The reliability of a breath‐hold protocol to determine cerebrovascular reactivity in adolescents

This is the published version. Available on open access from Wiley via the DOI in this recordPurpose Cerebrovascular reactivity (CVR) is impaired in adolescents with cardiovascular disease risk factors. A breath‐hold test is a noninvasive method of assessing CVR, yet there are no reliability data of this outcome in youth. This study aimed to assess the reliability of a breath‐hold protocol to measure CVR in adolescents. Methods Twenty‐one 13 to 15 year old adolescents visited the laboratory on two separate occasions, to assess the within‐test, within‐day and between‐day reliability of a breath‐hold protocol, consisting of three breath‐hold attempts. CVR was defined as the relative increase from baseline in middle cerebral artery mean blood velocity following a maximal breath‐hold of up to 30 seconds, quantified via transcranial Doppler ultrasonography. Results Mean breath‐hold duration and CVR were never significantly correlated (r  .08). The within‐test coefficient of variation for CVR was 15.2%, with no significant differences across breath‐holds (P = .88), so the three breath‐hold attempts were averaged for subsequent analyses. The within‐ and between‐day coefficients of variation for CVR were 10.8% and 15.3%, respectively. Conclusions CVR assessed via a three breath‐hold protocol can be reliably measured in adolescents, yielding similar within‐ and between‐day reliability. Analyses revealed that breath‐hold length and CVR were unrelated, indicating the commonly reported normalization of CVR to breath‐hold duration (breath‐hold index) may be unnecessary in youth

The acute and postprandial effects of sugar moiety on vascular and metabolic health outcomes in adolescents

This is the author accepted manuscript. The final version is available from Canadian Science Publishing via the DOI in this recordThis study explored the cardiometabolic responses to sugar moieties acutely, and following a subsequent mixed meal tolerance test (MMTT). Twenty-one healthy adolescents (N=10 female, 14.3±0.4 years) completed three experimental and one control condition, in a counterbalanced order. These consisted of different drinks to compare the effect of 300 mL of water (control), or 300 mL of water mixed with 60 g of glucose, fructose or sucrose, on vascular function (flow-mediated dilation; FMD, microvascular reactivity (total hyperaemic response; TRH); and cerebrovascular reactivity; CVR), and blood samples for [uric acid], [glucose], [triglycerides] and [lactate]. FMD increased 1 hour after glucose and sucrose (P<0.001, ES≥0.92) but was unchanged following fructose and water (P>0.19, ES>0.09). CVR and TRH were unchanged 1 hour following all conditions (P>0.57, ES>0.02). Following the MMTT, FMD was impaired in all conditions (P0.40) with no differences between conditions (P>0.13, ES<0.39). Microvascular TRH was increased in all conditions (P=0.001, ES=0.88), and CVR was preserved in all conditions post MMTT (P=0.87, ES=0.02). Blood [uric acid] was elevated following fructose consumption and the MMTT (P0.40). Consumption of a sugar sweetened beverage did not result in vascular dysfunction in healthy adolescents, however the vascular and metabolic responses were dependent on sugar moiety

Rice Straw Management Effects on Greenhouse Gas Emissions and Mitigation Options

Lowland rice is a significant source of anthropogenic greenhouse gas emissions (GHGEs) and the primary source of agricultural emissions for many developing countries in Asia. At the same time, rice soils represent one of the largest global soil organic carbon sinks. Straw management is a key factor in controlling the emissions and mitigation potential of rice primarily by affecting methane (CH4) from anaerobic decomposition and carbon losses from burning. Achieving climatesmart management of rice while also improving yields and farm profits, however, is challenging due to economic-environmental trade-offs. This balance could be met with appropriate site-specific practices. This chapter discusses these straw management practices that affect yield-scaled GHGEs and mitigation options in different rice environments