Cardiovascular changes induced by cold water immersion during hyperbaric hyperoxic exposure

The present study was designed to assess the cardiac changes induced by cold water immersion compared with dry conditions during a prolonged hyperbaric and hyperoxic exposure (ambient pressure between 1.6 and 3 ATA and PiO(2) between 1.2 and 2.8 ATA). Ten healthy volunteers were studied during a 6 h compression in a hyperbaric chamber with immersion up to the neck in cold water while wearing wet suits. Results were compared with measurements obtained in dry conditions. Echocardiography and Doppler examinations were performed after 15 min and 5 h. Stroke volume, left atrial and left ventricular (LV) diameters remained unchanged during immersion, whereas they significantly fell during the dry session. As an index of LV contractility, percentage fractional shortening remained unchanged, in contrast to a decrease during dry experiment. Heart rate (HR) significantly decreased after 5 h, although it had not changed during the dry session. The changes in the total arterial compliance were similar during the immersed and dry sessions, with a significant decrease after 5 h. In immersed and dry conditions, cardiac output was unchanged after 15 min but decreased by almost 20% after 5 h. This decrease was related to a decrease in HR during immersion and to a decrease in stroke volume in dry conditions. The hydrostatic pressure exerted by water immersion on the systemic vessels could explain these differences. Indeed, the redistribution of blood volume towards the compliant thoracic bed may conceal a part of hypovolaemia that developed in the course of the session.     

Finger skin blood flow in response to indirect cooling in normal subjects and in patients before and after sympathectomy

Finger skin blood flow was measured in 80 healthy subjects, using laser Doppler imaging during basal vasodilatation at a local temperature of 40°C. The response to cooling of the contralateral hand at 15°C was studied. A vasoconstriction index was calculated in all subjects and a nomogram was constructed, taking age into consideration. Compared with these normal subjects, four patients operated on with transthoracic endoscopic sympathectomy due to hand hyperhidrosis showed clearly attenuated responses. The results indicate that the test can be used to assess disturbances in the sympathetic regulation of the peripheral blood flow.     

Skin temperature changes and changes in skin blood flow monitored with laser Doppler flowmetry and imaging: a methodological study in normal humans

The aim of the present study was to elucidate the interrelation between changes in skin temperature and changes in skin blood flow, as measured by laser Doppler techniques. Therefore, 17 healthy volunteers were studied upon immersion of both feet in water of 15°C for 10 min followed by body warming for 30 min. Measure-ments using laser Doppler flowmetry (LDF) were performed from the nailfold of the big toe, while measurements using laser Doppler imaging (LDI) were performed from the dorsum of the foot. Temperatures were recorded simultaneously from the toe tip and the dorsal foot skin. Temperatures at the toe tip were significantly lower than at the dorsal foot skin. Cooling caused decreased values in all parameters, with restitution during indirect heating. There was an exponential interrelation between LDF and temperature readings from the toe owing to very high LDF values at the end of indirect heating. On the dorsum of the foot, relative changes in LDI and temperature showed a linear relationship (r_s=0·65), although LDI values were consistently higher than tem-peratures. It is concluded that temperature readings constitute an ambiguous measure of skin blood flow. On the toe tip, blood flow through opened arteriovenous shunts during indirect heating does not correlate with temperature. Cooling of the foot decreases skin temperature, mainly by heat conduction, whereas skin blood flow is only slightly reduced.     

Muscle force recovery in relation to muscle oxygenation

The aim of this study was to investigate the relative contribution of human muscle reoxygenation on force recovery following a maximal voluntary contraction (MVC). Ten athletes (22·9 ± 4·0 years) executed a plantar‐flexion sequence including two repeated MVCs [i.e. a 30‐s MVC (MVC₃₀) followed by a 10‐s MVC (MVC₁₀)] separated by 10, 30, 60, 120 or 300 s of passive recovery. A 10‐min passive recovery period was allowed between each MVC sequence. This procedure was randomly repeated with two different recovery conditions: without (CON) or with (OCC) arterial occlusion of the medial gastrocnemius. During OCC, the occlusion was maintained from the end of MVC₃₀ to the end of MVC₁₀. Muscle oxygenation (Near‐infrared spectroscopy, NIRS, [Hb_diff]) was continuously measured during all MVC sequences and expressed as a percentage of the maximal changes in optical density observed during MVC₃₀. Maximal Torque was analysed at the start of each contraction. Torque during each MVC₁₀ was expressed as a percentage of the Torque during the previous MVC₃₀. Torque recovery was complete within 300 s after MVC₃₀ during CON (MVC₁₀ = 101·8 ± 5·0%); 88·6 ± 8·9% of the Torque was recovered during OCC (P = 0·005). There was also a moderate correlation between absolute level of muscle oxygenation and Torque (r = 0·32 (90% CI, 0·09;0·52), P = 0·02). Present findings confirm the role of human muscle oxygenation in muscular force recovery during repeated‐maximal efforts. However, the correlation between absolute muscle oxygenation and force level during recovery is only moderate, suggesting that other mechanisms are likely involved in the force recovery process.     

