Peebles Karen C, Horsman Helen, Tzeng Yu-Chieh
Cardiovascular Systems Laboratory, University of Otago, Wellington, New Zealand.
PLoS One. 2013 Aug 15;8(8):e72624. doi: 10.1371/journal.pone.0072624. eCollection 2013.
Cigarette smoking is associated with an increased risk of stroke but the mechanism is unclear. The study examined whether acute and chronic cigarette smoking alters the dynamic relationship between blood pressure and cerebral blood flow. We hypothesised that acute and chronic smoking would result in a cerebral circulation that was less capable of buffering against dynamic fluctuations in blood pressure. Further, these changes would be accompanied by a reduction in baroreflex sensitivity, which is reduced after smoking (acute smoking).
We recruited 17 non-smokers and 15 habitual smokers (13 ± 5 pack years). Continuous measurements of mean cerebral blood flow velocity (transcranial Doppler ultrasound), blood pressure (finger photoplethysmography) and heart rate enabled transfer function analysis of the dynamic relationship between pressure and flow (gain, normalised gain, phase and coherence) and baroreflex sensitivity during supine rest before and after smoking a single cigarette (acute smoking).
There were no between-group differences in gain, phase or coherence before acute smoking. However, both groups showed a reduction in gain and coherence, associated with a reduction in baroreflex sensitivity, and increase in phase after acute smoking.
Contrary to our hypothesis, these findings suggest that in the face of a reduction in baroreflex sensitivity acute smoking may potentially improve the ability of the cerebral circulation to buffer against changes in blood pressure. However, chronic smoking did not alter the dynamic relationship between blood pressure and cerebral blood flow velocity. These results have implications on understanding mechanisms for attenuating stroke risk.
吸烟与中风风险增加相关，但机制尚不清楚。本研究探讨急性和慢性吸烟是否会改变血压与脑血流量之间的动态关系。我们假设急性和慢性吸烟会导致脑循环缓冲血压动态波动的能力下降。此外，这些变化将伴随着压力反射敏感性的降低，吸烟后（急性吸烟）压力反射敏感性会降低。
我们招募了17名不吸烟者和15名习惯性吸烟者（吸烟量为13±5包年）。通过连续测量平均脑血流速度（经颅多普勒超声）、血压（手指光电容积描记法）和心率，对吸一支烟前后（急性吸烟）仰卧休息时压力与血流之间的动态关系（增益、标准化增益、相位和相干性）以及压力反射敏感性进行传递函数分析。
急性吸烟前，两组在增益、相位或相干性方面无组间差异。然而，两组在急性吸烟后均出现增益和相干性降低，与压力反射敏感性降低以及相位增加有关。
与我们的假设相反，这些发现表明，面对压力反射敏感性降低，急性吸烟可能会潜在地提高脑循环缓冲血压变化的能力。然而，慢性吸烟并未改变血压与脑血流速度之间的动态关系。这些结果对理解降低中风风险的机制具有启示意义。
