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At least 865 records · Page 48Linked to original sources
PubMed1988

Use of disposable ear canal electrodes in auditory brainstem response testing.

In this study a disposable ear canal electrode and stimulus delivery system (the Enhancer l) was evaluated for its clinical utility and the observed enhancement of the auditory brainstem response Wave I with its use. Data were collected from normally and abnormally hearing subjects, with both the conventional forehead-to-mastoid electrode array and the forehead-to-ear canal electrode arrangement provided by the Enhancer I ear canal electrode setup. For the normally hearing group, simultaneous acquisition of forehead-to-ipsilateral ear canal and forehead-to-ipsilateral mastoid electrode linkages was obtained. For the abnormally hearing subjects, a comparison was made between the Enhancer I system and the conventional forehead-to-mastoid electrode configuration used with a TDH-49 transducer for click delivery. Our findings indicate that Wave I was enhanced substantially when using the disposable ear canal electrode compared with the more conventional forehead-to-mastoid electrode configuration for both normally and abnormally hearing subjects. The Enhancer I electrode evaluated in this study proved to be painless for the subjects and extremely easy to use, requiring no more time in subject preparation than the more common surface recording electrode application.

Adult↗
PubMed1997

[Outcome of profile-improving operations in craniofacial abnormalities].

In 52 children with craniosynostosis, we studied the effect of fronto-orbital advancement onto the forehead profile and the growth tendency of the forehead and midface. As a reference, the following kephalometric data were used: SN line. N-Spna line, SNA angle, N-tf line (as an indicator of the forehead profile) and the tf-TF line (as an indicator of the forehead size). The operation was carried out at an mean age of 10.5 months. Follow-up with X-ray control covered a period of 37.2 months on average. In patients with brachycephalus the SNA line was reduced and the post-operative growth tendency was the most unfavorable. Also the forehead profile (N-tf-line) did not become normal after the operation in patients with brachycephalus. Besides this, the increase in the forehead size indicated a new growth-tendency disorder. In all children with brachycephalus as well as in most children with oxycephalic growth tendency, sagittal midface growth was inhibited (NSA angle) while vertical midface growth was normal (N-Spna line). The success of fronto-orbital advancement was dependent on the kind of growth disorder, the location, and the age when the operation was carried out. Only early operative treatment could interrupt the pathological growth tendency even in cases with a major development disorder.

Cephalometry↗
PubMed2004

Effect of volume and concentration on the diffusion of botulinum exotoxin A.

OBJECTIVE: To investigate whether the volume of solution used to inject equivalent units of botulinum exotoxin A affects the diffusion of toxin and areas of rhytid diminution in the treatment of dynamic forehead lines. DESIGN: Ten volunteers with dynamic forehead lines were included. Each study patient received a single injection at a point 2.5 cm above the orbital rim on either side of the forehead with equivalent units, but in different volumes, of botulinum exotoxin A. The sides of injection were randomized; one side of the patient's forehead was injected first with 5 U of botulinum exotoxin A in 0.25 mL (2 U/0.1 mL) of preserved saline in the midpupillary line, followed by injection of the other side with 5 U in 0.05 mL of preserved saline (2 U/0.02 mL). There was a 5-fold difference in volume injected. Subjects were evaluated 14 days later for total area affected during visual inspection of the subjects' foreheads during active muscle contraction. SETTING: Private dermatology office. MAIN OUTCOME MEASURE: Visual inspection to measure the area of rhytid effacement in both height and width. RESULTS: The area affected by the botulinum exotoxin A injection was 50% greater in the side with the larger volume in 9 of 10 subjects. The average area affected was 6.05 cm(2) for the injection of the larger volume compared with 4.12 cm(2) for the injection with the smaller volume. The shape of rhytid effacement was oval, rather than round, with the average width longer than the average height. CONCLUSIONS: In this prospective, randomized, controlled study, we found that injection of botulinum exotoxin A in low concentration and higher volume resulted in greater diffusion and a larger affected area. The pattern of toxin spread is altered by muscular contraction in the injected sites. These results show that the dilution has implications on the desired effect of botulinum exotoxin A.