Determination of blood flow in the finger using near-infrared spectroscopy

Wavelengths in the near-infrared range have much better penetrance in organic substances than visible light. We used near-infrared spectroscopy to determine non-invasively blood flow in the fingertip. We used laser Doppler technology to measure skin blood flow as a comparison procedure. We performed several manoeuvres to change blood flow. These included restriction of flow, thermal stimulation and post-occlusion hyperaemia. Near-infrared measurements had coefficients of variation of 10–15% at the various wavelengths, contrasting with variability of 30–40% with laser Doppler measurement. With restriction of blood flow, there was a downward shift in the absorbance curve. With thermal stimulation and with post-occlusion hyperaemia, there was a rise in the curve. The flow-induced shifts in the absorbance curve were particularly pronounced in the range of 850–970 nm. The correlation between absorbance values and laser Doppler-determined blood flow was also highest in this range, averaging about 0·69 (n = 625). Near-infrared spectroscopy can therefore be used to scan the fingertip. The absorbances obtained do reflect changes in blood flow. There is a correlation with skin blood flow, although near-infrared measurements are affected by blood flow in the full breadth of the finger, not just the skin. We can measure this blood flow with significant reproducibility. It may be possible to use near-infrared spectroscopy to measure the concentration of individual blood components.     

通过1H磁共振波谱和经颅多普勒超声观察急性脑梗死患者早期代谢物及血流动力学的变化

目的　利用1H磁共振波谱 (1HMRS)和经颅多普勒超声 (TCD)研究脑梗死早期代谢物、梗死大小、血流速度、血流量的变化及与临床神经功能缺损的相互关系 ,为脑梗死早期诊断提供更多信息。方法　15例急性脑梗死患者行1HMRS和TCD检查 ,同时对临床神经功能缺损进行评分 ,计算脑梗死灶容积V(ml)。1HMRS选择PRESS序列 ,检测比较病灶区和对侧相应部位N 乙酰天门冬氨酸 (NAA)、乳酸 (Lac)、肌酸 (Cr)、含胆碱化合物 (Cho)各谱线下面积的变化。TCD探测颅内动脉血流收缩期峰速 (Vs)、峰值平均速度(Vm)等 ,并由此估算病灶责任血管血流量。结果　梗死病灶中NAA和Cr含量、Vm、血流量与对侧相应部位比较下降明显 ,差异有显著意义 (P <0 .0 5) ;在病灶侧均可检测到倒置的Lac双峰。NAA与Cr、Lac、V之间存在相关性 (r分别为 0 .56,-0 .55,-0 .68)。Lac与V之间存在相关性 (r =0 .55)。多元直线回归分析显示 ,急性脑梗死灶内NAA的减少与梗死灶容积V之间存在相互依存关系 (t =-3 .3 10 ,P =0 .0 0 6)。结论　脑梗死早期代谢物和血流动力学发生了较明显的变化。血流速度的减慢、血流量的不足是导致脑梗死的直接原因。而Lac的出现是早期脑缺血灵敏性极高的指标 ;NAA为反映梗死灶容积大小的最主要因素     

Effect of local cold provocation on systolic blood pressure and skin blood flow in the finger

