The effects of physical activity on arterial stiffness during pregnancy: an observational study.

The objective of the present study was to investigate the relationship between moderate-to-vigorous physical activity (MVPA) and arterial stiffness in pregnancy. Thirty-nine women participated in this study, resulting in 68 measurements in non-pregnant (NP; n = 21), first (TM1; n = 8), second (TM2; n = 20), and third trimesters (TM3; n = 19). Compliance, distensibility, elasticity, ß-stiffness, and carotid to femoral (central) and carotid to finger (peripheral) pulse wave velocity (PWV) were assessed. MVPA was measured using accelerometry. Multilevel linear regressions adjusted for multiple tests per participant using random effects to generate ß coefficients and 95% confidence intervals (CIs) were performed. Distensibility, elasticity, ß-stiffness, and central- and peripheral-PWV did not differ between pregnant and non-pregnant assessments. Carotid artery compliance was higher in TM2 compared with NP. Central PWV (ß coefficient: -0.14, 95% CI: -0.27, -0.02) decreased from early to mid-pregnancy and increased in late pregnancy. Meeting the MVPA guidelines was significantly associated with central-PWV (adjusted ß coefficient: -0.34, 95% CI: -0.62, -0.06, p = 0.016), peripheral-PWV (adjusted ß coefficient: -0.54, 95% CI: -0.91, -0.16, p = 0.005), and distensibility (adjusted ß coefficient: -0.001, 95% CI: -0.002, -0.0001, p = 0.018), in pregnancy. These results suggest that MVPA may be associated with improved (i.e., reduced) arterial stiffness in pregnancy. Novelty: Central PWV, distensibility, compliance, elasticity, and ß-stiffness, but not peripheral PWV, exhibited curvilinear relationships with gestational age Central and peripheral PWV were lower in pregnant women who met the physical activity guidelines of 150 minutes of moderate-to-vigorous physical activity per week.

Longitudinal study of cerebral blood flow regulation during exercise in pregnancy.

Cerebrovascular adaptation to pregnancy is poorly understood. We sought to assess cerebrovascular regulation in response to visual stimulation, hypercapnia and exercise across the three trimesters of pregnancy. Using transcranial Doppler (TCD) ultrasound, middle and posterior cerebral artery mean blood velocities (MCAvmean and PCAvmean) were measured continuously at rest and in response to (1) visual stimulation to assess neurovascular coupling (NVC); (2) a modified Duffin hyperoxic CO2 rebreathe test, and (3) an incremental cycling exercise test to volitional fatigue in non-pregnant (n = 26; NP) and pregnant women (first trimester [n = 13; TM1], second trimester [n = 21; TM2], and third trimester [n = 20; TM3]) in total 47 women. At rest, MCAvmean and PETCO2 were lower in TM2 compared to NP. PCAvmean was lower in TM2 but not TM1 or TM3 compared to NP. Cerebrovascular reactivity in MCAvmean and PCAvmean during the hypercapnic rebreathing test was not different between pregnant and non-pregnant women. MCAvmean continued to increase over the second half of the exercise test in TM2 and TM3, while it decreased in NP due to differences in ΔPETCO2 between groups. Pregnant women experienced a delayed decrease in MCAvmean in response to maximal exercise compared to non-pregnant controls which was explained by CO2 reactivity and PETCO2 level.

Studying third-parties and environments: New Zealand sun-safety research.

Wearable cameras have been used to study health behaviours, but their utility in assessing third-party behaviours and the built environment is uncertain. This paper reports on the feasibility of using wearable cameras for this purpose in a study of sun-protective behaviours and shade availability during school lunch-breaks. The Kids'Cam study provided 168 children (aged 11-13 years), recruited from 16 randomly selected schools in the Wellington region of New Zealand, with wearable cameras. The devices automatically captured images every 7 s from the child's perspective. Images captured during school lunch-breaks by a random sample of 15 children who took part during terms 4 and 1 (October 2014-April 2015) were selected and assessed for usability. The feasibility of studying third-party sun-protective behaviours and school shade availability was assessed for a subset of 320 images. Of the 3492 eligible lunch-break images, 96.4% were useable; the remainders were excluded due to obstruction, blurriness or unsuitable camera position. Overall, 1278 children and 108 shade structures were observed in the sample images. The use of shade, hats, sleeves, collars and sunglasses could be determined for 97.0%, 77.2%, 74.4%, 47.6% and 54.9% of children, respectively. All shade structures could be classified according to type, and canopy composition could be assessed for 95.4% of structures. Wearable cameras are a feasible tool for assessing sun-safety, particularly shade availability, hat wearing and shade use. This methodology could be used to objectively study other third-party health-related behaviours, and other features of the built environment.

