A Case Study on the Effects of Pregnancy on Expiratory Flow Limitation and Operating Lung Volumes During Exercise
Faculty Advisor Name
Stephanie Kurti-Luden
Department
Department of Kinesiology
Description
This project was an exploratory, single participant, prospective case study following an active, 35-year-old subject throughout the course of her pregnancy to evaluate the effects of pregnancy on operating lung volumes and expiratory flow limitation (EFL) during exercise. We also aimed to examine how the above two measures impacted the subject’s rating of perceived dyspnea (RPD) and exercise tolerance as the pregnancy progressed. Testing was conducted every other week starting at 8 weeks gestation and ending at 38 weeks gestation, as parturition occurred at 39 weeks gestation. We also completed one testing day about 6 weeks postpartum. Each testing day involved anthropometric measurements (height, weight, and body composition), a pregnancy symptoms inventory (PSI), and two exercise tests. Each exercise test was an incremental test to 85% of the subject’s age-predicted maximum heart rate; one was conducted on the treadmill while the other was conducted on a stationary Velotron cycle ergometer. The exercise tests were used to collect pulmonary function and cardiorespiratory data in order to assess operating lung volumes and EFL. EFL is an anatomical limitation in which expiratory flow rates cannot increase, even with further expiratory effort, at a given lung volume during rest or exercise. It is typically associated with increases in operating lung volumes, termed dynamic hyperinflation, and increased rates of dyspnea. Several studies up to this point had shown that EFL occurred in other subgroups, but it had never been studied in pregnant individuals. We hypothesized that the anatomical and physiological changes that are known to occur in pregnancy (namely the expansion of the uterus causing an upward displacement of the diaphragm as well as increased production of progesterone) would lead to EFL occurrence. We also hypothesized that EFL would occur at lower absolute workloads in the latter stages of pregnancy. Comparison of our outcomes between the treadmill and cycle tests was an exploratory aim of the study. At this point, not all results are complete, but so far, we found that EFL did occur during our subject’s pregnancy during submaximal workloads on both the bike and the treadmill. On the treadmill, EFL occurred more frequently and at earlier absolute workloads as her pregnancy progressed. Though, there are weeks within the third trimester (TM3) where EFL still does not occur. Results appear different on the bike. EFL also occurred on the bike throughout pregnancy; however, highest EFL prevalence was seen during the second trimester (TM2). Data analysis for this project is still ongoing, and further work needs to be done to examine the relationship between operating lung volumes, RPD, and EFL. But currently, our hypothesis appears true on the treadmill, but not on the bike. It is unclear why EFL presence and severity is highest during the second trimester on the bike, though several factors could be contributing.
A Case Study on the Effects of Pregnancy on Expiratory Flow Limitation and Operating Lung Volumes During Exercise
This project was an exploratory, single participant, prospective case study following an active, 35-year-old subject throughout the course of her pregnancy to evaluate the effects of pregnancy on operating lung volumes and expiratory flow limitation (EFL) during exercise. We also aimed to examine how the above two measures impacted the subject’s rating of perceived dyspnea (RPD) and exercise tolerance as the pregnancy progressed. Testing was conducted every other week starting at 8 weeks gestation and ending at 38 weeks gestation, as parturition occurred at 39 weeks gestation. We also completed one testing day about 6 weeks postpartum. Each testing day involved anthropometric measurements (height, weight, and body composition), a pregnancy symptoms inventory (PSI), and two exercise tests. Each exercise test was an incremental test to 85% of the subject’s age-predicted maximum heart rate; one was conducted on the treadmill while the other was conducted on a stationary Velotron cycle ergometer. The exercise tests were used to collect pulmonary function and cardiorespiratory data in order to assess operating lung volumes and EFL. EFL is an anatomical limitation in which expiratory flow rates cannot increase, even with further expiratory effort, at a given lung volume during rest or exercise. It is typically associated with increases in operating lung volumes, termed dynamic hyperinflation, and increased rates of dyspnea. Several studies up to this point had shown that EFL occurred in other subgroups, but it had never been studied in pregnant individuals. We hypothesized that the anatomical and physiological changes that are known to occur in pregnancy (namely the expansion of the uterus causing an upward displacement of the diaphragm as well as increased production of progesterone) would lead to EFL occurrence. We also hypothesized that EFL would occur at lower absolute workloads in the latter stages of pregnancy. Comparison of our outcomes between the treadmill and cycle tests was an exploratory aim of the study. At this point, not all results are complete, but so far, we found that EFL did occur during our subject’s pregnancy during submaximal workloads on both the bike and the treadmill. On the treadmill, EFL occurred more frequently and at earlier absolute workloads as her pregnancy progressed. Though, there are weeks within the third trimester (TM3) where EFL still does not occur. Results appear different on the bike. EFL also occurred on the bike throughout pregnancy; however, highest EFL prevalence was seen during the second trimester (TM2). Data analysis for this project is still ongoing, and further work needs to be done to examine the relationship between operating lung volumes, RPD, and EFL. But currently, our hypothesis appears true on the treadmill, but not on the bike. It is unclear why EFL presence and severity is highest during the second trimester on the bike, though several factors could be contributing.