Demonstration of increased vascular cold reactivity in patients with Raynaud’s syndrome is difficult. For medico‐legal reasons, it is important to get objective measures of vasospasm in these patients. Evaluation of the degree of vasospasm also provides prognostic information which is useful for patient management. In this study, we compare two methods of arterial circulation measurement. The laser Doppler scanning is a new method, which uses the recently developed laser Doppler perfusion imaging (LDPI) instrument. The aim of the present study was to compare the effect on finger skin blood flow measured with LDPI with changes in finger systolic blood pressure during local cold provocation. The effect of such provocation, skin blood flow and systolic blood pressure, were studied in 15 healthy controls. Six patients with known traumatic vasospastic disease (TVD) were also tested with both methods. Finger skin blood flow was measured with LDPI on the distal phalanx of the index finger of the left hand, every minutes during 6 min of local heating at 40°C followed by local cooling for 3 min at 15°C and then for 3 min at 10°C. Finger systolic blood pressure was measured with strain‐gauge method before and after local cooling to 10°C with a cuff perfused with water of desired temperature. The test was performed in the same finger within a week of the laser Doppler scanning. Local finger cooling to 15°C and 10°C caused a significant decrease in blood flow, most marked at 10°C. There was, however, no correlation between the decrease in blood flow and blood pressure. In the TVD‐patients decreases in skin blood flow were similar compared with the healthy controls. In contrast, the changes in systolic blood pressure, were outside normal range (systolic quotient <0·65) in five of the six patients (83%), and also in 11 of the 15 healthy controls (73%). In conclusion, there is no correlation between the decrease in finger skin blood flow and systolic blood pressure during local cold provocation. For diagnosis of traumatic vasospastic disease (TVD), local cold‐induced changes in finger systolic blood pressure seems superior to changes in skin blood flow, but the ideal clinical method for demonstrating increased cold‐induced vasospasm is, however, still lacking.     

Supraorbital cutaneous blood flow rate during carotid endarterectomy

BACKGROUND: The supraorbital skin region is supplied by the supraorbital artery, which is a branch of the internal carotid artery. The supraorbital cutaneous blood flow rate may therefore be influenced by changes in the internal carotid artery flow during carotid endarterectomy. METHODS: The supraorbital cutaneous blood flow rate was measured by the application of heat to the skin and following the subsequent dissipation of the heat in seven patients undergoing carotid endarterectomy. At the same time, the oxygenation in the right and left frontal region was monitored by near-infrared spectroscopy (NIRS). RESULTS: During cross-clamping of the carotid artery, the ipsilateral NIRS-determined frontal oxygenation tended to decrease [67 +/- 13% to 61 +/- 11% (P = 0.06); contralateral 68 +/- 11% to 66 +/- 8%] as did the supraorbital cutaneous blood flow rate from 56 +/- 23 to 44 +/- 7 ml 100 g(-1) min(-1). With the opening of the external carotid artery, the NIRS-determined frontal oxygenation reversed to 66 +/- 8% (P<0.05) on the ipsilateral side, with no significant change on the contralateral side and the supraorbital cutaneous blood flow rate increased to 53 +/- 11 (P<0.05). Opening of the internal carotid artery did not significantly affect the NIRS (67 +/- 8% and 69 +/- 9%; ipsilateral, contralateral), but the supraorbital cutaneous blood flow rate increased to 88 +/- 10 ml 100 g(-1) min(-1) (P<0.001). CONCLUSION: Cross-clamping of the internal carotid artery affects the supraorbital cutaneous blood flow rate as well as the frontal lobe oxygenation.     

近红外光谱技术用于运动和运动想象时大脑皮质血氧反应监测的研究

目的:使用近红外光谱技术监测运动和运动想象时大脑血氧反应的变化以探讨运动和运动想象运用于脑卒中偏瘫患者康复治疗和评价的理论依据。方法:选取64名健康大学生,随机分为两组:运动组32名,运动想象组32名。运用近红外光谱技术监测运动组受试者安静时和运动时大脑皮质的血氧代谢相应变化情况,以及运动想象组受试者安静时和运动想象时大脑皮质的血氧代谢相应变化情况,并将监测结果进行统计学比较和分析。结果:①运动时,大脑氧合血红蛋白和总血红蛋白明显增加,而还原血红蛋白下降。②运动想象时,也呈现大脑氧合血红蛋白和总血红蛋白增加,而还原血红蛋白下降。与安静时进行比较,差异均有显著性意义。结论:运动想象与实际运动同样会提高大脑皮质血氧饱和度,改善相应区域大脑皮质血氧供应。     

Effects of blood flow restriction duration on muscle activation and microvascular oxygenation during low‐volume isometric exercise