Adult↗
PubMed1997

Intracranial and extracranial blood flow during acute anxiety.

While large numbers of studies are available on anxiety and cerebral blood flow (CBF), little is known about their relationship to extracranial (forehead) flow. The participants were 24 generalized anxiety disorder (GAD) patients and 26 normal volunteers. A randomized, between groups, repeated measures design was used to evaluate changes in cerebral blood flow. Measurements of CBF, forehead skin perfusion and ratings of anxiety and physiologic indices were made under resting conditions and during anxiety induction with epinephrine or saline infusions, given under double-blind conditions while subjects inhaled room air or 5% CO2. These subjects were divided into three groups; those with decreased anxiety, those with mild anxiety, and those with more severe anxiety increase. Subjects with severe anxiety showed least hypercarbic CBF increase (indicating cerebral vasoconstriction) and maximal increase in forehead skin perfusion. Those with minimal anxiety had most hypercarbic cerebral vasodilation and least increase in forehead skin perfusion. Forehead skin perfusion correlated positively with anxiety levels, and negatively with hypercarbic cerebral vasodilation. In animals, sympathetic activation limits hypercapnic cerebral vasodilation. Thus, the restricted hypercapnic cerebral vasodilation during severe anxiety may be mediated through cervical sympathetic fibers which innervate cerebral vessels.

Acute Disease↗
PubMed1997

Influence of thermoregulatory vasomotion and ambient temperature variation on the accuracy of core-temperature estimates by cutaneous liquid-crystal thermometers.

BACKGROUND: Recently, liquid crystal skin-surface thermometers have become popular for intraoperative temperature monitoring. Three situations during which cutaneous liquid-crystal thermometry may poorly estimate core temperature were monitored: (1) anesthetic induction with consequent core-to-peripheral redistribution of body heat, (2) thermoregulatory vasomotion associated with sweating (precapillary dilation) and shivering (minimal capillary flow), and (3) ambient temperature variation over the clinical range from 18-26 degrees C. METHODS: The core-to-forehead and core-to-neck temperature difference was measured using liquid-crystal thermometers having an approximately 2 degrees C offset. Differences exceeding 0.5 degree C (a 1 degree C) temperature range) were a priori deemed potentially clinically important. Seven volunteers participated in each protocol. First, core-to-peripheral redistribution of body heat was produced by inducing propofol/desflurane anesthesia; anesthesia was then maintained for 1 h with desflurane. Second, vasodilation was produced by warming unanesthetized volunteers sufficiently to produce sweating; intense vasoconstriction was similarly produced by cooling the volunteers sufficiently to produce shivering. Third, a canopy was positioned to enclose the head, neck, and upper chest of unanesthetized volunteers. Air within the canopy was randomly set to 18, 20, 22, 24, and 26 degrees C. RESULTS: Redistribution of body heat accompanying induction of anesthesia had little effect on the core-to-forehead skin temperature difference. However, the core-to-neck skin temperature gradient decreased approximately 0.6 degree C in the hour after induction of anesthesia. Vasomotion associated with shivering and mild sweating altered the core-to-skin temperature difference only a few tenths of a degree centigrade. The absolute value of the core-to-forehead temperature difference exceeded 0.5 degree C during approximately 35% of the measurements, but the difference rarely exceeded 1 degree C. The core-to-neck temperature difference typically exceeded 0.5 degree C and frequently exceeded 1 degree C. Each 1 degree C increase in ambient temperature decreased the core-to-fore-head and core-to-neck skin temperature differences by less than 0.2 degree C. CONCLUSIONS: Forehead skin temperatures were better than neck skin temperature at estimating core temperature. Core-to-neck temperature differences frequently exceeded 1 degree C (a 2 degrees C range), whereas two thirds of the core-to-forehead differences were within 0.5 degree C. The core-to-skin temperature differences were, however, only slightly altered by inducing anesthesia, vasomotor action, and typical intraoperative changes in ambient temperature.

