Prakash Kiran, Chandran Dinu S, Khadgawat Rajesh, Jaryal Ashok Kumar, Deepak Kishore Kumar
Department of Physiology, All India Institute of Medical Sciences, New Delhi, India.
Department of Endocrinology and Metabolism, All India Institute of Medical Sciences, New Delhi, India.
J Stroke Cerebrovasc Dis. 2014 Apr;23(4):630-5. doi: 10.1016/j.jstrokecerebrovasdis.2013.06.003. Epub 2013 Jul 4.
Changes in cerebral blood flow velocity to hypercapnia are associated with changes in systemic blood pressure (BP). These confounding BP-dependent changes in cerebral blood flow velocity cause misinterpretation of cerebrovascular reactivity (CVR) results. The objective of the study was to determine the relationship between CVR assessed by breath holding and 6% CO2 breathing after correcting for BP-dependent changes in cerebral blood flow velocity.
In 33 patients of uncomplicated type 2 diabetes mellitus, CVR was assessed as percentage changes in cerebral blood flow velocity and cerebrovascular conductance index.
Percentage change in cerebral blood flow velocity during breath holding was positively correlated with that of during 6% CO2 breathing (r = .35; P = .0448). CVR during breath holding and 6% CO2 breathing were better correlated when expressed as percentage changes in cerebrovascular conductance index (r = .49; P = .0040). Similarly, breath-holding test results expressed as percentage changes in cerebral blood flow velocity correctly identified only 37.5% of the poor reactors to 6% CO2 breathing. However, when the breath-holding test results were expressed as percentage changes in cerebrovascular conductance index, 62.5% of the poor reactors to 6% CO2 breathing were correctly identified indicating a better agreement between the test results obtained by the 2 methods.
Cerebrovascular response to breath holding is better correlated with that of 6% CO2 breathing when changes in cerebral blood flow velocity were corrected for associated changes in BP.
脑血流速度对高碳酸血症的变化与全身血压（BP）的变化相关。这些与血压相关的脑血流速度变化会导致对脑血管反应性（CVR）结果的误解。本研究的目的是在纠正脑血流速度与血压相关变化后，确定屏气和吸入6%二氧化碳时评估的CVR之间的关系。
在33例无并发症的2型糖尿病患者中，CVR以脑血流速度和脑血管传导指数的百分比变化来评估。
屏气期间脑血流速度的百分比变化与吸入6%二氧化碳期间的变化呈正相关（r = 0.35；P = 0.0448）。当以脑血管传导指数的百分比变化表示时，屏气和吸入6%二氧化碳期间的CVR相关性更好（r = 0.49；P = 0.0040）。同样，以脑血流速度百分比变化表示的屏气试验结果仅正确识别出37.5%对吸入6%二氧化碳反应较差的患者。然而，当屏气试验结果以脑血管传导指数的百分比变化表示时，62.5%对吸入6%二氧化碳反应较差的患者被正确识别，表明两种方法获得的试验结果之间具有更好的一致性。
在校正脑血流速度相关变化中的血压变化后，屏气时的脑血管反应与吸入6%二氧化碳时的反应相关性更好。