Sun protection and shade availability in New Zealand's outdoor recreation spaces.

AIMS: We aimed to investigate sun protection behaviours and shade availability in outdoor recreation spaces using images captured by children who, in 2014/15, wore wearable cameras for four consecutive days. METHODS: The 168 participants visited 16 outdoor recreation spaces between 10am and 4pm, capturing 378 images, on average, in each setting. People observed in the images (n=2,635) were coded for age, sex, clothing worn (38 clothing types) and shade used. Mean temperature and ultraviolet index (UVI) values were linked with the time-stamped and geo-referenced images. RESULTS: The UVI in most settings was high enough to warrant sun protection, but only 4.3% of people wore sun-protective hats (broad-brim, bucket and legionnaire styles) and 10.7% used shade. Areas most popular with children, including playground equipment, beach sand and pool areas, had little or no shade available. CONCLUSIONS: Despite New Zealand having the highest incidence of melanoma skin cancer in the world, the results indicate that few New Zealanders wear hats and seek shade in outdoor recreation settings. The findings highlight the need to improve policy and environmental support for skin cancer prevention activities.

Wellington Playgrounds Uncovered: An Examination of Solar Ultraviolet Radiation and Shade Protection in New Zealand.

Providing effective shade in summer recreation spaces can reduce children's risk of skin cancer. This study explored the quantity and protective quality of shade in Wellington, New Zealand playgrounds. Two researchers visited 50 randomly selected playgrounds during peak ultraviolet radiation (UVR) hours in summer and recorded the mean shade cover of playground equipment, seats, tables and open areas. A solar meter was used to calculate the proportion of UVR blocked by each built structure and tree. The results found that 95% of playground equipment and 64% of sitting and eating areas had no shade protection. Trees blocked a mean of 80.1% (95% CI: 66.0-94.1) of direct solar UVR, but mostly covered open areas, not playground equipment, seats and tables. The findings demonstrate that Wellington playgrounds have insufficient shade available. Increased shade in Wellington playgrounds is urgently needed to protect children from harmful UVR exposure, particularly through planting trees with heavy foliage and building structures with large, protective roofing. This may well be the case for other regions of NZ and for other countries where UVR exposure is dangerous. The method used in this study provides a reliable means to evaluate shade.

Sun Protection Among New Zealand Primary School Children.

Schools are an important setting for raising skin cancer prevention awareness and encouraging sun protection. We assessed the clothes worn and shade used by 1,278 children in eight schools in the Wellington region of New Zealand. These children were photographed for the Kids'Cam project between September 2014 and March 2015 during school lunch breaks. Children's mean clothing coverage (expressed as a percentage of body area covered) was calculated. Data on school sun-safety policies were obtained via telephone. Mean total body clothing coverage was 70.3% (95% confidence interval = 66.3%, 73.8%). Body regions with the lowest mean coverage were the head (15.4% coverage), neck (36.1% coverage), lower arms (46.1% coverage), hands (5.3% coverage), and calves (30.1% coverage). Children from schools with hats as part of the school uniform were significantly more likely to wear a hat (52.2%) than children from schools without a school hat (2.7%). Most children (78.4%) were not under the cover of shade. Our findings suggest that New Zealand children are not sufficiently protected from the sun at school. Schools should consider comprehensive approaches to improve sun protection, such as the provision of school hats, sun-protective uniforms, and the construction of effective shade.

Central respiratory chemosensitivity and cerebrovascular CO2 reactivity: a rebreathing demonstration illustrating integrative human physiology.

One of the most effective ways of engaging students of physiology and medicine is through laboratory demonstrations and case studies that combine 1) the use of equipment, 2) problem solving, 3) visual representations, and 4) manipulation and interpretation of data. Depending on the measurements made and the type of test, laboratory demonstrations have the added benefit of being able to show multiple organ system integration. Many research techniques can also serve as effective demonstrations of integrative human physiology. The "Duffin" hyperoxic rebreathing test is often used in research settings as a test of central respiratory chemosensitivity and cerebrovascular reactivity to CO2. We aimed to demonstrate the utility of the hyperoxic rebreathing test for both respiratory and cerebrovascular responses to increases in CO2 and illustrate the integration of the respiratory and cerebrovascular systems. In the present article, methods such as spirometry, respiratory gas analysis, and transcranial Doppler ultrasound are described, and raw data traces can be adopted for discussion in a tutorial setting. If educators have these instruments available, instructions on how to carry out the test are provided so students can collect their own data. In either case, data analysis and quantification are discussed, including principles of linear regression, calculation of slope, the coefficient of determination (R(2)), and differences between plotting absolute versus normalized data. Using the hyperoxic rebreathing test as a demonstration of the complex interaction and integration between the respiratory and cerebrovascular systems provides senior undergraduate, graduate, and medical students with an advanced understanding of the integrative nature of human physiology.

