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Updated: Jul 2, 2026

Dual Test Gas Pulmonary Diffusing Capacity Measurement During Exercise in Humans Using the Single-Breath Method
Published on: February 2, 2024
[Airflow limitation in Brazilian Caucasians: FEV1/FEV6 vs. FEV1/FVC]
André Luis Pinto Soares1, Sílvia Carla Sousa Rodrigues, Carlos Alberto de Castro Pereira
1Hospital do Servidor Público Estadual de São Paulo, São Paulo, SP, Brasil. drandrepinto@globo.com
Objective:
To evaluate the use of the forced expiratory volume in one second/forced expiratory volume in six seconds (FEV1/FEV6) ratio as an alternative to the FEV1/forced vital capacity (FVC) ratio in the detection of mild airway obstruction.
Methods:
Reference equations for the Brazilian population in 2006 were used in order to determine the lower limits of normality for the FEV1/FEV6 and FEV1/FVC ratios. The spirometry findings of 155 patients from 20 to 84 years of age were analyzed. All of the patients presented the following: a < 15% difference between predicted and observed FEV1/FVC ratio; an FEV1 > 60% of predicted; and an exhalation time of at least 6 s. The Brazilian Thoracic Society criteria for acceptability and reproducibility in spirometry were met.
Results:
Mean values (+/- SD) for FEV1/FEV6 and FEV1/FVC were 73 +/- 4% and 75 +/- 3%, respectively. Using the FEV1/FVC ratio, we identified airflow obstruction in 61 patients, compared with only 46 patients when we used the FEV1/FEV6 ratio, showing a sensitivity of 75% (p < 0.001).
Conclusions:
The FEV1/FEV6 ratio has poor sensitivity and should not be used to replace the FEV1/FVC ratio in the diagnosis of mild airway obstruction.
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