When the FEV1 is plotted against CO2 levels in patients with obstructive lung disease, CO2 retention is not seen until FEV1 levels drop below 800 ml. The expected 5 year survival of patients with CO2 retention is less than 50%. Exceptions to this rule should be considered if the patient is not obstructed. Some old women will not even have a predicted FEV1 of 1.6 liters and can have perfectly normal lungs. These patients will be able to tolerate predicted post-op FEV1 values of less than 800 ml. Thus, the criteria of post-op FEV1 volume of 800 ml as the cut off point applies only to patients with obstructive lung disease.
Return to Preop PFT