activity of the pump, the value being saturated when the level of activity of the pump is at or below a threshold level of activity and the value is unable to be further increased or decreased even though the value should further change responsive to the level of activity of the pump according to the function which is used to adjust the value, detect presence of a blockage in the fluid flow path using the level of activity of the pump and without using a pressure in the fluid flow path, and in response to detecting presence of the blockage in the fluid flow path, provide an indication of the blockage in the fluid flow path, determine a level of activity of the pump, maintain a value in a memory responsive to the level of activity of the pump, the value being saturated when the level of activity of the pump is at or below a threshold level of activity and the value is unable to be further increased or decreased even though the value should further change responsive to the level of activity of the pump according to the function which is used to adjust the value, detect presence of a blockage in the fluid flow path using the level of activity of the pump and without using a pressure in the fluid flow path, and in response to detecting presence of the blockage in the fluid flow path, provide an indication of the blockage in the fluid flow path, wherein the controller is configured to detect the presence of the blockage in response to determining that the value is saturated wherein a clamped state has been reached. <EOS>