Integrative Physiology
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/21630
Browse
Browsing Integrative Physiology by Author "Rosenburg, Alexander"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Examining the Sex Effect on Oxidative Stress during Simulated Hemorrhage Induced by Lower Body Negative Pressure(2019-03-05) Luu, My-Loan; Kay, Victoria; Sprick, Justin; Rosenburg, Alexander; Mallet, Robert T.; Rickards, Caroline; Park, FloraPurpose Traumatic hemorrhage is one of the leading causes of death in both the military and civilian settings. Massive blood loss is known to elicit an increase in oxidative stress as a consequence of tissue ischemia and hypoxia. We have recently demonstrated that simulated hemorrhage via application of lower body negative pressure (LBNP) also elicits an increase in oxidative stress (indexed by circulating F2-isoprostanes). It is not clear, however, whether oxidative stress responses to stimulated hemorrhage are differentiated based on sex. The aim of this study was to assess sex differences in the oxidative stress response during simulated hemorrhage via application of pre-syncopal LBNP. Methods Fifteen healthy human subjects (11 M, 4 F) participated in a LBNP step protocol until presyncope (-15, -30, -45, -60, -70, -80, -90, -100 mmHg LBNP for 5-min each). Venous blood samples were collected at baseline and at presyncope then analyzed for F2-isoprostanes. Stroke volume and mean arterial pressure were obtained via finger photoplethysmography, while muscle oxygen saturation was measured via a near infrared spectroscopy device attached to the forearm. Time to reach presyncope was measured in seconds. Results The following results are only preliminary based on the small number of female subjects tested (N=4). There was no difference in tolerance to LBNP between males and females (Males: 1616 ± 132 s vs. Females: 1486 ± 216 s; P=0.63). F2-isoprostane concentrations were similar between the sexes at baseline (P=0.27), and there was no statistical difference in the % change in concentration with application of maximal LBNP (Males: 37.0 ± 15.4 % vs. Females: 5.0 ± 10.1; P=0.11). The decreases in stroke volume (Males: -52.4 ± 5.3 % vs. Females: -56.5 ± 5.5 %; P=0.50),mean arterial pressure (Males: -11.9 ± 3.4 % vs. Females: -14.6 ± 4.2 %; P=0.63), and muscle oxygen saturation (Males: -9.1± 1.7 % vs. Females: -9.4 ±2.3 %; P=0.91) were also similar between males and females. Conclusions These preliminary data indicate that there is no effect of sex on the oxidative stress response induced by application of simulated hemorrhage with maximal LBNP. This analysis is limited and inconclusive, however, as there were only 4 females and 11 males in this group of subjects. In our current study, we plan to recruit equal numbers of males and females to further explore whether biological sex plays a role in the oxidative stress response to blood loss injuries.Item Peak Analysis of Cerebral Blood Velocity Responses to Forced Low Frequency Oscillations during Simulated Hemorrhagic Stress in Humans(2019-03-05) Anderson, Garen; Rosenburg, Alexander; Park, Flora; Sprick, Justin; Rickards, Caroline; Barnes, Haley J.Peak Analysis of Cerebral Blood Velocity Responses to Forced Low Frequency Oscillations during Simulated Hemorrhagic Stress in Humans Haley J. Barnes, B.S., Garen K. Anderson, M.S., Alexander J. Rosenberg, Ph.D., Flora S. Park, M.S., Justin D. Sprick, Ph.D., Caroline A. Rickards, Ph.D Purpose: Tolerance to blood loss injuries (actual and simulated) varies across individuals. Higher amplitude of low frequency oscillations (10-s cycle; ~0.1 Hz) in brain blood flow and arterial pressure have been associated with higher tolerance to simulated hypovolemic episodes using lower body negative pressure (LBNP). We have previously demonstrated that forcing oscillations in cerebral blood flow and arterial pressure at 0.1 Hz and 0.05 Hz with oscillatory LBNP (OLBNP) protects cerebral oxygenation during central hypovolemia. However, there was no protection of mean cerebral blood flow (indexed via mean middle cerebral artery velocity, MCAv) with these oscillatory conditions. We hypothesize that the peak mean MCAv will be higher in the 0.05 Hz and 0.1 Hz OLBNP conditions compared to the 0 Hz condition, which may account for the protection of cerebral tissue oxygenation. Methods: Fourteen healthy human subjects (3 female/11 male) were randomly exposed to 10-min of non-oscillatory (0 Hz) and oscillatory (0.05 Hz and 0.1 Hz) LBNP conditions with an average LBNP chamber pressure of -60 mmHg. Measurements included MCAv via transcranial Doppler ultrasound, frontal lobe cerebral oxygenation (ScO2) via near infrared spectroscopy, and stroke volume and arterial pressure via finger photoplethysmography. Peak analysis was performed in 10-s and 5-s windows for the 0.05 Hz and 0.1 Hz profiles, respectively. Peak responses to the three LBNP conditions were compared using a linear mixed model for repeated measures with Tukey post hoc tests. Results: As previously reported, tolerance to the two OLBNP conditions was higher compared to the 0 Hz condition (P ≤ 0.09 for both vs. 0 Hz). In partial support of our hypothesis, when compared to the 0 Hz profile, the peak MCAv was higher with 0.05 Hz OLBNP (51.0±4.2 cm/s vs. 46.3±3.4 cm/s; P = 0.004) but not with the 0.1 Hz profile (49.0±3.9 cm/s; P = 0.11 vs. 0 Hz). Conclusions: The higher peak MCAv during the 0.05 Hz OLBNP profile may contribute to the attenuated decrease in cerebral oxygenation. These findings demonstrate the potential contribution of oscillatory peaks in cerebral blood flow to the protection of cerebral oxygenation and increased tolerance to simulated hemorrhage.