A negative pressure wound therapy system includes at least one sensor coupled to a wound dressing for a wound of a patient, and a processing circuit. The at least one sensor is configured to output a measurement of the pressure in the wound dressing. The processing circuit is configured to open a sealable aperture, receive the pressure measurements in the wound dressing, calculate a rate of pressure decay, correlate the rate of pressure decay in the wound dressing to a wound dressing fluid absorbent capacity and other therapy parameters, and output the wound dressing fluid absorbent capacity and other therapy parameters to a remote electronic device.