Baroreflex sensitivity (BRS) and cerebral autoregulation (CA) play an important role in maintaining constant cerebral blood flow (CBF) during systemic changes in blood pressure (BP). Impaired BRS and CA have been reported in acute traumatic brain injury (TBI) which may also contribute to secondary injury and poorer recovery after acute TBI; however, their status during chronic stages remains elusive. Thus, the goal of this study is to determine whether cardiac BRS and dynamic CA (dCA) were impaired during the chronic stage in patients with single TBI and persistent neurological symptoms. Twenty-two subjects with blunt head TBI ≥6 months prior to the study (13 mild and 9 moderate to severe TBI) and persistent symptoms on Rivermead Post-Concussion Symptoms Questionnaire at enrollment were compared to 22 age/sex/fitness level -matched healthy control subjects. Beat-to-beat changes in heart rate, BP, and CBF velocity were measured at rest and during a repeated sit-stand maneuver. Hemodynamic variability, dCA, and cardiac BRS were calculated using spectral and transfer function analyses. We found dCA phase in low frequency (LF) range of 0.07-0.195 Hz was lower in subjects with TBI than in control subjects (0.51±0.19 vs. 0.63±0.26, p=0.043) during the resting condition. Among subjects with TBI, the lower dCA phase in LF was correlated with poorer performance on measures of cognitive function (all p<0.05). These findings suggested that subjects with chronic TBI showed impaired dCA which may contribute to persistent cognitive impairment. Cerebrovascular measures may provide a physiological measure to evaluate interventions for chronic TBI and accompanying functional deficits.

压力反射敏感性 (BRS) 和大脑自动调节 (CA) 在血压 (BP) 全身变化期间在维持恒定的脑血流量 (CBF) 方面发挥重要作用。据报道，急性创伤性脑损伤 (TBI) 中 BRS 和 CA 受损，这也可能导致急性 TBI 后的继发性损伤和较差的恢复；然而，它们在慢性阶段的状态仍然难以捉摸。因此，本研究的目的是确定在慢性期单一 TBI 和持续神经系统症状患者的心脏 BRS 和动态 CA (dCA) 是否受损。研究前 22 名患有钝性头部 TBI ≥ 6 个月的受试者（13 名轻度和 9 名中度至重度 TBI）以及在 Rivermead 脑震荡后症状问卷中出现持续症状的受试者与 22 名年龄/性别/健康水平匹配的健康受试者进行比较控制科目。在休息时和重复的坐-站操作期间测量心率、BP 和 CBF 速度的逐次变化。使用光谱和传递函数分析计算血流动力学变异性、dCA 和心脏 BRS。我们发现，在静息状态下，TBI 受试者在 0.07-0.195 Hz 的低频 (LF) 范围内的 dCA 相位低于对照组（0.51±0.19 vs. 0.63±0.26，p=0.043）。在患有 TBI 的受试者中，LF 中较低的 dCA 阶段与认知功能测量的较差表现相关（所有 p<0.05）。这些发现表明患有慢性 TBI 的受试者表现出受损的 dCA，这可能导致持续的认知障碍。脑血管测量可以提供一种生理测量来评估慢性 TBI 和伴随的功能缺陷的干预措施。