Clinicians should be aware of the indications of the PFTs, and how results are interpreted. The main goal of PFTs in preoperative evaluation of surgical patients is to determine if patient has normal lung functions (at time of testing) Or has obstructive or restrictive lung disease and the severity of that disease, and his response to medication and also to determine the risk indices for developing postoperative pulmonary complications and measures used perioperatively to reduce that risk.