The purpose of the investigation was to observe how varying occlusion durations affected neuromuscular activation and microvascular oxygenation during low‐volume isometric knee extension exercise. Healthy, recreationally active males performed isometric knee extension at a variety of submaximal intensities under different blood flow restriction (BFR) occlusion durations. The occlusion pressure (130% SBP) was applied either 5 min prior to exercise (PO), immediately prior to exercise (IO) or not during exercise (CON). Surface electromyography (sEMG) and near‐infrared spectroscopy (NIRS) was used to record the neuromuscular activation and microvascular oxygenation of the knee extensors during exercise. No difference in sEMG was observed in the vastus lateralis or vastus medialis during any exercise condition or any submaximal intensity. PO elicited greater microvascular deoxygenation (deoxy‐[Hb + Mb]) compared to CON (P≤0·05) at all submaximal intensities and also compared to IO at 20% maximal voluntary contraction (MVC). IO resulted in a greater deoxy‐[Hb + Mb] response during low‐intensity exercise (20% and 40% MVC) compared to CON (P≤0·05). These findings suggest that applying BFR 5 min before exercise can enhance the exercise‐induced metabolic stress (i.e. deoxy‐[Hb + Mb]), measured via NIRS, during low‐intensity exercise (20% MVC) compared to applying BFR immediately prior to exercise. Furthermore, the increased metabolic stress observed during IO is attenuated during high‐intensity (60% MVC, 80% MVC) exercise when compared to CON conditions. Knowledge of the changes in exercise‐induced metabolic stress between the various occlusion durations may assist in developing efficient BFR exercise programmes.     

Peripheral blood cell changes in response to acute hypoglycaemia in man

Peripheral white and red blood cell changes were studied in response to acute insulin-induced hypoglycaemia in six normal, six splenectomized and five sympathectomized (tetraplegic) subjects. The normal subjects were restudied during beta (propranolol) and beta 1-selective (metoprolol) adrenergic blockade. In the normal subjects a lymphocytosis immediately followed the acute hypoglycaemic reaction (R) with a neutrophilia 2 h later. The early lymphocytosis was absent in sympathectomized subjects (P less than 0.001) and reduced under beta blockade (P less than 0.02) in normal subjects, indicating mediation via an adrenergic mechanism. The later neutrophilia from R + 60 min was not abolished by adrenergic blockade or preceding sympathectomy; the enhanced response with propranolol was associated with an elevated plasma cortisol. Haemoglobin, packed cell volume and total erythrocyte count rose maximally at R in all groups except the sympathectomized subjects in whom all parameters declined progressively from basal values. These peripheral erythrocytes changes appear to be mediated via an adrenergic mechanism which is unaffected by beta adrenergic blockade and which does not involve splenic contraction.     

Muscle metabolism in patients with polymyositis simultaneously evaluated by using 31P-magnetic resonance spectroscopy and near-infrared spectroscopy

Simultaneous measurements of muscle energy metabolism using (31)P-magnetic resonance spectroscopy ((31)P-MRS) and the kinetics of muscular oxygen metabolism using near-infrared spectroscopy (NIRS) were conducted in polymyositis (PM) patients. The subjects were 12 PM patients (age 45 +/- 12 years) and 12 normal controls (age 41 +/- 12 years). The muscle phosphocreatine (PCr) index and intracellular pH (pHi) were determined with (31)P-MRS and the changes in intramuscular oxygenated (oxy-Hb), deoxygenated (deoxy-Hb), and total haemoglobin (total Hb) were evaluated with NIRS . The pHi and PCr index before steroid therapy in PM patients were significantly lower during exercise than in normal controls, and their recovery was statistically significantly delayed compared with the controls. The pattern of changes in NIRS over time before steroid therapy in PM patients differed from that in normal controls. There were smaller changes in deoxy-Hb and oxy-Hb during exercise, and total Hb decreased during exercise. In contrast, the kinetics of muscular metabolism after steroid therapy showed changes similar to those seen in normal controls. Simultaneous (31)P-MRS and NIRS measurements to determine the kinetics of muscular metabolism are expected to be useful as a noninvasive approach for the evaluation of treatment effects in PM patients.     

Femoral artery blood flow and its relationship to spontaneous fluctuations in rhythmic thigh muscle workload

