[Evaluation of respiratory tract function in healthy women in the last month of uncomplicated pregnancy]

Abstract

The aim of this work was to examine the function of the respiratory system in pregnant women in the last month of non-complicated pregnancy. Spirometry with Lungtest 1000 was performed in 31 pregnant women at a mean gestational age of 37.72 weeks. In 24 of them the test was repeated after delivery (mean time from delivery = 39.40 days). The results were compared with a control group of 31 healthy non-pregnant resident of Szczecin. Prior to spirometry, all women underwent a physical examination with measurement of blood pressure, heart rate, body weight and height, chest and abdominal circumference, symphysis-fundus distance and blood analysis. Dyspneic symptoms characteristic of pregnancy were assessed with the St. George Hospital questionnaire. Spirometric parameters were recorded during three stages of the examination: 1. Components of vital capacity (IRV, ERV, TV, IC), breathing rate and minute ventilation. 2. Forced respiratory parameters (FEV0.5, FEV1, FEV1/FVCEX, FEV1/FVCIN, FEV2, FEV3, FVCEX, VPEF, FIV1, PIF, MIF50, FVCIN, VPIF, PEF, MEF25, MEF50, MEF75, FEF25/75, FEF75/85, MEF25/FVCIN, MEF50/FVCEX, MEF50/FVCIN, MEF75/FVCIN, FET, FET/FIT, FIT, TTOT, TMEF25, TMEF50, TMEF75, TPEF, TPIF, TPEF/FET, TPIF/FIT, MTT, AEX). 3. Maximum voluntary ventilation, maximum breathing frequency and breathing reserve. The results in all groups were compared with reference values. Furthermore, comparative analysis was performed in the same women before and after delivery. Data from questionnaires were related to results of spirometry. Parametric and nonparametric tests were applied. Spearman's rank test was used to study relations between respiratory symptoms and spirometric parameters. Most spirometric parameters deviated from reference values. Vital capacity was greater than expected. FEV0.5, FEV3, FEV1/FVCEX were reduced. FEV1/FVCIN were reduced in pregnant women only. Parameters of forced expiratory flow: FEF25/75, FEF75/85, MEF25, MEF25/FVCIN, MEF50/FVCEX were lower than expected. Significant difference were disclosed for MTT, AEX and MVV. MTT and MVV were increased and AEX was reduced. PEF and MEF75 were decreased in pregnant women. Other parameters did not differ significantly. Detailed analysis performed in 24 women before and after delivery revealed differences in components of vital capacity. Additionally, FEV0.5, FEV1/FVCEX, FEF25/75, MEF25, MEF50, MEF25/FVCIN, MEF50/FVCEX were increased in pregnancy. Time parameters of forced expiration--FET and TMEF25 were shorter. Minute ventilation was increased in pregnancy although the breathing rate was decreased. Values of maximum voluntary ventilation and breathing reserve were decreased in pregnancy. Correlation analysis revealed that respiratory symptoms in pregnant women depended on changes in proportions among static components of vital capacity and abnormalities in forced inspiration (FIT, TPIF/FIT). Intensity of symptoms was related to increased heart rate and diastolic pressure.

Conclusions: 1. Chief spirometric parameters in the examined women differed significantly from reference values. Reliable information about respiratory function in pregnant women requires comparison of findings during and after pregnancy. 2. Vital capacity in the last month of pregnancy did not differ from values after delivery and in the control group. Component volumes changed: tidal volume was increased, expiratory reserve volume was decreased, inspiratory reserve volume remained unchanged. 3. Minute ventilation recorded at rest in pregnancy increased despite decreased breathing rate, whereas maximum voluntary ventilation was lower than after delivery and in the control group, evidencing reduced breathing reserve. 4. Chief forced expiratory parameters remained unchanged in pregnancy. Parameters characterizing bronchioles revealed increased air flow (bronchodilation). 5. Dyspneic symptoms found in pregnant women correlated with changes in vital capacity components. Symptoms depended on the mechanics of ventilation and not on the status of bronchi.