Adult↗
PubMed1999

Sibling correlations of skin pigmentation during growth.

The present study is focused on the analysis of skin color correlations in a sample of 1039 siblings aged 4 to 20 years from the province of Biscay (Basque Country, Spain). Measurements were taken at the upper inner arm and forehead by means of an EEL DS29 Digital Unigalvo reflectance spectrophotometer fitted with filters 601, 605, and 609. The reflectance data were internally standardized according to sex and age of the individuals, and the analysis of the degree of similarity between siblings was based on the calculation of intraclass correlation coefficients. All 3 filters gave fairly high and statistically significant correlations regarding forehead skin color (between 0.28 and 0.45) for all types of siblings under consideration. However, with respect to filter 609 the arm reflectance values did not reveal correlation either between brothers (0.01) or between siblings (0.02), even though it did reveal correlation between sisters (0.29). When other filters or type of sibling were considered (also for arm), all coefficients happened to be statistically significant and relatively high (0.35-0.43). This study confirms that the degree of sibling resemblance with regard to skin pigmentation is influenced by growth factors and that the upper inner arm and the forehead skin patterns change with age in the sense that, during and especially after puberty, the coefficients of correlation are higher for arm reflectance than for forehead reflectance; the forehead is a site that is more influenced by environment.

Adolescent↗
PubMed1986

Pattern of intracranial and extracranial projections of trigeminal ganglion cells.

The trigeminal sensory innervation of the major cerebral vessels is thought to carry the nociceptive information during a migraine headache, and this pain is usually referred to the forehead area. Using retrograde tracing techniques, we have described the distribution of sensory trigeminal cells that innervate the middle cerebral artery (MCA) and the forehead. Nearest-neighbor analysis of the ophthalmic division of the trigeminal ganglion revealed that cells innervating the forehead tend to be clumped around individual cells that innervate the MCA. An average of less than 1 cell per animal was found to project divergent collaterals to both areas. The close association of ganglion cell bodies innervating the cerebral vasculature and those innervating forehead areas may underlie the convergence of their central processes onto common brain-stem trigeminal nucleus cells, and thus the referral of headache pain. In contrast to the lack of ganglion cells with axonal collaterals to the cerebral vasculature and forehead, a significant population of cells that innervate the MCA also have collateral projections to other cerebral arterial branches (branches of the middle meningeal artery), as well as the surrounding dura. Thus, the innervation targets of individual trigeminal cells are very widespread intracranially (including arteries and dura), but separate cells in the ophthalmic division innervate extracranial targets.

Animals↗
PubMed1994

[Comparison of a reflectance sensor and a transmittance sensor for pulse oximetry].

We have investigated a new optical reflectance sensor for pulse oximetry in 70 patients under general anesthesia. The reflectance sensor was applied to the forehead, the dorsal manus, the inguinal region, and the anterior crus of the patients. We could obtain a reliable SpO2 value when the reflectance sensor was applied on both forehead and anterior crus. It was difficult to obtain a reliable SpO2 value with the reflectance sensor without using an additional attachment especially for children. We compared the SpO2 value using the reflectance sensor attached to the forehead, with the SpO2 value obtained by the transmittance sensor attached to a finger or an ear lobe, in 7 volunteers who held the breath as long as possible. When we attached the probes on both ear lobe and forehead, the response time was faster, but and the maximum changing value was much larger, compared with those on the finger. We could obtain a reliable and stable SpO2 value using the reflectance sensor, when it was placed on the appropriate site as the forehead or the anterior crus.

Adolescent↗
PubMedDate not supplied

Modifications of eyebrow position with botulinum exotoxin A.