Background and aim: Limb femoral arterial blood flow (LBF) is known to increase linearly with increasing workload under steady‐state conditions, suggesting a close link between LBF and metabolic activity. We, however, hypothesized that sudden physiological and spontaneous changes in exercise rhythm, and consequently workload temporarily alter blood flow to the working muscle. LBF and its relation to fluctuations in the contraction rhythm and workload were therefore investigated. Methods: LBF, measured by Doppler ultrasound, and the achieved workload, were continuously measured in nine subjects, aiming to perform steady‐state, one‐legged, dynamic knee‐extensor exercise at 30 and 60 contractions per minute (cpm), at incremental target workloads of 10, 20, 30 and 40 W. Results: In agreement with previous findings, LBF increased positively and linearly (P<0·05) with increasing target workload. However, LBF was inversely and linearly related (P<0·05) to the actually achieved workload, when measured over 60 consecutive contraction–relaxation cycle bouts, for each target intensity at 30 and 60 cpm respectively. Thus any sudden spontaneous increase or decrease in the achieved workload transiently altered the relationship between LBF and the achieved workload. The influence upon the magnitude of LBF, due to fluctuations in the achieved workload from the target workload, was furthermore similar between target workload sessions at 30 and 60 cpm respectively. LBF was, however, not associated with variations in the contraction frequencies. Conclusions: These findings indicate that a transient sudden increase in the workload more rapidly impedes LBF and that vasodilatation may be elicited to restore the intensity related steady‐state LBF response in relation to the average metabolic activity.     

Age-related differences in the endogenous analgesic response to repeated cold water immersion in human volunteers

Recent animal studies using stress-induced analgesia have suggested a general age-related decline in endogenous pain inhibitory systems. The aim of the current study was to examine age-related differences in the magnitude of endogenous analgesia in human volunteers, using psychophysical measures of neuroselective electrical, and thermal CO(2) laser induced pain thresholds, before, immediately after and 1 h after repeated cold water immersion of the hand. Sensory detection thresholds did not differ between age groups indicating that the functional integrity of primary afferent sensory fibres appears to be intact in older people. Consistent with many previous studies, older adults required a higher intensity of noxious stimulation in order to first report the presence of pain. The cold water immersion task was effective in eliciting a powerful analgesic response, regardless of age; pain thresholds were shown to increase by up to 100% immediately after the cold pressor test. This effect was relatively transient with thresholds returning to baseline within 1 h. The magnitude of analgesic response, however, was found to be significantly less in older people. Age differences in the efficacy of endogenous analgesic systems may be expected to reduce the ability of older adults to cope with severe persistent pain states and may help explain some of the variation in the literature on pain report.     

A comparison of changes in rhythms of sacral skin blood flow in response to heating and indentation

OBJECTIVE: To differentiate blood flow control mechanisms associated with indentation from those associated with heating and to discern heat-induced and pressure-induced changes by comparing the effect of externally applied stress on skin blood flow (SBF) to the response to externally applied heat. DESIGN: Repeated-measures design. SETTING: A university research laboratory. PARTICIPANTS: Ten healthy, young adults (5 men, 5 women; mean age +/- standard deviation, 30.0+/-3.1y). Intervention Incremental heat (35 degrees -45 degrees C, 1 degrees step/min) and pressure (0-60 mmHg, 5 mmHg step/3 min) on the sacrum using a computer-controlled indenter. Sessions for heat and pressure protocols were separated by 7+/-2 days. MAIN OUTCOME MEASURES: We used a Laserflo Blood Perfusion Monitor 2 and Softip pencil probe to measure capillary blood perfusion and wavelet analysis to decompose the blood flow signal. The power spectrum was divided into 5 ranges corresponding to metabolic, neurogenic, myogenic, respiratory, and cardiac control mechanisms. The average relative (ie, normalized) power in each frequency range was computed to determine of the relative contribution of each control mechanism. RESULTS: Power in the myogenic frequency range was higher after incremental pressure and lower after incremental heating, whereas power in the metabolic frequency range was lower after incremental pressure and higher after incremental heating ( P <.01). Mean blood flow decreased as pressure increased from 0 to 15 mmHg; mean blood flow increased as pressure increased from 15 to 60 mmHg. CONCLUSIONS: SBF, as recorded by the laser Doppler, suggests that there may be a myogenic control mechanism mediating blood flow after incremental tissue loads and that a metabolic control mechanism may mediate blood flow after heat application to the tissue. The study of local blood flow control mechanisms and their response to pathomechanical perturbations may be possible using wavelet analysis of blood flow oscillations. More research is needed to establish the clinical utility of these findings in the development of support surfaces intended to reduce the risk of developing pressure ulcers.     

