Physiological sensor delivery device and method

A method of measuring Fractional Flow Reserve (FFR) in a patient, the method comprising:

• advancing a guidewire through a patient's vasculature to a location of interest in a patient;
• advancing a guiding catheter over the guidewire to the location of interest;
• advancing a sensor delivery device within the guiding catheter to the location of interest, the sensor delivery device comprising a distal sleeve, a distal sensor located on the distal sleeve, a proximal sensor located on the distal sleeve and proximal to the distal sensor, a proximal portion, and a communication channel, the sensors adapted to generate signals proportional to fluid pressure;
• advancing only a distal portion of the distal sleeve outside of the guiding catheter such that the distal sensor is outside of the guiding catheter and downstream of the location of interest and the proximal sensor is inside of the guiding catheter;
• generating a first distal fluid pressure signal with the distal sensor at a location outside of the guiding catheter and distal to the location of interest;
• generating a reference fluid pressure signal with the proximal sensor at a location inside of the guiding catheter, the reference fluid pressure signal representing a fluid pressure within the guiding catheter;
• calculating FFR using the first distal fluid pressure signal and the reference fluid pressure signal.