OBJECTIVE: To determine if clinically used botulinum exotoxin A (Botox) injections to the forehead and glabellar and crow's-feet regions result in modifications of eyebrow position. DESIGN: Prospective study. SETTING: Academic medical center in St Louis, Mo. SUBJECTS: Twenty-nine adult patients treated with botulinum exotoxin A injections for rhytids. INTERVENTION: The eyebrow position at 13 different sites was measured before injection and 2 weeks after treatment. The areas injected were based on patient preference and physician assessment. Of the 29 patients, 14 received injections into the glabella only and 15 received injections into the glabella and forehead, with or without treatment of the crow's-feet. RESULTS: In 29 patients at rest, we found no significant (P value range,.17 to.97) change in eyebrow position, except for a point depression at the right lateral eyebrow. The 15 patients who received injections into the forehead and glabella, with or without treatment of the crow's-feet, had no significant (P value range,.11 to.84) change in eyebrow position, except for a point of depression at the left medial eyebrow. Both groups exhibited eyebrow depression in the active state (eyebrow maximally elevated). CONCLUSIONS: Botulinum exotoxin A injections into the forehead and glabellar, and crow's-feet regions did not significantly change the resting eyebrow position. However, forehead injections contributed to eyebrow depression in the active state.

Adult↗
PubMed1996

Regional differences in age-related decrements of the cutaneous vascular and sweating responses to passive heating.

Ten older (aged 64-76 years) and ten younger (aged 20-24 years) healthy men were exposed to a standard heat stress [by placing the lower legs and feet in a water bath at 42 degrees C while sitting in a controlled environment (ambient temperature 35 degrees C and 45% relative humidity) for 60 min]. During passive heating, the rectal temperature of the older men was significantly greater (P < 0.05) and mean skin temperature was lower (P < 0.001), compared to the younger men. Skin blood flow by laser Doppler flowmetry (LDF) was significantly lower on the chest and thigh for the older men (P < 0.001), but forehead LDF did not differ between the groups. The percentages of total LDF in the older men to total LDF in the younger men for the last 30 min were 99%, 58% and 50% on the forehead, chest and thigh, respectively. The age-related differences in LDF responses mirrored cutaneous vascular conductances (CVC), since no group and time effects were observed in mean arterial blood pressure during the test. During the last 30 min the local sweat rates (msw) on the back and thigh were significantly lower for the older men (P < 0.02), but not on forehead, chest and forearm, although the older men had lower msw during the first 30 min exposure regardless of site (P < 0.03). The percentages of total msw in the older men to total msw in the younger men during the last 30 min were 105%, 99%, 63%, 106% and 88% on the forehead, chest, thigh, forearm, and back, respectively. During the latter half of the exposure, the older men had similar LDF, CVC and msw on the forehead, lower LDF and CVC and a similar msw on the chest, and lower LDF, CVC and msw on the thigh, compared to the younger men. These results suggest firstly that regional differences exist in the age-related decrement of cutaneous vasodilatation as well as sweat gland function, secondly that the age-related decrement in cutaneous vascular function may precede a decrement in sweat gland function, and thirdly that the successive decrements may develop sequentially from the lower limbs to the upper body, and head.

Adult↗
PubMed1995

Skin blood flow oscillations respond more effectively to rhythmic thermal stimulation than to continuous or periodic breathing in newborn infants.

Effect of continuous (n = 30) and periodic (n = 5) breathing on forehead skin blood flow (SBF) oscillations was studied in healthy 3-day-old preterm and term infants. Femoral SBF was measured in 10 of the term infants during continuous breathing. Respiratory and SBF signals were analysed by power spectrum during the control period. The signal analysis was repeated during rhythmic thermal stimulation which was applied to the skin of each infant in order to synchronise spontaneous SBF oscillations. During the control period, the forehead and femoral SBF of all the studied infants oscillated at frequencies corresponding to the frequency of regular continuous breathing. External thermal stimulation decreased these high-frequency oscillations of forehead SBF in both preterm and term infants. Oscillations in femoral SBF of term infants remained unchanged. During periodic breathing, the spontaneous forehead SBF oscillation was synchronised to the frequency of respiratory amplitude variation. Despite periodic breathing, thermal stimulation was able to resynchronise the SBF oscillation to the stimulation frequency in 4/5 infants. Forehead SBF oscillates at the frequency of both continuous and periodic breathing in preterm as well as in term infants on postnatal day 3. Rhythmic thermal stimulation synchronises SBF and affects SBF more effectively than continuous or periodic breathing. These results suggest functional neural control of cutaneous vasculature at birth.