中风后非流畅型失语症患者语言激活时左前额皮层血氧反应及血流动力学变化:NIRS的研究

目的：探讨NIRS检测认知激活状态大脑功能性变化的临床应用价值。方法：运用近红外光谱(near infrared spectroscopy，NIRS)技术监测脑血管病(CVD)失语症组、CVD非失语症组及正常人组共36名被试语言活动时大脑左前额氧代谢和血流动力学的相应变化，并将CVD合并非流畅性失语症患者的参数变化与正常的成年人及脑血管病未合并失语症患者的变化进行了比较。结果：①NIRS参数的变化在CVD非失语症组及正常人组中均各有50％被试呈现氧合血红蛋白和总血红蛋白同时上升。而还原血红蛋白无明显改变或稍有下降。②CVD失语症组中50％的被试、CVD非失语症组与正常人组各有16．7％被试显示随着氧合血红蛋白和总血红蛋白的增加，还原血红蛋白亦有所增加。结论：语言激活在各组被试的左前额皮层的脑血氧反应和血流动力学变化呈现多样性，失语症患者的还原血红蛋白随着氧合血红蛋白和总血红蛋白的增加亦有所增加，提示失语病人的左前额皮层在语言任务期间比非失语病人利用更多的氧。     

The effect of phenylephrine on arterial and venous cerebral blood flow in healthy subjects

Aim: Sympathetic regulation of the cerebral circulation remains controversial. Although intravenous phenylephrine (PE) infusion reduces the near‐infrared spectroscopy (NIRS)‐determined measure of frontal lobe oxygenation (S_cO₂) and increases middle cerebral artery mean blood velocity (MCA V_mean), suggesting α‐adrenergic‐mediated cerebral vasoconstriction, this remains unconfirmed by evaluation of arterial and venous cerebral blood flow. Methods: We determined S_cO₂, MCA V_mean, and right internal carotid artery (ICA) and internal jugular venous (IJV) blood flow (duplex ultrasound) during infusion of PE in eight supine young healthy men [26 (3) years, 177 (7) cm and 74 (8) kg; mean (SD)]. Results: Compared with saline, during infusion of PE, mean arterial pressure increased 26 ± 3% (mean ± SE) and MCA V_mean by 4·8 ± 1·9% (P<0·05), while S_cO₂ decreased by 13·7 ± 3·7% (P<0·05) with no significant changes in the arterial oxygen or carbon dioxide tensions. ICA blood flow did not change significantly in response to PE administration (351 ± 12 versus 373 ± 21 ml min^?1; P = 0·236), while IJV blood flow increased (443 ± 57 versus 507 ± 58 ml min^?1; P = 0·023). Conclusions: These findings confirm that PE induces a reduction in S_cO₂ measured by NIRS and causes an increase in MCA V_mean indicative of cerebral arterial vasoconstriction, although ICA was preserved and IJV increased. These results suggest that a decrease in S_cO₂ during infusion of PE reflects an altered cerebral contribution of arterial versus venous blood to the NIRS signal, although we cannot rule out that an effect of PE on skin blood flow is important.     

经颅多普勒超声监测OSAS患者睡眠呼吸暂停期间的脑血流变化

目的采用经颅多普勒超声(TCD)对阻塞性睡眠呼吸暂停综合征(OSAS)患者的睡眠呼吸暂停期间脑血流变化进行监测。方法选取符合OSAS诊断标准的50例患者,并选取同时期就诊的正常人50例作为对照组,对上述研究者采用TCD仪2 MHz脉冲波探头监测大脑中动脉平均血流速度(MFV),观察有无出现狭窄、闭塞、血流频谱的改变。结果 50例患者中,TCD检查共发现39例异常,发生率为78.0%(39/50),其中有29例为血流速度减慢,发生率为58.0%(29/50),9例为血管狭窄,发生率为18.0%(9/50);12例正常,概率为24.0%(12/50)。50例对照组中,共有10例患者出现TCD检查异常,发生率为20.0%(10/50),OSAS患者TCD异常检出率相比于正常对照组显著升高(P0.01)。中重度OSAS患者的脑血流异常情况发生率显著高于轻度患者。随访1年,OSAS组共出现8例脑血管事件,发生率为16.0%(8/50),对照组仅有1例,发生率为2.0%(1/50),组间比较差异有统计学意义(P0.05)。OSAS患者屏气前后大脑中动脉血流速度均相对于正常者升高(P0.01),屏气后的增加率明显低于正常人群(P0.01),随着OSAS疾病的严重程度上升,其屏气前后大脑中动脉血流速度明显上升(P0.05)。结论 OSAS患者由于长期的缺氧而使其容易出现动脉硬化改变,引起脑血流下降或是出现脑动脉狭窄。OSAS越严重,则出现脑血流动力学的异常发生率也就越高,越容易发生脑血管事件。