To provide an accurate calibration method for a measurement system and a computer assisted calibration system for a whole body plethysmographic measurement chamber that does not require active, manual participation of a medical technician to conduct the calibration.

The method comprises processes of (a) measuring the combined volume of a plethysmographic measurement chamber and a known calibration volume coupled to the chamber by an opening to obtain a baseline volume measured value, (b) sealing the known volume from the chamber with an electronically controlled value coupled to the opening, (c) measuring the volume of the measurement chamber sealed from the reference volume to obtain a comparison volume measured value, and (d) calibrating the plethysmographic measurement system based on the known calibration volume a comparison of the baseline volume measured value and the comparison volume measured value.