Abstract
Background: The frequently measured index of pulmonary function is vital capacity which gives useful information about the strength of respiratory muscles and other aspects of lung function. The purpose of the study was to investigate changes that occur in vital capacity in different postural attitudes like standing, supine, right lateral, left lateral positions compared with the reference position such as upright sitting in normal subjects.
Methods: Young non-smoker healthy male medical students (n=20, age 19-22 years) of PSG Medical College participated as volunteers in this study. Pulmonary function tests like forced vital capacity (FVC), Forced Expiratory Volume in one second (FEV1), FEV1 to FVC% i.e. (FEV1%) was recorded in various postures using computerized spirometer in BIOPAC systems, Inc., MANBSL3S, student version, following the standard procedure.
Results: A repeated measure ANOVA-multiple comparison study revealed FVC, FEV1 and FEV1% values in standing posture was significantly higher than supine, sitting, right and left lateral positions.
Conclusions: Naturally, in standing posture factors contributing to increased vital capacity are increased, vertical diameter of thorax which increases thoracic capacity volume and lung compliance increasing lung volume.

Key words: Postural changes, Pulmonary functions, Vital capacity