Performance of new spirometry reference values in preoperative assessment of lung function

Pulmonary function is not routinely assessed in patients without respiratory disease and symptoms before surgery, even if they are smokers. We aimed to check whether the new spirometric reference values of the worldwide Global Lung Initiative (GLI) affected the preoperative assessment of lung function in allegedly lung-healthy patients compared with the still commonly used old predicted values.

Two hundred nineteen allegedly lung-healthy non-smokers, past and current smokers were examined by spirometry before elective surgery. The obtained values of forced expiratory volume in 1 second (FEV₁ ), forced vital capacity (FVC) and FEV₁ /FVC were transformed into z-scores according to the GLI guidelines. A comparison between the new and old reference values was performed. FEV₁ was used for the grading of airway obstruction.

One hundred eighty-three subjects performed the ventilation manoeuvre according to the GLI recommendations and were analysed. Most non-smokers and past smokers met the new references ranges for spirometric values. Only z-scores of FEV₁ /FVC distinguished among all three patient groups, FEV₁ between smokers and the other two groups and FVC did not discriminate the groups, irrespective of the reference values used. Airway obstruction was identified in 24% of asymptomatic smokers by z-scores of FEV₁ /FVC but in only 14% by the old predicted values. In elderly smokers (>60 years), the corresponding values rose to 50% and 30%. Old predicted values of FEV₁ underestimated the degree of airway obstruction mainly in middle-aged smokers.

Allegedly lung-healthy current smokers showed a higher proportion of preoperatively reduced lung function when z-scores were used, especially in elderly subjects.