Reference Equations for Static Lung Volumes and TL_CO from a Population Sample in Northern Greece

The most commonly used reference equations for the measurement of static lung volumes/capacities and transfer factor of the lung for CO (TL_CO) are based on studies around 30-40 years old with significant limitations.

Our aim was to (1) develop reference equations for static lung volumes and TL_CO using the current American Thoracic Society/European Respiratory Society guidelines, and (2) compare the equations derived with those most commonly used.

Healthy Caucasian subjects (234 males and 233 females) aged 18-91 years were recruited. All of them were healthy never smokers with a normal chest X-ray. Static lung volumes and TL_CO were measured with a single-breath technique according to the latest guidelines.

Curvilinear regression prediction equations derived from the present study were compared with those that are most commonly used. Our reference equations in accordance with the latest studies show lower values for all static lung volume parameters and TL_CO as well as a different way of deviation of those parameters (i.e. declining with age total lung capacity, TL_CO age decline in both sex and functional residual capacity age rise in males).

We suggest that old reference values of static lung volumes and TL_CO should be updated, and our perception of deviation of some spirometric parameters should be revised. Our new reference curvilinear equations derived according to the latest guidelines could contribute to the updating by respiratory societies of old existing reference values and result in a better estimation of the lung function of contemporary populations with similar Caucasian characteristics.