Publications -- Caroline Rickards

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/31947

This collection is limited to articles published under the terms of a creative commons license or other open access publishing agreement since 2016. It is not intended as a complete list of the author's works.

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    Transfer function analysis of dynamic cerebral autoregulation: A CARNet white paper 2022 update
    (International Society for Cerebral Blood Flow and Metabolism, 2022-08-14) Panerai, Ronney; Brassard, Patrice; Burma, Joel S.; Castro, Pedro; Claassen, Jurgen AHR; van Lieshout, Johannes J.; Liu, Jia; Lucas, Samuel JE; Minhas, Jatinder S.; Mitsis, Georgios D.; Nogueira, Ricardo C.; Ogoh, Shigehiko; Payne, Stephen J.; Rickards, Caroline A.; Robertson, Andrew D.; Rodrigues, Gabriel D.; Smirl, Jonathan D.; Simpson, David M.
    Cerebral autoregulation (CA) refers to the control of cerebral tissue blood flow (CBF) in response to changes in perfusion pressure. Due to the challenges of measuring intracranial pressure, CA is often described as the relationship between mean arterial pressure (MAP) and CBF. Dynamic CA (dCA) can be assessed using multiple techniques, with transfer function analysis (TFA) being the most common. A 2016 white paper by members of an international Cerebrovascular Research Network (CARNet) that is focused on CA strove to improve TFA standardization by way of introducing data acquisition, analysis, and reporting guidelines. Since then, additional evidence has allowed for the improvement and refinement of the original recommendations, as well as for the inclusion of new guidelines to reflect recent advances in the field. This second edition of the white paper contains more robust, evidence-based recommendations, which have been expanded to address current streams of inquiry, including optimizing MAP variability, acquiring CBF estimates from alternative methods, estimating alternative dCA metrics, and incorporating dCA quantification into clinical trials. Implementation of these new and revised recommendations is important to improve the reliability and reproducibility of dCA studies, and to facilitate inter-institutional collaboration and the comparison of results between studies.
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    Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters
    (American Physiological Society, 2022-07-01) Baker, Jacquie; Safarzadeh, Mohammad A.; Incognito, Anthony V.; Jendzjowsky, Nicholas G.; Foster, Glen E.; Bird, Jordan D.; Raj, Satish R.; Day, Trevor A.; Rickards, Caroline A.; Zubieta-DeUrioste, Natalia; Alim, Usman; Wilson, Richard J. A.
    Cerebral hypoxia is a serious consequence of several cardiorespiratory illnesses. Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into cerebral hypoxia in critical illness. In addition, although sex-specific differences in cardiovascular diseases are strongly supported, few have focused on differences in ocular blood flow. We evaluated the retinal microvasculature in males (n = 11) and females (n = 7) using functional optical coherence tomography at baseline (1,130 m) (day 0), following rapid ascent (day 2), and prolonged exposure (day 9) to high altitude (3,800 m). Retinal vascular perfusion density (rVPD; an index of total blood supply), retinal thickness (RT; reflecting vascular and neural tissue volume), and arterial blood were acquired. As a group, rVPD increased on day 2 versus day 0 (P < 0.001) and was inversely related to [Formula: see text] (R(2) = 0.45; P = 0.006). By day 9, rVPD recovered to baseline but was significantly lower in males than in females (P = 0.007). RT was not different on day 2 versus day 0 (P > 0.99) but was reduced by day 9 relative to day 0 and day 2 (P < 0.001). RT changes relative to day 0 were inversely related to changes in [Formula: see text] on day 2 (R(2) = 0.6; P = 0.001) and day 9 (R(2) = 0.4; P = 0.02). RT did not differ between sexes. These data suggest differential time course and regulation of the retina during rapid ascent and prolonged exposure to high altitude and are the first to demonstrate sex-specific differences in rVPD at high altitude. The ability to assess intact microvasculature contiguous with the brain has widespread research and clinical applications.NEW & NOTEWORTHY Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into consequence of cerebral hypoxia in critical illness. This study demonstrates dynamic regulation of the retina during rapid ascent and prolonged exposure to high altitude and is the first to demonstrate sex-specific differences in retinal microvasculature at high altitude. The ability to dynamically assess intact microvasculature contiguous with the brain has widespread research and clinical applications.
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    Effects of Acute Vaporized Nicotine in Non-Tobacco Users at Rest and during Exercise
    (Western Kentucky University, 2016-11-01) Fogt, Donovan L.; Levi, Michael A.; Rickards, Caroline A.; Stelly, Steven P.; Cooke, William H.
    Smokers, and even non-smokers, may utilize vaporized nicotine delivered by electronic cigarette (EC) due to the perception that EC are "healthier" than traditional tobacco cigarettes. The effects of vaporized nicotine delivered by EC on resting blood pressure (BP) and resting metabolic rate (RMR), or BP and aerobic power during exercise have not been studied. This investigation tested the effects of acute vaporized nicotine inhalation by EC on resting BP and RMR and cycle exercise BP, metabolic responses, and aerobic power in young, normotensive non-smokers. Using a double-blind design, 20 subjects (10 female) participated in two randomized trials: placebo (0 mg nicotine) or nicotine (18 mg nicotine). Participants inhaled from EC once every 30 s for 10 min (20 inhalations total). RMR was assessed 40 min later by indirect calorimetry followed by an incremental cycle test. RMR was not different between trials (p=0.79). Compared to the placebo, resting diastolic pressure (DBP) was 3 mmHg higher with nicotine (p=0.04). VO2peak was not different between the nicotine trial (2.3+/-0.8 L*min(-1)) and placebo (2.3+/-0.7 L*min(-1)) trials (p=0.77), and Wmax was also similar between nicotine (201.0+/-53.8 W) and the placebo (204.8+/-57.8 W) (p=0.29). During the cycle exercise test, average DBP was higher following nicotine use compared with placebo trial (p=0.05), and exercise DBPpeak after nicotine (79.4+/-7.6) was significantly higher than placebo (74.9+/-8.3 mmHg) (p=0.02). Resting systolic blood pressure (SBP) was 3.7 mmHg lower for nicotine trial (p=0.04) but no SBP treatment effect was observed during exercise (p=0.14). Our results show that acute vaporized nicotine inhalation via EC increases resting and exercise DBP but does not affect RMR or cycle aerobic power in young, normotensive non-smokers.