Alterations in minute ventilation, maximum voluntary ventilation and dyspneic index in different trimesters of pregnancy.

Respiratory function in pregnancy is of special importance since the life of fetus depends primarily upon its oxygen supply. Thus this study was designed to evaluate the Minute ventilation (MV), Maximum Voluntary Ventilation (MVV) & Dyspneic Index (DI) in different trimesters of pregnancy & compare the results with non- pregnant control group. A cross-sectional study was carried out in 200 healthy women in the age range of 19-35 years with 50 subjects each in 1st, 2nd, 3rd trimesters of pregnancy and non-pregnant control group. We recorded respiratory parameters in study and control groups. Statistical analysis was done by ANOVA and Tukey Krammer post Hoc tests. It was observed that there was a significant decrease in MVV and dyspneic index in all trimesters of pregnancy and an insignificant variation in MV when compared to the control group. The changes in pulmonary function are influenced by the mechanical pressure of enlarging gravid uterus, elevating the diaphragm and restricting the movements of lungs thus hampering forceful expiration. The decrease seen in MVV in 1st trimester might be due to bronchoconstriction effect of decreased alveolar Pco2 on the bronchial smooth muscles.