Influence of a neck compression collar on cerebrovascular and autonomic function in men and women

Objective Neck compression collars have been proposed to reduce injury to the brain caused by head impacts. Our objective was to test if compression of the carotid artery affected the baroreflex and influenced blood pressure control. Methods Cerebrovascular and autonomic responses of healthy young men and women (n = 8 each) to paced deep breathing, Valsalva, and 70o head-up tilt with or without use of a Q-collar were determined. Continuous measurements of heart rate, beat-to-beat blood pressure, transcranial Doppler, and end-tidal gases were obtained. Heart rate variability was measured during supine rest and head-up tilt. Carotid artery and jugular vein cross-sectional area were measured at end-inhalation and end-exhalation using cross-sectional ultrasound images at diastole. Results Wearing the collar reduced carotid cross-sectional area (CSA; P = 0.022; η2 = 0.03) and increased jugular CSA (P = 0.001; η 2 = 0.30). In both men and women, wearing the collar increased systolic blood pressure during Valsalva (P0.05), and there were no effects of the collar on cerebrovascular function, hemodynamics, cardiovagal baroreceptor sensitivity, or heart rate variability (P>0.05) during upright tilt. Conclusion Use of the Q-collar compresses both the jugular vein and carotid artery influencing sympathetic nerve activity in both men and women while influencing brain blood flow in women.York University Librarie

Bodyweight Perceptions among Texas Women: The Effects of Religion, Race/Ethnicity, and Citizenship Status

Despite previous work exploring linkages between religious participation and health, little research has looked at the role of religion in affecting bodyweight perceptions. Using the theoretical model developed by Levin et al. (Sociol Q 36(1):157–173, 1995) on the multidimensionality of religious participation, we develop several hypotheses and test them by using data from the 2004 Survey of Texas Adults. We estimate multinomial logistic regression models to determine the relative risk of women perceiving themselves as overweight. Results indicate that religious attendance lowers risk of women perceiving themselves as very overweight. Citizenship status was an important factor for Latinas, with noncitizens being less likely to see themselves as overweight. We also test interaction effects between religion and race. Religious attendance and prayer have a moderating effect among Latina non-citizens so that among these women, attendance and prayer intensify perceptions of feeling less overweight when compared to their white counterparts. Among African American women, the effect of increased church attendance leads to perceptions of being overweight. Prayer is also a correlate of overweight perceptions but only among African American women. We close with a discussion that highlights key implications from our findings, note study limitations, and several promising avenues for future research

Cardiovascular responses of women to orthostatic stress, the effects of the menstrual cycle and age, and a comparison to men

