Reference equations for pulmonary function variables among apparently healthy adult Nigerian population

Abstract

Objectives: To determine the reference equations for pulmonary function variables (PFVs) among apparently healthy adults in the population.
Design: This cross-sectional study randomly involved 1125 participants (501 males and 624 females). Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were assessed using a spirometer, and FEV1/FVC was calculated. The peak expiratory flow rate (PEFR) was assessed using a peak flow meter. Linear regression was used to obtain equation for reference values for PFVs. Paired T-test was used to assess for difference between predicted and measured PFVs.
Setting: Anambra State, Nigeria
Participants: Apparently healthy adults
Main outcome measures: FVC, FEV1, FEV1/FVC and PEFR.
Results: In males, age, height and weight contributed 23% to the prediction of FEV1, and 24% to the prediction of FVC, whereas only age contributed 18% to the prediction of PEFR. In females, age and height contributed 27.7% to the prediction of FEV1, 27.7% to the prediction FVC, and 20% to the prediction PEFR. Age and height contributed only 2% to the prediction of FEV1/FVC in males whereas age contributed only 2% in females. The values from derived equations for the predictions of FEV1, FVC, PEFR and FEV1/FVC in males and females were not significantly different from their respective objectively measured values, and their respective equations for the lower limit of normal (LLM) are reported.
Conclusions: The derived reference equations from this study are recommended for determining age- and gender-specific PFVs reference values when assessing respiratory functions.