Prediction equations for spirometry in adults in western India

Spirometry is an essential investigation in pulmonology. The predicted normal spirometry values depend on various physiological parameters. This study was conducted to collect updated information on pulmonary functions in normal adults from western India.

A prospective observational study was undertaken at a tertiary hospital in Mumbai enrolling healthy subjects, 18-75 years, with ethnic origin from western India. Spirometry measurements were carried out as per ATS/ERS-2005 guidelines using a non-heated Fleish Pneumotachograph spirometer. Data was analyzed using SPSS for Pearson's correlation analysis, multiple linear regressions and log transformations of variables to get the best prediction equations.

310 subjects (185 males, 125 females) were included. Lung function values were higher in men as compared to women. In multivariate linear regression models, age and height were major predictor variables for all spirometry parameters. Addition of weight as a determinant variable did not make significant contribution to the models except for PEFR in males and F₇₅ in females. Regression equations were established for FVC, FEV₁, FEV₁/FVC ratio, PEFR, F_25-75, F₅₀, and F₇₅. The standard-error-of-estimate was provided to enable computation of lower limits of normal for these parameters.

We propose regression equations for spirometry variables developed using the current standards for adult West Indian population fulfilling the long-felt need for updated equations.