Spirometry test measures the volume of inhaled and exhaled air and shows valuable information about the cardiovascular condition of the human body. Besides, this tool is used for diagnostic and monitoring the development and evolution of diseases as well as treatments and epidemiologic survey to the public health system (9,11).
The ATS highlights two fundamental variables in the spirometric analysis, the FCV defined through the association as the maximum volume of air exhaled at the top of a forced expiry, and FEV1 as the maximum volume of exhaled air in the first-second expiration after a complete expiration (9).
There was an increase in the HRV and FEV1 values mean for both sexes in the comparison between this study and 2007’s (12).
In comparison to other populations, similar values have been found in Hispanics (13) and Asian (12) residents in the United State, to Nigerians (16), higher value appeared.
In 2007, Pereira et al. developed referenced equations for Brazil's white population (17), using linear regression models. This type of modeling demonstrated satisfactory results in developing predictive values (16,21,22). However, Brazil is a country of continental size, and great ethnic-cultural diversity. The southern region of the country has climatic and geographical characteristics diverting from the rest of the country, leading to later colonization of predominant Europeans. These factors have impacted the demographic differences and social dynamics of the region, in the same manner, it occurs in the United States and New Zealand. Consequently, using regional criteria for an accurate diagnosis is relevant. According to men's comparison of the predicted values, all individuals were classified below by Pereira et al. (17). The obstruction diagnostic differs due to the criteria, which may lead to false-positives diagnoses, resulting in possible expenditures of the public system as additional tests, and treatments avoided only with local diagnostic criteria.
FVC predicted values were among the younger women were lower than the comparative study, however, higher values were found among older women. On the other hand, the majority of FEV1 predicted values, are higher than those proposed by the author. This difference shall be related to the large presence of young women. In this study, 523 women were evaluated, 22.7% (n = 121) between 18 and 35 years old, against 19.8% (74) in accordance with previous study. The stature factor is directly related to lung capacity, in this study, the evaluated were 64.7% (n = 353) higher between 156 and 167 centimeters, whereas, in Pereira et al (12). study, most women-centered between 145 and 164 centimeters (n = 309;82.6%).
Differences in predicted values found in this study compared with 2007’s (17) were statistically significant between them. These variations were already expected as it is an update of the proposed values. The highest health organizations WHO (9), ATS (11), and European Thoracic Society (ETS) (10) recommend updating them every five years. Revisions of the values seek to correct the variations caused by changes in anthropometric pattern and lifestyle, physical activity, occupational and environmental factors (6).
Ethnicity has been one of the most influential factors of respiratory function (6). Even homogeneous populations such as China have differences between population groups including lung capacity. In a study conducted with inhabitants of the ethnic minorities, a significant difference between the groups evaluated using criteria produced for the general population was found (23).
In this sense, another point proposed in this paper is the establishment of local classification criteria in Brazil. In addition to the extensive territorial strip, the country has received populations from several locations in Africa and Europe. These ethnic groups mixed with the local indigenous population giving rise to the Brazilian population. This occupation was heterogeneous, leading to the consolidation of different population groups throughout the territory.
There are other direct and indirect factors that may influence lung capacities such as daily habits, level of physical activity, climatic factors and air quality which were not considered in this study. Another limitation is that the sample is not representative of the general population of the country, however, this limitation is necessary due to regional differences between populations. It is also suggested to conduct similar studies in other regions of the country, each one with their own classification criteria.