Blood Flow Velocity↗
PubMed2004

Effect of facial cooling and cold air inhalation on sympathetic nerve activity in men.

In nine healthy subjects, cold stimuli were administered to the forehead and hand, to the oral and nasal cavities via ice cubes and to the bronchial system via inhalation of cold air (-25 degrees C). Blood pressure, heart rate and muscle sympathetic nerve activity (MSNA) from the peroneal nerve were recorded. MSNA expressed as total activity increased during cold air inhalation, cooling of the forehead (P < 0.001, ANOVA), hand and mouth (P < or = 0.05), paralleled by a rise in blood pressure during cold air inhalation and cooling of the forehead and hand (P < 0.01). Cooling of the forehead provoked a faster increase of MSNA expressed as total activity (P < 0.05) and higher levels of diastolic blood pressure (P = 0.05) compared with cooling of the hand. Bradycardia was observed only during cooling of the nasal cavity (P < 0.001) and the forehead (P < 0.05). It is concluded that cooling of the skin and mucous membranes of the tracheobronchial tract elicits sympathetically mediated hemodynamic adaptations, probably via stimulation of cold-sensitive afferents.

Action Potentials↗
PubMed2001

The acute effects of smokeless tobacco (snuff) on gingival blood flow in man.

Snuff-induced blood flow responses in the gingiva were evaluated in 22 healthy casual consumers of tobacco. Laser Doppler flowmetry (LDF) was used to measure blood flow simultaneously and continuously on two gingival sites (buccal aspect of the papillae between the upper lateral incisors and canines). In addition, measurements of skin blood flow in the forehead and palmar side of the left thumb were performed. Arterial blood pressure (BP) and heart rate (HR) were also recorded. Unilateral application of commercial snuff (500 mg, 1%) caused a marked and rapid increase in gingival blood flow (GBF) on the exposed side (p < 0.001). Blood flow increased also in the contralateral gingiva and forehead skin (p < 0.05). Skin blood flow in the thumb showed an insignificant decrease. BP and HR increased. Vascular conductance increased significantly in the snuff-exposed gingiva but not in the contralateral gingiva or the forehead. Vascular conductance was largely unaffected in the thumb. It is concluded that acute application of snuff, besides giving rise to typical changes in BP and HR, increases GBF in and around the exposed area, probably through activation of sensory nerves and the subsequent release of vasodilatory peptides from their peripheral endings. Blood flow in unexposed gingival and forehead skin may increase probably due to humoral or nervously mediated mechanisms. However, a passive pressure-induced hyperaemia in the unexposed gingiva and forehead skin can not be excluded.

Blood Pressure↗
PubMed1993

Ethnicity, gender, family history of myocardial infarction, and hemodynamic responses to laboratory stressors in children.

Relationship among ethnicity, gender, grandparents' histories of early myocardial infarction, and hemodynamic responses to forehead cold and treadmill exercise were examined in 87 6-to-8-year-olds (57 White, 30 Black). Boys had greater increases in systemic vascular resistance and decreases in cardiac index to forehead cold. Girls had greater increases and quicker recovery in heart rate to dynamic exercise. Blacks had greater increases and slower recovery in diastolic pressure to exercise and forehead cold. Blacks showed greater increases and slower recovery in systemic vascular resistance to forehead cold. Positive-family-history children had greater increases in diastolic pressure and systemic vascular resistance to forehead cold and greater diastolic pressure increases to exercise. Positive-family-history Blacks had greater increases in systolic pressure to exercise and slower recovery than all other groups.