Young women are known to exhibit a greater incidence of orthostatic hypotension than men. The exact mechanisms for this are unclear and it has been proposed to be related to cardiac filling, peripheral resistance, and/or regional blood pooling. The sexually dimorphic effects of lower body negative pressure (LBNP) or upright posture were investigated throughout this study. Women could experience these changes due to effects of the sex hormones estrogen and progesterone. Chapters 3 and 4 in this thesis investigated the responses of women to LBNP in both the follicular and the luteal phase of the menstrual cycle (and age-matched men). Women at these points of the cycle have approximately equal levels of estrogen with high levels of progesterone in the luteal phase. Furthermore, Chapter 5 investigated the responses of pre-menopausal and post-menopausal women (and age-matched men) to sitting and standing. These studies will help to explain the effects of female sex hormones on cardiovascular responses to simulated or real orthostatic stress. LBNP simulates an orthostatic stress by causing a caudal fluid shift and was used in Chapters 3 and 4 as a stimulus to optimize the position of the participants for cardiovascular measurements. A supine-to-sit-to-stand test (i.e. actual orthostatic stress) was used in Chapter 5 as a stimulus. Head-down bed-rest (HDBR) is a model used to simulate microgravity and induces a fluid shift away from the legs towards the head. It has been shown to augment the responses to LBNP and was thus used to enhance the cardiovascular and hormonal responses of men and women to LBNP. A seated control (SEAT) was also used in an attempt to control for the equivalent period of inactivity and circadian rhythm. Blood pressure responses to LBNP were not different between menstrual phases although the physiological mechanisms may be somewhat different. Women in the luteal phase had higher portal vein resistance index which would contribute to moving splanchnic blood pools to maintain venous return during an orthostatic stress. When comparing women in the follicular phase to men, there was a decrease of blood pressure in women during LBNP which was not observed in men. This decrease was likely a result of reduced venous return as evidenced by a greater loss of central venous pressure and a greater increase of thoracic impedance during LBNP. This could have been a result of 1) splanchnic blood pooling in women as men had a greater increase of portal vein resistance index during LBNP, and/or 2) attenuated activation of the renin-angiotensin-aldosterone pathway in women during LBNP. After considering the effects of circadian rhythm and inactivity in all participants, HDBR resulted in 1) higher heart rate with a greater increase during LBNP, 2) a greater decrease of stroke volume during LBNP, 3) a greater increase of thoracic impedance during LBNP, 4) smaller inferior vena cava diameter, 5) lower norepinephrine, and 6) lower blood volume. These changes indicate that after 4-hours of HDBR resting venous return and venous return during LBNP was lower in all participants. However, the mechanisms by which each sex or menstrual phase responded were different. After HDBR men had higher pelvic impedance, higher vasopressin, and higher endothelin-1 compared to women in the follicular phase. After HDBR women in the luteal phase also had higher vasopressin and higher pelvic impedance compared to women in the follicular phase. During the supine-to-sit-to-stand protocol young women (follicular phase) exhibited a greater increase of heart rate during the 3rd minute of each posture likely due to reduced stroke volume compared to young men and post-menopausal women. During the transitions to sitting or standing young women also had an impaired ability to maintain stroke volume and cardiac output compared to post-menopausal women and age-matched men. These results imply that young women had lower venous return than older women and age-matched men during an orthostatic stress. In comparison to older men, post-menopausal women also had slightly reduced venous return, but the difference was smaller than that seen in the younger groups. There were no differences in middle cerebral artery blood flow velocity when comparing younger and older groups of men and women. The results of this investigation have outlined how men respond to an orthostatic stress differently than women (i.e. via a decrease in splanchnic pooling and a greater increase of vasoconstrictors), and have helped to outline a role for female sex hormones in the cardiovascular responses to an orthostatic stress (i.e. post-menopausal women exhibit greater venous return during an orthostatic stress compared to younger cycling women)

Teaching Anatomy with Multiple Techniques

I will be describing different teaching strategies that could be used to teach anatomy to large groups of students. It is important to use multiple techniques in order to reach as many different types of learners as possible. Furthermore, in my experience anatomy has only been taught by using the transmission technique (i.e. lecture), and with today’s technology there are many other ways that could be used. This is an important topic for people in my discipline as most anatomy classes contain over 200 students, and these students will all have different learning styles. In order to effectively instruct all of these students to the best of our abilities we need to use a variety of teaching strategies above and beyond the normal course of lecture

Sex differences in the ventilatory and cardiovascular response to supine and tilted metaboreflex activation

Abstract Women have attenuated exercise pressor responses compared to men; however, their cerebrovascular and ventilatory responses have not been previously measured. Furthermore, recent evidence has shown that posture change can influence the response of the metaboreflex but this has only been tested in men. Young and healthy men (n = 14; age: 21 ± 2) and women (n = 11; age: 19 ± 1) underwent 40% MVC static handgrip exercise (HG) for 2 min followed by 3 min of post‐exercise circulatory occlusion (PECO) in the supine and 70° tilted postures. In supine position during HG and PECO only men had an increase in ventilation (Men: Baseline: 12.5 ± 1.7 L/min, HG: 18.6 ± 5.3 L/min, PECO: 17.7 ± 10.3 L/min; Women: Baseline: 12.0 ± 1.5 L/min, HG: 12.4 ± 1.2 L/min, PECO: 11.5 ± 1.3 L/min; Sex × Time interaction P = 0.037). In supine position during HG and PECO men and women had similar reductions in cerebrovascular conductance (Men: Baseline: 0.79 ± 0.13 cm/sec/mmHg, HG: 0.68 ± 0.18 cm/sec/mmHg, PECO: 0.61 ± 0.19 cm/s/mmHg; Women: Baseline: 0.87 ± 0.13 cm/sec/mmHg, HG: 0.83 ± 0.14 cm/sec/mmHg, PECO: 0.75 ± 0.17 cm/sec/mmHg; P < 0.015 HG/PECO vs. baseline). When comparing the response to PECO in the supine versus upright postures there was a significant attenuation in the increase in mean arterial pressure in both men and women (Supine posture: Men: +23.3 ± 14.5 mmHg, Women: +12.0 ± 7.3 mmHg; Upright posture: Men: +15.7 ± 14.1 mmHg, Women: +7.7 ± 6.7 mmHg; Main effect of sex P = 0.042, Main effect of posture P < 0.001). Our results indicate sexually dimorphic ventilatory responses to HG and PECO which could be due to different interactions of the metaboreflex and chemoreflex. We have also shown evidence of attenuated metaboreflex function in the upright posture in both men and women

Influence of a neck compression collar on cerebrovascular and autonomic function in men and women.