Steady-state tilt has no effect on cerebrovascular CO2 reactivity in anterior and posterior cerebral circulations.

NEW FINDINGS: What is the central question of this study? We investigated the effects of superimposed tilt and hypercapnia-induced cerebral arteriolar dilatation on anterior and posterior cerebrovascular CO2 reactivity using hyperoxic rebreathing in human participants. What is the main finding and its importance? The main findings are threefold: (i) cerebrovascular CO2 reactivity in the anterior and posterior cerebrovasculature is unchanged with tilt; (ii) cerebral autoregulation is unlikely responsible due to unchanging cerebrovascular resistance reactivity between positions; and (iii) cerebral blood flow is not pressure passive during tilt as it is with pharmacological or lower body negative pressure-induced changes in mean arterial pressure, suggesting that sympathetic activation or balanced transmural pressures during head-down tilt regulate cerebral blood flow. Cerebral autoregulation is a protective feature of the cerebrovasculature that maintains relatively constant cerebral perfusion in the face of static and dynamic fluctuations in mean arterial pressure (MAP). However, the extent that the cerebrovasculature can autoregulate in the face of superimposed steady-state orthostasis-induced changes in MAP (e.g. head-up and head-down tilt; HUT and HDT) and CO2 -mediated arteriolar dilatation is unknown. We tested the effects of steady-state tilt on cerebrovascular CO2 reactivity in the middle and and posterior cerebral artery in the following five body positions: 90 deg HUT, 45 deg HUT, supine, 45 deg HDT and 90 deg HDT on a tilt table during a modified hyperoxic rebreathing test. Absolute and relative cerebrovascular CO2 reactivity [cerebral blood velocity (CBV)/CO2 ], cerebrovascular resistance (CVR) reactivity (CVR/CO2 ) and MAP reactivity (MAP/CO2 ) were quantified using linear regression. Mean arterial pressure was significantly elevated in 90 deg HDT compared with other positions during baseline steady-state tilt (P < 0.01). Absolute CBV/CO2 and CVR/CO2 were greater in the middle cerebral artery than the posterior cerebral artery (P < 0.01) in all body positions, but relative measures were not different (P = 0.143 and P = 0.360, respectively), nor was there any interaction with tilt position. In addition, there was no difference in absolute (P = 0.556) and relative MAP/CO2 (P = 0.308) between positions. Our data demonstrate that cerebral blood flow remains well regulated during superimposed steady-state orthostatic stress and dynamic changes in the partial pressure of end-tidal CO2 during rebreathing. Cerebral autoregulation is likely not the mechanism responsible, but rather sympathetic nervous system activation or a balanced cerebrovascular transmural pressure with HDT maintains resting cerebral blood flow and cerebrovascular CO2 reactivity during rebreathing.

The effects of head-up and head-down tilt on central respiratory chemoreflex loop gain tested by hyperoxic rebreathing.

Central respiratory chemosensitivity is mediated via chemoreceptor neurons located throughout brain stem tissue. These receptors detect proximal CO2/[H(+)] (i.e., controller gain) and modulate breathing in a classic negative feedback loop. Loop gain (responsiveness) is the theoretical product of controller (chemoreceptors), mixing/feedback (cardiovascular and cerebrovascular systems), and plant (pulmonary system) gains. The level of chemoreceptor stimulation is determined by interactions between mixing and plant gains. The extent to which steady-state changes in body position may affect central chemoreflex loop gain in response to CO2 is unclear. Because of the potential effects of tilt on pulmonary mechanics, we hypothesized that plant gain would be altered by head-up and head-down tilt (HUT, HDT) during hyperoxic rebreathing, which theoretically isolates plant gain by eliminating systemic arterial-tissue gradients. Sixteen subjects (eight females) underwent hyperoxic rebreathing tests on a tilt table to quantify central chemoreflex loop gain in five steady-state positions: 90° HUT, 45° HUT, supine, 45° HDT, and 90° HDT. Respiratory responses (tidal volume, VT; frequency, fR; minute ventilation, VE) were quantified during steady-state and increases in CO2 during rebreathing by linear regression above the ventilatory recruitment threshold (VRT). Using one-factor analysis of variance, we found that there were no differences in the respiratory responses between the five positions (VRT, P=0.711; VT, P=0.290; fR, P=0.748; VE, P=0.325). Our findings suggest that during steady-state orthostatic stress, the ability of subjects to mount a normal ventilatory response to increased CO2 was unaffected, despite any potential changes in pulmonary mechanics associated with positional challenges.