Black or African American↗
PubMed2004

Ultrasound imaging demonstration of the improvement of non-ablative laser remodeling by concomitant daily topical application of 0.05% retinaldehyde.

BACKGROUND: Retinaldehyde has been proven to be effective in the reduction of facial wrinkles. It has also demonstrated its usefulness when used before and after laser skin resurfacing. OBJECTIVE: A monocentric, comparative, randomized, double-blind study was performed to evaluate the efficacy of retinaldehyde versus excipient in combination with non-ablative laser remodeling treatment. METHODS: A total of 16 female patients (mean age 45 years) were enrolled for neck line and forehead rhytid treatment. They were randomly assigned into two groups. The RAL group (eight patients) was treated with a non-ablative laser (1540 nm Er:glass, 10 J/cm2 per pulse, three pulses, 2 Hz repetition rate, 4 mm spot, +5 degrees C cooling) and daily topical application of 0.05% retinaldehyde immediately after the first laser treatment and up to 3 months after the fifth treatment. The CTRL group (eight patients) was treated under similar conditions, except with a daily application of excipient. The thickness of the skin (forehead and neck) was measured by ultrasound imaging before the first treatment, 1 month after the third treatment, 1 month after the fifth treatment and 3 months after the fifth treatment. RESULTS: An increase of dermal thickness was observed for all patients treated by laser (groups RAL and CTRL) on the forehead and neck. However, the increase was greater for the RAL group (retinaldehyde) when compared with the CTRL group (excipient). Three months after the fifth treatment, the increase in dermal thickness (%) was, respectively, 5.27 versus 1.13 for the forehead and 10.54 versus 3.57 for the neck. The difference between groups was statistically significant in favor of the retinaldehyde group for the forehead (p<0.05) and of limited significance for the neck (p=0.08). CONCLUSION: When considering the reduced number of patients in each group, the statistical analysis demonstrates an evident advantage of using retinaldehyde versus excipient. This study demonstrates that irradiation with a 1540 nm Er:glass laser can be potentiated with concomitant daily topical application of 0.05% retinaldehyde.

Administration, Topical↗
PubMed1989

Reflex control of facial flushing during body heating in man.

Facial temperature and amplitude of capillary pulsations from the forehead and cheeks were measured shortly before and after pharmacological blockade of the stellate ganglion in 9 patients with reflex sympathetic dystrophy of an upper limb, and in 1 other patient with erythromelalgia of all four limbs. Patients were then heated to determine the effect of sympathetic blockade on mediation of thermoregulatory facial flushing. Release of vasoconstrictor tone following stellate ganglion blockade was invariably followed by an increase in orbital and cheek temperature, and by similar but less consistent increases in temperature of the forehead, lips and chin. The amplitude of capillary pulsations recorded from the forehead and cheeks also increased on the side of stellate ganglion blockade. Flushing of the forehead and cheek on the sympathetically intact side during body heating far outweighed the extent of flushing after release of vasoconstrictor tone. The thermoregulatory response was prevented by sympathetic blockade, indicating that an active sympathetic vasodilator pathway had been interrupted. In contrast, the temperature of the orbit during body heating was not influenced by sympathetic blockade. Asymmetry of forehead temperature was detected before sympathetic blockade in 8 of 9 patients with reflex sympathetic dystrophy, suggesting that autonomic disturbances in this condition may influence cervical sympathetic outflow. The results indicate that sympathetic vasodilator fibres passing through the stellate ganglion mediate thermoregulatory facial flushing, and that release of vasoconstrictor tone has only a minor influence on this response in most areas of the face.

Adult↗
PubMed1996

Mode and site of analgesic action of epidural buprenorphine in humans.

This study was designed to clarify the site of analgesic action of epidural buprenorphine and its spinal segmental analgesia. Fifty patients undergoing gastrectomy were randomly assigned to five groups according to the dose of buprenorphine and route of administration: epidural saline group, epidural buprenorphine 2- and 4-micrograms/kg groups, and intravenous buprenorphine 2- and 4-micrograms/kg groups. The changes in pressure pain threshold (PPT) and visual analog scale (VAS) were compared within groups of patients receiving either buprenorphine, 2 or 4 micrograms/kg epidurally, and between groups of patients receiving buprenorphine 2 or 4 micrograms/kg either epidurally or intravenously. The PPT near the surgical incision was significantly greater (P < 0.05) in the epidural buprenorphine group compared to the intravenous group during the middle period (between 2 and 6 h after administration) of analgesia obtained after administration of buprenorphine. VAS response significantly (P < 0.05) decreased in the epidural group compared to the intravenous group at the same dose. In the smaller dose buprenorphine epidural group, PPT at the forehead (an index of systemic analgesia) exceeded the preoperative value during the 12 h after administration of buprenorphine. PPT near the surgical incision decreased by 30% from the preoperative value and did not exceed the preoperative value throughout the study. PPT at the forehead significantly exceeded the PPT changes measured near the surgical incision (an index of regional analgesia) (P < 0.05). In the larger dose buprenorphine epidural group, during the early period (up to 2 h after administration), PPT at the forehead increased by 30%-40%, while PPT near the surgical incision decreased by 10%-25% compared to the preoperative value (P < 0.01). However, in the middle period, there were no significant differences in the changes between PPT at the forehead and near the surgical incision. In the late period (more than 6 h after administration), PPT at the forehead maintained the level of preoperative value, whereas PPT near the surgical incision decreased by more than 25% from the preoperative value (P < 0.01). VAS value significantly (P < 0.01) decreased in the larger dose buprenorphine epidural group compared with that in the smaller dose group during the middle period. The larger dose of epidural buprenorphine provided better analgesia than the smaller dose. We conclude that epidural buprenorphine acts predominantly at the supraspinal region and produces spinal segmental analgesia in a dose-related manner.

Adult↗
PubMed2002

Synchronous rhythmical vasomotion in the human cutaneous microvasculature during nonpulsatile cardiopulmonary bypass.

BACKGROUND: The origin, control mechanisms, and functional significance of oscillations in microvascular flow are incompletely understood. Although the traditional belief has been that only low-frequency oscillations (0.04-0.10 Hz) can originate at the microvascular level, recent evidence in healthy volunteers has suggested that high-frequency oscillations (> 0.10 Hz) also may have a microvascular origin (as opposed to being mechanically transmitted respiratory-induced variations in stroke volume). The current study determined if such oscillations would emerge in the absence of cardiac and respiratory activity during nonpulsatile cardiopulmonary bypass (NP-CPB). METHODS: Forehead and finger laser Doppler flow, arterial pressure, and core temperature were simultaneously recorded in eight patients during NP-CPB. Analyses included time- domain indices, frequency-domain indices (auto power spectral density), and a measure of regularity (approximate entropy) for standardized time segments. RESULTS: Nonpulsatile cardiopulmonary bypass was associated with the emergence of rhythmical oscillations in laser Doppler flow, with characteristic frequencies for the forehead (0.13 +/- 0.03 Hz) and finger (0.07 +/- 0.02 Hz). Forehead vasomotion became progressively synchronized, with a gain in high-frequency spectral power from 17.5 (minute 1) to 89.1 (minute 40) normalized units, and a decrease in approximate entropy from 1.2 (before NP-CPB) to less than 0.5 (minute 40). CONCLUSIONS: The emergence of forehead microvascular oscillations at greater than 0.10 Hz (characteristic of parasympathetic frequency response), in the absence of cardiac and respiratory variability, demonstrates their peripheral origin and provides insights into parasympathetic vasoregulatory mechanisms. The progressive synchronization of forehead vasomotion during NP-CPB, suggestive of increased coupling among microvascular biologic oscillators, may represent a microcirculatory homeostatic response to systemic depulsation, with potential implications for end-organ perfusion.

Aged↗