Study of Forced Expiratory Volume in First Second ( FEV 1 ) and Ratio of Forced Expiratory Volume in First Second and Forced Vital Capacity in Percentage ( FEV 1 / FVC % ) in Pregnant Women

Background: A few data are available on the effects of pregnancy on pulmonary function in different countries. But no such established data are available in our country. So we designed this study in our population. Objectives: To observe the forced expiratory volume in first second (FEV 1 ) and ratio of forced expiratory volume in first second and forced vital capacity (FEV 1 /FVC%) in different trimesters of normal pregnant women and to compare them with those of healthy non-pregnant women. Materials and Methods: This observational and analytical study was carried out in the department of Physiology, Dhaka Medical College during July 2004 to June 2005. Total 100 women aged from 25 to 35 years without any recent history of respiratory tract diseases were selected as study population. Among them, 75 normal pregnant women were taken as experimental and 25 healthy non-pregnant women were taken as control groups. The experimental group included 25 pregnant women in first trimester, 25 in second trimester and 25 in third trimester. Forced expiratory volume in first second (FEV 1 ), ratio of percentage of forced expiratory volume in first second and forced vital capacity (FEV 1 /FVC%) were measured in pregnant and non-pregnant control women. The FEV 1 and FEV 1 /FVC% were measured by using an ‘automatic spirometer’. Statistical analyses were done by unpaired Student’s ‘t’ test between the study groups and p value <0.05 was taken as significant. Results: The mean ± SD of measured values of FEV 1 were 2.41 ± 0.87, 2.28 ± 0.59, 2.15 ± 0.74 and 1.89 ± 0.76 liters in non-pregnant women and in pregnant women during first trimester, second trimester and third trimester. The mean ± SD of measured values of FEV 1 /FVC% were 75.22 ± 16.77, 74.86 ± 11.06, 74.42 ± 17.43 and 71.81 ± 15.87% in nonpregnant women and in pregnant women during first trimester, second trimester and third trimester. Conclusion: The FEV 1 and FEV 1 /FVC% were significantly lower in third trimester pregnant women than that of non-pregnant and first trimester of pregnant women and FEV 1 /FVC% gradually decreased from first to third trimester of pregnant women. DOI: http://dx.doi.org/10.3329/jemc.v2i1.11926 J Enam Med Col 2012; 2(1): 29-32


Study of Forced Expiratory Volume in First Second (FEV 1 ) and Ratio of Forced Expiratory Volume in First Second and Forced Vital Capacity in Percentage (FEV 1 /FVC%) in Pregnant Women
Abdominal muscles have less tone and are less active during the pregnancy causing respiration to be more diaphragmatic.Moreover it has been seen that alteration occurs in lung volumes and capacities during pregnancy. 1Mechanical effects of progressively increasing size of the uterus decrease the lung volumes and capacities by the fifth month of pregnancy which at term are about 20% below those of the non-pregnant state. 2 During pregnancy, changes in the thoracic configuration subsequent to progressive increase in the abdominal volume have a moderate effect on respiratory function. 3It is observed that pregnancy is associated with significant changes in respiratory functions even in healthy pregnant women. 4,5n the other hand, FEV 1 gradually decreases as the pregnancy advances.After 28 weeks of gestation FEV 1 significantly decreases than that of the normal values.These results suggest that FEV 1 changes gradually during pregnancy especially after the 28 th week of pregnancy. 6Though the Indian population showed significant changes in total and timed vital capacity (FVC and FEV 1 ), FVC did not significantly decrease in the third trimester than that of the second trimester. 7Again it was also found that airway obstruction due to any cause reduces the FEV 1 and FVC but to a lesser extent which in turn causes the FEV 1 /FVC% ratio to be reduced below 60%.
However, in another study reduced FEV 1 and FVC were observed among the study population with unchanged FEV 1 /FVC% ratio. 8So it was important to observe the lung function assessment in pregnant women both physiologically and clinically.A few data are available on the effects of pregnancy on pulmonary function in different countries as shown by different researches. 6,7But no established data is available in our country on this aspect.Therefore, the aim of this study was to observe the normal value of FEV 1 which is frequently used for lung function test in different trimesters of normal pregnant women and compare them with those of healthy nonpregnant women.

Materials and Methods
This observational and analytical study was carried out in the department of Physiology, Dhaka Medical College during July 2004 to June 2005.The study subjects were taken from different areas of Dhaka city and belonged to lower, middle and poor socio-economic classes.A total of 100 women aged from 25 to 35 years without any recent history of respiratory diseases were selected --75 were in the experimental group and 25 were in the control group.Experimental group included 25 first trimester (Group B-I), 25 second trimester (Group B-II), and 25 third trimester (Group B-III) pregnant women.25 healthy non-pregnant women were taken as control (Group A).Forced expiratory volume in first second (FEV 1 ), ratio of percentage of forced expiratory volume in first second and forced vital capacity (FEV 1 /FVC%) were measured in normal pregnant and healthy non-pregnant women.
The FEV 1 and FEV 1 /FVC% were measured by automatic spirometer during different trimesters of pregnant women and compared with that of nonpregnant women.Statistical analyses were done by unpaired Student's 't' test between the study groups and p value <0.05 was taken as significant.

Results
Table I shows the FEV 1 and FEV  II shows that the mean ± SD of measured values of FEV 1 was significantly lower in third trimester compared to that of the non-pregnant women and first trimester pregnant women.There were no statistically significant differences of FEV 1 in first trimester and second trimester compared to that of non-pregnant women, in second trimester compared to that of first trimester pregnant women and third trimester compared to that of second trimester pregnant women.
Table III shows that the mean ± SD of measured values of FEV 1 /FVC% was significantly lower in third trimester compared to that of the non-pregnant women and first trimester pregnant women.There were no statistically significant differences of FEV 1 /FVC% in first trimester and second trimester 30