Differential cerebrovascular CO2 reactivity in anterior and posterior cerebral circulations.

The potential differences in cerebrovascular responses between the anterior and posterior circulations to changes in CO2 are unclear in humans. Using transcranial Doppler ultrasound, we compared the CO2 reactivity of the (1) BA and PCA and (2) MCA and PCA during hyperoxic rebreathing in supine position. The reactivity in the BA and PCA was similar in both absolute (1.27 ± 0.5 and 1.27 ± 0.6 cm/s/Torr; P=0.992) and relative (3.98 ± 1.3 and 3.66 ± 1.5%/Torr CO2; P=0.581) measures, suggesting that the PCA is an adequate surrogate measure of reactivity for the BA. The MCA reactivity was greater than the PCA in absolute (2.09 ± 0.7 and 1.22 ± 0.5 cm/s/Torr CO2; P<0.001), but not relative measures (3.25 ± 1.0 and 3.56 ± 1.6%/Torr CO2; P=0.629). Our findings (a) confirm regional differences in the absolute reactivity in the human brain and (b) suggest that in cerebrovascular studies investigating functions mediated by posterior brain structures (e.g., control of breathing), the posterior vasculature should also be insonated.

A stress and coping model of adjustment to caring for an adult with mental illness.

This study investigated the utility of a stress and coping framework for identifying factors associated with adjustment to informal caregiving to adults with mental illness. Relations between stress and coping predictors and negative (distress) and positive (positive affect, life satisfaction, benefit finding, health) carer adjustment outcomes were examined. A total of 114 caregivers completed questionnaires. Predictors included relevant background variables (carer and care recipient characteristics and caregiving context), coping resources (optimism, social support, carer-care recipient relationship quality), appraisal (threat, control, challenge) and coping strategies (problem-focused, avoidance, acceptance, meaning-focused). Results indicated that after controlling for relevant background variables (burden, caregiving frequency, care recipient symptom unpredictability), better caregiver adjustment was related to higher social support and optimism, better quality of carer-care recipient relationship, lower threat and higher challenge appraisals, and less reliance on avoidance coping, as hypothesised. Coping resources emerged as the most consistent predictor of adjustment. Findings support the utility of stress and coping theory in identifying risk and protective factors associated with adaptation to caring for an adult with mental illness.

Identification of stress and coping risk and protective factors associated with changes in adjustment to caring for an adult with mental illness.

There is a paucity of theory guided longitudinal research into how carers of an adult with mental illness adapt to caregiving. This study examined changes in carer adjustment over 12 months and identified risk and protective factors using stress/coping theory. Eighty-seven carers completed questionnaires at Time 1 and 12 months later (Time 2). The risk/protective factors were background variables, coping resources, appraisals, and coping strategies. Adjustment outcomes were stable over 12 months. Stress/coping variables were associated with one or more Time 2 adjustment outcomes when controlling for initial adjustment and the direction of these associations were consistent with predictions. Findings support the application of stress/coping theory to guide identification of modifiable risk and protective factors associated with caregiver adjustment.

Measurements of the solar UVR protection provided by shade structures in New Zealand primary schools.

To reduce ultraviolet radiation (UVR) exposure during childhood, shade structures are being erected in primary schools to provide areas where children can more safely undertake outdoor activities. This study to evaluate the effectiveness of existing and purpose built shade structures in providing solar UVR protection was carried out on 29 such structures in 10 schools in New Zealand. Measurements of the direct and scattered solar UVR doses within the central region of the shade structures were made during the school lunch break period using UVR-sensitive polysulfone film badges. These measurements indicate that many of the structures had UVR protection factors (PF) of 4-8, which was sufficient to provide protection during the school lunch hour. However, of the 29 structures examined, only six would meet the suggested requirements of UVR PF greater than 15 required to provide all-day protection.