The Effect of Cetirizine HCl on Exercise-induced Arterial Hypoxemia in Highly-trained Swimmers

Exercise-induced arterial hypoxemia (EIAH), a reduced amount of oxygen in the arterial blood during exercise, has been observed in otherwise healthy, highly-trained endurance athletes during exercise at sea level. The extent of the arterial deoxygenation may be influenced by a histamine-mediated inflammatory response at the pulmonary capillary-alveolar membrane limiting oxygen diffusion. Moreover, while EIAH has been routinely explored in running and cycling, swimming is understudied despite potential mechanistic avenues which may put swimmers at further risk for EIAH. The purpose of this study is threefold: 1) to determine whether highly-trained swimmers experience EIAH during submaximal and maximal exercise, 2) to determine the extent to which histamine release influences oxyhemoglobin saturation during swimming exercise, and 3) to determine whether cetirizine HCl (CH), an H1-receptor competitive inhibitor, can improve oxyhemoglobin saturation during submaximal and maximal swimming exercise. Twenty-four (12 men, 12 women) highly-trained swimmers will complete an intense swimming protocol to assess the histamine response to intense exercise. A subset with the highest histamine responses will participate in three additional sessions (placebo, NS, and CH conditions) which will include a swimming aerobic capacity test and 5-minutes of swimming at both 70 and 85% of their maximal oxygen uptake.

For the first testing session, participants will report to the Indiana University Human Performance Laboratory to complete a medical screening and, if willing, consent to the procedures of the study. The medical screening will include measurements of height, weight, resting heart rate, resting blood pressure, and resting pulmonary function along with a health history questionnaire. The second testing session consists of an assessment of risk factors for development of EIAH, specifically changes in blood biomarkers pre- and post-swimming exercise. Participants will report to the Counsilman-Billingsley Aquatics Center and complete an exercise protocol designed to elicit an inflammatory response. Venous blood draws will be performed to assess participants' pre-exercise complete blood count and pre- and post-intense exercise concentrations of plasma IL-1β, IL-8, plasma histamine, whole blood histamine, and histamine release. Measurements of hemoglobin concentration and hematocrit will also be performed pre- and post-exercise in order to correct biomarker concentrations for fluid loss during exercise. Swimmers of each sex that exhibit the largest histamine release will be selected for further study until at least four swimmers of each sex complete all three experimental trials. Twelve swimmers (n = 6 men, n = 6 women) will be selected for further trials. Those selected for further study will visit the Human Performance Laboratory on two occasions separated by at least 48 hours and no more than 60 days. Apart from receiving a placebo (PL) or drug treatment (cetirizine HCl, CH) prior to exercise, participants will perform identical protocols on each visit to the laboratory. Participants will report to the lab and consume either a placebo or CH pill, followed by a health history update questionnaire and their resting pulmonary function will be measured. Participants will then complete a self-selected warm-up that will be standardized across all testing sessions, followed by instrumentation. The exercise protocol beings with a progressive swimming test to maximum aerobic capacity (V̇O2max) in a swimming flume, followed by two constant load work bouts at approximately 70 and 85% of the previously recorded HRmax while peripheral capillary oxyhemoglobin saturation (SpO2) is continuously monitored. Participants will receive a 20-min break between each work bout. Drug treatments will be assigned in a double-blind, randomized crossover fashion such that each participant receives each treatment. Concentrations of plasma histamine, whole blood histamine, and histamine release will be assessed from pre- and post-exercise blood samples.