ObjectiveNeck compression collars have been proposed to reduce injury to the brain caused by head impacts. Our objective was to test if compression of the carotid artery affected the baroreflex and influenced blood pressure control.MethodsCerebrovascular and autonomic responses of healthy young men and women (n = 8 each) to paced deep breathing, Valsalva, and 70o head-up tilt with or without use of a Q-collar were determined. Continuous measurements of heart rate, beat-to-beat blood pressure, transcranial Doppler, and end-tidal gases were obtained. Heart rate variability was measured during supine rest and head-up tilt. Carotid artery and jugular vein cross-sectional area were measured at end-inhalation and end-exhalation using cross-sectional ultrasound images at diastole.ResultsWearing the collar reduced carotid cross-sectional area (CSA; P = 0.022; η2 = 0.03) and increased jugular CSA (P = 0.001; η 2 = 0.30). In both men and women, wearing the collar increased systolic blood pressure during Valsalva (P0.05), and there were no effects of the collar on cerebrovascular function, hemodynamics, cardiovagal baroreceptor sensitivity, or heart rate variability (P>0.05) during upright tilt.ConclusionUse of the Q-collar compresses both the jugular vein and carotid artery influencing sympathetic nerve activity in both men and women while influencing brain blood flow in women

The association between shift work exposure and cognitive impairment among middle-aged and older adults: Results from the Canadian Longitudinal Study on Aging (CLSA).

BackgroundShift work, especially rotating and night shift work, has been linked to a wide range of detrimental health outcomes. Occupational factors like shift work and their potential impact on cognitive functions have received little attention, and the evidence is inconclusive. The objective of our study is to explore associations between shift work exposure and cognitive impairment indicators based on comparisons with the normative standards from the Canadian population.MethodsCross-sectional analyses were performed using baseline Canadian Longitudinal Study on Aging database, including 47,811 middle-aged and older adults (45-85 years). Three derived shift work variables were utilized: ever exposed to shift work, shift work exposure in longest job, and shift work exposure in current job. Four cognitive function tests were utilized, Rey Auditory Verbal Learning Tests (immediate and delayed) representing memory domain, and Animal Fluency, and Mental Alteration, representing the executive function domain. All cognitive test scores included in study were normalized and adjusted for the participant's age, sex, education and language of test administration (English and French), which were then compared to normative data to create "cognitive impairment' variables. Unadjusted and adjusted multivariable logistic regression models were used to determine associations between shift work variables and cognitive impairment individually (memory and executive function domains), and also for overall cognitive impairment.ResultOverall, one in every five individuals (21%) reported having been exposed to some kind of shift work during their jobs. Exposure to night shift work (both current and longest job) was associated with overall cognitive impairment. In terms of domain-based measures, night shift work (longest job) was associated with memory function impairment, and those exposed to rotating shift work (both current and longest job) showed impairment on executive function measures, when compared to daytime workers.ConclusionThis study suggests disruption to the circadian rhythm, due to shift work has negative impact on cognitive function in middle-aged and older adults and this warrants further investigation

Influence of sex, menstrual cycle, and oral contraceptives on the cerebrovascular response to paced deep breathing

Purpose Deep breathing assesses autonomic function; however, many researchers/clinicians do not account for hyperventilation, brain blood flow or blood pressure. Methods Men and women (with/without oral contraceptives) participated. women participated during low and high hormone phases of the menstrual cycle. Blood pressure, end-tidal carbon dioxide, middle cerebral artery velocity and cerebrovascular resistance were assessed. Results Deep breathing decreased end-tidal carbon dioxide and middle cerebral artery velocity while increasing cerebrovascular resistance in all participants; blood pressure decreased in men. There were no influences of menstrual cycle or oral contraceptives. Conclusions Men have different autonomic responses to deep breathing compared to women.Funding provided by the Faculty of Health, York University, and a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC)