Drug-induced alterations in cochlear blood flow as recorded by the laser Doppler flowmeter

A number of clinical entities may result from a decrease in inner ear blood flow. Investigators have attempted to determine a relationship between decreased blood flow and such entities. In this article, we shall relate the effects of administration of drugs in animal models on cochlear blood flow, using the laser Doppler flowmeter.     

A comparison of laser Doppler and intravital microscopic measures of cochlear blood flow

Many inner ear disorders may be caused by alterations in cochlear blood flow (CBF). However, each measurement technique used to monitor CBF has limitations in examining the relationship between otopathologic states and blood flow. This study investigates laser Doppler flowmetry (LDF) and its fundamental drawback: the unknown relationship of LDF output to actual CBF. LDF readings are directly compared with concurrent intravital microscopy (IVM) measures of erythrocyte velocity in the lateral wall of the guinea pig cochlea. Positive end expiratory pressure, spontaneous respiration of 5% and 10% carbon dioxide, phenylephrine, and direct electrical stimulation of the cochlea were used to manipulate CBF. High, positive correlations were found between simultaneous LDF and IVM measurements of CBF. In addition, the study demonstrated that current microdissection techniques used to perform IVM do not cause changes in CBF. IVM measurements of CBF are a more sensitive indicator of CBF changes than are LDF measures. Despite the high correlation between measurement techniques within a single manipulation, simultaneous LDF and IVM measurements differed between manipulations. This may reflect regional changes in CBF affected by these manipulations and differences in the sampled vascular beds contributing to these two measures. It is unlikely that a single calibration factor can be defined that would allow the conversion of LDF output to actual units of blood flow across different manipulations used to alter CBF.     

Tendon blood flow assessed by laser Doppler flowmetry.

Laser Doppler flowmetry was applied to the surface of both achilles tendons in 10 mature albino rats. A prompt decline in flux values by about 60% was noted when the blood supply to the limb was interrupted by clamping the femoral artery. Increased values, indicating a hyperaemic reaction, often followed release of the clamp. Flux values reached a minimum after death, and this was used as a baseline measurement to eliminate Doppler signals generated by factors unrelated to flow. Although readings in two animals had to be omitted for technical reasons, the present study shows that reliable laser Doppler flow readings can be obtained from the surface of a tendon. The response to reversible ischaemia is prompt and reproducible. Laser Doppler flowmetry may offer a new approach to the assessment of tendon blood flow at the microvascular level.     

Serial measurement of blood flow in expanded tissue by laser Doppler velocimetry

This study provides additional information about changes in blood flow in expanded tissue as measured by laser Doppler. Five one-kilogram albino Hartley guinea pigs were implanted with commercially available hemispheric expanders. The expanders were inflated every 3 days on four successive occasions. Blood flow measurements were taken on each animal just before each inflation, immediately after inflation, and then at 1, 2, 3, 4, and 24 hours after expansion. Measurement of flow changes immediately after each inflation of the expander showed that, initially, blood flow in the tissue overlying the expander recovered quickly, but as the expansion process was continued, the flow did not return to baseline values so rapidly. This might be an indication that tissue expansion in patients could be carried out more rapidly during the initial inflations, with increasing recovery periods between inflations as the expansion process continued.     

The assessment of skin blood flow in peripheral vascular disease by laser Doppler velocimetry

The helium-neon laser Doppler (LD) is designed to measure skin blood flow velocity (SBFV). Flow velocity and pulse wave amplitude are expressed in millivolts (mv) relative to a zero-flow reference. The authors have reviewed their initial experience in ten persons (20 limbs) without peripheral vascular disease (PVD, group I) and nine patients (12 limbs) with severe PVD (group II). The finger, palm, great toe, and forehead had a significantly (P less than 0.05) greater flow velocity than the plantar and dorsal foot, distal and proximal leg, thigh, chest, arm, and forearm. Baseline and hyperemic SBFV, measured at the great toe, were compared in groups I and II. In group I, the baseline SBFV (mv, mean +/- standard error of the mean (SEM] in the great toe was 197 +/- 38 compared with 67 +/- 12 in group-II patients (P less than 0.05). The pulse wave amplitude (mv, mean +/- SEM) was 77 +/- 14 in group I and 5.4 +/- 1.1 in group II (P less than 0.05). The time to maximal hyperemic response (seconds, mean +/- SEM) in group I was 18 +/- 1.5 compared with 150 +/- 14 in group II (P less than 0.05). LD is a sensitive indicator of changes in SBFV, allowing differentiation between normal persons and patients with PVD. The LD tracing in patients with PVD is characterized by a baseline SBFV that is significantly less than normal and also by the attenuation or absence of pulse waves. The diagnostic accuracy is enhanced by the use of reactive hyperemia.     

Assessment of blood flow through the lung using laser Doppler flowmetry

The value of laser Doppler flowmetry in measuring blood flow through the lung was assessed comparing it with flow measured by electromagnetic flowmetry. This was an experimental laboratory-based prospective study performed in an approved University animal research facility. Ten beagle dogs were used. Simultaneous measurement of pulmonary blood flow by laser Doppler flowmetry and electromagnetic flowmetry was carried out at varying degrees of pulmonary artery constriction. There was a linear relationship between the two methods of assessing blood flow (regression equation: y = 0.9x + 5.5; p = .00001) using a least-squares, best fit, straight line analysis (160 data points). The results of this study demonstrate that laser Doppler flowmetry provides an accurate indicator of pulmonary blood flow, which in practice is both simple and reproducible.     

Clinical evaluation of laser Doppler blood flow measurements in free flaps

Adequate assessment of blood flow in free flaps with early detection of circulatory failure is an unresolved clinical problem. In 23 patients undergoing microvascular free tissue transfers, laser doppler blood flow measurements and clinical observations were made hourly for the first two postoperative days. There was 1 flap failure in 6 instances in which it was clinically necessary to intervene, by reexploration or draining a hematoma, to ensure the survival of the flap. It was hypothesized that the laser doppler measurements would predict future clinical events. However, it was found that although these measurements did correlate with clinical observations, they did not predict them and were actually less accurate in indicating the need for clinical intervention or the final outcome of the free flap procedure.     

Intraoperative assessment of blood flow and tissue viability in small-bowel ischemia by laser Doppler flowmetry

Laser Doppler flowmetry (LDF) was used for intraoperative assessment of blood flow and tissue viability in 23 patients with small-bowel ischemia, and the signal levels in ischemic bowel were compared with previously obtained reference values from normal ileum and jejunum. The average LD signal was 6.8 +/- 2.9 V in nonischemic bowel, 0.3 +/- 0.2 V in segments with macroscopically irreversible ischaemia and 2.1 +/- 1.2 V in segments with clinically uncertain viability. In 12 cases with strangulated bowel it was possible, following LDF, to avoid resecting nine of ten bowel segments with clinically uncertain viability. In four of the six patients with mesenteric vascular occlusion, LDF indicated that clinical judgement had underestimated the extent of severe ischemia. Among the five cases of iatrogenic ischemia there was one failure, with postoperative irreversible ischemia and anastomotic leakage. LDF is concluded to be a useful method for intraoperative assessment of intestinal blood flow in patients with small-bowel ischemia and it provides substantial information on tissue viability affecting surgical strategy.     

Acetazolamide produced blood flow velocity changes measured by laser Doppler in gerbils with reduced CBF

Summary The effect of acetazolamide on the cerebral blood flow was studied in gerbils with unilateral carotid ligation. According to the effect of ligation the animals were divided into three groups: first group — the reduction more than 70%, second — CBF reduction 30–70% and the third group — CBF reduction less than 30%.The effect of acetazolamide administration was closely related to the effect of carotid ligation. More reduction of CBF was produced by carotid ligation, less increase of CBF after acetazolamide injection was noticed. The acetazolamide vascular reserve test was found a sensitive and useful method for detecting even modest reduction of vascular reserve in animals with slight — less than 30% CBF decrease following carotid ligation.     

Correlates of human sperm motility assessed by laser Doppler spectroscopy

The sperm motility characteristics of 140 men (percentage motile and average velocity of all sperm in motion; percentage progressive and the average velocity of sperm swimming more than 15 microns/sec) were determined using a laser-Doppler technique and correlated with other aspects of sperm quality, including the concentration and the proportion of abnormal and dead sperm in the ejaculate. In addition, the influence of the length of the period of abstinence, the viscosity of seminal plasma and the volume of the ejaculate were also assessed. The four motility characteristics were all highly correlated with each other. The magnitude of all four parameters increased in an exponential fashion with increasing sperm number up to 400 x 10(6) per ejaculate. At higher numbers, no further improvement in motility was observed. Moreover, increasing sperm number was associated with a decline in the proportion of sperm exhibiting abnormalities in morphology but with an increase in viable sperm 30 min after ejaculation. The relative viscosity of the ejaculates had generally no influence on sperm motility. In contrast, certain of the sperm motility characteristics, including the average velocity, were significantly negatively correlated with the length of the abstinence period.     

Human sperm motility--enhancement and inhibition measured by laser Doppler spectroscopy

Laser Doppler spectroscopy is an excellent instrument to measure motility parameters of human spermatozoa. Experiments have been performed by the aid of a now commercially available instrumental setup called LAZYMOT to study enhancement and inhibition as well as influences of different physical treatments on the motility of human spermatozoa. The motility enhancing influence of Kallikrein (up to 40% with 4 KU/ml) and prostaglandin E2 could be proven, thereby verifying some sort of mechanism of action within the Kallikrein-Kinin system. Furthermore tested substances in this context were bradykinin (no effect), caffeine (enhancement), salicylic acid (slight decrease), and other prostaglandins (no effect). The influence of washing, centrifugation, resuspension liquid, and temperature has been examined. It turned out that the lowest motility degradation is to be achieved by washing twice at a pH value of 7.4 at forces of 200 g for 10 min each time. The optimal temperature during this process and the measurements thereafter was found to be 36 degrees C. Unsaturated fatty acids like arachidonic acid have been found to be very strong motility inhibiting substances, which can totally block any movement of spermatozoa.     

Measurement of blood flow in the rotator cuff using laser Doppler flowmetry

The aim of this study was to define the microcirculation of the normal rotator cuff during arthroscopic surgery and investigate whether it is altered in diseased cuff tissue. Blood flow was measured intra-operatively by laser Doppler flowmetry. We investigated six different zones of each rotator cuff during the arthroscopic examination of 56 consecutive patients undergoing investigation for impingement, cuff tears or instability; there were 336 measurements overall. The mean laser Doppler flowmetry flux was significantly higher at the edges of the tear in torn cuffs (43.1, 95% confidence interval (CI) 37.8 to 48.4) compared with normal cuffs (32.8, 95% CI 27.4 to 38.1; p = 0.0089). It was significantly lower across all anatomical locations in cuffs with impingement (25.4, 95% CI 22.4 to 28.5) compared with normal cuffs (p = 0.0196), and significantly lower in cuffs with impingement compared with torn cuffs (p < 0.0001). Laser Doppler flowmetry analysis of the rotator cuff blood supply indicated a significant difference between the vascularity of the normal and the pathological rotator cuff. We were unable to demonstrate a functional hypoperfusion area or so-called 'critical zone' in the normal cuff. The measured flux decreases with advancing impingement, but there is a substantial increase at the edges of rotator cuff tears. This might reflect an attempt at repair.     

Comparison of two laser Doppler flowmetry systems for bone blood flow analysis

Summary The development of laser Doppler flowmetry (LDF) has provided a real-time, reliable method for monitoring capillary perfusion in multiple tissues. LDF has potential for the experimental and clinical assessment of bone blood flow. To compare the accuracy and ease of use of two commercially available laser Doppler flowmeters with different mechanisms for processing the Doppler-shifted component of light, estimates of bone blood flow were obtained in a sheep model using the two systems, and the values derived then compared with estimates of bone blood flow also obtained in a sheep using the technique of injection of labeled microspheres. The single-channel laser Doppler flowmeter, the LD 5000, processes the reference and Doppler-shifted beams on the surface of a single photodetector using optical heterodyning for measurement. The dual-channel flowmeter, the Periflux 2, uses two optical fibers to transmit reference and Doppler-shifted light to two separate photodetectors. The differential amplification and detection system improves the signal-to-noise ratio. Measurement of both metaphyseal (cancellous) and diaphyseal (cortical) blood flow using both LDF systems was compared with values obtained with an injection of⁸⁵Sr-labeled microspheres in three sheep. The LDF measurements were repeated after occlusion of the left femoral artery, and a⁴⁶Sc microsphere injection was performed prior to animal sacrifice. Two of the animals developed vasomotor instability, resulting in poor correlation between the measurements obtained with the Periflux 2, which is motion sensitive, and the values obtained with the microsphere method. High correlation was apparent in two of the three animals for the LD 5000 and the microsphere values. Four additional sheep were evaluated using only the Periflux 2, and the data collected yielded R values of 0.6–0.98. Both the single- and dual-channel LDF systems offer accurate assessment of local cortical and cancellous bone blood flow.     

The use of laser Doppler flowmetry to evaluate anterior cruciate blood flow

The purpose of this study was to quantitate the blood flow of the anterior cruciate ligament in vivo. Functional flow was evaluated using laser Doppler flowmetry (LDF), for which the output signal, blood cell flux (BCF), is expressed in terms of volts. Ten patients undergoing routine arthroscopic surgery with clinically intact anterior cruciate ligaments were selected at random for participation in the study. Under arthroscopic visualization, a 2.2-mm probe was placed through a trocar sleeve into the anterior cruciate ligament after the arthroscopic procedure. Pulsatile flow within the ligament was observed in all patients. The mean maximum BCF value ranged from 101 to 274 mV; SD range was +/- 3-9 mV. The mean minimum BCF ranged from 75 to 197 mV; SD range was +/- 0 to 9 mV. Laser Doppler flowmetry offers significant promise as a method for measurement of in vivo anterior cruciate and cruciate substitution blood flow.     

