Valid results are sometimes elusive.
They are compromised toward the average hospital user and the average hospital patient. These systems are built to streamline operation of the cart, and to expedite production of a final report, so that they can obtain reimbursement for the test. Furthermore the measurements done with these carts are compromised toward the range of ventilation rates to be found in a hospital patient, and the accuracy necessary to detect an abnormal exercise response. In a clinical facility, great accuracy is an expensive luxury. Physio-dyne carts are built for research and teaching.