Microvascular testicular blood flow as evaluated by laser Doppler flowmetry after the surgical induction of varicocele

This study was conducted to evaluate the changes in microvascular testicular blood flow (microvascular TBF), which may be associated with varicocele. The pathology was developed through partial ligation of left renal vein in 4 groups of rats. Controls of each group underwent sham surgery. It was observed that microvascular TBF dropped and its vasomotion became inhibited once the left renal vein was partially ligated as studied by laser Doppler flowmetry (LDF). Four to five minutes later, blood flow rose to the pretreatment level and that of controls. Vasomotion reappeared with a uniform frequency and amplitude. At different periods of varicocele bearing (1, 3, 6, and 14 weeks) microvascular TBF was reevaluated. Vasomotion appeared intact without any abnormalities in the 4 groups. To examine the response of testicular microvasculature after surgical creation of the varicocele to pharmacological stimulation another group of animals received human chorionic gonadotropin (hCG) treatment 6 weeks after varicocele creation. Vasomotion was inhibited in these animals. In conclusion, LDF is a suitable tool to evaluate microvascular TBF in vivo. It can detect acute changes in blood flow that may happen at surgical induction of varicocele. In addition, the vasculature of the testis with a surgically induced varicocele can still respond to hCG stimulation.     

Skin blood flow: a comparison of transcutaneous oximetry and laser Doppler flowmetry

In normal limbs skin blood flow (SBF) falls on standing, but in ischaemic limbs there is a characteristic blush on dependancy. We studied the effect of changing posture in a range of ischaemic limbs, using two non-invasive techniques--laser Doppler (LD) and transcutaneous oximetry (TcPO2). Warmed TcPO2 and LD probes were placed over the first metatarsal cleft and SBF recorded with the limb horizontal, dependant and elevated. Ankle to brachial pressure ratios (A:B) were also measured. Twelve patients with lower limb ischaemia, mean A:B ratio 0.5 +/- 0.21 (+/- S.D.) were compared with 21 asymptomatic controls, mean A:B ratio 1.2 +/- 0.15. In the controls, neither TcPO2 nor LD values changed significantly with limb position. Both flux and oxygen tension were significantly lower in ischaemic limbs in all positions; on lowering the ischaemic limb, flux unexpectedly rose to 23.5 +/- 17.7 V from a mean of 14 + 9.0 V (horizontal). Both TcPO2 and LD correlated well with A:B ratio in two positions: horizontal r (TcPO2) = 0.73, r(LD) = 0.57; elevated r(TcPO2) = 0.78, r(LD) = 0.68. Overall there was a highly significant correlation between LD and TcPO2 (r = 0.6, P less than 0.001, Student's test), but this was strongest in the elevated position (r = 0.87, P less than 0.001). LD and TcPO2 relate to A:B ratio and to each other, particularly in the stressed limb; in the well perfused limb, the poorer correlation suggests skin perfusion is not linearly related to tissue oxygen tension.     

Comparison of two laser Doppler flowmeters for the monitoring of dermal blood flow

Laser Doppler flowmetry (LDF) is a noninvasive and continuous method of monitoring dermal blood flow in free flaps. There are two LDFs available for clinical application: the LD5000 Laser Doppler Perfusion Monitor and the Periflux Laser Doppler Flowmeter. Varying degrees of arterial (N = 46) and venous (N = 28) occlusion were induced in saphenous island flaps of the dog, while simultaneous measurements with the LD5000 and Periflux LDFs were made. The millivoltage output of both the LD5000 and the Periflux showed a high degree of correlation with arterial and venous occlusion and with each other.     

激光多普勒血流仪测量股骨头坏死的血流改变

目的 应用激光多普勒血流仪(laser doppler flowmetry,LDF)检测临床确诊为股骨头坏死患者的坏死区和头颈交界正常区的血液灌注量.方法 2007年至2008年对50例股骨头坏死患者82侧行股骨头钻孔减压自体干细胞植入,按照ARCO分期Ⅱ期为A组,46髋(ⅡA 6髋、ⅡB 22髋、ⅡC 18髋);Ⅲ期为B组,36髋(ⅢA 20髋、ⅢB 10髋、ⅢC 6髋),术中用激光多普勒血流仪检测股骨头坏死区及头颈交接区的血流灌注情况,对数据进行统计学处理.结果 A组坏死区灌注量为(30.2±3.0)PU,头颈交界区灌注量为(103.4±4.4)PU,B组坏死区灌注量为(30.6±2.8)PU,头颈交界区灌注量为(103.4±3.9)PU,A组和B组坏死区灌注量均低于正常区,二者比较差异具有统计学意义(P<0.01).而A组和B组之间坏死区和头颈交界区的灌注量差别无统计学意义(P>0.01).结论 LDF可以有效地检测股骨头坏死区血流灌注量减少,为进一步研究股骨头坏死的发病机制提供了理论依据,在股骨头坏死的研究中有应用价值.